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i have a shifter kart but i have a 1986 yamaha yz80 engine on it and i dont know why but everytime i go to open it up it will just bog down and wont go and if i double tap the gas pedal it will go for another 2 seconds and then it will bog down again and i dont get it so if anyone knows what there talking about please help me if you have any suggestions what so ever just send it to me please

Thanks,
Todd

Some things to check.....

Air filter clean?
Reed Valves split or frayed?
Compression test?
Blocked or gummed carb jets, float height?
Exhaust clear and muffler not blocked?

the air filter is clean and i cleaned the jet so i know nothings in there and theres nothing blocking the exhaust and im pretty sure the float height is good i dont know about compresion or the reed valves

What does the spark plug look like?

How did you clean the jet?

It almost sounds carburation related.... but hard to tell over the net. Bad reeds can create problems like this suddenly. Did it happen suddenly or over time?

its been doing it since i got the kart but its getting worse b/c before it would do it only when it was cold now it does it no matter what and its gettin worse i cleaned the jet by taking it off and blowing some air through it and it did get some stuff out but didnt really make that much of a difference...how do i check the reed valves?

The reeds are installed in a block between the carb intake boot and the cylinder. You have to take the intake and carb off, then unbolt the reed block to remove it.

How many hours are on the engine? You might be due for a top-end rebuild. A compression test will help tell if the rings are pooched or not.

You still might have dirty carb issues as well. A varnished jet often needs a little scrubbing with something softer than the brass the jet is made of. You don't want to scratch the passage or enlarge it by any amount at all. The same applies to the rest of the fuel passages in the carb.

well i found the reeds and they look fine i cant really tell tho bc i just took the carb off and looked through the manifold but it looked fine through there and i ran it again tonight and its doing the exact same thing and whatever its doing it just keeps getting worse bc everytime i run it seems worse bc the very first time i ran it it ran GREAT i have no clue how many hours are on the engine ill check the the compression tom and let you know...but did you say that a reed valve problem will cause this to happen suddenly?....bc it did happen pretty suddenly

You have to take the reed block out to get a good look at both sides of the reeds. Once out, hold it upside down and fill it with a solvent like varsol or kerosene. No solvent, or very little anyway, should leak out if the reeds are sealing well. If they don't appear visually perfect from both sides, they aren't. No cracks, no chips, no frayed edges. If they are made of metal(possible for that era, but I don't know for sure what yours are made of) they can look perfect and still not seal.

When re-assembling the reed block, be sure to either use new gaskets or that the old ones are in very good condition(there are 2 gaskets, one between the cylinder and reed block, and one between the reed block and intake boot). Silicon is not an option here, the fuel will eat at it and you will have air leaks or even bigger issues down the road. Other kinds of sealants may work if they are fuel resistant, but they make taking it apart later a real P.I.A.

ok ill take them out and take a look at them and let you know what they look like thanks for all your help