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Author Topic: First AVL ownership/build... tech questions...  (Read 2996 times)

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ringoism

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on: March 30, 2018, 10:01:37 am
Hi folks, figured it was time I finally join this forum, which I’d originally come across quite some time ago… reason being that I’m finally the owner of a 500AVL (“Machismo” in Indian parlance).  I'll try and keep future posts shorter...

Been quite interesting / enlightening reading through so many of the related threads – BW/Basanti/Tooseevee/DanB/Ace and many other long-term tinkerers / contributors.  Basic personal objective is just to have the thing a little more punchy and stronger all-round, especially in the midrange, without spending a lot of time/money or killing the low-end.   

I’m an American living over a decade and a half over here in S. Asia… never was much of a Bullet fan (have ridden many of all types), but have had some good experiences on them, and there’s something special about the 500AVL’s in my view.  Very much the traditional British single with a good bit of useful upgrading over the old iron units.  Having ridden the CI/AVL/UCE 500's side-by-side, all have their strong/weak points but somehow it seems the best compromise. 

My particular bike is a little unlike what most of you would have started out with… in that it has spent its whole life in the Himalayas, and is fairly well-worn, till recently a workhorse for a motorcycle tour company commonly doing the Manali-Leh Highway and other stunning routes in the region.  Early 2010 model, so one of he last produced here.  The engine as received started easily (often first kick even at freezing temps), ran fairly well and had good compression but was a bit noisy (internally) as is typical of used AVL’s here.  Under load, probably most of it was piston slap on account of its having around .008” clearance there, but there was 1mm side-to-side in the rod too, and senior mechanic here (who has been working years on this fleet of over 30 bikes for a decade now) felt that was contributing some rattle as well.  It had been rebuilt earlier, I was to discover.  God alone knows how many miles it has covered, how much abuse it has survived.  Besides the engine, the gearbox seemed to too often jump out of 2nd/3rd after initially engaging, clutch slipped a bit, etc, so figured it was time to just refresh the whole thing, and hopefully improve it a bit in the process.  Not a lot of time to go into great detail and many here have done it earlier and better, so initially will just be seeking advice / info here.

I bought a new cylinder kit to keep aside as a spare (under $125 here, and most domestic AVL parts supplies drying up, probably because of the demand for them from the U.S. / U.K.), but decided to do a 0.75mm (.030”) overbore instead.  Piston is a dished unit (1.5mm) from the UCE (AVL overbores not available) which with the near 85mm bore would’ve put compression down to 8.3:1, so decided to try BW’s shortened barrel/piston crown mod, especially as the low atmospheric pressures up here effectively lower your compression ratios and really sap the power (the thing runs SO much better 4,000ft down the mountain from here – we’re above 7,000).  So I’ve got a 64mm dia, 1mm raised section on the piston at 64mm dia., having cut the barrel and outer crown down by 2.5mm each.  My calculations put me at 9.1:1 with the raised section and added overbore volume.  Maybe a little more considering that the volume between the top ring and deck is now less as well.  Didn’t want to push it too much as I already did have some light detonation at low speeds on normal (87 octane?) fuel (a fair bit of carbon in there, and moreover Hitchcocks says they have found the Electra X’s advanced by over 7-degrees over factory spec, thus the offset woodruff keys, which I could probably make here).  Will have to see how the squish works out but both the barrel/case and head gaskets are pretty thick (nearly 2mm (.080”) thick fire-ring on the latter, .075” in the composite area, uninstalled) and if we’re aiming for .020-.060” squish (as per ACE), am thinking I may have to eliminate the barrel gasket in favor of RTV, or else cut a thinner one to fit there (I do have some gasket material available).  I doubt there are many options for head gaskets unless perhaps the UCE one would work - the AVL500 was a rare bird here (only 500 made the first year, supposedly limited thereafter as well, and only 3 years production).     

1.  One question would be re: any limitations as to how far the piston can sit above the deck, in the event I can’t find a thinner head gasket.  Stock gasket’s fire-ring is of course assuming an 84mm piston, so has an ID of 85mm which will decrease a little when compressed.  Which means I guess I’d have to bevel the top edge of the piston if it’s going above-deck?  Any issues with the top compression ring being a few mm’s closer to the deck than originally designed?  If my head gasket can compress down to .060 or so (not sure of this), I’d be right at the outer squish limit with the piston even with the deck, and more ideally I’d have to have it sticking out .020 or so.

