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Confused
Jul 29, 2020 17:41:30 GMT -5
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Post by sjfishon on Jul 29, 2020 17:41:30 GMT -5
Have a 4 year old Byshan 49cc gy6. Just recently,it will not run on a normal idle. Have checked all I can think of. I have the idle higher than I want,but if I turn it down just a little,it will kill.Have checked all vacume hoses, have adjusted the fuel air,it's at 2 turns out. Any thoughts on what to check,oh,I also put a hose clamp in front of carb.
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Confused
Jul 29, 2020 22:02:36 GMT -5
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Post by bullybike on Jul 29, 2020 22:02:36 GMT -5
ussually the intake boot gets cracked or damaged or some vacuum line or fitting leaks. Do a really good inspection and make sure everything is sealed and no hissing sounds
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Confused
Jul 30, 2020 10:10:05 GMT -5
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Post by sjfishon on Jul 30, 2020 10:10:05 GMT -5
Thanks,have checked all vac. Hoses.gonna check tightness of 2 bolts that hold the manifold today, Mabey take off and reseal with gasket maker.
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Post by Scooters To Go on Jul 31, 2020 5:43:00 GMT -5
Most likely it’s the idle jet inside the carb. They get oxidized from the ethanol in gas over time.
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Post by Steve B on Jul 31, 2020 9:40:46 GMT -5
For the 139QMB 50cc engines, the valve clearance specification is . 004". Its simple really just take your 9mm wrench and loosen the locking nut on the valve tappet. Then you loosen the tappet until you can get your feeler gauge between the tappet and the valve stem. You want to tighten the tappet down on the feeler gauge snug but not to tight. You can also try running some sea foam through the carburetor and see if it clears up.
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Confused
Jul 31, 2020 9:59:06 GMT -5
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Post by bullybike on Jul 31, 2020 9:59:06 GMT -5
I'll second the clogged idle jet SJ!
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Post by sjfishon on Jul 31, 2020 13:23:35 GMT -5
Thanks all. today put 3oz of seafoam,in1gal of gas. Have ran it once,about 30 min.will see,and get back.
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Post by FrankenMech on Aug 1, 2020 19:21:26 GMT -5
For the 139QMB 50cc engines, the valve clearance specification is . 04 mm. Its simple really just take your 9mm wrench and loosen the locking nut on the valve tappet. Then you loosen the tappet until you can get your feeler gauge between the tappet and the valve stem. You want to tighten the tappet down on the feeler gauge snug but not to tight. You can also try running some sea foam through the carburetor and see if it clears up. .04mm would only be .0015" or way too tight, try 0.004"
Edit to follow your changes:
.004mm is essentially no clearance at all, use .004 INCHES
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Confused
Aug 2, 2020 9:25:04 GMT -5
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Post by sjfishon on Aug 2, 2020 9:25:04 GMT -5
Have ran seafoam 2 days now, I did change the choke. When it starts its like there is no choke,must keep twisting to keep running,after warm up it runs good,but will kill on ideal after a while. Thinking now about bypassing the pet clock,was wondering, is it there just as a safty,or if I eliminate it can the carb leak,when off?
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Confused
Aug 2, 2020 9:26:42 GMT -5
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Post by sjfishon on Aug 2, 2020 9:26:42 GMT -5
I did run with the new choke out and it did expand..
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Post by mikehailwood on Aug 2, 2020 9:45:08 GMT -5
Have a 4 year old Byshan 49cc gy6. Just recently,it will not run on a normal idle. Have checked all I can think of. I have the idle higher than I want,but if I turn it down just a little,it will kill.Have checked all vacume hoses, have adjusted the fuel air,it's at 2 turns out. Any thoughts on what to check,oh,I also put a hose clamp in front of carb. Did this scooter sit without running for a period before these symptoms developed or, was the scooter being ridden regularly when the symptoms appeared?
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Post by mikehailwood on Aug 2, 2020 9:53:52 GMT -5
Have ran seafoam 2 days now, I did change the choke. When it starts its like there is no choke,must keep twisting to keep running,after warm up it runs good,but will kill on ideal after a while. Thinking now about bypassing the pet clock,was wondering, is it there just as a safty,or if I eliminate it can the carb leak,when off? Seafoam works sometimes but is a poor substitute for actually looking at the inside of your carburetor for problems.
Vacuum activated diaphram fuel valve seems to be a safety feature for riders who cannot seem to remember to turn the traditional petcock to the "off" position when not riding. If you bypass the stock vacuum fuel valve you should not have a problem "if" the float valve in the carb is working properly. However, one small tiny of debris between the float needle and the seat will prevent a proper seal and you could end up with gasoline all over the floor.
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Confused
Aug 2, 2020 19:53:32 GMT -5
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Post by bullybike on Aug 2, 2020 19:53:32 GMT -5
definitely the idle pilot! (maybe) seafoam wont help if its a tiny piece of metal or rock in there. break out the sewing needles!
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Post by GrumpyUnk on Aug 3, 2020 11:19:58 GMT -5
If you are adventurous, you can loosen the air inlet and outlet clamps to rotate the carburetor towards the right side. Then remove the three screws holding the float bowl. If your 'screws' don't have slots, you can make slots using a 'dremel' type tool. You can grab the sides of the screw heads with small Vise Grip pliers to break them loose. Once removed you will see two brass/goldish looking things near the center, forwardish. The frontmost is the PILOT jet. It is likely to be clogged if you cannot idle. You can remove it and attempt to see light through it. If clogged, you can use a wire brush strand. One. straight. and poke it through the pilot jet center. It should go through with some manipulation. If difficult, try from the other end. Once cleared, you can check the 'jet' in the float bowl. It is near the hole that the choke feeds from. The choke 'tube' sticks into a well that fills with fuel over time. It provides a good slurp of fuel for startup, then feeds a bit extra via that tiny jet until the choke(byvalve) extends and cuts the flow. If that tiny jet build into the float bowl is clogged, no fuel, no choke enrichment, and hard to start. Again, use a wire brush strand to poke through the jet. The brush I use is shaped like a 'scrub brush' used in olden times(20th century) to clean floors, decks, etc. I pick a straight strand that is standing(pointing) off by itself, leave it in the brush, and poke into the jet center. Re-assemble, twist back in place, tighten the clamps, and see if it will start and run. Remember, the float bowl will be empty, unless you provide suction to open the vacuum petcock or have replaced it with manual shutoff valve. tom
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Confused
Aug 3, 2020 11:34:24 GMT -5
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Post by sjfishon on Aug 3, 2020 11:34:24 GMT -5
Thanks Grump very clear..
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