[AzCal Retred]

Got the top end off today. Piston showed new light seizure scuffing above the top ring, along with some old chew marks. All three rings were lightly bound in their land grooves on the exhaust side preventing good sealing. That explains the power loss and oil consumption. Lots of hard carbon on the piston & head. Barrel seemed to be all OK. The OEM piston/rings were the "fuse" in this case. The carbon at the spigot/head junction did a nice job gluing the head to the barrel. A WD-40 soak thru the spark plug hole, a few whacks to the exhaust & intake ports, a little cautious prising with my giant well worn Snap-On flat blade screwdriver and voila, success!

My "light seizure" happened this way - it was a 55F day, gradual steady slight uphill grade, running about 50 in 4th, so maybe 3500 RPM? All stock gearing. Pretty much exactly what Ace said.

Ace - does retarding the inlet cam 1 tooth buy you anything with stock compression? Maybe make it run "free-er?" Otherwise I guess I'll just leave the cam timing stock and just "buzz" it a bit more in 3rd. The new forged slug should be idiot proof. It felt lighter in hand and is a lot stronger, and so should be immune to the "drop the skirt into the crankcase" disease.

Maybe a good excuse to try those Hitchcocks "Road Gears"...bring 4th closer to 3rd. First is pretty tall anyway, so not much of a loss to raise it a bit.

https://accessories.hitchcocksmotorcycles.com/accessory-shop/4-speed/3279
PART No. 200150 ; CLOSE RATIO GEAR SET (2 gears), 4 SPEED ; £165.00
These 2 gears have been specially designed to run together in the standard 4 speed Indian Bullet gearbox and 1959 onwards Redditch Bullets and Twins. They replace the kickstart gear on the layshaft and the mating gear on the mainshaft, both gears must be changed as a pair.
This pair of English made gears raises the 1st, 2nd and 3rd ratios, reducing the gap between 3rd and 4th. Ideal for road or track use. Getting the gearing correct is one of the first steps to tuning your Bullet.
Suitable for 4 speed Bullets from 1959 onwards. They change the ratios from:
1st = 2.78:1
2nd = 1.84:1
3rd = 1.36:1
4th = 1:1
To:
1st=2.50:1
2nd = 1.66:1
3rd = 1.23:1
4th = 1.:1

 

[ace.cafe]

Yes, you'll get more top end power which comes more easily and feels less frantic up there.

It works better with the higher compression piston, especially in the rpms below torque peak. It pulls better.
But, it will work with the lower compression piston too, just not as punchy.

[Bullet Whisperer]

I have done this retarding the inlet cam by 1 tooth in many engines I have worked on and it will certainly improve a standard 500 Bullet, as well as any tuned ones using standard cams. The 500 has enough 'cubes' to carry it off, whereas the 350 does not and will only benefit where a high compression ratio is used, or else it will need revving hard to get anywhere and be frustrating to ride. I even tried it with a pre war AJS 250, which revved beautifully as I warmed it up, but it could barely move away, off the yard!
 However, where a 500 Bullet is concerned, I would say 'Go for it!'

 Here is a not too far from standard 500 Bullet I demonstrate with the inlet cam retarded by 1 tooth. Check out the overtakes!
 https://youtu.be/aB06Kdey2Jc

 B.W.

[Paul W]

Post deleted due to duplication.

[Paul W]

Regarding ring butting from heat, only the top ring is really heavily affected, and it gets less for 2nd and oil control rings because they get progressively further from the big heat.

Regarding longevity/reliability, it is more common to get a seizure at 2500 rpm than at 5000 rpm.
With a 4-sp iron barrel, the big gap between 3rd and 4th sometimes leads to a bit of lugging due to reluctance to change down to 3rd, particularly going uphill. This is when they blow. The ignition is already at full advance and the torque curve is below peak, and the load is high so more throttle opening is needed, and heat goes thru the roof.That is the recipe for disaster. People typically are shocked and say, " I was just leisurely plodding up the hill on this lovely Sunday morning and it suddenly went BANG!"

That's what to watch out for. Changing down to 3rd and using a higher rpm above torque peak saves the engine in that type of circumstances. Those are iron barrel Bullet words to live by.

Good advice!

Thirty years ago, during my RAF service, I used to instruct on small single engined aircraft with a 200 hp Lycoming (Bulldogs).

