Author Topic: Bullet 350 tuning question  (Read 440 times)

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TonyVanda

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on: January 10, 2022, 10:11:13 pm
G'day, I have 1987 Bullet 350. It's the SuperStar model and is a 1987 Australian delivery. It's had Hitchcock roller big end and conrod, high comp piston installed. The head has been tidied up and just about everything else has been updated. Its got the close ratio gearset and an 18 tooth sprocket on the front.

It's a great bike but I'm having a power issue with it. It loses power when under load like going up a hill. It's so annoying. It takes off ok, revs out pretty good and cruises great on the flat but as soon as there is a hill and I power on, it doesn't do anything. When I'm doing a long trip and cruising on a flat road (ideal conditions), it'll sit on 85-95 in the sweet spot. If I apply full throttle it feels like something is stopping it from getting full power.

So tuning wise, I've replaced the coil, points plate, auto advance springs, spark plug, and we've timed it using a dial guage that fits into a spark plug gadget so the timing is spot on 0.8mm before TDC. It runs a Mickarb VM24, 95 main jet (at present. Didnt make much difference between the 90 and the 95) slight larger pilot jet and the standard slide (number 2 I think). Exhaust is the standard 350 header pipe with a 500 bazooka muffler and an adapter at the join. I'm running the original airbox. The plug colour is about normal if a bit on the rich side. I measured the inlet port on the head and it's 26mm.

I've tried the Goldie open muffler and sports air filter and a range of main jets and nothing seems to work. How do I get that little bit of extra power to get me up the hill? I'm thinking it's not getting enough air at full throttle but as I said, I've tried just about everything. Any clues would be greatly appreciated.
Aarrrgh, an oil drip!


Paul W

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Reply #1 on: January 10, 2022, 11:05:00 pm
Could be that the gearing is just too “tall” with an 18 tooth sprocket. The standard is 16 for a 350 with a 38 rear. A 17 might be better.

My tuned 350 struggled like yours but fitting a five speed gearbox transformed it.
« Last Edit: January 10, 2022, 11:10:58 pm by Paul W »
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Adrian II

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Reply #2 on: January 10, 2022, 11:36:59 pm
Paul's right, it's way over-geared, and that's fighting against your other tuning mods. Try it on the stock 16T gearbox sprocket. Bigger gearbox sprockets only make you go faster if there's enough engine oomph to back them up. 18T would be better for a tuned 500 Bullet.

Trying to get much out of that engine without porting the cylinder head and fitting a bigger carby is a bit of a handicap too. Also, what cams are you using?

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


TonyVanda

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Reply #3 on: January 11, 2022, 12:56:39 am
Thanks for the replies. Will source another sprocket(s). One of our fellow enthusiasts did mention that and I forget he did. Cams are original. Still doesn't answer why, under perfect conditions, it wont wind out, regardless of the front sprocket size.

If the inlet port is 26mm and a VM24 fitted, would a VM26 make any difference? Or, to feel any real difference, port the head out to 28mm. Just asking cos don't really want to go down the 'hotting up the motor' path.
Aarrrgh, an oil drip!


Adrian II

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Reply #4 on: January 11, 2022, 02:37:02 pm
Perfect conditions don't include hills! Move to the Netherlands? Also you might be shorter, lighter and leaner than some of us pie eaters  :-[, so less weight/sail area for the engine to have to deal with.

The VM24 is an economy-biased carb, at least the Indian licenced copy is. Paul W has posted elsewhere about the difference a 26mm carb made. If you don't want an Amal there are Keihin PWK26 clone kits for the 350 Bullet that are supposed to pep things up at the top end a bit. It's worth noting that when the factory in India brought out the UCE engine 350 they went from a 24mm carb (size same on both iron barrel and AVL350s) to a 29mm carb.

I'm into a 350 Redditch Bullet project at the moment which has an Indian 350 Bullet head with the inlet ported out to 28mm, with PWK28 clone on there.



"Hotting" up the motor IS tuning! You've already started by fitting a high-comp piston. Now let it breathe at higher rpm, as well as sorting the gearing out. Mabe some sportier cams, too?

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


richard211

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Reply #5 on: January 11, 2022, 06:34:39 pm
The engine looks fantastic with the magneto, is the head a late model IB with the casting port for the PAV? Any indication of what the power output would be?


Adrian II

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Reply #6 on: January 11, 2022, 07:20:26 pm
Yes that is a late Indian IB head, the lump must have been intended for a PAV union same as the 500 AVL/Electra-X, but I think the factory just used a union on the exhaust down pipe instead. Had the IB continued in production that's probably what they would have done. That lump might get ground off before the engine goes back in the frame. I still have the Redditch original but this head came up cheap and low mileage. The SR1 mag was standard kit for '56 - '59 Bullets, it bolts straight onto the later Bullets including most Indian IBs. I was lucky enough to get a decent auto-advance to go with it, though new ones are available again - at a price.

Besides the carb and head work, there's a lightened crank and shortened alloy cylinder barrel optimised for a Meteor Minor Sports piston (it's one of Bullet Whisperer's ASBO engines), a set of Henry Price's "R" cams and needle roller conversion for the drive side mains and big-end. Power output? Don't know what that will be, but if I get the carb set-up correctly, "it shouldn't disappoint".

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


TonyVanda

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Reply #7 on: January 11, 2022, 11:43:04 pm
Ok, that all sounds good. I'll look up Pauls post about the 26mm carb.

