slight hesitation between 3500-4500 rpm

[nayasoldman]

I recently had my bike totally tuned (twice!, but thats another story), carbs rebuilt, carb housing replaced-the first mechanic said the set screws were frozen and he could'nt get them out- valves adjusted, new plugs , air filter cleaned, etc. Problem is that the bike has a slight hesitation between 3500-4500 rpm if you are not accelerating hard. Its really frustrating when driving around town. My mechanic says that he doesn't want to richen the mixture, because when we get into the Colorado summer-high temps and dry air the bike will run just fine. The thing is that for 9,000 miles the bike, with the last tune up being in New England, ran fine in all sorts of different weather conditions. The person i got the bike from said he had a similar problem and his local mechanic drilled out , or otherwise modified some EPA thing and the bike ran fine. I'm wondering if , when they replaced the carb housing, if something might have been left unaltered that my local guy isn't catching. Any ideas? Oh, the bike is a 1980 850G with 18,000 miles on it.

[KEITH KRAUSE]

Hesitation can be caused by a lean mixture. It can also be a fuel venting problem. My bike was hesitating at the exact same rpm. The feeling was like the very first stage of running out of gas. After a lot of looking I found a small piece of rubber had lodged itself in the floatbowl vent hole going to the #1 carb. It took 150 psi to blow it out. The partial blockage was not noticable at lower speeds,only when I got to about 60 and up. I only found it by taking off the 4 floatbowls and blowing into the vent tubes. When I blew into the #1 carb while plugging the hole to #2 I had more resistance than testing the #3 and 4 carbs the same way. It took me several weeks before I found the problem. You may have some kind of blockage too. The easiest thing to check first is the gas cap vent. Clean it out with carb cleaner and see if that works. Otherwise I would completely check the carb venting system before trying to richen the mixture. During your carb body change,some dirt or something could have got stuck in the float bowl venting passage. It is just a vent, so with no vaccuum a small piece of dirt can stay stuck forever. KK.

[nayasoldman]

Thanks Keith-it appears that the bike was running abit lean, but my mechanic added some octane booster(PJ1) and the thing ran great. He told me not to use Conoco or Texoco here in Colorado-said for some reason he has had several people with the same hesitation problem who cured it merely by switching gas. I got some aviation gas, added it to fill my tank, ran the tank out and now it seems to be fine.

[KEITH KRAUSE]

Glad to hear it was such an e-z fix. KK.

[Dark Jedi]

Thanks Keith-it appears that the bike was running abit lean, but my mechanic added some octane booster(PJ1) and the thing ran great. He told me not to use Conoco or Texoco here in Colorado-said for some reason he has had several people with the same hesitation problem who cured it merely by switching gas. I got some aviation gas, added it to fill my tank, ran the tank out and now it seems to be fine.

Damn. Here in Northern Colorado the choices get real slim without Conoco or Texaco.... but good info to keep in the noggin.