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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 26026
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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25 hp v twin model ch730 with fixed jet carb part number

Customer Question

25 hp v twin model ch730 with fixed jet carb part number 24-853-91S runs too rich at lower rpm and really bad at idle. When first idled down it is good but within 15 seconds it goes into a heavy load of fuel and can't recover without full throttle. Has been this way since new and am certain that air cleaner is clean and choke is working correctly.Please help.
Submitted: 10 months ago.
Category: Small Engine
Expert:  Curtis B. replied 10 months ago.

CH730 is twin engine, Have you ran a cylinder balance test, to see that both cylinders are firing at idle? Remove one spark plug wire at a time , to see if engine will continue to run. If engine dies when wire is removed, the opposite cylinder is not firing. If it is not firing on both cylinders at idle, you get the loading up with fuel, and poor idle. Have you had carburetor apart, and it is clean?

Customer: replied 10 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Curtis B. replied 10 months ago.

I can call for additional charge, but did you see my response, and make the cylinder test?

Customer: replied 10 months ago.
Have completed cylinder balance check and machine continues to run on both cylinders. Remember when returning to idle I get a good response for about 15 seconds before loading on idle. will tear down and clean carb this weekend.Enginering hasn't caused this by chance
Expert:  Curtis B. replied 10 months ago.

CH model has been around for years, Sounds like carb problem. Here is link to service manual.

Customer: replied 10 months ago.
After review of the service manual it appears there is some adjustment of the idle fuel mixture, is this correct? You also think this can be fixed?
Expert:  Curtis B. replied 10 months ago.

You can try the adjustment, but I doubt it is the problem. I figure you will need to check the float and needle valve area.

Customer: replied 10 months ago.
Curtis I pulled top off carb and I find that the float can move all the way to that cover and I don't think the needle is shutting off fuel. The service manual did not have setting information for float. Can you advise. And what else should I be looking for! Thanks!
Expert:  Curtis B. replied 10 months ago.

Float should have a metal tab, that can be bent , to stop the upward movement of the float, and let it push against the needle. I don't find a good picture of it, if it is not there, do you see where it could be broken off?

Customer: replied 10 months ago.
Tab is there and I dropped the fuel level some with noticeable change in idle instead it now takes 5 times longer to start loading and does not get as bad. Is needle and seat defective or should I lower it some more? How will I Know if I have gone too far
Expert:  Curtis B. replied 10 months ago.

Float should be set where it is basically level, when needle is seated. You may need a new needle valve and seat, if it does not shutoff fully.

Expert:  Curtis B. replied 10 months ago.

Is th efloat you have the black plastic material or a brass float. Brass float can be leaking, and have fuel in the float. The black float is not hollow and can't leak.

Customer: replied 10 months ago.
Black plastic. I notice if I start up at idle and leave it there it is even better, does this tell us anything? Also notice slight engine noise on idle but goes away with the least bit of acceleration. 400 hours on machine is this normal. Should I lower fuel a bit more?
Expert:  Curtis B. replied 10 months ago.

You have had carburetor off, and the mounting gasket is good? No intake leaks? I think needle is not seating good. You could try lowering bowl a bit more, but if float is not hitting the top of carb, it should be shutting off the needle passage,

Customer: replied 10 months ago.
With the checking and adjusting that I have done there is change in performance but the problem is still there. It takes longer for it to start to load but still not acceptable. This morning at 24 temp the machine started on idle with absolutely no choke and this to me seems strange. What advise do you have, try a carb kit install $68.00 or complete carb $375.00 or can it be something else completely.
Expert:  Curtis B. replied 10 months ago.

The carburetor is the only thing that affects the fuel to the engine . I would try a carburetor kit, but that would be your choice, I do see new carburetors on Ebay for $300. I think problem is the needle valve and float.

Expert:  Curtis B. replied 10 months ago.

Please accept and rate to close.Thanks.