Exhaust studs just spin

[Ebuddy]

In my experience, there are 3 things that you can do:

1. 1. Switch to bolts/lock washers that are 1 size larger than the studs. This is the least desirable solution however and there are risks. It is the cheapest however. Some folks have been able to have this solution go a long way. I've done it successfully, but only on a scoot that could die tomorrow and I wouldn't care. Suckers held for a couple thousand miles before I got rid of the scoot.
2. 2. Use heli-coils (or similar) as directed. I've actually only had only 50/50 success (1 for 2) with this method but the failure was the first attempt so I could chalk it up to my error/inexperience.
3. 3. The new head solution is probably the best, especially if the scoot has a few thousand miles on it. Gives you a chance to look at everything and get an idea if something else might be going bad.

[blueboy5000]

The studs are pretty crappy stock. I always drill out the stud holes and tap to the next size up and install quality bigger studs from NAPA.

I disagree with Helicoil for any exhaust repair, and for that matter, any repair at all.

In fact, I have never used a helicoil on anything related to a) aluminium or b) a gy6.

I cannot recommend against Helicoil anymore than I do. Just drill and tap.

[Shadowfire]

A heli-coil is actually a GOOD thing in a soft substance like aluminum or plastic. You can torque smaller bolts down harder with a helicoil, because the weakest link isn't, say, an M8 thread in the aluminum head... it's now an 9.5mm diameter thread in aluminum, which has more surface area and can withstand greater forces.

[blueboy5000]

No. That's not how heli-coil works. It's not going to allow better torque of studs, as it's not very tightly attached to the bored hole you have to drill to insert the heli-coil.

Heli-coil falls under the category of compression fittings: absolute junk that actually takes longer and costs more than doing it the right way.

It is always better to drill a stripped thread one size larger. New threads are always preferable to inserts, ESPECIALLY on exhaust, where sealing is critical.