Hey guys. I have a few questions about 99 900RR. I have been getting a slight pop/backfire at idle sometimes, it doesnt happen every time i run the bike. This started happening after i layed the bike down. I havent been able to ride the bike to see how it acts at speed because it had a broken clipon and rearset. I have finally replaced my cli pon and fixed the rearset and now im trying to diagnose this issue. I just started with plugs, and i noticed a couple of other things while doing that. First off i noticed that a skinny hose was disconnected from a small fitting on the bottom of the gas tank. I also noticed that there is a 1/2 inch hose coming from the carbs that has a small black box attatched to it with a sponge like filter in it. that filter is dissintigrated and has a hole in it. I am not sure what that filter is for, but i was wondering what its called so i know what to ask for when i go to buy a new one. My old plugs werent fouled, just a little black with carbon on them. So does anyone think that any of these problems could be causing the backfire/popping i am hearing? I dont know how to check carbs if they are operating correctly, but i am aware it could be something to do with that too. Any advice on anything else to check before i put it back together would be appreciated. I was thinking of replacing the coils too. Im hoping that its something simple and that one of these things im doing will remedy it. Thanks for any help. Kyle
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At the emboldened...

Firstly...

Did you re-connect the hose to the fitting?


2. How did the bike run BEFORE the crash? By that I mean...did the bike ever stumble coming off a low rpm turn?
Any hesitation in the engine, when warmed up, if you blipped the throttle?

3. What idle speed do you have the bike set at?

 

Also, reach down...make sure with gloves on...or when the bike is cool...and see if any of the pipes up by the manifold...
(where the pipes come out of the engine) are loose.

If they are loose because of the crash...tighten the bolts.

Let us know what happens...

 

Back in an hour or two...

Check on the outcome...

 

Thanx for the reply. Unfortunately im gonna have to wait a couple days to put it back together, im waiting for a new air filter to come in, the old one was clogged solid, and i dont want to put it together and take it apart again. When i reassemble it hopefully on monday i will let you know what happens. Also something odd that i noticed, on the underside of the carbs, there is a small nipple on each one. Sitting on the bike, the second one from the right has a hose attatched to the nipple, but none of the others do...just that one. Is that correct or did someone just pop a hose on there for some reason? The hose comes from a vaccuum splitter piece, with one hose going to the tank, and the other looks to be a drain or something. And before the crash, the bike ran excellent and strong, never any hesitation or stuttering. This is all post crash, the way it runs now. i will check the manifold pipes to see if they are loose. Is there any way to check the coils? I have a suspicion that they are a cause of the problem...I am not good at describing the problem through typing...but along with the slight backfire there was a definite stutter/hesitation when trying to rev it at around 120-160 degrees. Once it was a bove 160 or so it started to clear out and rev and run A LOT better. I am pretty sure you can check the impedence of the coils to see if they are good or bad, but im not sure what they are supposed to read. Thanks for any more info .

Kyle
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