Clinician
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Post by chemicstry on Apr 28, 2011 13:39:39 GMT -6
Smoke is white.
I have a clue that my intake valve isn't hermetic because when I gently turn the flywheel it slowly moves and in ~10sec piston gets to the top. Carb has some black dust on it's sides and i don't think it's oil.
Today I cleaned my carb and checked jet size, it's 81 (at least it's written so). And one more thing: My scoot goes faster when I bend my air filter tube (limit the air passing to the engine). I think this means that I'm running too lean.
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Clinician
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Post by chemicstry on Apr 28, 2011 7:39:59 GMT -6
Boy it is not sounding healthy... I'm hearing cam chain rubbing in the guides... are you certain you have tension on the chain? I agree with Zug.. sounds like the chain is off a link or isn't tensioned right You were right. My cam chain tension screw was broken. Now it runs as it was before. I inspect this as carb problem because it throws a lot of smoke and it normalizes when engine warms up. Can't find any suitable tachometer, all shops are full of infrared ones. |
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Clinician
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Post by chemicstry on Apr 20, 2011 8:30:54 GMT -6
Cam shaft chain is shifted to a one by a half tooth (due to crankshaft repair and big bbk gasket (~2mm)) but i don't think it could make that big difference.
Today I had a very strange problem.
You should listen:
I checked all carb, cleaned air filter but it was still the same and after few moments it magically fixed O.o
Tomorrow I might buy a tachometer and test rpm.
EDIT: I guess I will pick pre-jetted carb with high flow air filter and new gear set from scrappy dogs. My current carb isn't in very good standing...
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Clinician
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Post by chemicstry on Apr 19, 2011 8:25:38 GMT -6
I cleaned carb, adjusted A/F correctly but still the same. This might help: when I set A/F too low engine was bogging and when I set it too high acceleration was a bit slow. Spark isn't big but blue. Here is how my plug looks:  I think it's ok, yes? I don't have tach to check rpms but I will buy one if I find any cheap one or I will make it by myself with avr. I also noticed that it drops idle rpms after full throttle. And one more thing: could it be because of too high compression? Starter hardly turns engine and kick starter sometimes hits back. |
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Clinician
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Post by chemicstry on Apr 18, 2011 14:45:57 GMT -6
Riding 2 up on Qmb is asking a lot from the engine even at 70cc. Unless its 2 100lb teenagers. ;D. You say 2 is too much?  8 persons is my record... This is how i killed my 60cc ;D  End of offtopic. I will check everything tomorrow. Thanks for help. |
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Clinician
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Post by chemicstry on Apr 18, 2011 11:27:28 GMT -6
Diaphragm needle is now on middle setting, tried setting it in both ways but didn't notice any difference.
CDI and ignition coil are stock, i'll check plug and spark tomorrow.
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Clinician
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Post by chemicstry on Apr 18, 2011 9:38:39 GMT -6
I just tested variator and belt climbs to about 3mm from edge.
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Clinician
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Post by chemicstry on Apr 18, 2011 2:26:17 GMT -6
Hi everyone,
I have baotian scooter with 139QMB engine. Originally it was 60cc and it ran ~55mph. Then I purchased 72cc kit, did 400mile break-in.
Acceleration is now much better but top speed doesn't reach 45mph down hill and it feels that engine is braking whole scooter. I tried changing variator rollers 4-6g and 6g were the best when driving with 1 person, with 2 persons acceleration was very slow.
I have changed my crankshaft bearings before installing 72cc kit because they broke.
I didn't do any modifications to the carb except top needle settings but they didn't change anything at all.
I hope someone could help me with this problem.
Thanks.
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