AJS & Matchless Owners Club

Now you're getting somewhere...

It certainly looks like oil has been leaking past the oil feed. The "damage" near the exhaust valve is just where the valve seat insert is. Maybe nothing to worry about. However, you should clean the head up and do a check to make sure the valve seat hasn't come loose (fill the exhaust port up with meths or petrol & check it doesn't leak).

Next, loosely fit the head without a gasket and measure the gap to the barrel to make sure it's pulling up OK.

Did as you suggested clanger. No fluid leak past exhaust valve. Measured head gap, bolts nipped up only, 0.65mm, 0.0256" and within a thou all round. That doesn't seem to me that like enough pull down. The composite is only about 1mm. What do you think? Oh by the way I notice you live in Chester, my place is Farndon CH3 although neither me or the G5 are there at the moment.

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I think that gap is OK. Can anyone else confirm?
My composite head gasket measures up at 1.7mm thickness - thread here: http://www.jampot.com/forum/viewtopic.p ... 99#p199002

I'd fit a new head gasket & 5th bolt. If it all pulls up OK, at least you've eliminated one potential cause...

Farndon is a nice ride out from Chester (and vice-versa). Give me shout if you're in the area!

I couldn't measure the gasket accurately but I will order new one, bolt and rear innertube. Back in a Farndon 5th August for 6 weeks, G5 is having it's summer hols in Bavaria where I spend 50% of my time. I'll see if there is a personal contact poss. with this forum and contact you then.

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So gents
G5 rescue attempt restarted. All the head and gasket (old and new) measurements are good. My attention has now been drawn to the head 5/16 BSF bolt, the new bolt does not fit in the threaded hole, some previous owner has helicoiled it and it's not our BSF bolt.
That in itself would not be a problem but the existing bolt has no markings and needs replacing, could have been locally made . It has a pitch of 1mm (BSF bolt 1.15mm) and is x 8mm. The head bares evidence of overtightening and only threads 8 turns into the hole before binding up, 30% of hole depth.

With head loosely fitted without gasket the old bolt binds up but but the head is still loose. So in conclusion I think a metric helicoil has been fitted and I think even that is now damaged.
I will visit an oldtimer bke shop tomorrow here in Germany and see how far I get.
All comments are welcomed



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Hi

It sounds like your Helicoil is either M8 25.4 TPI or 5/16" BSCY 26TPI, (BSF is 22 TPI). Try known M8, 5/16" BSCY and 5/16" BSF bolts and see which offers the best fit.

Looking down the Helicoil with a good torch will show any damage. You need to determine the current thread before trying to fix it.

Regards Mick

If it is metric and you do want to correct it then I imagine that that helcoil will need to be pulled out, drill out and retap the next size up and perhaps use brass to make up a bush with the 5/16 BSF inner thread and whatever thread you've used for the outside and Loctite the bush into the alloy. It may be easier to make up a bolt or stud to suit.

Or you may need to go down my route as described earlier in this thread if the hole in the barrel is too far gone

So Gents
I seem to be having some degree of success. The 5th bolt head to barrel is an M8 fine thread, 25tpi. New gasket, new bolt fitted and nipped up, head torqued. The 5th bolt however, binds or bottoms after 10 threads, I'm thinking the helicoil tang is obstructing, anyway head is back on.
Engine started and ran for 5mins still too much blue smoke and plug wet oily black, I decided too look elsewhere. I couldn't accept that oil was getting passed the head gasket into combustion chamber. How else then?
The inlet valve lub. Needle was worth investigating, sucking in oil along with fuel/air mix? It was only open a gnats so I closed to half a gnats, just barely open not even 1/16 turn.
Restarted and ran, a world of difference, no blue smoke, acceptable exhaust fumes from an old bike. I don't want to shout bingo but I think tomorrow I will tinker with the carb setup and apart from a gearbox that leaks like a collander driveside,kickstart and selector, I could have a result.

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vigo wrote:The 5th bolt however, binds or bottoms after 10 threads, I'm thinking the helicoil tang is obstructing

The tang is supposed to be broken off once the Helicoil is inserted - too late now, but next time the head is off.

Regards Mick