Fitting a new oil plug

DISCLAIMER: The modifications described in the following text are for educational purposes only. In no way do I recommend that you apply these modifications to your own motorcycle. If you do choose to go ahead and modify your motorcycle based on the information in this document you will accept all responsibility for your own actions. The author(s) of this document, and host(s) providing it for you, accept no responsibility whatsoever. If you are unqualified to make any of the changes described herein but are bent on doing the modification, seek out a knowledgeable friend or professional mechanic for assistance.

Fitting a replacement oil plug in the cylinder head

It is surprising how often these little blighters leak and start to make a mess of your engine.

Their function is to blank off the hole that would otherwise be occupied by a de-compressor mechanism. The picture below shows a decompressor fitted and I have arrowed where the cable would have attached.

Tools needed:- plain screwdriver and a large pair of pliers

Parts/supplies: New plug - p/n 90338-18067 - which looks like this:

(An alternative to the rubber plug is now available - see here.)

The symptoms of a leaking plug are obvious - a real mess and the smell of burning oil when the engine gets hot:


Use the screwdriver to prise out the leaking seal and clean around the hole:

Old and new plugs:

Squeeze the new plug in evenly. It doesn't require a great deal of force so I used a large pair of pliers with an old cloth over the jaw to protect the plug. There is a handy blanking bolt to use in this process:

Hopefully I will have a clean engine again now! New plug fitted:


Job done!

PS An alternative to the rubber plug is now available - see here.

Brian Sussex

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