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Primary Drain Bolt Stripped!

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Primary Drain Bolt Stripped!

Posted by mike_sullivan at April 15. 2017

Eee, there's always something!

Re-assembling the primary cover I discovered that the thread for the drain bolt has stripped. It looks to me as if this can be tapped out to take a slightly larger bolt - any advice on size/thread?

I plan to take the take the cover to a local machine shop Tuesday, it looks like the bore is close to vertical in the  cover so should not be too difficult to tap out.

In the meantime I've nipped the bolt up & added blue hylomar to 'glue' in place whilst I try to get Nellie restarted after her winter break.

Mike, Mk III Commando

Re: Primary Drain Bolt Stripped!

Posted by richard_payne at April 15. 2017

There is plenty of material on the Mk3 outer, but why not get them to put an insert in and make it better than new ?

A larger plug will usually have a larger head and this may make it difficult to remove with the exhausts in place.

Re: Primary Drain Bolt Stripped!

Posted by christopher_winsby at April 16. 2017

Previously mike_sullivan wrote:

Eee, there's always something!

Re-assembling the primary cover I discovered that the thread for the drain bolt has stripped. It looks to me as if this can be tapped out to take a slightly larger bolt - any advice on size/thread?

I plan to take the take the cover to a local machine shop Tuesday, it looks like the bore is close to vertical in the  cover so should not be too difficult to tap out.

In the meantime I've nipped the bolt up & added blue hylomar to 'glue' in place whilst I try to get Nellie restarted after her winter break.

Mike, Mk III Commando

Helicoil or tap 5/16 UNF. Original on MK 3 1/4UNF. If 5/16 gets stripped Use 3/8 UNF and make plug tapped with 1/4 UNF.

I use Dowty seals, only have to be nipped up to seal.

I have already done this repair for another member, taking his to 5/16 UNF. I also made a plug from a 3/8 bolt tapped 1/4 UNF to make sure it could be done ok.

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