I have read the thread by greymustang, and am having simular problems, but some differences as well. I tried the suggestion under his thread, but didnt help. Bike died.

I just bought this cbr 1 week ago. The bike had sat for sometime around a year only being started once. I knew the gas was probably bad, so i went and topped off the tank with fresh gas. I have gone through 3 tanks now and still have an idle problem.

So I start the bike, let it warm all the way up, and set the idle. Then I go for a drive and every time I ride faster than 5000 RPMs, And pull the clutch, the bike will idle between 4 and 5 grand, until I give the throttle a quick snap, then it will drop back down to 1100 or so. Usually, if i dont drive the bike faster than 4500 to 5000 RPMs, the bike will drop the idle back to about 1100. I drove down an old highway and pulled the clutch, it idled around 5 grand. I adjusted the idle as it was high, so it would idle at 1100. But as soon as I came to a stop the bike died. So i set the idle back to 1100 so it would idle at a stop. And then back out on the road, it would idle around 5 grand.

I know, or at least I think I know it is a carb problem. I was going to rebuild the 4 carbs this weekend, but i cant find any carb kits in my area. I dumped half a bottle of this stuff called sea foam in my tank, I have gone through half a tank, and the problem still exists.

Any one have any suggestions?

CompFX

 

It sounds like you have a sticky throttle cable -- or something else is sticking and holding the throttle open. With the bike turned OFF and the tank up or off twist the throttle open and closed several times and make sure nothing is gummed up and holding it open. There's no reason to go into the carbs unless you're having an idle problem all the time or if you're running poorly at the higher rpms.

 

That is what a few others have said. I have popped off the tank, and air filter housing, played with the throttle but I cant ever seem to get it to stick. It seems to react slower than what I think it should, but I dont know if that is due to the throttle cable or if the carbs are to blame. I am going to go out there, ripper appart and lube everything see what happens.

Thanks for the help,

Will post results.

CompFX

 

you might want to make sure that the throttle cable coming out of the throttle handle is tight and that there is enough free play,
on the actual throttle body.......

if you decide to take off the tank, you might want to try soaking the entire carb in carb cleaner before you actually take it apart...
hope that helps...

 

Actually, after monkeying around with it, It seems to have something to do with the air cleaner. I have a K&N oiled air filter. Well I took it off and just drove the bike a few miles and it didnt hardly act up. It would hold Idle and then drop on its own. But as soon as I put that filter back on it was holding that high Idle. So i took the filter back off and plugged the carbs with my hands and it jacked the idle up to about 5 grand. So I think it has something to do with not getting enough air, or having to work to hard to get that air. Since; I have take that K&N washed it good with dishsoap and dried er out and slapped her back on with out oil, and it seems to be running better until the bike get really warm then the idle prob starts again.

Dont know what to do now.

CompFX

 

I'm not saying it can't be the K&N but I've never heard of them doing that. If you don't have a shop manual get one. Then check out the TPS (throttle position sensor) and second the IAP (intake air pressure sensor) if the bike has an IAP.

 

I know what the TPS is and does, but I cannot find it in the book, nor can I locate it on the bike. And I have no Idea about IAP, or if my bike has one.

I do have a shop manual, Clymer, but I am not finding it very usefull. The book has not been much help with my problem yet.

Can you tell me where I should look for the TPS?

Thanks

CompFX

 

Also, what are the chances of this being a vaccuume leak? Would that cause my current problem? So far I have found 4 severed hoses. Two of them have been bolted off, but I just found two more that are open. I dont know what they do, the book makes no refference to them. I will have to take a pic and post.

CompFX

 

Vacuum leak could very well be the culprit. Not all bikes have a TPS -- if you have one it'll be on the left side of the carbs attached to the rod that actuates the butterflies. You might wanna look into getting an 'official' manual

 

I dont have "butterflys"; I have these things that sort of look like small popcans. As i turn the throttle, they slide up, but only when the motor is running. I notice a difference in the 4 as far as how much they slide up and the 'tension' when they drop back down. One seems to move easier than the others.

I took my throttle housing appart and sprayed some lube down the cables untill it started comeing out the end on the carbs, sparyed the all three throttles on the carbs, it dosnt seem to have done much. Still just as smooth. I tightened the cables though. Right now I am in the middle of painting the bike, so i cannt take it for a drive yet, but my nights end I hope to be ridding it.

I dont see a TPS, or IAP.



What happenes when the carbs are out of sync? For some reason, as i keep trouble shooting this problem, it keeps leading back to the carbs internals. The only thing I can think of is that the float needle(s) are gummed up and are not making a proper seal until i snap the throttle.


Oh yes, I just found out that the bike is from California. So at one time it had all the Cali emission B.S. on it. But they are no longer there. 2 of the hoses that are not connected to anything are part of the cali emis stuff. I fired up the bike and felt for blowing or sucking from the hoses, but there was nothing. So i just left them as I found them.

The other two hoses come from the head itself. I thought i read somewhere that they are for sync.ing the carbs, but I cant remember for sure. And seems how i have no idea how to sync carbs, i couldt tell ya what they could be for.