stripped threads in engine for exhaust

[Siloxious]

Hello


Just now, an inner thread of the exhaust stud whole in the engine has snapped. I can move the exhaust stud freely in this hole. This sucks...

My idea was to tap a new M8 thread in the engine and try to fasten the exhaust pipe with a M8 bolt.

Does anyone have any experience with this? Do you think this would be a good idea or do you have alternatives? I already used loctite but it didn't work...


Thanks in advance!

[Trigger]

You put a time sert in to do a thread repair or helicoil it   

[McCabe-Thiele (Ted)]

The Helicoil will also return it to a M6 thread as well if you are not aware.

[deltarider]

Time sert is the best option in my experience. You could also use oversize (7mm?) ones from Hondafour.nl, but I can't find them right now on the website. You may want to contact them. https://honda4parts.nl/index.php?language=en&ceid=aa606bade50a51044ab8e895fe2bc3cd

[SumpMagnet]

For an area of high heat like an exhaust port, I'd go Timesert over Helicoil.

I have had helicoils 'unwind' themselves due to the differential expansion comared to the alloy head. More hassle than a Helicoil....but worth it in the long run

[Bryanj]

You have to be certain you have the meat for a timesert, i think they are an m10 outer thread but you need a different tap as its not the common m10

[Matt_Harrington]

Your initial thought of a larger bolt could work. You could always machine (or get machined) a stepped bolt - ie M8 for the head and then stepped down to M6 for the Flange. Just a thought

[Oddjob]

The early CB1300 SCC54 engine used stepped down exhaust studs, 8mm into the head but 7mm on the outside. They changed them to 8mm all the way through later on.

I have some somewhere if you'd like to try.

[Siloxious]

The Helicoil will also return it to a M6 thread as well if you are not aware.

Just a heads up, the helicoil worked! I stripped these threads because I thought the exhaust pipe joint should touch the block. I suddenly realised this and wow, I was annoyed with myself.

Now with the helicoils, the exhaust pipes fit nicely on the block and I haven't had any problems so far.

I'll update if the helicoils loosen when riding the bike for a bit.

Thanks everyone!