Otherwise, would lapping the head/barrel and using a thin copper gasket be an option?  My 2-stroke Kawasaki uses one of these pretty fine. 

2.  Would it be highly advisable to change to the CI followers/guides while I’ve got the cases apart? I’ve heard of and seen the AVL tappets break here and mentioned in these forums.  What is involved, and how do we deal with the new pushrod lengths (someone said 3/8” shorter would be required?), without having to order expensive bits from abroad?  Any reason the stock ones couldn’t be shortened, being that they’re aparently tubular aluminum (adjusters press-fit in the ends?)?

3.  Anyone done anything inside these gearboxes?  Head mechanic here says they never go bad, which sounds ridiculous, especially since mine obviously pops out of gear sometimes and others I’ve ridden never did.  I bought three new selector forks and a new indexing spring (will check the indexing plate/disc once apart), and hope to install both along with the refreshed engine.  Will see what the engagement dogs on the gear sides look like, on another bike I once resurfaced these with a die grinder to restore the 90-degree mesh surface.  Will check for loose shaft bearings, etc… Any other ideas?

4.  Re: the near-miraculous "S" cams... has anyone noted a drop in fuel efficiency after installation?  If it's mainly a change in lift it shouldn't be, but duration/overlap can start to cause negative effects in that realm.  I know that most in the U.S. / UK don't really think about that much (the stock bike gets something like 90mpg), but while I'd like a punchier, stronger pulling bike, I could care less about the "ton" and would probably kill myself trying it just about anyplace in the subcontinent.  And the fact that 90mpg is only about 25% less than I get from my 13.5hp, 150cc dual-sport makes it a little less difficult to justify owning this (third) motorcycle on what is a fairly slim budget...

I once made a set of high-lift cams myself using a precision grinder attachment on a lathe, reducing the base circle and just kind of blending it in to the existing lobe.  This was a ported, milled, relieved, self-built flathead 4hp Briggs and in finished form it would easily outrun an 8hp, so I guess I could say it worked.  But then, I only needed it to last through a six-hour enduro event in that case, and with AVL followers being fragile already... mmm... maybe not.  Basanti had said the stock iron cams were "way better" than the AVL's but never have seen specs on them or any other confirmations.  Anyone?  Other options?

Many Thanks,
Eric











ringoism

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Reply #1 on: March 30, 2018, 10:53:37 am
Oh, one more thing - any recommended, improved lubricants for engine/primary/gearbox?  We rarely see 85F up here in the hills, and I do a lot of short rides. 

1. The owner of this fleet of AVL's was of the opinion that tappets were less prone to failure with timely oil changes and quality (conventional) motor oil.  Not sure if I want to shell out for three liters of full-synthetic, but any of you have advice/views/experience on semi-synthetics / other grades?  (And do the tappets mainly break from merciless revving/neglect, or would even "normal" riders like myself be at risk?)

2.  Saw mention in the forum concerning the use of ATF in the clutch/primary drive.  I know Ford used it way back basically just to reduce drivetrain losses / improve MPG.  Any negative effects for the possible RE application?  I read the bit about using a liter in there vs. the factory-recommended half-liter, to save the high-mounted starter sprag.  Not sure if ATF could do that already challenged piece of hardware further harm. 

Same question for the gearbox.  Occasionally would do long uphill runs so the heat buildup could be there.  Any harm in using ATF?  Or even motor oil, since the UCE's are running their almost identical gear components in it?

Sorry for so many questions. 

To add a little info to the former post, I've got a 32mm Mikuni BS (CV) to replace the 28, found a manifold from a domestic Honda using that carb, ported the manifold (which oddly tapered down to maybe 25mm on the port side) to match the stock port.  But with the AVL port being "too large" (ACE), I wonder whether the taper-down could actually help "shoot" the charge into the port/chamber?  Should I have left it alone?  Why did Honda (CRF230 engine basically) do it in their application?  Going to ditch the toolbox-mounted air filter and figure out something less convoluted/freer-flowing.  Managed to remove the "hot tube" from the header pipe (royal pain).  Did a 3-angle valve job, cleaned up / matched the ports a bit - one very sharp edge on the floor of the exhaust port removed, in particular. 

