I have a 1994 Project CBR900RR. The bike in question has the 918cc. 1996 engine. The bike has been running great up until today. Suddenly the tone of the bike became a bit different than usual. It became deeper. Not only that, I seem to have lost quite a bit of power.

Is thre anyone here that may be able to give suggestions as to the cause of this before I take it to a Tech? If it's something simple I would really like to repair it myself.

 

How does it idle? It sound to me like all the cylinders aren't firering.

 

The only problem I have with the idle is the tone change I mentioned. I did notive today that the bike seemed to surge forward at different rpm's while riding. It had a jerking feeling. When I got on the throttle the power was still terrible, but it also began to spit and sputter a bit.

I ran the bike up to about 11,000 rpm's in 1st through third gear and it seemed to have cleared up the cough the bike had, and it even brought the bike's tone back to normal. Could it have been trash in the carbs? Did I have a fouled plug that mysteriously cleaned itself during my temorary thrashing?

Any answers will be greatly appreciated.

 

Well the fact that the tone changed...check to ensure that the carbs are seated in the manifolds and are clamped down...sounds like a MAJOR air leak, or maybe a carb manifold cracked...try spraying some carb cleaner in the area and see if the bike idle changes ..if it changes you most likely have an air leak or unseated carb bank

 

That's a good idea sirlimpzalot. For some reason I hadn't thought of that. I knew an air leak was possible, but I didn't really think about the manifold. I'll check that and see what happens.

I made sure the air filter and box were seated, it would have made sense to have done that too.

Then again, the tone change was only in the exhast and not coming from the engine\tank area.

 

OK, I checked the manifold out. Everything is fine in that dept. I added a fuel system cleaner just in case there was any trash in the carbs or if I had a valve sticking.

I let the bike sit up for 2 days, started it up again and got the same results. Sputtering, low tone, loss of power, and an irritated rider (me). Could I have fouled plugs or a bad wire? What other ideas do you guys have?

 

The spark plugs are the window into the soul of your engine. Pull them and read what they have to say.