Keihin carb problem

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Posts: 32
Joined: Wed Nov 14, 2012 10:56 pm
Main scooter: Lambretta series 2

Mon Sep 26, 2016 11:33 am

Having just rebuilt my engine I have a problem with fuel pouring out of the carb all over the exhaust manifold, and I need to use it to get home from work today.

I have had this before but after stripping, and not finding anything wrong it was ok on re-assembly.

I was wondering if I need to bend the float down a little, thinking it might be fouling/ sticking at the top of its travel....any comments appreciated

Has anyone else experienced this with these carbs and if so how did you deal with it.

Hoping for some quick feedback/ suggestions please


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Posts: 3688
Joined: Wed Jan 07, 2009 12:35 pm
Location: London and Norfolk

Mon Sep 26, 2016 1:20 pm

They work just the same as a dellorto, you can bend the tab so that the valve shuts with the float sitting lower but be careful not to go too far as you don't want to lower the level too much. PWK carbs have a smaller float bowl than the equivalent dellorto and if you lower the float too much there is a real danger that the bowl will run dry on full throttle :o Maybe it's just some dirt blocking the valve?

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Posts: 118
Joined: Sun Feb 07, 2016 10:08 pm
Main scooter: 1969 Lambretta gp

Mon Sep 26, 2016 6:40 pm

Take float bowl off, (care must be taken removing float bowl or the float and/or brass pipe can be bent and catch/rub), take needle valve out and check for dirt/blockage etc, also check valve is working, check float is straight and not bent as if it is it can rub/catch on the brass overflow pipe or sides of the float bowl, check float level (I set it at 19mm) carefully reassemble carb (give it a little shake and see if you can hear float moving) re-fit and give it a try

Hope that helps

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Posts: 124
Joined: Sun Sep 30, 2012 2:16 pm
Main scooter: sx 200

Mon Sep 26, 2016 10:22 pm

the floats also run close to the jet stack, where it flares out(anti surge i think) i filed away some moulding flash that may have caused sticking

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Posts: 695
Joined: Wed Feb 01, 2012 2:00 pm
Main scooter: Li230 S3
Location: Perth, Western Australia

Tue Sep 27, 2016 2:26 am

Float possibly leaking and filling with petrol?
Just one more thing to check :)

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Posts: 134
Joined: Tue Apr 07, 2009 8:52 pm
Location: Cambridge

Tue Sep 27, 2016 7:11 am

I had a similar issue with a PWK when it was fitted with a clear plastic bowl, it warped over time on the back edge and would not seal. Threw it away & fitted an ally one all is good and has been for a few years now.
Best Regards


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