Changing rear rim/tire to the C5 (120/80-18) setup (I hope it fits, a little tight tire-to-swingarm clearance), and the front to a fairly soft-compound (Ralco) 90/90-19 available here, down from the tallish hard-compound 3.25.  Hard rubber and cold / wet pavement don't get along too well and I ride in all sorts of weather, incl. snow on occasion. 

This is to be a low-budget, medium-impact, fun build and learning experience.  Tourist season brings horrible traffic jams up here and by car it takes hours to cover the four miles to town, so the bike is often the family vehicle.  Registered in my wife's name in fact, who wants to ride it by year's end (currently practicing on my Kawi KH125)...

Besides Briggs&Strattons have built some 2-stroke bikes and American V-8's in my time, but this is my first Enfield attempt, and while the basics are similar, it is a weird machine in some respects (couldn't believe the amount of work involved in changing out the front chain sprocket... and adjusting the steering head bearings will be interesting to be sure).       

Regards,
Eric


REpozer

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Reply #2 on: March 30, 2018, 12:31:02 pm
Welcome Eric,
Many good questions. I’ve never had my AVL engine apart or the 5 speed gear box. But mine is not used as yours was.

I have used all different kinds of lube in my Primary Drive. And I’ve always used a full Liter. Currently using ATF - F . It seems to work fine. I’ve also used 20w-50 motor oil, 10w-30 motor oil , 15w-40 motor and Diesel motor oil , and 50/50 motor oil and ATF, with no real noticeable difference.

The 5 speed gear box has always used 90w gear oil.

The engine , I’ve used 20w50 motor oil, and currently using 15w-40 diesel truck motor oil( for the ZDDP).

The  front shocks , I’ve tried 10w-30 motor oil( ride too hard) currently using ATF-F ( better ride).

As you can see , many off the shelves lube will work fine if you know what your doing ( sounds like you do)

Hope this answers a few questions. Others will jump in for more technical stuff.
2008 AVL Classic Bullet in British Racing Green
REA # 84 ( the first time)


tooseevee

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Reply #3 on: March 30, 2018, 01:33:02 pm
Hi folks, figured it was time I finally join this forum, which I’d originally come across quite some time ago… reason being that I’m finally the owner of a 500AVL (“Machismo” in Indian parlance).  I'll try and keep future posts shorter...

Been quite interesting / enlightening reading through so many of the related threads – BW/Basanti/Tooseevee/DanB/Ace and many other long-term tinkerers / contributors.  Basic personal objective is just to have the thing a little more punchy and stronger all-round, especially in the midrange, without spending a lot of time/money or killing the low-end.   


              Welcome To The Monkey House.

               Wow - your bike has been rode hard and put away wet many times being a recovering Himalaya Basher. I've watched many many many of the Youtube Himalaya Lunatics video clips bashing their way up and down those unbelieveable roads. Mine's a pampered show girl princess compared to yours.

              Good luck and have fun.
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


DanB

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Reply #4 on: March 30, 2018, 04:20:38 pm
Welcome Eric! 

Wow, you got a whole lot going on. I’ll take a stab at a couple of issues.

1. Base gasket. Don’t need one. Use good rtv and make sure to be generous around the pushrod tunnels. Go slow and let the stuff setup before final compression. (Had to do mine twice).

2. Head gasket. I used stock; it’s thick. Our hosts do sell an avl copper gasket at 1 mm thick. Not sure if that’s an option for you. You could have one made. W/o base and stock gasket, I was able to get barely into target squish range. 1 mm is the perfect target for me.

3. Piston to deck clearance. I don’t think you’ll have a problem. Mine protruded the deck plane by around .8 mm when all’s said and done. Used a stock piston for avl.

4. Check your valve clearances. Especially the inlet. Clay is good for this. I had to cut into piston.

5. Adrian is the man for replacing the stock tappers with IB versions. If you’re there, do it.

6. S cams or aces cams will really open things up. It’s the lift plus duration. I like the idea of grinding a set. Not for me personally.

7. Gear box. Before going to town on it, I’d work on the clutch adjuster. Open that little panel and try backing it off a sqoosh.

I’m sure ace will chime in on the carb setup. I’ve heard good things about the 32 cv carb. In terms of mileage.  No way do I get close to stock. Most likely it’s do to me being heavier on the throttle cuz it’s fun!

Oh yeah, stick with the 90 Wt gear box oil. Use whatever you have that’s slippery in the primary. If it is an electric start, use a liter.
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra


Adrian II

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Reply #5 on: March 30, 2018, 06:14:08 pm
Quote
5. Adrian is the man for replacing the stock tappets with IB versions. If you’re there, do it.


