Cylinder head removal

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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Cylinder head removal

Postby Steve S » Thu May 16, 2019 8:59 am

Decided to remove the head to change the gasket in the hope of curing my top end oil leak, but got stopped when the inlet valve spring hit the frame preventing the head being lifted off.

I tried all manner of angles to pull it, but it appears I'm 5 or 6 mm in need of further clearance.

Surely you don't need to remove the spring?

Does the engine need to be dropped in the frame?

Where am I going wrong?

Steve S.
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Re: Cylinder head removal

Postby Rob Harknett » Thu May 16, 2019 9:59 am

Seems you have managed to get all the bolts out, if not get them out. You can then move the head more to get it off. You should not have to remove the springs, I'm sure you not be able to get them back on again. Ah I think I see the bolts are not all out, wriggle them out and the head should move about more to get it off.

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Re: Cylinder head removal

Postby cbranni » Thu May 16, 2019 10:07 am

I wonder if you have a 250cc frame, there is a difference in the length of the front down tube, 350 is inch longer at 7 3/4 inches the 250 is 6 3/4 inches.

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Re: Cylinder head removal

Postby Steve S » Thu May 16, 2019 11:09 am

cbranni wrote:I wonder if you have a 250cc frame, there is a difference in the length of the front down tube, 350 is inch longer at 7 3/4 inches the 250 is 6 3/4 inches.

Colin


Measuring the front down tube between the welded shoulders is 6 3/4 inches. This would also explain why there is insufficient room for a rocker box stay, Steve S.

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Re: Cylinder head removal

Postby Steve S » Thu May 16, 2019 2:04 pm

Got it off by removing the valve spring. Now new gasket and re-assembly, Steve S.

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Re: Cylinder head removal

Postby Ozmadman » Fri May 17, 2019 9:57 am

cbranni wrote:I wonder if you have a 250cc frame, there is a difference in the length of the front down tube, 350 is inch longer at 7 3/4 inches the 250 is 6 3/4 inches.

Colin
Reckon that's the answer, mine lifts off no problem
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Re: Cylinder head removal

Postby alanengineer » Fri May 17, 2019 10:05 am

somethings not right, but at least you can move on

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Re: Cylinder head removal

Postby Steve S » Thu May 23, 2019 3:37 pm

Managed to re-fit the head and rocker box and fired her up today. Short run proved no head oil leak as before.

The photo shows just how limited the clearance is. I'm resigned to learning my bike is a complete bitsa, 350 engine, 250 frame, wrong tinware.

On the plus side, I've taken off the NOS rear shocks which were correct for a 350 and refitted the original ones which means my centre stand now works without a plank of wood!

Steve S.
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Re: Cylinder head removal

Postby Martin.S » Thu May 23, 2019 9:03 pm

I gather then you don't have the head steady bracket?
Top Mount3.jpg
- it wouldn't fit any how! - you could make one to fit though.
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Re: Cylinder head removal

Postby Duncan » Thu May 23, 2019 11:14 pm

Martin.S wrote: it wouldn't fit any how! - you could make one to fit though.


A fabricated "L" shapped one like the heavyweights use may be an eaiser to fit option.

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