1954 AJS 500, tightening the pushrod locknut

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Dibnah
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1954 AJS 500, tightening the pushrod locknut

Post by Dibnah »

Evening All,

Setting the tappets using useful info found on other threads. Problems tightening the locknut on the pushrod. Is there likely to be an issue if I rotate the engine to lift the pushrod and hold the pushrod with cloth and a pair of grips?
JohnHewes
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by JohnHewes »

YES! DONT DO IT!
Grind down a spanner to make it thinner at the working end and use that.
Always check after tightening that the adjustment is still correct.
John
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Rob Harknett
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Rob Harknett »

Terry's made thin spanners that were just right. A few years back at an Aero jumble, a stall had a box full selling at 10p. The guy wondered why they were suddenly selling so well. Old thin cycle spanners can also be adapted. ( Old as they fitted cycle thread nuts ) They may be multi size ring type. No need to grind flat, just grind to make it open ended.
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Dibnah
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Dibnah »

Thanks for the replies, some poor wording on my part.

I have suitable spanners for the adjustment nut and the locknut, but the pushrod spins when I tighten the locknut. I can't see flats on the top of the pushrod (which would be logical!).
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1608
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by 1608 »

The steel top of the push-rod should have flats . It has been suggested in the past that turning the engine till push-rod contacts the rocker arm can be used to hold the push-rod still. ( I know Itma did anyway). Its not good prctice to cause any scoring of the alloy push-rod, any marks should be blended out as with scoring on con-rods. I'll stop going on now :)
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Rob Harknett
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Rob Harknett »

The lock nut should spin quite freely by hand when loosened. Having done that, adjust tappet clearance, spin the lock not down. Then the thin spanner is needed at the very bottom, while you nip up the lock nut. Re check clearance.
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Dibnah
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Dibnah »

Thanks for the replies. I've had another look with the aid of a torch, no flats visible so I wrapped some inner tube around the jaws of a small pair of grips and held the pushrod. I tried the ITMA method but the pushrod span before I had applied sufficient torque for my piece of mind. Annoying.
56G80S
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by 56G80S »

Must be strange push rods, not original or not made to anywhere near original spec.

Rob has it right, the lock nut should spin nice and freely down to where it does it's job of locking; engine warm, both valves closed TDC, nil clearance but free spin of the pushrod once adjusted.

Turn it over and check at TDC again after adjustment.

Johnny B
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Rob Harknett
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Rob Harknett »

picture of the tappet etc would help us to tell you whats wrong. If you see no flats/lock nut surely some thing is missing
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Dibnah
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Re: 1954 AJS 500, tightening the pushrod locknut

Post by Dibnah »

Thanks again for the replies, I would guess that the pushrods are non-standard. Bike is running well with plenty of compression as measured by my right foot and runs past an indicated 70 mph. On to the next problem!
Locked