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Beta 4t Carb - Gas Overflow Mystery

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Asking for a friend who is presently without internet access. His 4t Beta with the 300 kit is pouring gas overboard through the carb overflow. Our local dealer switched out the carb 3 times with the same results. The dealer then put the offending carb on another 4t w/300 kit and there was no leaking. We're all baffled. Any input, suggestions or experiences with this problem are greatly appreciated. Many thanks.

Digging around looking for information on the carb. Man it's like pulling teeth! Doesn't seem to be even a mention of what model carb it is let alone technical documantation.

Does it run? Or backfire? It could be valve timing or he could have a hung up valve and it's pressurizing the carb.

Edited by motofire

Another thought...did he keep the same needle/slide and just swap the carbs?

O.K> I,m at work and can get on internet. I can take a carb off a good running 4t, with out an over flow issue put it on my bike it over flows. My bike runs great with any of the three carbs that I have,but they all over flow. Only work done was 300 kit. At first bike would start then die. thats why I started re-checking the work that was done everything looks good so I started changing carbs.

Edited by ohno

Gday, does is overflow at any particular time, eg immediately fuel is turned on, or does it take a few minutes etc?

Cheers,

Stork

O.K> I,m at work and can get on internet. I can take a carb off a good running 4t, with out an over flow issue put it on my bike it over flows. My bike runs great with any of the three carbs that I have,but they all over flow. Only work done was 300 kit. At first bike would start then die. thats why I started re-checking the work that was done everything looks good so I started changing carbs.

If it's overflowing with new/different carb on it then it has to be something already on your bike. make sure the fuel valve swithch is in the up position, if it's down the fuel runs continuously into the carb.

But what on the bike? It over flow right at start up, and the needle and seat should stop any over flow issue. What throws me off is I can put the carb on another bike and the carb doesn't over flow.

bit of a long shot on this one but its a possibility.

take off the filler cap and see if it still leaks - reason behind this is that there is a air vent in the cap, if this is blocked it could create a vacuum or if the engine in hot then fuel expansion which could be enough to push past the float bowl needle valve.

as i say its a long shot but easy enough to check.

Yes on switch,have removed gas cap, does it cold have not run it long enough to get hot.

gunged up air filter could create a constant vacuum and cause starting issues and constant demand for fuel in the carb - take out , try it , if so clean or replace.

clear ducting from air filter to carb (same reason as above)

only other thing that comes to mind would be the reed valves allowing back pressure into the carb and making the fuel in the float bowl bubble up the overflow.

i would go with the air filter first as its easy to check, the reed valve block would have to be taken out and inspected to make sure the petals are seeling properly.

other than that i would be at a total loss aswell

good luck on this one

With or without air cleaner in same. reeds? can I start bike with a I.V. by pass pet cock? I just wanna ride.

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