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Post by sgorman90 on Jul 25, 2015 19:38:41 GMT -5
So my Bintelli Sprint GY6 139QMB 50cc scooter with a 72cc big bore kit had been running pretty well but I recently was going around 45 on it when I heard something blow and then my scoot slowing down and stopped. Now I can kind of get the engine to run if I open the throttle all the way, but not fast enough for the wheel to turn. I noted that a lot of oil of some kind seems to have leaked out of the belt cover and when I took the cover off it looked like there was some soot or burned oil covering the inside of the case. Please reply if you have any advice for me. I also noticed that there was very little engine oil when I checked the dip stick, so I added some but it still barely runs.
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Post by Fox on Jul 25, 2015 19:43:24 GMT -5
The crap in the belt cover is dust from the drive belt wearing down. It sticks to everything in there. It's normal. It should be cleaned out every so often. I use an old paint brush and compressed air but you have it all covered in oil now so it's rags and more rags but first you'll need to figure out what went wrong and fix it before you worry about cleanliness.
Do you have access to an impact wrench?
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Post by sgorman90 on Jul 25, 2015 19:45:30 GMT -5
I do not have access to an impact wrench, though if they aren't incredibly expensive and it's worth it I might be willing to purchase one.
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Post by Fox on Jul 25, 2015 19:54:13 GMT -5
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Post by Fox on Jul 25, 2015 19:55:28 GMT -5
Who did the Big Bore Kit on it and how long ago?
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Post by sgorman90 on Jul 25, 2015 19:57:49 GMT -5
I did the big bore kit myself about a month ago, and it was running beautifully during that time.
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Post by Fox on Jul 25, 2015 20:04:53 GMT -5
Okay well then that makes it easier cause it means you have some knowledge and some tools. You gotta get that variator off there so you can inspect the oil seal and check for a cracked engine case behind it. You can also check for side play in the crank bearing on that side once you get the variator out of the way.
I have a feeling that the BBK is toast.
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Post by Fox on Jul 25, 2015 20:08:07 GMT -5
I gotta go back and lie down now cause I had a knee operation but I leave you in good hands. The guys here can talk you through anything. Good luck!
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Post by sgorman90 on Jul 25, 2015 20:35:31 GMT -5
Thank you very much!!
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Post by Availien on Jul 25, 2015 22:32:04 GMT -5
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Post by sgorman90 on Jul 26, 2015 9:38:48 GMT -5
Thanks for the advice Availien. I just checked the compression on the engine, it's at 95 psi, which is a little low since if I recall it was in the neighborhood of 150 psi last time I checked. So I'm thinking there's some sort of leak in the front end... looks like I'll be busy taking it apart this afternoon...
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Post by Availien on Jul 26, 2015 10:16:33 GMT -5
The stock Cranks on these scooters were not designed to handle the extra weight from a larger piston. As I've said on other posts, Start throwing high performance parts in a chinese bike and SOMETHING is going to go wrong. It weeds out the week parts though, so eventually you will end up with a nice engine if you keep at it.
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Post by sgorman90 on Jul 26, 2015 10:38:26 GMT -5
Looks like I'm missing one of the tappet adjuster nuts, would that cause major issues?
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Post by Fox on Jul 26, 2015 10:53:59 GMT -5
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Post by Availien on Jul 26, 2015 12:21:24 GMT -5
Looks like I'm missing one of the tappet adjuster nuts, would that cause major issues? Heck yeah it could. Especially if it's inside of your crank-case tearing things up. (What Fox said)
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