Popping Help!

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Popping Help!

Postby nathanharley » Fri Nov 04, 2011 3:31 pm

Hi Lads, just purchased an old R100, have finished the first stage of restoration, and upon fitting a new exhaust and the K&N filter, the bike is popping on decel/ overrun, i assume it is running a little lean (carby novice!!).

Does any one else here have any advice on what to change next?

I checked for air leaks on the exhaust and intake, all good.

Should i be looking at going up a size on the main jet? It starts and idles nicley.

Or can i simply adjust the mixture slightly out to enrichen the idle mixture??

Cheers!!

Nathan
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Re: Popping Help!

Postby wightman » Sat Nov 05, 2011 9:43 am

Hallo Nathan

Don't go up a main jet size, unless the bike hesitates on acceleration (when the main jet takes over from the idle). I find putting in new needles makes a huge difference on fuel consumption (because the atomisation of the fuel vapour is so much better) It might improve the "popping". Did you check the balance pipe between the exhausts? There's often a leak there. If your timing is spot on (did you check s mark static and f mark dynamic at 3500+ rpm?) and ur tappets are right (0.2 or less on exhaust and 0.15 or less on inlet) then it will be your air/fuel mix.

The gurus can set those carbs just right. If you've got the pre electronic ignition R100, you can comfortably do each side separately, with the opposite spark plug lead pulled off the spark plug.

John :mrgreen:
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Re: Popping Help!

Postby bully1 » Sat Nov 05, 2011 5:48 pm

check the paramedic thread, front up on the day with the bike and I'm certain that we will have the brains trust and the tools here to check/fix your problem.
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Re: Popping Help!

Postby nathanharley » Sun Nov 06, 2011 7:09 am

Cheers John + Bully, i will have a tinker today and try to adjust the mixture, there is no hesitation when riding, only alot of noise on decel, i looked at the needles, and they appear quite new, no damage or wear, however they are seated in the highest notch, (Richest??) apart from that, has the 160 main, all looks very clean. The previous owner looked after it rather well. I checked the cross over pipe, no leaks too. Cheers guys, I work away, so may not be able to catch up Bully, but if im home i will most definitely swing by on the next workshop day. Thanks again. Nate
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Re: Popping Help!

Postby wightman » Mon Nov 07, 2011 3:49 pm

Hallo Nathan. I run my needles on the "second richest" notch. THe higher the needle, the richer. The commonest fault is the one slide pulling up earlier than the other (and also shutting off later) causing irregular running. Also, (it's been said often before) these old bikes really like 98 octane fuel and 1ml of valve master per litre fuel added, won't hurt.

John :mrgreen:
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Re: Popping Help!

Postby nathanharley » Tue Nov 08, 2011 6:44 am

Cheers John, i had a fair crack at it yesterday, went up to Munich Motorcycles and got a new set of needles/jets and an assortment of other stuff. I raised the needle to the 4th position and have a 162 main. I reset the butterfly stops and did the synchronization, and both cylinders are now very close. How close can you actually get these? Is there a vacuum reading i should be looking for? I simply just got them bot as low as i could and at the same pressure, then adjusted the butterfly's to get the same idle. I c heck valve clearances too and they were both spot on. I will take for a ride as soon as this bad weather passes (which doesn't look any time soon). I think if it still pops on decel, it is simply just the shortness + noisiness of the pipes, and will look at repacking with more baffling mat. Cheers lads!!
Nate
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