900RR missfire... HELP !

glhracing · 08-02-2004, 07:31 AM

I have a 1996 900 RR.
Up till now It has been running great.
Just recently it has started to break up real bad under acceleration.
It started to do it only when it was cold, but now it does it all the time.
It seems to be getting worse. The thing runs fine just crusing along, but as soon as you get on it, even a little, it breaks up..
it also breaks up anytime over 4000 rpm.
it is like one cyl is not fireing correctly or something..

I have replaced :
Spark plugs
Carbs (all four)
cleaned carbs many times.
cleaned fuel tank
new ignition coils and wires
added inline fuel filter

I am at a total loss at this point, not sure what to do next.
Any direction or ideas will be greatly appreciated.

-Brian

L8 Braker · 08-02-2004, 05:10 PM

Have you replaced the hoses?...And what about fuses?

glhracing · 08-02-2004, 05:21 PM

I replaced the fuel line.
Not sure which hoses you mean..
The only hoses I see are the fule lines, the fuel sender
vacume line and the short hose from the air cleaner to the carb.

Are there some vacume lines somewhere.
Like maybe a map sensor or something?

Thanks...
B~

L8 Braker · 08-03-2004, 12:14 AM

Quote:

Originally Posted by glhracing

I replaced the fuel line.
Not sure which hoses you mean..
The only hoses I see are the fule lines, the fuel sender
vacume line and the short hose from the air cleaner to the carb.

Are there some vacume lines somewhere.
Like maybe a map sensor or something?

Thanks...
B~

Three hoses...Two that take fuel to the carbs from the petcock, and then the vacuum line, which is also attached to the petcock...

glhracing · 08-03-2004, 07:27 AM

yes..
those are all fine. though I only have one that goes from the thuel tank to the carbs.

-Brian

twinspool · 08-03-2004, 11:47 AM

Have you switched the needle position on the carbs? My buddies 7r was having problems 2 days after he switched his (more fuel) and ended up putting it back and now the thing runs fine.

L8 Braker · 08-03-2004, 05:08 PM

Loose wiring or fuses is the only left that I can think of...

cully · 09-17-2004, 12:44 PM

Try taking the gas cap apart and cleaning the gunk out of the rubber breather gasket.

Reckless01 · 09-29-2004, 09:45 AM

you guys forgot to mention valve adjustment (or the lack there of) that created a bad valve seal which under pressure will cause blow-by and a "miss" sound...that or the fuel pump...if yours has one....mine does, others dont.....it could be one of the following: Fuel delivery issue, Ignition issue, or Internal engine component issue. just use the process of elimination. If all else fails take it to the shop to get looked at, theres no shame in that sometimes it just takes a strangers eye to catch something you missed