Paul mentioned the 5speed gearbox - that sounds a bit ambitious for me but I have fitted the close ratio gearset from H's and it makes a huge difference. I have a 17T drive sprocket coming and my learned RE expert friend is coming over from Tassie at the end of the month and bringing some electronic ignitions to try out. In the meantime, I'll see what I can dig up for exhaust/carb (stuff I gave away thinking I didn't need it). Hotting up indeed...  :) yeah!

Thanks all for the help. Adrian, that 350 motor looks fast just sitting there.
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Adrian II

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Reply #8 on: January 12, 2022, 01:30:24 pm
Hadn't thought of that, who needs a rolling chassis after all? I might need that shopping trolley back at some stage, though.  ;D

Is your mate from Tasmania called Bob, by any chance?

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


richard211

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Reply #9 on: January 12, 2022, 03:44:35 pm
Yes that is a late Indian IB head, the lump must have been intended for a PAV union same as the 500 AVL/Electra-X, but I think the factory just used a union on the exhaust down pipe instead. Had the IB continued in production that's probably what they would have done. That lump might get ground off before the engine goes back in the frame. I still have the Redditch original but this head came up cheap and low mileage. The SR1 mag was standard kit for '56 - '59 Bullets, it bolts straight onto the later Bullets including most Indian IBs. I was lucky enough to get a decent auto-advance to go with it, though new ones are available again - at a price.

Besides the carb and head work, there's a lightened crank and shortened alloy cylinder barrel optimised for a Meteor Minor Sports piston (it's one of Bullet Whisperer's ASBO engines), a set of Henry Price's "R" cams and needle roller conversion for the drive side mains and big-end. Power output? Don't know what that will be, but if I get the carb set-up correctly, "it shouldn't disappoint".

A.

Wow, that is a lot of work, Adrian would you be able to share some more information about the needle roller bearings used for the drive side mains and the big end? Is it to reduce friction and rolling resistance. Does the Lucas SR1 magneto produce a much better spark compared to the IB ignition coil / TCI unit? I have never worked on a magneto IB bullet before and always have been curious about them. 
 
 The 2006 and later IB Indian models did have the PAV installed, but most people just install a bolt and block the PAV port on the cylinder head.
« Last Edit: January 12, 2022, 03:47:18 pm by richard211 »


Adrian II

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Reply #10 on: January 12, 2022, 07:53:43 pm
The needle roller main bearing conversion is one of Mr H's for Redditch (and presumably pre-'78 Indian-built) Bullets. Later engines don't need this as the Chennai factory changed to metric crankshaft main bearings with a standard NU205 roller bearing on the timing side instead of the strange bespoke RE roller main running directly on the mainshaft.

The big-end bearing conversion is supplied by Henry Price over here with a custom crankpin running in the same size caged needle roller assembly used on the EFI and Electra-X/AVL Bullets, all supplied fitted with a new alloy con-rod.

The SR1 is because I like magnetos, as they're a self-generating spark solution which doesn't rely on batteries. This particular one still manages a reasonable spark with a resistor spark plug, so I'm guessing it's pretty healthy.

I need to post a bit more about this bike over in the vintage section and will do in due course.

The head-fitted PAVs on the 350 IBs must have been a home-market thing, I don't recall seeing one in the UK.

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


TonyVanda

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Reply #11 on: January 15, 2022, 10:11:41 am
Ok so let it breathe - I removed the stock air filter box. Got the old pod filter out and washed it thoughly in petrol, blasted it with air then just to make sure, put it through the ultrasonic cleaner a couple of times. I fitted it and a 95 main jet and rode it about 80k's and it went better but still lacking at full throttle. Came back and fitted a 90, round the block for about 30k's and not much better. I dont have a 100 so thought I'd try the 105 and now she really goes. 100kph up the Gunamatta road. Yaay! I might see if I can define 'hotting up' to myself. Next time I pull the bike to bits, I'll investigate some of the tips youse have suggested for the top end. Thanks.

So I'm polishing and polishing the bike ready for tomorrows club ride. I notice a cable on the outside of tank on the right hand side. It's at the bottom of the tank so I havent noticed before. While I'm polishing polishing, the steering sort of flops to the left and the cable goes tight. What is it? It's the decomp cable and I was wondering why the thing would conk out when idling and the handlbars fell over to the left. Derr... Anyway, unscrew and remove the front tank bolt, lift the tank and slip the cable underneath and all good. More polishing...
Aarrrgh, an oil drip!


Paul W

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Reply #12 on: January 15, 2022, 06:18:19 pm
Having done quite a lot of work on my own 350 over the last three years or so, I found that opening up the exhaust made a surprising amount of difference. I had initially gas flowed the inlet side and fitted the 26mm Concentric carb but at a later date worked on the exhaust port and it was instantly noticeable once I'd put it back together.
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TonyVanda

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Reply #13 on: January 15, 2022, 09:56:41 pm
Thanks for the tip Paul. I'll give it some thought. After going through this exercise, I can see/feel how the engine could perform so much better. I've got the quality bottom end in it so when the top end is due for a rebuild, I'll port the head and get a better carb.

Aarrrgh, an oil drip!


Paul W

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Reply #14 on: January 15, 2022, 10:22:09 pm
It looks very nice, a similar colour to my own. I especially like the fuel tank  8)
Paul W.