Er... I paid Bullet Whisperer to do it for my project bike engine!

Seriously, I would do this or have it done. My own Electra-X (the export version of the 500 AVL sold in the UK) snapped a cam follower foot of its stem, the foot then bounced around and bent the other follower. Other cam follower failures have also destroyed the timing gears. Ironically my project bike's engine started with another set of 500 AVL crankcases which had also had a broken cam follower. The fact is, the stem diameter was reduced too much in the AVL redesign, I can see the benefits of keeping the oil nice, but it can't make up for too little metal.

The AVL tappet/cam follower guides have a smaller outside diameter, so Iron Barrel guides will need turning down to match the AVL's, you may also have to sleeve them to preserve the correct fitting height. B.W. used a set of bronze guides from a Redditch (UK built) Bullet turned down to match, but with an alloy collar to set them at the right height when fitted. He took a few pictures.

With the wider stem followers you also loose the valve lifter collar. You will note that he also replaced (at my request) the adjustable cam spindles with solid spindles, something less to come undone.

The other thing you will have to do is play with different push rods, tappet adjusters and push rod tops. The push rods need to be about 3/8" or roughly 10mm longer if using Iron Barrel cams, Indian or Redditch "S".

The point of replacing the AVL cams with the "S" is that the originals have been found to cause valve bounce at 5,800 RPM, they can be used with the original tappets/followers, though, if you slacken off the tappet adjusters enough.

Also, watch inlet valve head to piston crown clearance with "S" or Indian iron barrel cams, particularly if you're timing the cams on the original timing dots. You can grind a pocket in the piston crown if you have to.

A.





Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


ringoism

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Reply #6 on: March 31, 2018, 12:27:02 am
Wow, thanks to all of you who responded - I was hopeful, but didn't expect this much help this quickly.  Great community here. 

I'll check into the tappets today... lathe available locally, so the conversion shouldn't be too tough... but kinda need to get on the lathe personally as the local hacks don't really work to thousandths!  Need to have a look at the pushrods and see what would be involved to shorten them, also check whether new ones are easily enough available that I can afford to experiment. 

I'd probably stick with the AVL cams for now since I'm looking more at midrange and going above 5,800 isn't highly important to me. 

But anyone know the lift figures of the "S" cams vs. stock AVL?  And anyone know the rocker-arm ratio?   

If I get adventurous later and try grinding a set of cams, I could take the stock cams or else larger-base-circle CI units, reduce the base circles to something closer to the AVL's, take up the difference with the pushrod adjusters, and voila, high-lift cams that have roughly stock duration for the sake of fuel economy, but more lift/flow to improve power across the full rpm range.  If I had the heavier CI tappets / guides I'd worry less about the self-styled cams being ground a little less than perfectly or whatever.  Worst that could happen is the followers might wear faster, I suppose... at any rate, the highest (spring) pressures would be on the upper parts of the lobes, which would remain untouched.  Assuming proper tappet clearance, base circles see no load at all, and first part of the ramps relatively less pressure/more surface area anyway.  Might rig up a degree wheel and actually try this... 

Bike's sitting apart in someone else's shop, so not wanting to delay things too much, but I've got a day or two here - head mechanic still stuck in Delhi trying to source various Enfield parts - The "two wheeler" market there (Karol Bagh) was closed for a couple days due to some protests / government sealing of unauthorized commercial properties... such is life...

Thanks again to all,
Eric


ace.cafe

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Reply #7 on: March 31, 2018, 09:01:36 am
AVL inlet cam is about.280" lobe lift. Rocker ratio is about 1.2. I say "about" because probably no 2 cams or rockers are the same.

Std Bullet cams and "S cams" are about. 312" lobe lift.

The AVL cams are the ones with the larger base circle.

If you want more low-mid rpm torque,  then advance the cams with the Hictchcock 3-way pinion. Also, do the compression increase and set the squish. Do the tappets and cam spindles as reliability mods. I would also get the Wossner 87mm flat top piston, and put that in.

Don't do iron barrel performance cams for low-mid power. They are for upper rpm power. Don't do a bigger carb for low-mid power. Make a longer header and longer inlet stack for low-mid rpm power.


