replacement Bolt for esxaust

[Ruffus]

@ashrauth,
usually a stud, when it gets loose, does not destroy the thread in which it's located at.
The mufflers movement does.
However there is a reason why it got lost.
Mostly by overtightening. Then there might be some gunk or even a part of your old stud in there.
 
So, pry carefully with a small pointed tool to terminate how deep the thread really is. Compare depht with new stud. The shorter end goes into your cylinderhead.
Try now with a normal (softmetal) 8 mm bolt tenderly to log out what's going on there.
Keep in mind, a cylinder head is expensive.

Once you are sure the bore is deep enough to house your new stud, use your tap and tie set to
re-cut your thread.
Your thread cutter will be pointed, so it will NOT cut your new thread until the end.
 You have to be very careful not to shear out your newly cutted thread.

[aschrauth]

@ashrauth,
usually a stud, when it gets loose, does not destroy the thread in which it's located at.
The mufflers movement does.
However there is a reason why it got lost.
Mostly by overtightening. Then there might be some gunk or even a part of your old stud in there.
 
So, pry carefully with a small pointed tool to terminate how deep the thread really is. Compare depht with new stud. The shorter end goes into your cylinderhead.
Try now with a normal (softmetal) 8 mm bolt tenderly to log out what's going on there.
Keep in mind, a cylinder head is expensive.

Once you are sure the bore is deep enough to house your new stud, use your tap and tie set to
re-cut your thread.
Your thread cutter will be pointed, so it will NOT cut your new thread until the end.
 You have to be very careful not to shear out your newly cutted thread.

I'm not sure how it happened. I have installed numeroous helicoil inserts and normally have good results. Trick is to use lubricant and have patience.

[CROSSBOLT]

I'm not sure how it happened. I have installed numeroous helicoil inserts and normally have good results. Trick is to use lubricant and have patience.

My big problem with Helicoil and similar is the drill bit hogging into the hole too fast. So adopted modifying the special tap drill by grinding the cutting edge to a smaller rake. More like a scraper and less like a chisel. Works on drilling plexiglas, too!

[Ruffus]

Ah okay, didn't know you have already experience with helicoil or similar. 👍

[JJJoseph]

I wanted to use long acorn nuts but I cannot find any retailer that sells them in 8mm size

You won't find these at Home Depot!  Learn to find your scooter parts online, they're there and not difficult to find. This is from Amazon, nuts, bolts, gaskets, etc, all for $9.95:

https://www.amazon.com/1PZ-EBG-001-Scooters-Sandrail-Coolster/dp/B0777JNVKC

[Ruffus]

@JJJ, very good source.
But this studs are 6mm pieces  (pls see screenshot from this offer) and can't be used on our motors.

[aschrauth]

You won't find these at Home Depot!  Learn to find your scooter parts online, they're there and not difficult to find. This is from Amazon, nuts, bolts, gaskets, etc, all for $9.95:

https://www.amazon.com/1PZ-EBG-001-Scooters-Sandrail-Coolster/dp/B0777JNVKC

Bought one of those and had to take it back to Amazon. Not the right size, the bolts on the head are 8mm.

[JJJoseph]

I wanted to use long acorn nuts but I cannot find any retailer that sells them in 8mm size

You didn't say what machine you're working on, so we readers are mostly guessing at what might work.  Almost all scooters use the 6mm bolts, so if your machine is 8mm, you could contact the maker and get the factory bolts?

[Ruffus]

Pls see..
https://www.kymcoforum.com/index.php?topic=31668.msg221737#msg221737

[JJJoseph]

Pls see . . .

LOL! Now that we've circled around the the beginning again, can we assume that we've found useful solutions to this problem?

[aschrauth]

I have already fixed the issue. The studs are 8mm. Bought an 8mms helicoil kit and tapped threads and reinstalled new hardware. As far as I'm concerned I shouldn't have a problem with just using bolts to hold the exaust.

[Ruffus]

@aschrauth good to read you solved.
 And yes, using 8mm bolts of any quality would be a solution, but a temporary one only.
Using studs on nearly any motor seen has several reasons.
- thermal stress is less on studs
- all exhaust studs or bolts harden out by time
- it's way cheaper /easier to remove a broken stud than bolt which shears nearly always even with surface
- studs have a non thread part which allows the muffler flange to "vibrate" a little to avoid greater damage on an expensive silencer.

[aschrauth]

@aschrauth good to read you solved.
 And yes, using 8mm bolts of any quality would be a solution, but a temporary one only.
Using studs on nearly any motor seen has several reasons.
- thermal stress is less on studs
- all exhaust studs or bolts harden out by time
- it's way cheaper /easier to remove a broken stud than bolt which shears nearly always even with surface
- studs have a non thread part which allows the muffler flange to "vibrate" a little to avoid greater damage on an expensive silencer.

I plan on using the 8mm Nuts temporarily until I can order some longer ones. Went to my local Lowes and all they did not have any metric size coupling nuts. I might have to get some from amazon.

[aschrauth]

Here are some pictures of the repair if you all are interested. Upper left hole is the one that is repaired with the helicoil.


file:///C:/Users/alexs/Desktop/IMG_20211003_141913.jpg

[CROSSBOLT]

Here are some pictures of the repair if you all are interested. Upper left hole is the one that is repaired with the helicoil.


file:///C:/Users/alexs/Desktop/IMG_20211003_141913.jpg

Link is inop...