Valve springs

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
mikeydpippin
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Valve springs

Post by mikeydpippin »

Changed my cylinder head for a spare I had, but left the springs on the spare.
Took 57 g3 for a run tonight and the inlet pushrod jumped off the rocker cam, Had a bit of a job to get cam to drop down onto pushrod, I'm guessing either a weak spring or incorrect setting of pushrod ( did check pushrods when cold)
How do I check if any of the springs I have in my stock have weakened, or is it a case of buying a replacement set.
Mike
SPRIDDLER
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Re: Valve springs

Post by SPRIDDLER »

Hairpin spring height between the jaws: 2 in. Replace if less than 1 11/16 in

See pages 7 and 12 here:

http://www.jampot.com/article_read.asp?id=161


The cause is possibly a momentary sticking of the inlet valve..... :?
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Which taken at the flood............'
56G80S
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Re: Valve springs

Post by 56G80S »

I checked my springs before re-fitting them after getting re-worked head back from T&L. They were not far inside the spring wear guidance but I've had no problems.

There've been quite a few threads on this topic, including taking the option to use coil springs. I think I took my guidance from the Army service manual?

I have a couple of used sets of springs, one set from the 14CSR and another for the G80S when it looks like I replaced them too early!

At the recent IJR I was being advised that if using the Matchless for the long "high speed" (ha ha) usage that is required for attending far away events it would be better to set the tappets as per manual and than drop back one flat. Certainly, I wouldn't expect that setting cold would have the effect you experienced on a short run.

In other words, Sprid is probably right!

Johnny B
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clive
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Re: Valve springs

Post by clive »

I would agree with Spriddler, first thing I would look at is the inlet valve sticking. Sounds as though you used a head with the valves in place and I wonder if there is a problem with the oil supply to the inlet valve. Unless you were really gunning it, (unlikely on a G3!) sufficient to cause valve bounce I doubt either springs or tappet adjustment would cause a pushrod to jump off. I have once had it happen but it was because I did not correctly tighten the lock nut on the pushrod.
clive
if it ain't broke don't fix
SPRIDDLER
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Re: Valve springs

Post by SPRIDDLER »

mikeydpippin wrote:........the inlet pushrod jumped off the rocker cam, Had a bit of a job to get cam to drop down onto pushrod,
Mike. At risk of appearing pedantic but to avoid any confusion I'm assuming your reference to 'rocker cam' is in fact referring to the rocker arm in the rocker box at the top of the pushrod. The 'cam' is part of the valve gearwheel at the bottom of the pushrod in the timing case.
I doubt that even a weak spring would fail to return a valve unless you were revving really high or the valve was binding in the guide or the rocker shaft was seizing in its bushes (unlikely). If the head had been 'resting' for some time it could be an insufficient or clogged oil supply to the inlet valve stem.
You may have set the pushrod to rocker gap too large and the pushrod top became dislodged from the arm.
I've never had reason to measure hairpin valve spring wear/weakness on the basis of 'If it 'aint broke....' so forth, and never had any problems.

Do you know why the 'spare' head was removed previously? Maybe because a valve was sticking..... :twisted:
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Rob Harknett
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Re: Valve springs

Post by Rob Harknett »

Could be a lot of fussing here as to what the problem may be, which may be due to an error. Was the tappet locked up properly. Was the valve fully closed. Was the push rod properly seated. When doing adjustment, check 2/3 times, Each check after you have turned the engine over a few times, making sure both valves are fully closed before checking.
SPRIDDLER
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Re: Valve springs

Post by SPRIDDLER »

Rob Harknett wrote:Could be a lot of fussing here as to what the problem may be, ...
You're quite right, Rob, but it reminded me of my foreman Alan 'Sniffer' Scobey (who lost the tip his nose when his tie caught in a fanbelt) who ran a G3LS and was always having difficulty adjusting the pushrod clearance.
He used to tell me off for waffling during my apprenticeship days in Brighton from 1960 (May 23rd) to 1965 (June 9th) when I used to ride my 1952 (1953 model) Bantam Deluxe (the one with plunger rear suspension) to work at Moore's Garage, the Bentley and Jaguar main dealer which used to be opposite The Running Horse pub in Russell Square on the corner of what was, what is now, before they knocked it all down to build the shopping centre.
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mikeydpippin
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Re: Valve springs

Post by mikeydpippin »

Many Thanks for all the helpful replies and yes Nev, it was the rocker arm that came off the pushrod, and I WAS giving the bike "welly" as I was nearing a very steep hill climb.
I,m not going to strip down the top end as yet, I,m going to reset the tappets and see what happens by taking the same run again...
Maybe I didn't set the tappets correctly and lock them as I should have.
It seems everytime I go out on these bikes without tools I break down, ive now ordered a toolroll...
I,m trying to get the bike ready for the Jampot, almost all leaks now repaired, (I wont mention the chaincase leak)
I don't want to be the one in the rear view mirrors sat on the side of the road...on the first rideout :rofl: .
Mike
Mick D
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Re: Valve springs

Post by Mick D »

Hi Mike
mikeydpippin wrote:Had a bit of a job to get cam to drop down onto pushrod
If by this you mean the rocker arm is stiff to pivot, that's your problem, a weak spring will not help the situation but it's not the prime cause to be investigated.

If the rocker arm is free I'd suggest removing the valve and inspecting the shaft for scores or slight bend.

Not so sure I subscribe to poor push rod adjustment as to be this far out I don't think the engine would run and if it did, only for a few seconds - loose push rod adjuster would be easily detected after the event and would additionally probably result in a bent adjuster thread.

Regards Mick
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Rob Harknett
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Re: Valve springs

Post by Rob Harknett »

Sounds like it was a tappet fault as to why the bike threw the push rod. Come loose or not adjusted correctly with valve fully closed. Kicking the bike over a few time rechecking will discover adjustment fault. As it took time, sounds like it was not locked up. This can be tricky as you do need a very thin spanner on the bottom nut, to get on the top to lock it up tight. Trying with ordinary open end spanners you cannot get on good, So the spanner slips off, not getting the tappet locked tight.
Locked