Worn exhaust bolt threads

[salty_monk]

My 750 has worn header threads. Not uncommon when the pipe has been off for a lot of oil changes.

Thus leads to bolts working loose.

I need to helicoil a couple but don't want to do them all if I don't have to.

Any ideas on what to do with the worn but still there ones?

I'm going to put studs in but I want them to stay put....

Threadlock, high temp silicon maybe??

 

[rapidray]

Dan, studs with red Loctite will work well. Green Loctite if you NEVER want to be able to get the studs back out! (I don't recommend green!) Ray.

 

[Nessism]

Loctited studs sound like a great way to scrape the crap out of the frame if you ever have to do an engine change. Use caution.

 

[salty_monk]

Ray,

How do you get them out again without breaking them off once red loctited? Heat to Cherry red to break down the loctite or something?

Dan

 

[hampshirehog]

The red stuff aint so bad - heat them with a blowtorch and they'll undo. The green stuff is evil - you'll only get them out with a hammer and chisel (or small explosive charge). Sets like glass.

 

[salty_monk]

I remember this is how we used to get the red stuff out on press tools when I worked at a metal bashing factory...

Are we saying that blue loctite is no good for these?

Dan

 

[hampshirehog]

I
Are we saying that blue loctite is no good for these?

Correct - it's a tad too warm there for blue.

 

[salty_monk]

I'll have to check some datasheets... I remember there being a couple of grades of Red with different temp tolerances.

Have to check out the one that I have.

Dan

 

[hampshirehog]

271 is the one you want:

http://www.loctiteproducts.com/tds/T_LKR_RED_tds.pdf

 

[BadBillyB]

Hey there Dan, I might be the lone wolf on this one, but I would not use any loctite on the exhaust studs. Instead, I would measure the depth of the threads and get the appropriate length studs. They should thread almost all the way to the back, and stop when the shoulder (unthreaded portion) wedges into the threads. I would instead use anti-seize on the threads so they can come out later if necessary. The tension from the exhaust flange bending should keep the nuts from coming loose. If you use loctite, put it on the nut.....If the threads in the back of the holes look good, you may not have to heli-coil them.....My drag racing buddies used to say, theres a right way, theres a wrong way and there is Billy's way.......Billy

 

[salty_monk]

Billy,

I think these are worn beyond that point as longer bolts have already been used in them (with copious anti seize of the copper variety the last time around when I re-fitted it)... plus the bending of the exhaust flange didn't stop them from backing off last time.

Maybe I'll try it & see. Thanks for thoughts. You're not a lone wolf, a lot of people don't recommend Loctite on the studs as seen in a prior thread but nobody has got any really effective alternate suggestions.

Dan

 

[blowerbike]

run a 5/16x18 tap in your holes and start over.
good ole US of A bolts.

 

[Hammered]

You can use the heavier stuff if you dont mind using a little chemical to loosen it for the wrench. Methylene chloride, which is in common paint remover, will loosen all thread lockers if allowed to soak awhile. It will act like a penetrating oil in the sense that as it breaks down the bond, it will continue to react with the thread locker untill you can wrench it off. Just spray and let sit a few hours, then repeat til it breaks free.

 

[salty_monk]

That's good info. Not heard that before, only heat.

Blowerbike - also good info, will research that thread.... any need to drill first? (I think they are English bolts not USA )

Dan

 

[blowerbike]

That's good info. Not heard that before, only heat.

Blowerbike - also good info, will research that thread.... any need to drill first? (I think they are English bolts not USA )

Dan

whether it be right(correct % of threads achieved) or wrong.
i have ran a 5/16x18 flat tap into exhaust threads and quickly fixed stripped threads before.
no drilling just plenty of lube and blowing the chips off/out.

 

[salty_monk]

Tapping drill size is just under 7mm (17/24) I would think a 3/8 -16 or 3/8 24 tap would work but may require some drilling...

 

[BadBillyB]

Tapping drill size is just under 7mm (17/24) I would think a 3/8 -16 or 3/8 24 tap would work but may require some drilling...

Oops, I think you meant 17/64th's....This is the proper drill size for a 5/16" tap....If you put 8x1.25 heli-coils in, you need a 21/64th's drill bit. I personally would put heli-coils in, providing there is enough "meat" around the hole. Castings vary somewhat. Are you sure the threads way up in the hole are bad ???....I just rough measured the depth at around 1"....Thats pretty deep....Try a really long 8x1.25mm bolt and see if it gets tight when bottomed in the hole......Billy

 

[salty_monk]

You're right Billy... my typo, thanks