Exhaust studs keep breaking

[claude]

I have a YPVS F2 with F1 engine, 1WT frame and 31K motor, standard F2 pipes and it keeps breaking the exhaust studs. Any ideas why that could be?

A possible solution is to buy the Microns my mate is trying to flog me. Would that require rejetting?

[Tobyjugs]

Welcome to the forum.

Do you have the tie bars fitted to the engine?

[looey]

Never had that problem myself, are you sure that you're not over-tightening them ?.

They don't take too much tightening to seal on the gaskets.

I always use a second set of nuts to lock against the first, then there's no need to over-tighten to keep them from undoing.

[oldbritguy]

Welcome to the forum Claude
Another thing to check is the mounting rubbers on the exhaust hangers.
If these are solid and the engine can still flex in the rubber mounts, the studs will let go. Are you using OEM studs and not just cheap bolts?

[kostas]

Have the same problem with mine
3 studs broken this year and counting

Can’t seem to find why

[midlifecrisisrd]

I'd change the tie bars

I have a pair that the rubber dampers have gone really soft so no longer any use

Steve

[looey]

My Hybrid is forever cracking it's exhaust headers

Think mine's a combination of the wafer thin metal on the headers and not quite so much flexibility on the rear set hanger mounts as would be on standard hangers.

This winter I will either get the headers strengthened or maybe even get new pipes

My engine was completely rebuild 1,000 miles ago and had all new engine mount rubbers at the time.

[shaunthe2nd]

I had same thing and was down to a curvature in the exhaust flange on the exhaust from years of overtightening. This causes the studs to bend slightly and put them in shear. I solved by using tapered washers below the nuts.

[claude]

Thanks to all for your suggestions. I do have the tie bars fitted and their rubbers seem to be OK. I am investigating the hanger rubbers next. My local bike shop owner has worked on LCs and YPVS since they first came out and he says its always been a problem. He's now using some Suzuki studs that are 10mm internal and 8mm external thread I think. I'm leaning towards some aftermarket pipes as I know they are much lighter.

[Tobyjugs]

A very good method to combat the breaking of studs is to use longer studs and a spacer so the nut tightens up at the end of the stud. This will give the stud the ability stretch and compress a little more before breaking.

[4l04ever]

Maybe engine mounts worn, as could allow excessive movement. Easy check is to run the bike under load on a dyno and watch what is moving. The engine twists loads with no tie bars fitted.

[claude]

Thanks guys.

[bare]

Nov 17, 2018 22:06:44 GMT 1 claude said:

[/div]

A possible solution is to buy the Microns my mate is trying to flog me. Would that require rejetting?

[/quote]
Good plan... Microns use slider/slip joint connections, so there are Much fewer, if any Bolted rigid ex flange problems.
And No... they will not normally require a rejet.

[steven]

Nov 18, 2018 19:50:26 GMT 1 claude said:

Thanks to all for your suggestions. I do have the tie bars fitted and their rubbers seem to be OK. I am investigating the hanger rubbers next. My local bike shop owner has worked on LCs and YPVS since they first came out and he says its always been a problem. He's now using some Suzuki studs that are 10mm internal and 8mm external thread I think. I'm leaning towards some aftermarket pipes as I know they are much lighter.

Hi Claude,
If your bike shop man has worked on LC,s since they came out, he should be aware of the "Exhaust Hanger Top Hat" mod.
Im sure the origonal exhaust studs were "waisted" or "undercut" which will allow them to stretch, rather than shear/break, but im sure lots of us DONT use waisted/undercut studs, with no probs.
The thinking behind the exhaust hanger Top Hat mod, is to allow the pipes to move more with the engine, rather than be rigidly clamped to the hanger.
Regards,
Steven.
rdlccrazy.proboards.com/thread/22911/cracked-exhaust