Carbs backfiring on 98 cbr900rr,need help - Sportbike Forum: Sportbike Motorcycle Forums
 
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post #1 of 4 (permalink) Old 03-17-2013, 07:40 PM Thread Starter
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Carbs backfiring on 98 cbr900rr,need help

Cleaned and rejetted carbs with dynojet kit,put her back on the bike and she started up and ran high 3000rpms then settled to low 1000rpms,periodicly she would backfire from the #3 carb,i turned her off and checked her restarted her and she did the same,shut her off then tightened all the boots and vacuum plugs started her then i warmed her up for about 10 mn and no backfire so i synced the carbs with a motion pro carb synchronizer,after i let her cool off while i plugged the intake ports with the screws,started her and once again same issue,anyhelp would be highly appreciated

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post #2 of 4 (permalink) Old 03-17-2013, 08:21 PM Thread Starter
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Re: Carbs backfiring on 98 cbr900rr,need help

Here's a video i made so you can witness her bad behavior lol,but this time shes backfiring out of the #2 carb

https://www.youtube.com/watch?v=5iHv...e_gdata_player

https://www.youtube.com/watch?v=5iHv...e_gdata_player

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Last edited by twiztedtatz77; 03-17-2013 at 08:24 PM.
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post #3 of 4 (permalink) Old 05-13-2013, 05:49 PM
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Have you tried inspecting the Carburetor diaphragm number 3 it could be leaking or worn out.
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post #4 of 4 (permalink) Old 07-31-2013, 09:07 AM
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Did you plug the vacume line that goes to the gas tank that comes from below #2 carb when you tested?

I just watched your video. Sounds like its running on two cyclinders. Might want to check the 2-3 ignition coil, leads, plugs, and plug wires.

I had done a valve lash check one day, drove my 900 to the shop, checked lash, put it back together and it would not fire. Went through everything, two hours later i decided to change the plugs in a whim, even though they had no sighns of fault. Soon as i stuck the plugs in she fired right up...still baffled by that one to this day.

Last edited by IdleHandsTX; 07-31-2013 at 09:18 AM.
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