Conversion Hairsprings to coil springs

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Marsden
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Posts: 3
Joined: Fri Oct 07, 2022 4:33 pm
Location: France

Conversion Hairsprings to coil springs

Post by Marsden »

Hi everbody.
I have a 1957 16MS with of course hairsprings.
I think that mine might be a bit feable, but new ones appear to be like gold dust.
Has anyone ever converted to coil springs and if so with which parts or even head change are involved.
Thanks for your erstwhile comments :)
SPRIDDLER
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Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Conversion Hairsprings to coil springs

Post by SPRIDDLER »

Hi and Welcome. :beer:
(Tip: Your posts will be more likely to attract targeted responses if you put them in the dedicated G 3 / Model 16 section rather than the Frequent Questions section which is intended for listing only solutions to Frequently Asked Questions, not new questions).

As a rough guide the gap (height) between the jaws of a new spring is nominally 2" and replacement is recommended at 1 11/16" (one inch and 11 sixteenths) but if it's running O.K. there's no need to replace them.........yet.

Club spares have hair spring sets made but all spares are only available to subscribing members. The club, website and spares development and sourcing are funded by members' subscriptions. Joining will be good value vs the cost of a conversion. You'll also receive the monthly Jampot magazine plus be able to view photo attachments and have full access to search the Forums and view the technical articles ;).

Membership details here:

https://www.jampot.com/membership.asp


There's a general discussion in this thread about conversion.........

viewtopic.php?p=195708&hilit=hairspring ... on#p195708
'There is a tide in the affairs of men
Which taken at the flood............'
Marsden
Member
Posts: 3
Joined: Fri Oct 07, 2022 4:33 pm
Location: France

Re: Conversion Hairsprings to coil springs

Post by Marsden »

Hi thanks for the quick reply.
Are the jaws represented by the top end of the spring and the base?
The bike was running corectly but has little compression ( at the end of a run the bike stalled and has since been difficult to start) and I have the impression of air being forced OUT of the inlet valve, despite having lapped the valves and decoking.
I am a recent club member but I had not found the springs I will look again!
Thanks again
Marsden
MatthewC
Posts: 55
Joined: Thu Sep 23, 2010 9:28 pm
Location: West Sussex UK

Re: Conversion Hairsprings to coil springs

Post by MatthewC »

I bought a conversion kit from Russell Motors for mine several years ago, no complaints from me, and it wasn't too expensive. Might be worth seeing if they still supply them.
SPRIDDLER
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Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Conversion Hairsprings to coil springs

Post by SPRIDDLER »

Marsden wrote: Tue May 30, 2023 10:38 pm
Hi thanks for the quick reply.
Are the jaws represented by the top end of the spring and the base?
Welcome to the club, Marsden.
Yes, measure the spring between the cut ends at the base and the loop at the top.
The bike was running corectly but has little compression ( at the end of a run the bike stalled and has since been difficult to start) and I have the impression of air being forced OUT of the inlet valve, despite having lapped the valves and decoking.
Are the pushrods free to turn at TDC on the compression stroke?
After lapping the valves did you invert the head and fill with petrol to check for leakage?
Did you anneal the (new or old) cyl head gasket before fitting it?

When the cyl head gets hot the valve seat insert can loosen in the head and turn, spoiling the seal. When it cools it will become secure as if there hadn't been a problem.

A rough check for compression loss......
Operate kickstart and note the compression.
Put half an oeufcup of engine oil in the bougie hole.
Replace plug and note compression.
If compression improves it's likely to be a worn bore or broken piston ring problem.
If it doesn't it's likely to be a valve sealing issue.

Are you sure the compression seems to be leaking from the inlet valve rather than the exhaust or cyl head gasket?
At first glance I doubt that it's a weak valve spring problem.

Come back with more info which may help diagnosis.
Hairpin springs gap.jpg
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'There is a tide in the affairs of men
Which taken at the flood............'
Marsden
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Posts: 3
Joined: Fri Oct 07, 2022 4:33 pm
Location: France

Re: Conversion Hairsprings to coil springs

Post by Marsden »

Thank MathewC and SPRIDDLER for your inputs

For Mathew I'll follow your adress up as a long term job.

However it was not the springs!!

After regrinding the inlet valve (whooshing from inlet on compression and could definitely feel it on my hand) could see LIGHT around the valve!!!!
So, remilled the seat and still lihgt. So we checked the valve AND it was not round!! Nearly 1/10mm at the head.
So have ordered a new valve and will fit and let you know how things go.

This is a bike that I acquired recently from a freind and which I'd used on one rally and helped to rebuild (but not the engine where only the bottom had been done).
How it got to this condition I can't imagine

All the best
Marsden
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