I have an '01 FXDWG TC 88 with a Mikuni HSR 42 on it. Just out of the blue it started idling rough surging at cruise speed and back firing on the coast down. A friend suggested that i might have gotten into some bad gas and said i should put some Heet in the tank see if it runs better (it did, a little) but i was still having problems with rough idle and back firing. something i noticed while looking the bike over is that the accelerator pump push rod doesn't come back up to the accelerator arm after the throttle is twisted. after a while it will slowly come back up half way. i took the float bowl off made sure it was nice and clean (there was a little bit of fine particles in the bottom) and inspected the accelerator pump. it seams like there is a vacuum after the pump is pressed that prevents it from coming all the way up right away. Is this normal? what else could i be looking at? any help would be greatly appreciated.
Bryan

 

I hate snowmobile carbs-----------I traded a perfectly good s&s for one with all the promises of big power and big mileage .What I got was a difficult to keep in tune unpredictable mess that dynode about 2 horse more.The rubber around the accelerator pump shaft can get hard causing it to hang up,the spring also can collapse allowing it to stay down---------------or here is th big one Ihate the most.Those small particles in the bottom of the bowl can actually seize the pump in the housing galling the bore ,also I have set the town afire when my float stuck and ran all my gas out on the street.It seems every time this happens there is a a$$hole with a cigarette that has to start it.A super good filter and lots of care of the fuel system is all these carbs allow(at least my experience)



even your fuel line particles can cause a issue--------sand grain sized rust also will do it to

 

3408 Pete
At first I was thinking the rubber boot but having the float bowl off I could see it was the plunger not wanting to come up. Like I said in my original post there seams to be negative pressure on the back side of the plunger that is preventing the plunger from coming all the way up. Is there maybe something in the orifices that is preventing this? Like a little rubber valve that is suppose to act that way or is there particles that need to be cleaned out? Or is the spring to weak to return it to its idle position? Thanks for the help.

 

after about a years time I have to pull my spring out and stretch it -----------I hate them in comparison to a s&s or even one of the CVcarbs that sells on ebay