My bike has the original Keihen carburetor. It runs well except the occasional cough which is apparently common with the Keihen carbs. But, the coughing, over time, leaves carbon buildup that eventually affects performance. So, how do you know when to pull that carb off and rebuild it? I don't want to wait till it's getting ten miles per hour and wont run over 50 mph.

 

You can rebuild it anytime you want.
If you are concerned go ahead and rebuild it.

To the best of my knowledge there is no set time to rebuild a carb.

 

Now and then. I threw my Keihen in the trash and got a CV, and it coughs and spits too. And yes, threw that baby right in the trash....I was mad.

 

You rebuild them when the gas won't stay inside. Most other issues only require adjustment to fix.

Keihin carbys, both butterfly and CV usually cough because the pilot jet is too small.

Evo's like to run rich and the EPA doesn't want them to so stock sucks as far as jetting goes.

 

You don't have to rebuild your carb, just take it off the bike a clean the **** out of it, with spray carb cleaner. Take the bowl off and clean the **** in the bottom and spray clean all the jets

 

My carb on my 99 evo has never been off in 38,000 miles. I dropped the bowl off at about 20,000 to put in bigger jets, and the bowl was clean so I have never cleaned it and it runs great. I get right at 50 mpg.

 

Thanks a bunch for the replies. I have the butterfly version of the Keihen carb. I pulled the air cleaner and back plate yesterday. The air filter is a K&N so I washed it good, blew it out, let it dry good and re-oiled it. The carb has some signs of coughing, a little carbon build up. I didn't remove the carb just yet because it looks like the tank's gotta come off and it's full of gas etc (laziness). And, the bike runs fine at the moment so..

The reason I'm going through all these things is that I have a few road trips this year and would rather fix something now rather than wait till I'm out on the road in the pouring rain (been there done that).

Right now I have three road trips on the schedule and it's more fun without the break down. Last year on the way back from the spring rally in Myrtle Beach my buddies bike started losing power. I stayed with him and by the time we got home his top speed was about 50-55 mph. It turned out to be a carb that was full of carbon build up from the occasional. He was getting terrible gas mileage so, we stopped about every 50 miles for a tank of gas. I figured that it was a carb issue but, we didn't feel like rebuilding a carb on the side of the road and it was a Sunday morning, etc..

 

If you are serious about rebuilding your carb. to better than original then heed Spanners advise and check out the suppliers of carb. rebuild kits that include the updated jets etc. The kits are not expensive and come with full instructions . The job can be done in a couple of hours.

 

Does a good rebuild kit really only cost 30 bucks?

 

I paid $40, all I could use was the gasket for the float bowl, and a couple o-rings, didn't need anything I could use, waste of $40.