Fix for stripped muffler bolt?
 

I recently aquired an OS 35 2 stroke which has a stripped muffler mount bolt. Any one know a technique for repair?

Fix for stripped muffler bolt?
 

Helicoils work the best.

Muffler Bolts
 

If it is the kind that goes through the engine and screws into the muffler, it frequently happens. The metric threads on the muffler bolts don't have much depth and can easily strip the soft aluminum of the mufler. I recall I have been heard saying, "I hate those #@$%&## metric bolts!!"

You can run a 4-40 or 6-32 tap through the muffler, you'll have to determine the correct size. Compare the metric bolts with a 4-40 and 6-32 bolt and pick the next larger size. You may also have to ream the holes through the engine with the next size larger drill bit. It doesn't hurt anything, it just cleans the hole out.

I have done this to OS, Thunder Tiger and Tower .46 engines. The American bolts have deeper threads and hold much better.

Fix for stripped muffler bolt?
 

...and if all else fails on thru the engine bolts, use longer bolts and nuts! It works for me.

Bolt sizes
 

In my piddling in the shop I have seen that there is an order to the sizes of the screws. It starts at 4-40 then goes to 3mm then to 6-32 and finally 4mm. The muffler screws are probably 3mm so a 6-32 tap would fix it up. The longer screw idea would be easier if there was room at the bottom of the hole.