A forum for owners of Yamaha TTR250 trail and enduro bikes!

mariaKaigiwnis · Member

Exhaust stud threading issue

mossproof · Super Guru

Helicoil kits like that will work. Try to find a kit that has the thread inserts as close to the same length as the depth of the hole as possible. Some cheap kits have very short inserts, and with the exhaust studs, you need as much thread as possible because the aluminium is quite weak.

Mortown · Member

In the same light, is there any advice on fitting new exhaust studs?

There doesn't seem to be a specified torque, so I'm thinking dry stud, no thread locker, and probably around 20Nm.

Does anyone have a winning formula?

Nev · Veteran Member

I had the exact same issue on my exhaust- kept coming loose so installed new studs that immediately pulled out the threads when any torque was applied! Here's me picking the threads out with a wood screw...

I used an M8 Draper helicoil kit from everyone's least favourite but most convenient online mega retailer. Here's a quick step by step guide of how I fixed mine;

Get a helicoil kit (link) that contains the correct size drill and tap, and the tool to install the helicoil itself.
Remove the exhaust and stud, clean out any gunk or old thread from the hole.
Measure the depth of the current stud hole. As it's a very sensitive place, you really don't want to be drilling through into an oil gallery so It's important you don't drill it too deep! Once you know how deep the hole is, measure the same depth on your drill bit and mark it with a loop of tape- this way there's no chance of you going too deep and doing some damage. The aluminium is really soft so you'll have to be careful not to let it go too deep.
Drill your stud hole to the required depth, then make sure there's no leftover metal in the hole.
Mark your tap to the same depth as your drill bit so you know how far down you can take it. Spin the tap in, taking care to keep it straight. You can wind it in/out if it feels to be getting stiff. If you've got some, use some cutting and tapping fluid to keep it nicely lubricated and make the cut as clean as possible. WD40 will also work if that's what you've got to hand.
Once your hole is tapped, it's time to install the helicoil. You can set the depth with the collar on the helicoil winding in tool, but you can do it by eye- wind it in until its flush with the surface.
Last step is to knock off the tail of the helicoil with the flat punch and hammer. Make sure you get the end of it out of the hole when you've done it.
Wind in your new stud! The exhaust stud should now be stronger than ever before!

If you've never done a helicoil before, it's worth practicing or watching a video on youtube first to get your eye in!

mariaKaigiwnis · Member

Woww! Thank you so much for such a detailed replay, i really appreciate it!! I have never done this before indeed, but it does not seem super hard if you are careful. So for the threading, do you recall size and pitch that you used? From your answer i suppose that an M8 threading fits the stud, and for the pitch is it 1.25? I will try to measure it myself but if you already know it would be very helpful, thanks a lot again!

Nev · Veteran Member

Hello! Yes, the exhaust studs are M8x1.25, which is just regular M8. The tap size for the helicoil itself is specific to the OD of the thread insert and is obviously bigger than M8. Any of the helicoil kits that include a drill bit and tap will be perfect for what you need. Like this one: www.amazon.co.uk/Draper-Expert-Metric-Thread-Repair/dp/B008YFZ814