CBR600 f4 carb issue?

[andy777bmx]

When I fire up the engine, it now revs up to over 4000 rpm and wont go lower. The idle screw is all the way out, throttle cable is completely loose. I also tried revving it and it wouldn't go back down.

Any ideas? I'm worried that the holes are too large now but I'm not sure. Maybe I should just get a new jet kit? Let me know if anyone has had this problem before.

Thanks

[nutz4sand]

I am not familier with the specifics of this motor.

Slide carbs or butterflys? If slides you may have gotton one or more in backwards (easy to do) and then they do not close all the way.

Being you said Idle screw I am guessing its butterflys though. I would look for an air leak where a tube got popped off perhaps?

Unless you literally drilled out the jets cleaning them would not do this problem you having. Even then it needs fual AND AIR to rev. So an air leak would be needed too.

When you look down the carbs are they ALL closed completely?

[dunerocket]

Jet kit wouldn't help, that I could think of. That is for the upper and midrange (needle). Is the choke returning all the way?

Do you have any air leaks?

It could be a sync problem. Perhaps one cylinder is open more than another. Small adjustments can make a difference. It doesn't take much fuel and air to bring RPM up when there is no load on the engine. Also, people have a misunderstanding of what you are doing when you "sync" the carbs.

Each cylinder is drawing vaccuum. Depending on how far the butterfly is open the air will be moving faster, creating more vaccuum in the carb. The tool is measuring the difference in vaccuum between the carbs. The adjustments you are making is changing the relation between one butterfly to the next.

Try out the sync tool since you have it.

[andy777bmx]

I synced the carbs and it was still doing the high rpm. Then in struck me that I should try to screw out the idle screw even more. The lever wasn't in contact so I figured it was all the way out but wrong. I feel like an idiot. Anyway, backed it out even more and set it to 1600-1800rpm and works great. To recap; all the carbs were gummed up except one and after cleaning them, it worked great. Finally finished my first build. I'll post some pictures soon.

I'll try and run it every week or so to avoid this problem. I was wondering if I closed the fuel valve and ran the engine it would burn up all the gas in there. I used to do this with my CR250 dirt bike. Only problem is I would need to put a switch to turn off the pump so I don't burn it out running dry. Anyone see any issues with this?

[nutz4sand]

If its under a month of not running it should be fine. It its gonna sit longer than that buy some "Stabile" and put it in the gas. Its specially made to keep gas from doing this in sled that sit all summer and bikes that sit all winter. Same goes for Lawnmowers parked all winter and snowblowers parked all summer.

Any big store (Like Wal-mart) will have it as will any auto store.

[nutz4sand]

Evan with that are you sure the tanks not got crap in it? If the tank is not double super beautiful inside it may need some tank work. Either way a a realllly good $$ fuel filter is way easier to see and clean than carbs when dirty.

[andy777bmx]

Brand new tank, lines, etc; new build. Carbs were clean except some gunk from the gas evaporating; no solid crud. It had sat for about 2 months and was slightly acting up before that. Last time it ran fine was probably more like 6 months ago.

[nutz4sand]

I would still do a gooood filter if you don't have one. Too many think that a clean tank means they do not need one but even a little dirt in the gas can or the nozzle can get in the works.

[dunerocket]

Only takes about a week here for enough fuel to evaporate to cause problems for me. I unplug the pump and run the engine until it sputters. This lowers the fuel level low enough that I don't have problems. You can also just drain the bowls manually.

[andy777bmx]

I put a filter before and after the fuel pump so I'm good there. I'll prob run the carbs dry with the pump off. Thanks for all the tips...