Help! M6 hex screw socket threads stripped - any way to fix?

[RB55]

Hey everyone,
First of all, these Chinese engines are cheap but I can’t say enough about how poorly they are made. From a leaking exhaust to a clutch gear simply popping out to the clutch repeatedly failing to engage to excess vibration to gas leaks all over the place to the engine not starting, it’s been a rough road from the start. But I guess a lot of the fun of this hobby is learning how engines work and fixing them.

Since I’ve been having many issues with the clutch, I’ve taken off and put back on the engine chain cover (I don’t know the name, but it covers the gear of the motor the chain is attached to on the left hand side and has the clutch lever coming out on top) many times, probably about 12. I’m using the proper sized hex wrench and no threadlocker, Teflon tape, etc. on the the hex screws that hold it in. I have pretty weak hands and only tightened the bolts with a super small hex wrench, not over-tightening them but making sure they were tight enough to stay in and not come loose through engine vibration. Today I was tightening one, and suddenly the bolt came off. I tried another but it wouldn’t tighten, it just rolled around in the hole. The other two bolts hold well enough so that I feel comfortable, but I still want to find a way to put another bolt back in so I don’t over stress the others. Would this work for tapping a new thread? Thanks!

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[Frogslayer]

They might work but by looking at the picture they don't look deep enough and these bolts thread in a ways to help you get the cover on with the spring loaded clutch bar behind it. Maybe jb weld or braze the hole shut the re drill and tap it. If you have room you could drill it and tap it one size bigger and use a bigger bolt.

 

[MotorBicycleRacing]

Do not drill the stripped 6mm threaded hole.
Tap new threads with 1/4" 20
I presume it was one of the front 2 holes.

 

[gary55]

Just to add it might be best if the 1/4"20 is stainless. To get the old one out a reverse bit should work. then if it don't work you will still have a hole for a easy out. You can also drill just the head of the bolt off with a 1/4" bit then remove the cover and remove the bolt with pliers. Forget about all the crap I just said accept the stainless part. I didn't read your problem correctly.

 

[Frogslayer]

I think he was describing a stripped out hole in the case, not a broken off bolt, correct?

 

[gary55]

I think he was describing a stripped out hole in the case, not a broken off bolt, correct?

Yep your right. I thought it was stripped but stuck. He said he tried another in the hole though so it's stripped but removable. OOps.

 

[Frogslayer]

I got faith he can figure this out. He was smart enough to start checking out heli coils. If all else fails, aren't cases fairly cheap?

 

[CrazyDan]

The top bolt holding my pull start onto my block stripped out about 2 years ago. I'm worried to mess it up trying to fix it because there is no hs144f cylinder available. So I haven't bothered to fix it yet lol. I wrapped my bolt with a piece of a beer can and screwed it in, it's held up ok. That same bolt is one of 2 that holds my magneto to the block. So far, so good. Even ran a couple races, and another one in less than a month, don't think I'm gonna try to fix that anytime soon. If I had spare cylinders available I would have gave it a shot a long time ago.

 

[RB55]

Thanks everyone! Ended up following a mixture of your suggestions, and it's working perfectly now. Bolt does not come loose and fits well.