Issue with muffler screws loosening themselves

RB55

Active Member
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Joined
Sep 18, 2019
Messages
158
Location
Louisville, KY
Hello,
I recently got a 2 stroke 80cc gas bike kit off eBay and mounted it to my bike. Despite a lot of issues and frustrations at first (this is my first time doing this kind of stuff!) I managed to get everything working decently, and the bike has about 40 miles on it so far.

The issue I’m having started when I was first assembling the kit. The muffler screws just wouldn’t tighten enough with a hex wrench (I don’t have an impact driver). I tightened them as much as I could, but there was still a good centimeter or so between the locking washers and the muffler base. I just can’t tighten them anymore with a hex wrench because I’ll probably strip the head (would be a disaster!). So I tried using more washers and some superglue, which worked until yesterday when I noticed that the engine became super loud and started acting up (lack of back pressure I guess). The exhaust muffler screws had loosened themselves again. I came up with two solutions (could combine both of them):

1. Use some proper high-temperature thread locker (superglue probably melted)

2. Buy some M6 - 1.0 x 25 bolts instead of screws (bolts won’t strip and are easy to tighten really well)

Any suggestions or comments on what I should do would be greatly appreciated. Thanks!
 
Hello,
I recently got a 2 stroke 80cc gas bike kit off eBay and mounted it to my bike. Despite a lot of issues and frustrations at first (this is my first time doing this kind of stuff!) I managed to get everything working decently, and the bike has about 40 miles on it so far.

The issue I’m having started when I was first assembling the kit. The muffler screws just wouldn’t tighten enough with a hex wrench (I don’t have an impact driver). I tightened them as much as I could, but there was still a good centimeter or so between the locking washers and the muffler base. I just can’t tighten them anymore with a hex wrench because I’ll probably strip the head (would be a disaster!). So I tried using more washers and some superglue, which worked until yesterday when I noticed that the engine became super loud and started acting up (lack of back pressure I guess). The exhaust muffler screws had loosened themselves again. I came up with two solutions (could combine both of them):

1. Use some proper high-temperature thread locker (superglue probably melted)

2. Buy some M6 - 1.0 x 25 bolts instead of screws (bolts won’t strip and are easy to tighten really well)

Any suggestions or comments on what I should do would be greatly appreciated. Thanks!
Did You try adding a few more washers? Should help. And use the mounting bracket for muffler to help support it. #10 or #12 machined screws cut for proper depth... I used those on my 49cc and worked gr8. My 66cc hasnt experience this issue ....yet? LoL
 
Hello,
I recently got a 2 stroke 80cc gas bike kit off eBay and mounted it to my bike. Despite a lot of issues and frustrations at first (this is my first time doing this kind of stuff!) I managed to get everything working decently, and the bike has about 40 miles on it so far.

The issue I’m having started when I was first assembling the kit. The muffler screws just wouldn’t tighten enough with a hex wrench (I don’t have an impact driver). I tightened them as much as I could, but there was still a good centimeter or so between the locking washers and the muffler base. I just can’t tighten them anymore with a hex wrench because I’ll probably strip the head (would be a disaster!). So I tried using more washers and some superglue, which worked until yesterday when I noticed that the engine became super loud and started acting up (lack of back pressure I guess). The exhaust muffler screws had loosened themselves again. I came up with two solutions (could combine both of them):

1. Use some proper high-temperature thread locker (superglue probably melted)

2. Buy some M6 - 1.0 x 25 bolts instead of screws (bolts won’t strip and are easy to tighten really well)

Any suggestions or comments on what I should do would be greatly appreciated. Thanks!
These engines are known to vibrate loose, not just the exhaust but all the nuts and bolts. They also use cheap soft nuts and bolts that strip easily. Your best off to replace all off the bolts with 8.8 grade bolts. As far as your exhaust leak goes I would replace the nuts with allen head cap screw bolts and get some loctite, most guys use blue. One other thing is the threads pull out easily on these chinesium engines so be careful not to over tighten or you'll strip the threads
 
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Hello,
I recently got a 2 stroke 80cc gas bike kit off eBay and mounted it to my bike. Despite a lot of issues and frustrations at first (this is my first time doing this kind of stuff!) I managed to get everything working decently, and the bike has about 40 miles on it so far.

The issue I’m having started when I was first assembling the kit. The muffler screws just wouldn’t tighten enough with a hex wrench (I don’t have an impact driver). I tightened them as much as I could, but there was still a good centimeter or so between the locking washers and the muffler base. I just can’t tighten them anymore with a hex wrench because I’ll probably strip the head (would be a disaster!). So I tried using more washers and some superglue, which worked until yesterday when I noticed that the engine became super loud and started acting up (lack of back pressure I guess). The exhaust muffler screws had loosened themselves again. I came up with two solutions (could combine both of them):

1. Use some proper high-temperature thread locker (superglue probably melted)

2. Buy some M6 - 1.0 x 25 bolts instead of screws (bolts won’t strip and are easy to tighten really well)

Any suggestions or comments on what I should do would be greatly appreciated. Thanks!
I had that issue when my engine was new I would just slap a few washers on and tighten the muffler every few minutes when riding (you can hear when the muffler bolts are loose) but tighten it with a high quality allen key because cheap allen keys just strip and the problem goes away after a while
 
These engines are known to vibrate loose, not just the exhaust but all the nuts and bolts. They also use cheap soft nuts and bolts that strip easily. Your best off to replace all off the bolts with 8.8 grade bolts. As far as your exhaust leak goes I would replace the nuts with allen head cap screw bolts and get some loctite, most guys use blue. One other thing is the threads pull out easily on these chinesium engines so be careful not to over tighten or you'll strip the threads
Should I use heat resistant threadlocker though? The exhaust gets pretty hot so I’m afraid normal threadlocker might melt...
 
I stumbled on this solution while addressing a different problem. Of course it wont work unless the pipe is secured somewhere other than the port. The flange wouldn't index on my engine so I cut the head pipe to get it to bolt up, then used high temp silicone hose to re-attach. this isolated the flange connection from the weight and vibration of the pipe, and has never came loose. On bikes with this same pipe but a solid head tube the bolts still work loose so I just got lucky.
View media item 61906
 
Thanks for the ideas everyone! After considering your suggestions, I decided to upgrade my exhaust first of all (I’m going to invest in this bike) to a flexible expansion chamber poo-poo exhaust, which will help a bit since there won’t be as much vibration and I can secure it better. The issue with my current exhaust is that since I’m using a large road/mountain bike, the frame itself is really thick and the bracket won’t fit around it. Also, I found some posts on this forum saying that securing the muffler to the bike isn’t really necessary. All in all, I’ve ordered some high quality m6 bolts (I can tighten better without fear of stripping the head, blue medium strength threadlocker, and a flexible expansion chamber poo-poo exhaust with a gasket (stock one is already worn out!).

Aside from the exhaust, I’m planning to paint the engine and exhaust, upgrade to a racing carburetor, install a boost bottle, use a double pull bike lever for brakes, install a gas line and filter that don’t leak fuel like crazy, re-mount the engine with some 1/8 inch rubber, and install a better throttle grip. Lots of stuff in the bag!
 
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