Adrian II

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Reply #8 on: March 31, 2018, 05:47:56 pm
Eric,

your riding and atmospheric conditions will be different to what I have been used to in the UK at not much above sea level. However, for general blattability (is that a word? It is now...) my Electra-X needed three things:

1. A reasonably free-flowing exhaust. Lose the hot tube out of the stock header pipe and fit a less restrictive muffler unless your local police are clamping down, as seems to be happening elsewhere in India;

2. Depending on what carburettors are available where you are, get a decent 4 stroke performance carb. I have used 32, and 36mm Dell'Orto pumper carbs as well as a TM36-31 Mikuni flat slide pumper. A VM32 or 34 Mikuni once jetted correctly will work too, as will the TM32 flat slide.

3. I don't know about the 500 Machismo, but the Electra-X came with an 18T countershaft sprocket, overgeared for me - replace it with a 17T or even a 16T if where you are is very mountainous. Ignore the Hitchcocks' recommendations for a 19T.

The compression hike/squish band modification will help along with the above to give the plot a bit more poke, and that with the cam follower/tappet swap (and a properly hardened big-end pin and good quality main bearings) will give the sort of torquey and reliable bike you're after .

If AVL parts availabilty gets too tight the complete UCE top end will fit the AVL crankcases, you'll just need to run a custom rocker oil feed line to the oil temperature sensor take off in the UCE head. The AVL and UCE con-rod and big end are interchangeable too.

Hope this helps.

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


ringoism

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Reply #9 on: April 01, 2018, 12:20:47 pm
Eric,

your riding and atmospheric conditions will be different to what I have been used to in the UK at not much above sea level. However, for general blattability (is that a word? It is now...) my Electra-X needed three things:

Happy Easter to all, here the holiday is over and I've got a little time this evening (and back to the bike in the morning).  But better to ignore my post than to let it get in the way of anyone's celebrating one of the greatest events in history... I'm in no big rush here...

Adrian, "blattability" is exactly what I was after - and I've never even heard of it...!!!

From what you're saying it sounds like I'm on the right track with most things.  Appreciate your take on the sprockets, heard conflicting views on this - mine is an 18T, but will be going from a 19" wheel to a shorter 120/80-18 tire, effectively lowering my ratio.  Though the 18T didn't seem too high even on 19-inchers, I hardly ever see "real" highways so from what you're saying I expect this should be fine. 

Carb options fewer here unless I import, and in that case spares could be a future issue.  So for now I might just drill out the ports in the domestic Mikuni (UCAL) CV's piston for a little better response - been done here on the UCE's 33mm CV with good results (taking ports to 1/8").  Here in the hills (and in Indian conditions generally) the pumper carbs tend to take quite a toll on fuel economy - I know of only one domestic bike that used one, and while notably responsive, it was also notoriously thirsty for a 150. 

Re: the header / pipe, my hot tube is out (could not have been good at maybe 3/4" ID), but my header pipe ID is still only 1-3/16 initially.  I did grind out the flange a bit so that flow would taper into it - but it's still a lot smaller than the port itself. 

***(having trouble inserting my attached photos here - how is that done?)

I had I heard that the export models had a different pipe entirely, is that true?  The old CI bullets have an unrestricted 1.5" diameter pipe right from the port, and I could probably adapt one.  Though in view of what ACE is saying, that may be counterproductive in the lower rpm ranges?  Mine seems to remain at 1-3/16 from port through the entire bend, opening up to 1.5 approaching the straight section (with hot-tube out).  Does this sound workable, with midrange the general goal, or should I be looking at something else?

Re: muffler/silencer, yes, I've heard reports of people getting harassed by law enforcement re: the "Goldies", and with things moving increasingly that way, am thinking of a long-bottle glasspack, which would be quieter but still free-flowing.  In any case, should ID of the silencer ideally be same as the rest of the pipe (1.5")?  They often make the innards much larger ID here for the sake of getting the deeper tone this seems to produce. 

Re: parts supplies, I'd found out a few weeks ago as you say that the con rod/crankpins were the same; and more recently through ACE here of the top-end adaptability (though as of now OE AVL cylinder kits are still available).  Mechanic here swears that the gearbox parts interchange as well, let's see when I get it opened.  So I think mostly I'd have to stock up on any of the unique electricals / starter sprag (could live without ES) / etc?  What about the cams / lifters, in the event of a UCE top-end? 

