I have just taken the heads off my track bike and discovered there seems to be a break around the edge where the o-ring goes into the waterway, I presume this isnt supposd to be there. Can this be repaired/welded and re/machined?

Do you think a new seal will hold for a track day I have booked next week?

the seal is 60mm inside diameter, anyone know if this is standard RS250 size?

Cheers

Leigh

61 x 1.9mm is the size of the RS250 inner o-ring.

Part number: 12213-ND5-000

That's the real problem with O-ringing the NSR heads... it's something I've wanted to do and thought about for a long time, but always been put off by how little material there is to machine.

I expect it can be welded and re-machined, but I bet it's been like that for a long long time! A bit like when we pull barrels off and see cracked bridges and transfer ports... you're never sure how long it's been running perfectly OK with the "damage".

Although far from ideal, I would be inclined to build up the area with a good strong epoxy; something like JB Weld, and then dress it back to shape. Really you want to take the studs out so you can work with an unbroken flat edge.

I'm a bit concerned how the outside of the water jacket seals!
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Andy.
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It looks like instant gasket to me for the outside seal, to be fair they have never had a problem just the inner has failed so I expect it should be ok! Frank Wrathall himself was supposed to of done the tuning so maybe he beleived it would be OK and maybe there was not enough meat in there to machine the outer ring?

I think I will build it back with a fresh seal and see how it goes, at least I have finally found out after all these years that it does have o-rings...it was something I really did not know for sure...and no det rings in there. How about some liquid metal to build it up? Is that like JB weld? Just something the other side of the seal for support would be good.

Tom:- I might pop by and give those spare seals of yours a go if its OK?

Cheers

When I stripped my barrels I found I had had O rings machined into the barrels as well, both inner and outer, and a head gasket was also used. The deck hieghts seemed standard.

It is worring as to how little material there is left to get a seal from the water way to the bores.

After trying to get replacment o rings to fill the grooves as I planned to use head gaskets, I bought RS250 ones. The inner was a good fit but the outer was slightly to big and too thick.

I ended up just buying off the roll o ring material and cutting it to length and superglueing them together.

This was only last week so I havent finished the build yet, so I dont know how sucessful its been, and if they will hold. I take the view that I have two chances and time will tell.
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Russ

MC21SP

Leigh, I'm sure it could be welded but I think you would find it would require re-plating afterwards.

If I was going to try the liquid metal route I would try Devcon-F. Far from perfect but better than nothing.

I personally wouldn't run it like it is even with a new O ring fitted.
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If I have to take the carbs off once more...

Cheers steve, I was hoping for some advice from you

Well the old o-ring is shot so its definately a new ring minimum, I will also get some Devcon-F and see how it goes.

If not my other options for a week friday are (in order of preference):-

1. Fit MC18 barrels, but I would probably also need to change to 030 card, change to unleaded and rejet the RS carbs as best I can...any ideas on where to start with the PJ38's?
2. Take the standard MC28 fortuna bike with the trackbike bodywork, but it will get left for dead down the straights.
3. Take the RGV250 and get left for dead everywhere!
4. Take the 500 and hope it holds together for the day as its not really been run in any anger yet.

Just had a look for Devcon-F. £40 a pot! Thats a lot for a trial.....do you think it will hold out long term?

watfordhorn wrote:
Cheers steve, I was hoping for some advice from you

I'll keep me gob shut then... despite offering the same advice some 7 hours earlier!
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Andy.
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Devcon is the bollox

It's what we use and it is really good. If the barrel is prepared properly before the devcon is put on it may never need to be repaired again.
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If I have to take the carbs off once more...

Andy, your advice is always valued (unless its general advice about MC28s specifically - then its ignored!)

As you say its probably been like this for ages so I am going to have a go of just fitting a new 0-ring for next friday (against steve's advice), and then get it done properly after.

JB weld looks spot of for my temporary fix....just ordered some as its more in my price range than Devcon-F.

Cheers for all help and advice. Fingers crossed!

watfordhorn wrote:
Andy, your advice is always valued (unless its general advice about MC28s specifically - then its ignored!)

You rarely ignore it... else where would the fun be in it?!
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Andy.
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Well, I have learnt to ignore it now

We'll see...
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Andy.
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