80cc bottom end leak?

Lunatuck

New Member
Aug 8, 2019
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I bought a bike with a kit on it. It appears to be the typical 80cc Chinese kit. The previous owner only rode it a few times so I’m breaking it in.

It has a leak that seems to squirt oil over the drop tube. It is coming from the bottom most bolt in the photo. It sprays towards the front of the bike when I’m hitting the throttle on rides. Not so much on idle. It’s not coming from the carb.

I’m assuming this means I need to take the head off, and then work down from pistons. All this assumes I can just replace the gasket. I don’t see many youtube videos of bottom ends. Do I need special tools? If I had a secod motor lying around, would it be better to use that? Which gasket would I need?
 

Lunatuck

New Member
Aug 8, 2019
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I think I've convinced myself to swap the engine out for my new one. I'll rebuild it when I have more confidence in the process. For now, I want the bike up and running. Then I can start upgrading.
 

Lunatuck

New Member
Aug 8, 2019
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Well. Engine replaced. Took 5 hours, but I’m not happy with the front engine mount. Kit only has one U bolt and the engine mounted bolts arent wode enough to go around my front tube. So its only temporary until I find a better front engine mount.

Still, it started first start. Much easier to start then the last one. Couldn’t rode cause its dark. :(
 
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Greg58

Well-Known Member
May 1, 2011
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I make my own front mounts, I find a u-bolt that fit the frame tube tightly and start there. I run my engine as low as possible, usually its 1/4 flat stock with a 1/4 spacer at the engine end. One bolt mounts are ok, I've run one bolt for years.
 

Lunatuck

New Member
Aug 8, 2019
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Intwresting. That sounds like what I spent all day replacing. Lol.

It didn’t seem weak, but seemed like it was stressing the frame.
 

Jimmy Bloodmaker

Active Member
Nov 24, 2018
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little bit of black rtv, smear it on the seals on the bottom after you clean them of oil. let it sit for a few hours and ride. don't go to thick, it will take a long time to dry. if that doesn't work cause it's missing a piece of the gasket. then clean it up really good. then scuff it with some coarse sand paper, to get the paint off and leave some scratches for the epoxy you will use. get some gas tank epoxy. it comes in a dough like form in a stick. you break a piece off and kneed it really good. then lightly press it on the hole in the gasket and spread it out. not trying to shove a lot in the hole, but enough to light press into it. let tht cure for a day. then lightly sand it and add some black rtv thinly over and around the epoxy for flying debris protection and to blend it into the paint job.