Author Topic: Please help - carb issue  (Read 7360 times)

Offline funkquezzy

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Please help - carb issue
« on: December 23, 2015, 05:38:19 PM »
A few weeks ago my carbs were gunked up and wouldnt let me idle without full choke and the bike ran horribly
I cleaned the carbs, and put in new o-rings but now when i start the bike, it jumps straight to 10K rpms.
I noticed when i put on the new o-rings that the floats were sitting like they used to, they were slightly angled.
What could be wrong? It seems the carbs are flooding the motor with gasoline?

Offline Squishy

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Re: Please help - carb issue
« Reply #1 on: December 23, 2015, 06:11:45 PM »
A few weeks ago my carbs were gunked up and wouldnt let me idle without full choke and the bike ran horribly
I cleaned the carbs, and put in new o-rings but now when i start the bike, it jumps straight to 10K rpms.
I noticed when i put on the new o-rings that the floats were sitting like they used to, they were slightly angled.
What could be wrong? It seems the carbs are flooding the motor with gasoline?
Hehe, this is a very familiar problem. Happened to me as well.
My guess is while you were working on the carb you accidentally turned the idle-knob/throttle-stop wide open!

That, or the carb is somehow not connected properly and the engine is drawing in false air.

Remember, the engine can never rev to 10k RPM without air!

Offline funkquezzy

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Re: Please help - carb issue
« Reply #2 on: December 23, 2015, 07:36:25 PM »
Squishy,
Thanks for the reply, i did mess with it a bit, i opened it when working on the carbs to where there was a slight opening, thinking that that is how it should be. Should i turn it towards the back of the bike or towards the front to try and reduce this?

Offline Squishy

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Re: Please help - carb issue
« Reply #3 on: December 24, 2015, 08:00:17 AM »
Squishy,
Thanks for the reply, i did mess with it a bit, i opened it when working on the carbs to where there was a slight opening, thinking that that is how it should be. Should i turn it towards the back of the bike or towards the front to try and reduce this?
Just close it a bit further and start the bike. Or just start the bike and turn it down when it starts to rise in RPM. I don't know by heard whether it's front or back.. but you'll notice soon enough :)

Offline ventYl

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Re: Please help - carb issue
« Reply #4 on: December 25, 2015, 09:20:03 AM »
My recommendatation for this case would be to get workshop manual for the bike and perform a basic carb setup (basic throttle flap setup, basic float height setup. After the bike will start (don't be afraid if idle will be high - about 3k RPM - after basic throttle flap setup) perform carb sync. While doing the sync, be as precise as possible and possibly even more.

It might look like a lot of work but here you are working with small displacement engine which is sensible for any kind of mis-setup. There's no question if you should do that. The correct question is when it is good time to do that. Given the fact that you have to strip the bike to perform this the correct answer is: as soon as possible.

With B400 you are quite a lucky because the workshop manual is very detailed, quite complete and accurate. You can find there everything you'll need to finish this job. Additionally the manual contains details which allows you to understand why things are performed the way they are performed and how the stuff works. Very valuable reading.
Bandit 400 1991 - stock except of swap from GK75B to GK75A

Offline funkquezzy

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Re: Please help - carb issue
« Reply #5 on: December 25, 2015, 10:16:31 PM »
Fixed it this morning. The idle was open waaay too much. I turned it down and it's running perfectly now.
Thanks guys.