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Mikunis no fuel?


mistah mofro

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I have triple mikuni 40's with new gaskets, accelerator pump, shims, and needle valve assembly. One out the three carbs are actually spraying the fuel out and the other two are dry when pressing the throttle or cranking. This was a problem before I rebuilt the carbs even after cleaning them with a solvent washer and compressed air so i was wondering if theres any passage ways i missed?

 

Thanks.

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There are two balls in the accelerator pump circuit that ROUTINELY get corroded into the passageway. They are accessible externally by removing a screw cover, and inverting the carburettor. They SHOULD fall out. If these check balls are not in there, you won't squirt as it can't make pressure. Same goes if they are stuck, as they have to lift to let fuel into the chamber. I want to say they are under the screw cover that you remove to put the accelerator nozzle into the carbs. If you pull that cover off, you should be able to pump the carb and the fuel should rise (the ball will lift and let it pass.) If they are stuck, no fuel comes in. If they are missing when you let the throttle arm back up, it sucks air back into the accel pump from the nozzle size and you don't get a pump action as it won't draw it in from the bottom of the float bowl!

 

This was VERY common.

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So check balls seems be getting stuck because after taking them apart the second time seems the problem is present only in the carbs that dont spray fuel. How do i stop them from getting stuck i already have them apart and can post pics if needed. Thanks tony

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  • 2 weeks later...

Cleaned out the check ball area and they dont stick anymore but little progress. #1 carb has one strong stream and one that doesnt have anything, #2 carb two has strong stream and one stream that seems to get stronger as the other looses pressure, and finally #3 carb has one ok stream and one very very weak stream stream. Fuel pump pilots are soaking as i speak and i left them to soak friday and hoping whatever gunk is in them comes out now.

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  • 4 weeks later...

Yes, paying attention to ball care can really increase the volume of squirt produced when you jerk the lever quickly.

I met this ball specialist in Singapore who worked mine over in about 2 hours. I was amazed by the volume she produced.

To that point, I'd never experienced anything like it. I'd highly recommend that operation if you don't have adequate squirting volumes.

The Manager hangs out around the corner by Orchard Towers and can arrange a meeting whereby your balls get a proper working over...

 

 

 

 

B)

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