9 replies to this topic

[CMC84]

Hi all, my bike has been running for a wee while now, and I'm amazed at how capable it is. Having great fun on it and it makes a nice change from the modern bike.

However, the Bulto runs well for maybe half an hour, then will stall, and is a right pig to start. After getting it running, it runs for shorter and shorter periods before bogging/stalling. On inspection, there is plenty fuel in the bowl, and the plug is a little sooty, but not too bad. I'm starting to think hillclimbs and hopping logs make it prone to stalling. Not much to go on, but any ideas?

Chris

[wayne_weedon]

CMC84, on 19 January 2012 - 01:11 PM, said:

Hi all, my bike has been running for a wee while now, and I'm amazed at how capable it is. Having great fun on it and it makes a nice change from the modern bike.

However, the Bulto runs well for maybe half an hour, then will stall, and is a right pig to start. After getting it running, it runs for shorter and shorter periods before bogging/stalling. On inspection, there is plenty fuel in the bowl, and the plug is a little sooty, but not too bad. I'm starting to think hillclimbs and hopping logs make it prone to stalling. Not much to go on, but any ideas?

Chris

Still on points ignition? If so change your condensor and while you're at it relocate it to under the tank.

If that fails or not on points then start looking for other issues like crank seal condition.

Edited by wayne_weedon, 19 January 2012 - 01:45 PM.

[bullylover]

Hello CMC84. I would change the condenser, if it is still in the ignition backing plate I would put it up under the petrol tank where it runs a lot cooler. Then I would check the timing which sounds as if it is out as well. Then I would make sure the spark plug gap is at 15 thou (.40mm) and see how it goes then. Bully Lover.

[CMC84]

Great stuff guys, I'll get the condenser sorted out first, I'm sure I've saw posts on how to relocate it in the forum somewhere?

Regarding the timing, I've just set it up with the back plate lined up on the timing marks of some previous owner, from some point in the last 30 odd years - what is the correct way to set it up?

Also, if I can ask another, I feel as if the revs are a bit slow to pick up. I imagine it might be different than a modern bike in this respect, but I think its still a bit slow. Lofting the front wheel takes serious forward planning - do you think that could be relating to the timing, or is that just how they are? (Keep in mind the oldest bike I've ridden was a 2001!)

Thanks for your help, without this forum, it would still be a box of bits!

[smelling123]

Hi,
Mine did exactly this. I tried new condensor and also fitting it under the tank. Eventualy changing the points completely solved the problem.
FOr the money versus hastle Id just fit new points and condensor - they'll last for years.
cheers Stu

[bullylover]

Hello CMC84, The Sherpa`s timing needs to be set with a dial gauge to get it accurate. The points gap is 14/16 thou or .35 to .45 mm. You don`t say which Sherpa you have so it is hard to tell you what timing to use but the later 250`s were 2.6 mm before top dead centre (M158 on) and the 350`s anywhere from 3.10mm to 2.2 mm BTDC. You just have to work out how you like it to run. It was said not to run the earlier 350`s (151 or before) at less than 2.5 mm BTDC Have a look in the owners manual or a workshop manual. I hope this helps. Bully Lover.

[CMC84]

Luckily my local shop is a former Bultaco dealer, so should be able to pick up points & condenser there.

WHat about the slow pick-up, does that sound like a timing issue?

Its a 199a 350 by the way

Cheers,

Chris

[bullylover]

Hello all. Yes slow pick up does sound like timing. I like a 199A around 2.8 BTDC. This makes them reasonably snappy. They are an old bike with very heavy flywheels so they aren`t going to respond like a modern bike. If I can remember correctly the 199A`s were supposed to be 2.9mm BTDC. If you want it really smooth use 2.4/5mm BTDC but at this they are a little bit sluggish. Experiment and find what you like. One thing is watch using old condensers as they often fail really soon. I always just go down to a local car shop and buy one around the same size which has a mounting hole in it and bolt it up. By old I mean as in age not use. I hope this works. Bully Lover.

Edited by bullylover, 21 January 2012 - 02:17 PM.

[wayne_weedon]

Also when relocating the condensor it's often useful to bolt two of them under the tank, and leave one disconnected.

If you have a suspected failure at a trial then it's a 2 minute job to swap over to the spare.

[CMC84]

Thanks guys. To the garage.......