bought a 1991 Heritage,bike will start idle fine and even sounds good when blipping the throttle from idle. When going out onto the highway it starts out fine but stumbles badly (like its running out of gas) at half throttle. Now it doesnt look like the carb has ever been removed as it still has the crimped hose clamp. now here's what ive found so far, the tank gets a vaccum in it when i open the gas cap you can hear it releasing pressure. Also sometimes even at idle it will just pump fuel right out the overflow. The slider/vaccum piston works fine. Would a good cleaning take care of this or should i just go ahead and rebuild. Ive never dealt with a cv carb before I had an S&S on the old Shovel. Any input would be greatly appreciated. Thanks

 

Pull the carb with the plan of cleaning it. Might be all it needs. Take notes on jet sizes and inspect and clean as you go along. Sounds like float needle or seat is shot or dirty.

Just be careful. One of the most common mistakes people make is losing or putting the needle jet back upside down.

Also the needle that holds the float is directional. There is an arrow cast on the carb telling you the direction to remove the needle.

Check cv performance. They have good how to instructions on there website.

Also take note on which cable goes where. One is the throttle and the other is the return. Label their location. Yd

 

Thanks for the info, started to tear it down today found that someone has already had the vacum cover off. Slider was working correctly but when it wass put back together they used blue form a gasket and got it all over the diaphram. Got it soaking over night will complete the teardown tomorrow.

 

Blue silicone won't work with gasoline. Are you saying blue silicone sealer was used to seal the diaphragm?
The only thing that should be used on the edge of that diaphragm is a little silicone grease to hold the edges down for reassembly to prevent the cover pinching the diaphragm.
Hold the diaphragm up to the light and look for holes.
If is is a blue sticky substance, it might be hylomar. The only thing that removes it is brake cleaner. Don't get brake clean on the diaphragm. YD

 

 

Oh yeah thats exactly what they used (blue silicone sealer). Had a little trouble getting the Pilot jet out, found quite a bit of gunk in the bowl. Float height was within spec., Main jets a 175 Pilot a 45 A/F set at 2 1/2 turns,Diaphram actually looks good. Gonna let it all soak a bit before final cleaning and reassembly. Sure appreciate the help.