Thanks,
Eric


ringoism

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Reply #10 on: April 01, 2018, 01:17:55 pm
AVL inlet cam is about.280" lobe lift. Rocker ratio is about 1.2. I say "about" because probably no 2 cams or rockers are the same.

Std Bullet cams and "S cams" are about. 312" lobe lift.

The AVL cams are the ones with the larger base circle.

If you want more low-mid rpm torque,  then advance the cams with the Hictchcock 3-way pinion. Also, do the compression increase and set the squish. Do the tappets and cam spindles as reliability mods. I would also get the Wossner 87mm flat top piston, and put that in.

Don't do iron barrel performance cams for low-mid power. They are for upper rpm power. Don't do a bigger carb for low-mid power. Make a longer header and longer inlet stack for low-mid rpm power.

ACE, thanks, great info/advice.  The basic principles take me back to V-8 tuning - advancing cams and utilizing long-runner tunnel-rams (/mopar cross-rams) for increased torque... and the opposite for high-speed power.

As delivered, the AVL seems a bit odd really - too big port, too small carb / header.  Wonder if even back then RE had in mind the possibility of varying tuning as per market preferences.  The big port would flow enough for 40hp and higher revs for places that wanted that, but the whole thing could be tuned down to run well below 2,000rpms, at 90mpg, where Indians largely like to keep 'em. 

535 Wossner piston is out of stock at Royal Motorcycles, don't know what other sources there may be, but anyway their pricing at near $300 was way out of proportion for this project - believe it or not, I'll probably have less than half that much in the entire rebuild, with decent quality stuff.  Didn't import bearings but the Indian NRB's are supposed to be decent (better than OE anyway), which is what I've got on the rod/crank.  The 84.75mm piston (510cc), made here by SAM (OE-quality), cost me about $12 complete in Delhi!!!  At any rate re-bore is done, piston fitted (.0025" clearance) and modded (2.5mm crown cut) as of last week, so think I'll stick with this for now. 

To clarify, I don't necessarily need more low end torque, I just didn't want to hurt it in pursuing the midrange / all-round performance. 
 
I couldn't find the "3-way pinion" in the timing section at Hitchcock's.  What is it exactly?  If the stock cams have 40 teeth(?), then advancing/retarding, with cams running at half-speed to crank, means 4-1/2 degrees per toothShould both be advanced or could there be particular benefits in doing only one or the other? 

Leaving aside aftermarket cams, is there performance to be gained by using standard CI units, being that the lift is apparently higher (my shortened cylinder could help compensate for the smaller base circle, I assume)?  But would this extra lift additionally strain the marginal strength limitations of the thin AVL followers?


You're so right about the manufacturing variations and as they say "the proof is in the pudding".  I've ridden a number of stock AVL's from this fleet - a couple of them, despite having great compression and every indication of being pretty fresh felt like I was riding a 350 - in fact on one solo test ride I could hardly get ahead of a 350AVL that had two adults aboard.  Switching carbs with that of a stronger-running bike had no helpful effect.  I remember another "identical" bike that seemed a lot more powerful than all the others - on-throttle, the rear tire would struggle for grip on dry asphalt.  The engine also vibrated somewhat more than the others.  And I wondered, being that none of these bikes were modified, what was making the difference...  Maybe it had the unintentional 1.3:1 rocker arms, or high-lift cams, or a lighter crank, or maybe the factory ran out of hot-tubes / silencer baffles - or maybe all the above???   ;D

I'd like to hear more about velocity stacks. Any calculators out there for optimizing lengths?  UCE 500 has a pretty long runner directly from the "toolbox" filter to carb, which might be pretty effective, whereas the AVL's have that apparently useless intermediate "resonator box" which is what on the older models housed the filter itself.  I mean, I'd like to know how long the stack / runner actually ought to be, depending on diameter, cylinder displacement, and proposed ideal rpm range.  If some extra length is going to net me noticeable power where I want it (vs. something mounted direct on the carb), then maybe I should try to adapt the UCE's rubber tube and keep the filter in the toolbox (which I'd otherwise hoped to reclaim for, well, tools - or else lunch).  Anyone out there actually experienced noticeable effects, or is this going to be pretty nuanced (my Honda 150 has probably ten-inch long stack right from the airbox, supposedly is tuned for torque, but still doesn't produce any oomph till 5,500rpm)?   

