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Post by mr11979486 on Aug 13, 2018 8:12:55 GMT -5
I've bought a scooter without a belt. I found this engine is qj139qmb. It has the funny head, with standard cvt parts, except the belt isn't standard. I've bought the 669 (too short), 729 (needs to be just a little longer), 788 (too long). There's no info on these engines
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Post by dexameth on Aug 13, 2018 10:46:11 GMT -5
From my research, that motor uses the 836-17-30 size belt, but if you've tried different sizes and found it seems to be in between a 729 and 788... maybe try a 738-18-30.
How did you gauge the length of 788 being too long?
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Post by dexameth on Aug 13, 2018 10:47:05 GMT -5
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Post by mr11979486 on Aug 15, 2018 22:52:03 GMT -5
I found out the hard way that the 3 common belts didn't fit. I bought 1 after the other, went back to 729 belt after 788 belt wasn't even close. I thought I might have to run the scoot with 729 and maybe after the belt is warm it would fit different... of course not! But I tried anyway with 729 belt. 729mm sits right in the front variator, but it was about 1/2" sunk into rear clutch pulley. So just a bit small.
I bought 4th belt (743-20-30) definitely too wide(I figured, but worth the try)... also maybe just a tad too long. I just ordered the 738-18-30 belt hoping that it'll work. I'll be sure to report back in a few days
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Post by bajasc50 on Aug 18, 2018 23:24:15 GMT -5
What's the -# at the end of your engine code? I have a baja sc50 with a QJ139QMB-3 and that bike uses a 836-17-30 belt.
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Post by mr11979486 on Aug 25, 2018 6:15:07 GMT -5
What's the -# at the end of your engine code? I have a baja sc50 with a QJ139QMB-3 and that bike uses a 836-17-30 belt. SUCCESS!!! 738-18-30 is the right belt size for this engine... finally! The 2012 keeway f act qj139qmb does NOT have any additional digits after qj139qmb.
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