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Mikuni 38\'s, HOW do they work? I\'m lost

Hello, if anybody knows about the mikuni carburetors off of a 91 gsxr 750, I can't figure out how they work. I just installed a 91 engine in my 88 gixxer, and I can't get it running. I can't get the fuel to it. I tore the carbs all apart and cleaned everything out. But I just can't figure out how the sliders work. Theres no cable just that little vaccum thingy. When I try to start it, are the supposed to go up with the throttle or what. I can't figure them out, there's no gas getting to engine at all. But I know there's gas in the bowls because, I loosened the drain screw at the bottom and they have fuel in there. Maybe they just just need to be running to get them up. I'm having a hard time here. Any advice would be great. I appreciate anything. Thanks. Wade
 

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Re: Mikuni 38\'s, HOW do they work? I\'m lost

Are the butterflies opening with the throttle. Try starting the bike with the throttle 1/4 open if it starts and runs like this then try adjusting the Idle speed screw clockwise.

There should be a small gap open at the bottom of the slides when the bike isn't running.

Check that your petcock is flowing. set it on prime.

Check out the electric side of things as it may not be the carbs. Is the engine block grounded to the battery? Some people forget the ground strap when swaping motors. Plug wires in the right order? Do you have spark at all four plugs?

Good luck
-Dave
 

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Re: Mikuni 38\'s, HOW do they work? I\'m lost

The slider move up when a low presure is created by the motor.
 

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Re: Mikuni 38\'s, HOW do they work? I\'m lost

The carbs are very stand-alone, basically all you do is bolt them on and get fuel to them and they should work. The vacuum control for the slides is all internal, there is no external plumbing. The little vacuum "nipples" (heh heh heh) are used for various things like powering a vacuum fuel shutoff but in general they need to be capped and sealed. If you're missing those little caps the slides will not be opening and your bike won't run. There's really not much that can go wrong with them. Check the basic things, make sure you're getting spark and haven't miswired the plugs or something. If you can start the bike on starter fluid then the carbs may be the problem but I doubt it. Hope this helps.

Matt
 
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