Same goes for the header/pipe & muffler (silencer), of which from what I understand smallish diameter but unrestricted path is what we want for torque.  I could see the point of extra length, too.  But how large/long is actually ideal - any calculators out there?  As mentioned above, my header is 1-3/16 ID from port to maybe end of the bend, opening to 1.5" in the straight section. 

Re: carbs my thinking is that the orig. 28mm was really put there for cost reduction / fitment issues (tight around the tank mounts for typical CV diaphragm-chambers), and acceptable only because Indians typically like to run Enfields at very low revs - but that otherwise, strictly speaking, it's pretty undersized for the application.  My 150 Honda came with a 28mm, and the donor bike for the proposed 32mm was a 220cc, its sibling being a 200cc with a 33mm from this same company (UCAL/Mikuni).  CV's are a bit tolerant of oversizing but I don't think I'm in any danger of that, and I doubt my low-end or fuel economy would be affected (till riding hard).  The UCE500's have 33's and are pretty grunty / efficient.   

That said, anyone have a clue as to initial jetting on this?  It's currently got a #115 main and a #15 pilot, as set up for a 220cc single; Would I have to be going to larger or smaller jets here (twice the displacement, more fuel demand, but presumably also bigger cylinder pulling more air through the same size venturi, thus more vacuum sucking more fuel up from the bowl - lower vacuum requires larger jets, right (?), which is why my 150 with the 28mm had a big #132 jet, whereas a Bullet 350 with a 28mm uses a #95???)?  I've got a fairly wide range of jets on hand from 95 to 132 for the main, in pilots I think I've only got #20/15's.  Any thoughts/experience here? 

Still trying to decide about the tappet/guide upgrade...

The CI's stems are 9.5mm, the AVL's only 7mm, which does seem small considering the loads/speeds they're being subjected to.  Fleet owner confirms he's never seen a failure in this whole decade in the context of (highly grueling) tours, but occasionally on privately owned and less carefully maintained bikes; Again credits the difference to his extremely frequent oil changes, which kinda makes sense: additive breakdown = more friction on lobes/tappets = greater side loads = greater stresses on that thin stem = more likelihood of breakage.  Other possibility is partly RE's typical quality control - possibly some will never break, while others break early on / unpredictably? 

Just having a hard time understanding how the AVL-upgrade engineers could've made such a "mistake".  Could they have been assuming normal material strengths that in reality were never realized in Indian production?  I'm assuming they were trying in thinning them to make the valvetrain lighter...  And that gets me thinking of the problem these have already got with valve float - the CI tappets are definitely a LOT heavier, and I don't really want to get into aftermarket valvesprings and such. 
 
Thinking more about it, also not very confident about the level of lathework possible locally - huge machine I've got available must have about a 2-foot swing and huge chuck, not very suited to small-diameter parts - I'd really rather be using a collet to hold the guides for this level of precision, and to save the threaded portion, from which I'd have to hold it - but have yet to find a collet-equipped lathe in this land.  The OD is going to be critical as it's a press-fit piece (threads are only there to give the extractor/puller something to grip).  Also a little concerned about any need of modded pushrods, as they wouldn't exactly be available roadside in the event of some failure whilst touring. 

The CI/AVL tappets themselves measure almost exactly the same length, so pushrod length should not be much issue - but main trouble is that the CI's don't have the little socket built into the top of the tappet stem, which on the AVL's is what locates the pushrods.  Guess I could make a little cap above the lifter stem as the CI's used, but with the socket on the top face? But likely won't find toolbits here locally for making that radiused recess, and probably there are material contstraints (tool steel or?).  Tappet stems themselves presumably being hardened, don't think I could machine those sockets into the tappets directly AVL-style; And barring these options, we're speaking of hybrid pushrods (old-style lower ends with AVL top ends?) which may or may not be a pain to fabricate.  Or am I just supposed to use the CI pushrods (are the tops the same, workable on AVL rockers?), whereby my CI-style "socket" is on the lower end of the pushrod, and would match up to the cap atop the lifter?  In this case, does the stock length rod work?  And if so with which - the AVL or CI cams? 

Sorry, I must be exhausting you all... :)

And if I go further I'm going to get confused myself...

