Cutting out onto one cylinder but only at high speed 80+ ???

poshman · Post by **poshman** » Tue Aug 05, 2008 6:02 pm

Bike runs fine in first 4 gears no problem and at any rev range in those gears, tried it under load and all sorts and its fine . Get over 80 ( which means 5/6th ) and then thats when it starts to cut out onto one cylinder. It just will not go. seems to be worse when your on a steady throttle (just open not pinning it) crusing. tried going upto the ton+ and its just as bad. I suppose it fueling ( carbs??) or electrics (maybe a coil?) anyone had this or got any ideas before i start changing parts. Done the spark plugs still same problem. Bike has aftermarket cans on but ive done well over 20,000 with them on with no probs.
Many thanks for any help
Alex

warby221 · Post by **warby221** » Tue Aug 05, 2008 6:20 pm

Sounds like fuel starvation the breather in the tank cap could be blocked
If you have a spare key try running it with the cap open if it runs ok you need to clean out the breather

Just donâ€™t do it with a lot in the tank

or youâ€™ll be soaked in petrol

bikermike1411 · Post by **bikermike1411** » Wed Aug 06, 2008 11:17 pm

Have you had the tank off? When I had mine off I put the fuel vacuum pipe from the stop rock back on the wrong nipple (cue sniggering...) It ran like a dog, but that was stationary in the garage - it'd tick over fine but bog down when it tried to draw fuel through.

poshman · Post by **poshman** » Thu Aug 07, 2008 9:12 pm

Thanks for the help so far. Turned out the breather pipe was getting pinched by the aftermarket belly pan went for a spin after re routeing the pipe and blowing through to make sure it was clear and still the same problem. It does compleatly die on me sometimes but always cuts back in before grinding to a halt. Someone has suggested it could be something to do with the speedo?? Any ideas anyone. Think the next step is getting the carbs off and set up again. Weird as its only above speeds of 80

bikermike1411 · Post by **bikermike1411** » Thu Aug 07, 2008 10:25 pm

Just a thought... have you checked the plugs? It might be worth trying a new pair - on an old plug the spark can break down and seek a bad earth under load. Might also be worth checking the HT leads too.

gilson · Post by **gilson** » Thu Aug 28, 2008 10:57 am

I also think it's the HT leads. I suppose it's difficult to tell which one is cutting out?
Let us know if you cure it and by which method....

tony.mon · Post by **tony.mon** » Sat Aug 30, 2008 3:43 pm

Have you by any chance redone the cam timing?

I managed to set the cams 180 degrees out and got something like the same symptoms.

The exhaust note was much crisper, though- seemed to "bark" more.

If you've changed the CCT's or done something else and the problem started afetr you reassembled the engine my money's on that, but if it's been running fine and then started doing what you describe it isn't this idea causing your prob.

hope you find it.