Ossa Mar Front Pipe

[martin 305]

Hi there me again just a small problem this time ! I cant seem to get the locking ring on the front pipe to stay in place on my 1974 MAR after a ride of about an hour it comes loose . also i have no copper gasket between front pipe and cylinder , is this normal? so my question is should i loctite it ?? and fit a gasket. Other than that its ready to go crank seals, primary chain, and all case oil seals done. new bars levers mud gaurds looks great. i am going to have a go at posting some pics. cheers martin

[woody]

You have to be very careful with the exhaust locking ring as the thread is very fine and can easily get damaged if the ring comes loose and chatters around. Eventually the threads will strip, either from the chattering or when you're tightening it after it's come loose for the umpteenth time. It's an engineering job to repair with a new insert or oversized thread and new ring, so to be avoided at all costs.

First off, clean all of the crap and crud from the threads on the ring and in the cylinder if you haven't already. Aerosol brake cleaner and a small wire brush works well. Get all the threads perfectly clean. There should be a gasket between the pipe and the cylinder. A Yamaha TY fibre gasket can be made to fit or Dave Renham at Bultaco UK may have a copper one for the MAR - this will be better than the Yam one as it isn't so thick and you need to get the ring to screw right in to use as many of the threads as possible, again to minimise the chance of stripping them.

Use a proper C spanner on it when tightening - avoid the hammer and chisel method to turn it. Make sure it doesn't cross thread which it can easily do. Avoid really lamping it up, it needs to be tight obviously but don't overdo it as if the threads have had their edges taken off it is easy to go one tweak too many and strip what's left - trust me, I know.... When tight you can use locking wire or a spring from the ring to the left side front sumpguard bracket to stop it rotating undone. Just drill a small hole in the bracket to attach the wire/spring.

Personally, I'd avoid using loctite as it could be a real bugger to undo the next time you need to. Providing the threads are ok and cleaned up before fitting you shouldn't need it, it should stay tight.

[tony283]

Looks like Woody has the perfect answer. It was a constant problem but as Woody says get the correct "C" spanner and when suff tight wire lock it.

Tony

[motovintage]

I like the spring idea, used the same set up on my buddies cappra

[martin 305]

Thanks for your help Woody .I have got a gasket on the way from steve sell, also base and head gaskets so i will strip the top end and then have a good look at it all and if it needs doing i will get it blasted then re threaded . Thats a great idea with the wire/springi will use that for sure. cheers martin