-Eric


Adrian II

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Reply #11 on: April 01, 2018, 05:07:56 pm
On my AVL hybrid I used the longer exhaust pushrod in place of the inlet pushrod, and screwed in a late iron barrel tappet adjuster which used the same 6mm thread as the AVL version. For the exhaust I used the exhaust push rod and tappet adjuster from a 500 iron barrel engine, I made a bronze bush and fitted it to the top of the alloy section of the rod and pressed the top of the old inlet AVL pushrod into that. This means I have one metric and one imperial tappet adjuster, but nothing I can't live with!

A.
« Last Edit: April 02, 2018, 03:56:57 am by Adrian II »
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


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Reply #12 on: April 02, 2018, 04:58:15 am
Exhaust header pipes - The iron barrel 350s use a 1.5" outside diameter pipe, the 500s use 1.75". Some 350 pipes are swaged to 1.75" at the muffler end. Apart from the odd reduction at the cylinder head end which your pictures show, the 500 AVL and I believe the 350 AVL also have 1.75" O/D pipes. Over here you can get unrestriced AVL pipes from Hitchcocks' which are 1.75" O/D for their entire length.

There is a school of thought that an unrestricted 1.75" pipe is actually too much for a 500 Bullet. In the UK there was a classic bike dealership that raced Indian built iron barrel 500 Bullets in the 1990s, one of their tuning tricks was to fit the 1.5" header pipe off a 350 to speed up the exhaust gases. You can possibly fit the pipe off a 350 I.B. but it will need modifying to fit the AVL head's 1.75" exhaust port and fixing flange.

For purely styling reasons both my old Electra-X and the current AVL hybrid ended up in street scrambler guise using the high-level exhaust for the Woodsman model. (Historical note - the English Royal Enfield factory sold their motorcycles under the Indian badge in the USA in the late 1950s, the Indian Woodsman was one of the variants based on the 500 Bullet at that time. Nothing to do with actual Indians building Bullets in India). These pipes are made from 1.5" O/D tube (easier to bend) but swaged for 1.75" ends.

Every 500 AVL cylinder head I have seen has a very badly finished and restrictive exhaust port, so much so that the Hitchcock pipes actually come with a removable steel collar insert which (sort of) lines up with what's left for the gases to escape.  It's no big deal to open out and clean up the port a bit to match the I/D of whatever header pipe you end up using.

I know what you mean about the 500 AVL's sluggish performance, the 18 to 17T sprocket swap really did make the thing much more fun to ride with a bit more poke off the line in city traffic, without sacrificing anything in top end.

A.


Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


ringoism

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Reply #13 on: April 02, 2018, 12:06:22 pm
Exhaust header pipes - The iron barrel 350s use a 1.5" outside diameter pipe, the 500s use 1.75". Some 350 pipes are swaged to 1.75" at the muffler end. Apart from the odd reduction at the cylinder head end which your pictures show, the 500 AVL and I believe the 350 AVL also have 1.75" O/D pipes. Over here you can get unrestriced AVL pipes from Hitchcocks' which are 1.75" O/D for their entire length...

You can possibly fit the pipe off a 350 I.B. but it will need modifying to fit the AVL head's 1.75" exhaust port and fixing flange.

The trouble with mine is that there's an inner pipe the entire length of that header bend, and at only around 1.188"ID, a lot smaller than even the 350 pipes, which I should probably look into. 

My port was way off-center in relation to the pipe recess.  Hence the gasket was badly obstructing the flow path.  Really bad.  I did some regrinding to get it more concentric and re-sized the gasket, but it still seems that my header pipe's ID may be a lot smaller than it should be.

-Eric


ringoism

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Reply #14 on: April 02, 2018, 12:25:07 pm
Adrian (or anyone else), one more thing: 

I'm held up on the refitting at the moment because I rather stupidly let my top piston ring get broken whilst carrying the set in my knapsack (Aaaaargh!!!).  This was a +0.75mm (.030") oversize kit, and now can't find replacement rings here on the street. 

Ebay shows ring kits of this oversize being exported from Delhi suppliers (they get more money out of you guys than the domestic market) so they must be available here someplace. 

Thing I need to know is whether rings are the same size on all Bullets, CI/AVL/UCE - Are the (compression) rings the same 84mm diameter/ 1.5mm thickness on all these?  Listing says only "500cc Bullet". 

Ridiculous, but worst comes to worst, I'll have them shipped from India to a friend in the U.S. who can re-import and hand-deliver them to me when he comes over here in May... oh, brother...

Trying to contact the suppliers directly and see if we can arrange in-country delivery (preferably at domestic prices???).

-Eric