outlaw29

After a good day of flying, both exhaust adapter screws broke off inside the crank case mounting holes. I got one out but, the other broke off about half way in. Any ideas on how i can get this out? I don't know why they broke. They usually just come loose after 4 or 5 flights. Every thing seemed fine but i must have some excessive vibration. Has anybody welded the exhaust adapter on an os 91df? Do you think this would be a good idea. Thanks for any help.

Russ

Mokulele

My Feedback: (9)

Outlaw,
Craftsman has a DRILL-OUT micro power extractor. This tool woks great for small screws. You will need a reversible drill. Also heating the engine case will help to remove the screw.
Larry

Marty O

Russ- Do not weld the crackcase as this will warp everything out of tolerance.
You can find , hopefully a modeler to use a Ram EDM machine to remove the broken bolt or you can use a solution called tap-out. I believed this is found in McMaster-Carr but is also found in machine shop catalogs. It is an acid so take precautions. It will eat any ferrous metal out of aluminum. You may want to tear down your motor as it will attack the sleeve or anything else. with Iron in it.
To use it , make a dam out of modeling clay around the hole and put it in the hole. You may have to do this several times but it will get it out. Dip it in baking soda and warm water solution to neutralize the acid.
BE CAREFUL.
Hope that helps.

Marty O

outlaw29

Thanks for the info. I got it out with the micro extractor. I chewed up the threads a little. I drilled the holes a little bigger and put a heli-coil in it. Hopefully a bigger screw and some high temp red loctite will solve my problem. It's back together and looks good. I'll see how well it holds up on new years day. I talked to a buddy of mine that is a machinist at NAPA. He said that the tap out solution works suprisingly well. He has used it on aluminum heads. I will keep this in mind. Anyway thanks again.
Happy New Year.

Russ