Author Topic: Cb900 carburetor problems  (Read 771 times)

Offline Reaper87

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Cb900 carburetor problems
« on: June 20, 2019, 09:44:24 PM »
Morning all so I need to up jet my 81 cb900f but don't know what jets to put into it it's got k&n pods and 4 into 4 straight through exhausts it gets stuck at around 3000-4000rpm when I twist the throttle and only goes down  when I adjust the idle screw any help would be greatful as iv never done rejecting before thanks

Online K2-K6

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Re: Cb900 carburetor problems
« Reply #1 on: June 21, 2019, 07:02:05 AM »
Hi Reaper87,  very good bike that 900 but focus on here is for the older pre-twincam type bikes. We may not have experience to give you immediate advice and help with this.

Saying that,  you have with both air filters and exhaust altered, a particularly difficult problem to resolve.

First task is to ensure that the carbs and jets are absolutely clean else you'll be chasing your tail forever in that the running symptoms will lead you wrongly all over the place.

If it's generally running lean you can lift the needles in carb slides to bring it a bit richer to help start off.  But it's usually going to be much more involved than that.

Further thoughts about the Rev ceiling you have,  get a check on ignition advance as if it doesn't do this it really won't want to rev.  Need to verify so it doesnt catch you out. I seem to remember the possibility of the ignition control on these getting a non advance condition but it's a long time ago to remember,  worth getting to specific forum to help you.

If ignition was OK and carbs are clean it would generally (with that setup)  be a right pain around idle and pulling away,  would run something like the full rev range but lean and show very light colour plugs.  So it would be there or there abouts but a right pain to ride and get good acceleration.

Offline Reaper87

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Re: Cb900 carburetor problems
« Reply #2 on: June 21, 2019, 11:52:34 AM »
Thanks for your comments will get started on them right away

 

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