They had constant speed props, which roughly equates to an infinitely variable ratio gearbox, in that you could choose what RPM to set within a limited range. This allowed for good fuel economy in the cruise by reducing the revs (to 2400 or less) or better climbing performance and engine response at high revs (actually only 2700). To avoid detonation (very important on a slow revving, large capacity engine) the golden rule was “Rev up, throttle back”. What you never did was give the engine full throttle on reduced RPM, which would cause detonation, or increase revs at full throttle, which could cause an engine overspeed.

[AzCal Retred]

Thanks BW, I'll notch the intake back as part of this project. Good excuse to check the worm nut anyway. 

[AzCal Retred]

Decoked the combustion chamber, got the base gasket area copacetic. Great day to be outside, lots of light!

[Paul W]

I see you have removed the cat from your bike. Has it made any difference to the emissions?

[nonfiction]

Removed? I thought he was installing the cat.

[AzCal Retred]

Cat emissions collect largely in a separate tray filled with Fullers Earth, quite easily maintained...

The new piston & rings are installed, as far as I can tell they went into the barrel without breaking. The spigot has a nice tapered "forcing cone" which seemer to gradually compress the rings with a bit of wiggling and finger tip assistance. No "snap" sounds were heard and I didn't see any bits drop out....fingers crossed.

The 6 head bolts were cinched down by hand in a criss-cross pattern with a 4" ratchet until "light snug". When I took it apart, the head bolts were barely snug at all, I guess it doesn't take much to contain 6.5/1...

Cranking compression is noticeably improved already. Pushrods are looser, so the new cylinder must be a bit taller. Oil flow seen to both rockers. Tomorrow we see if the new bits play nice together!

[ace.cafe]

If you wish to torque the head stud nuts, 20 ft-lbs is good and long-term tested to be sufficient. The factory recommended 24 ft-lbs is too much, and sometimes pulls the threads out from the engine case stud holes.

Question.
Most times that I have received new alloy barrels, the cast iron cylinder spigot was too tall to allow any crush on the head gasket. Did you check that, or need to dress that down?

[AzCal Retred]

The "gap" on this 1999 head & similar era barrel was about 0.025", the gasket was around 0.040", so some crush. The alloy barrel was purchased probably 2004, and it was "NOS" then. Maybe that's why the numbers were relatively close.

I used the odd old "OEM" laminated copper/fiber/copper head gasket I had (142617) because it was a bit thinner than the newer premium "Cometic" brand composite gaskets. My old OEM head gaskets are different than the current H's stock which look improved. Around the pushrod tubes on this gasket I applied a thin ring of the Permatex "Grey" to attempt to ward off leakage there, one side being a bit concave. I also tried a fillet of Permatex aluminum anti-seize as a filler for outside the spigot on the theory that it might block carbon infiltration & later subsequent "bonding".

I have extra head gaskets if sealing becomes an issue. None of the head bolt recesses had the hardened washers inside when disassembled.  Fortunately I had stockpiled a set from H's a while back. Even more luckily I suppose the head bolts hadn't swaged the soft head material around the studs...

When I go back in to retorque in a couple hundred miles I'll try the torque wrench, 15-20 pounds, whatever feels "snug enough". No reason to create a problem. It didn't seem to have a compression leak at basically "hand tight" levels, so there is apparently margin on the stock engine.

I'll keep an eye on the head gasket while I try to scrub in the new rings. Hopefully the factory recommended tight end gaps won't cause a problem. Lots of heat/cool cycles should do the trick, we'll see.

Thank you for all your support, I'll let you know of any failures or other issues arising from this build.
Best Regards - ACR -

[ace.cafe]

.025" is a good gap, and allows good crush for sealing with the OEM sandwich type gasket. I always preferred that gasket on iron barrel engines.
I only use the Cometic on the Ace head GT535 or AVL because of the flat deck.

[AzCal Retred]

Heat-cycling the engine on my long driveway down to the lane( 300' long, 50' drop), about every 15 - 20 minutes I putt down & back up a couple times. The alloy barrel warms up within seconds, unlike the iron barrel which stayed cool for a minute or so. That's good news already! Motor sounds good, maybe a bit more "ringing" with the alloy vs. the iron barrel. Safari Sagoodie!

[AzCal Retred]

About 20 miles into it, all good. A bit spunkier on the casual roll on, idle good, compression braking improved, looks like a success to me!