head bolt

Luckily this helicoil was at the top of the hole . So as BigBill had posted , I used a pick , unseated enough of the top thread to be able to grap the coil and turn it out . Mine was close enough that I could grab it with a pair of diagonal pliers and turn it out just like unscrewing a bolt . When turning it the coil gets smaller releasing tension on the side of the hole . Sorry , I removed helicoil before seeing the request for pictures . I need to figure out how to attach pictures to the thread . I will work on that too . But I do see where a helicoil installed down in the hole would be a lot more frustrating to remove than this one was . Whatever my solution end up to be , I will take pictures and try to post those .

I've removed many helicoils that were installed wrong and crossed threaded. I repaired a few in my lifetime. I've also worked with the threaded inserts too. I've installed threaded plugs and redrilled and tapped new threaded holes too. I was the go to guy for doing repairs to large machined parts that had many hours of previous machining done to them. There was so much time and cost put into them they couldn't scrap them.

With the 6mm threads on the exhaust ports I was repairing them using the 7mm screws on the older Suzuki ts bikes. I'm sure it will work with any 6mm hole as a fix. By the time we drill and tap for a 6mm hole it's 7mm anyway. On my last job I setup the metric hardware when our over seas companies are metric we went metric. While the 7mm isn't that popular or widely used its a fix for stripped 6mm holes. Just make sure you can get the 7mm screws they were hard to get on my last order. The metric system has the thread size closer together than our inch system. Just one more thing in a pinch to remember.

I like to keep it all metric as much as possible.

for sure, nothing worse than standard on a metric machine or vice versa..

I agree 100% . I believe the original bolt was m8 x 1.25 , the outside of the old removed helicoin is 9.85mm and bore or the hole is measuring 8.95mm and is right against the lip of the sleave . So to my thinking I have damage threads just under 10 mm in diameter, how big would I have to open it up to get good solid metal ? Yes that is another option but unless I grind a little on the outside of the sleave the hole may have to be offset . Doable , yes . Just not sure if I want to go there yet . I have a friend with a m8 x 1.25 time sert kit ,want to check that out first . I'm thinking that may be my best solution but need to see if we have the room with the sleave right next to the hole .

As far as standard on metric , I am going to leave the bolt on the intake side standard since right now it's solid and don't want to create an additional problem . But if that one fails I should already have a workable solution .

A larger threaded rod could be used. Offset the hole and drill and tap it for the larger threaded rod. Loctite the threaded rod in the hole. Cut it off flush with the surface. File it smooth. Put the head on the cylinder put in the rear bolt. Put in bolts or studs to locate the head on the cylinder. Now transfer the hole in the head to the block. Then drill and tap it to 8mm.

A automotive machine shop could do this.

Or go with the threaded insert if there's room

That could work also , thank you .

Why don't you drill right down through with a 6.8mm drill until you break into the exhaust and inlet chambers. Then tap the hole M8 all the way through. Drop the head on and put in a bolt that comes just short of poking into the inlet / exhaust.

This way you should be able to get 3 x 8mm diameter (24mm - the optimum thread length) of good tapped hole.

The M8 head bolts should always be re-torqued after 1 hour as they will have come loose.

Andy

First I want to thank everyone for their responses. I went with a time sert for the repair and it looks like it may be the solution . It went in easy and then tightened up good . It was installed with red loctite , green is recommended but only had red . Let it set for a day and installed the head . The bolt torqued down and felt solid . The real test will be after I run the bike and re-torqued the head bolts . I did take pictures but having issues getting them on this thread . The time sert installs like a helicoil except that the head is recessed and the bottom expands to bite into the hole .

Sounds great glad you saved it.

Yeah those time-serts are pretty amazing. I used one long ago to fix a stripped head bolt thread on a 454 Chevy block and to my surprise the 75 lbs. of torque was not a problem. The block was cast iron but I don't see you having a problem with it staying put in your aluminum or magnesium cylinder, whichever it is.

As I understand the green locktite is a high heat product compared to the red but I think the locktite in this case is more of a second line of defense against the time-sert working loose.

Good job!

If you have any problem if you ever remove the head and it comes out just stake it after you reinstall it. Stake= prick punch were the threads meet on the insert to the cylinder. This indentation won't allow the insert to turn.

Don't worry just some future notes. With My luck everything happens.

Again just want to thank everyone for their input !