New Rider
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Post by flexo6 on Apr 14, 2013 16:38:05 GMT -5
Lost compression..did a compression test. Exhaust valve is burnt. What do you thik I should check?....When adjusting fuel/air mixture screw....does turning it in give it more air or more gas? Before I replace valve do you think I should up the jet some? Spark plug didn't look all that bad color wise. Thanks for any input!
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Post by millsc on Apr 14, 2013 16:42:22 GMT -5
replace the whole top end get a big bore kit that has the head included and of course upjet
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Sophomore Rider
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Post by indymoped on Apr 14, 2013 19:14:04 GMT -5
If you had a bad exhaust leak or a performance exhaust that could cause a burnt valve. Engines need to have a little back pressure otherwise they burn the valves.
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Post by joaoeu on Apr 17, 2013 1:58:55 GMT -5
For the A/F adjustment screws, here is the PDI link useful for carb adjustments: x1scooters.com/pdi.htmlTurn this screw in (clockwise) to richen (more gas) the fuel mixture. Turn this screw out (counter clockwise) to lean (less gas) the fuel mixture. |
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Post by rockynv on Apr 17, 2013 4:09:22 GMT -5
Was the valve simply too tight? The exhaust valve has a tendency to sink into the head and tighten up to the point that it no longer contacts the valve seat long enough to cool so it ends up burning so this could just be a symptom of a missed valve adjustment. Dirty carb could also cause this as the A/F adjustment is mainly to smooth out the idle while the midrange and high speed jets are fixed with the position of the needle on the slide fine tuning things based on vacuume differential. The needle on the slide being set too low could lend to this also however if you never touched it that should not be the case. Fuel pump/flow not able to keep up during heavy throttle also can cause overheating however if the valves are adjusted right you will usually burn a hole in the top of the piston before you burn the valve.
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