Helicoil

Matt Permahos /

I stripped the thread on my crankcase for my cylinder stud on my tomos a35. Is it easy to install a helicoil. Thanks

Re: Helicoil

Matt Permahos /

Also, does anybody know what size helicoil.

Re: Helicoil

Ben Van Zoest /

Yes, it's is. However you will need to enlarge the hole and tap to the bolt size you took out OR if there is not enough metal to do that consider a smaller dia. high strenght bolt w/ matching helicoil. You best do a look-up in helicoil specs.

Re: Helicoil

Jake Van Order /

Last summer I stripped out my sparkplug threads on a rare Sachs cylinder. Mind you, the Sachs cylinder is both head and cylinder in one piece so it wasn't just a simple matter of replacing the head. After getting some advice, I decided that the helicoil was the way to go. I went to pepboys and bought the kit specifically for spark plugs. Not being too knowledgable, I did a poor job of tapping out the old thread. Come to think of it, I didn't even use lubrication. Needless to say, it turned out terrible. The helicoil held tighter to the spark plug than the cylinder and although it still ran, it did so poorly.

My advice? Unless you are a tap and die expert, just shell out some money and take it to a machinist or a mechanic. They will do it right and you won't have any worries as to the integrety of the job. I recently had a friend take said screwed up cylinder to his dad who is a machinist. I hope that the cylinder can still be recovered. We'll see.

--jake

Helicoil

It's easy. You take a cylinder stud to an auto shop that carries helicoil kits and say 'find me a helicoil kit for this size bolt'. They'll find you one. You go back home, use the drill bit they gave you and drill out your stripped threads to the next size up. Then use cutting oil and tap new threads with the tap that they gave you. Screw till you hit some resistance, go half a turn, then back all the way out. Repeat until hole is completely tapped, cleaning the tap of metal shavings at each backout. Put some Loctite on the helicoil insert (you'll need 2) and screw the first in. Screw the second in, then cut it off where it sticks out. Break off the tabs using a thin rod.

Step 6: Fixed!

Re: Helicoil

Ben Van Zoest /

Congrats Matt!

Re: Helicoil

i did this same thing on my Motobecane, stripped out the bolt thread from the case. I went searching for a helicoil, only to find that it didn't exist. I needed a 7mmx125 thread. If anyone can think of a way to fix this without a helicoil, i'm all ears.

Re: Helicoil

How bad did you strip it? have you tried just running a die down the threads, to clean them up? Helicoils arent to bad to install, just take your time.

-chris

Re: Helicoil

not a lot of choices..

drill the head's bolt hole out to maybe 8 or 9 mm and then re-thread the base hole appropriately.

might think about doing all 4 bolts since this will avoid confusion in the future.

Re: Helicoil

I would try the helicoil first. With the helicoil you will be able to use tomos studs, if you drill it out to the next size you will have to find some other studs.

-chris

Re: Helicoil

yeah.. but bret says..

_ stripped out the bolt thread from the case. I went searching for a helicoil, only to find that it didn’t exist. _

Re: Helicoil

But that was for a Motobecane, which are infamous for having non-standard parts and configurations.

Re: Helicoil

don't get me wrong..i do agree with you.. If a helicoil is available, certainly use it.

if it's some weirdness on a motobecane and no helicoil is available, then you gotta do what you gotta do.

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