Poor Helicoil Repair

[xstian]

Has anyone got any advise on repairing poorly installed helicoils? I've got maybe 4-5 to repair, the ones in there at the moment either felt loose or where not square. Wurth Time-serts look ideal, but are not very cheap and being M7 I doubt I'll use them again.

The other option is to try and source some M8-M7 studs.

 

[Keithmac]

Wurth Timesert would have been my go too solution.

Hoe long are the studs? Some Hondas use hybrid exhaust studs, M7x1.0 one end M8x1.25 on the other.

 

[Brad93]

Keensert heavy will take you above the size of the helicoil

 

[jmp49]

Timeserts would be my preferred solution but I have made threaded sleeves on the lathe to recover a hole back to original size from time to time.
Thread the hole a few sizes up, drill & tap a bolt in the lathe the original size and cut the threaded bit to length & lock it in with locktite sparingly. You can wind it in with a bolt/locknut screwed into the inner thread and back the locknut off and wind the insertion bolt out & stake the edge of the insert with a dot punch for a bit of extra security about backing out.

 

[hotponyshoes]

It's easy to remove a helicoil, they do a proper removal tool but just google "helicoil removal tool" to see what it looks like as it's easy to make the tool yourself

 

[MetalMonkey]

EZ-LOK inserts, I've used these before with good success to repair damaged helicoils.

 

[xstian]

Timeserts would be my preferred solution but I have made threaded sleeves on the lathe to recover a hole back to original size from time to time.
Thread the hole a few sizes up, drill & tap a bolt in the lathe the original size and cut the threaded bit to length & lock it in with locktite sparingly. You can wind it in with a bolt/locknut screwed into the inner thread and back the locknut off and wind the insertion bolt out & stake the edge of the insert with a dot punch for a bit of extra security about backing out.

That's a good idea, I might try that on the cases which are less critical.

After doing a bit more research I've found a stud kit designed for this engine M8-M7 to get over this very problem. So I think I'll got for that on the cylinder barrel and do the above with less critical studs.

Cheers for the advise everyone.

 

[jmp49]

Stud kit is better for the cylinder too, because heat kills the loctite (that's how we get them out reliably after all, heat them up and tap when hot to break the bond), and may concievably get hot enough to cause this in service.
What motor is it? some here may have crossed the issues before and have good insight that helps around the specific case in other parts of the motor. I'd guess at a vespa cylinder stud given the m7 with m8 stepped stud solution and have no experience with them, but others...

 

[xstian]

Yes, it’s a Vespa.

 

[bricol]

Loctite 620 is good for 230C - if it's running at that continuously I suspect the repair winding out might be the least of your worries.

 

[jmp49]

The readings from my race bike's superturbo engine egt sensors at WOT were 900C, and the exhaust headers logged a external temperature of 300C and the engine is air cooled. Around the hot bits I dont use loctite on studs and I include near the cylinder joint in that bit. Studs into the crankcase should never get that hot though I agree.