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Ask Doug E. Your Own Question
Doug E.
Doug E., Kawasaki Master Technician
Category: Small Engine
Satisfied Customers: 2886
Experience:  Professional mechanic since the late 70's on Kawasaki, Arctic Cat, Jonsered, John Deere and others.
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why does gas leak from carburator when engine is shut off?

Customer Question

why does gas leak from carburator when engine is shut off?
Submitted: 4 years ago.
Category: Small Engine
Expert:  Doug E. replied 4 years ago.

Doug :

Hello

Doug :

The float valve shuts off the fuel in the carb, but you should also use an external shut-off when the bike is not running. Under certain conditions like high heat, the float valve will not be able to keep fuel from expanding and flooding the motor or out onto the ground.

Doug :

You may have dirt in the float valve, or it may be worn out. I would remove the float bowl, check for debris in the carb and inspect the float valve.

Doug :

The float height is adjusted by bending the tang on the float arm that pushes against the float valve. Adjusting it will not help if it's worn or has dirt under the tip.

Doug :

If this problem popped up suddenly, then you know it's probably not an adjustment issue. It would more then likely be dirt or rust sticking the needle.

Customer:

There is an adjustment screw on the bottom of the float bowl. What is that?

Doug :

That should be for your main jet. It's for adjusting the mixture at high RPM. There is a smaller one on top for low RPM mixture plus the idle screw.

Customer:

I should say the adjustment screw is on the low 'side' of the float bowl. So, either way the bowl needs to be taken off and looked at. This carb was supposed to have been rebuilt just before I bought the bike. Does this bowl just unscrew or how is it held up there?

Doug :

The center nut should remove it but I'm not exactly sure what motor/carb you have on there. I don't recall them using the Command motor unless it was repowered at one time. Being you were hill climbing, you may have stirred up some crud in the tank. Maybe they rebuilt the carb but didn't clean the tank.

Customer:

It has an inline filter. Would it flood itself on an incline, because now that I think about it it did stall out.

Doug :

If you get it on a steep enough hill, it will flood out. There isn't much you can do about that but to get up or down the hill as fast as possible.

Customer:

This owners manual is for CS4, CS6,CS8.5, CS 10,CS 12. and has COMMAND written on the bottom.

Doug :

The original carb was a Tillotson, which can operate at any angle. It doesn't have a float valve.

Doug :

OK, let's figure out exactly what you have so I give you the correct information.

Customer:

The gas was leaking from the foam air filter so that is probably what happened. Do I adjust the float by bending the tang? and if so which way?

Doug :

I first need to know what carb you have. The original motors were 2-stroke Chrysler engines. They went to a 6.6HP Kohler on the last few years of production. Give me a moment to post a photo of the carb they used.

Doug :

That is the carb it originally came with. Is that what you still have on there????

Customer:

There is a bolt in the bottom of the bowl of the carb. It doesn't look like the picture unless all those gaskets and plates are encompassed in a bowl.Now that brings up something else then. When I first brought it home the fuel shutoff was faulty when I got it home and flooded the crankcase with gas. I wondered how that could be if the needle was in the seat. But if it doesn't have a float? I have to take it off and see whats in it. Kinda like Nancy Pelosi and her Obamacare bill. Have to pass it to see whats in it.

Doug :

You have a float style carb then, not what's in the photo. There should be a float valve in it that is supposed to shut the gas off even if the petcock is bad.

Doug :

Can you post the frame number for me? I can look up and see what year it is. I've only worked on the vintage models, not on the ones the army used in the 80's-90's. Once I know exactly what it is, I should be able to get you the correct carb manual.

Customer:

frame # XXXXX

Customer:

Engine # XXXXX /p>

Doug :

That's a 1999 model. I do not have the manual on that one. I'm going to see if I can find the parts book for it. I have to log out and head home. I will be on later and hopefully will have the parts book.

Customer:

Ok. It does have a float. I wll take the carb off the bike.

Customer:

If you have diagram of how it is mounted to the engine that would be great to show where the gaskets and washers go.

Doug :

Is that what you have?

Doug :

That is the link for the service manual.

Doug :

It is a float carb so it will flood out if you go up any very steep hills. The old style carb could even run upside down.

Doug :

You will need to replace your fuel shut-off, and check the needle and seat in the carb. The manual shows the carb repair in full detail. Use the engine numbers to order up the parts from any Kohler engine dealer. It's going to be much easier then trying to find a Rokon dealer.

Doug E. and 3 other Small Engine Specialists are ready to help you
Customer: replied 4 years ago.
Good job Doug. Thanks
Expert:  Doug E. replied 4 years ago.
Happy riding!