AJS & Matchless Owners Club

Hello . I am struggling with removing these trunnions out of the Conrods. Please any advise how to do that and not damage the Conrods ?

First question is why are you wishing to remove them? If you really have to then drill out the tiny split pin in the centre of the trunnion before trying to unscrew the stud or you'll tear out the thread. Once you've undone the stud the trunnion should just slide out.

I guess that for people brought up to replace big end bolts automatically on other machinery for fear of their having stretched, it's counter-intuitive NOT to replace the studs at least Rob.
Which of course gets us into knocking out the pins in the trunnions etc. I've replaced them once or twice in half a century nearly, but only when rebuilding engines after major mishaps. Otherwise I've left well alone, just replacing the nuts.
What do other people do? (What should we do, ideally?)
Are the trunnions actually available these days (can't remember from whom I obtained the ones I have had)?
Do the studs have rolled threads?

So many questions, probably just paranoia as I have never had one of these rods let go myself, whatever people say about the design being the 'wrong way about' in terms of the stresses. But in all cases, getting the big end eyes checked for 'round' and rectified if necessary, is a must.

Trunnions and studs will be available from spares. I have only ever had to change 2 studs ever in close to 40 yrs. I've got 10 sets of rods at the engineers being checked for ovality and bushing small end if required. Usually it's only the 650's that run the small end regardless, many many 500's I've only had bushed a couple due to oil starvation!

I decided to keep the studs in conrods as they are not damaged . I thought first that they need to be replaced automaticly when the engine is rebuild.

Exactly what I thought the first time I had one of these apart, as I was also brought up (by my Dad who did military aircraft) to believe you changed these things as a matter of course!

If it's any comfort, the Model 20 I was worrying about back then is still running fine, with hundreds of thousands of kilometres behind it, using the same rods it had when I bought it in 1976. I did replace the trunnions and studs after a crankshaft breakage, when I had the rods checked for straight, round, and crack-tested - and they've done nearly 40 years since.
I replaced another set of studs and trunnions and did the same checks to rods that were unknown to me before putting them into my spare 500cc engine.
So, same as what ajscomboman is doing with his stock basically. Must be right then! I have never had to bush a small end on a 500 either - and my 650 runs a Club crankshaft and expensive new rods which I hope will last longer than me. When either of my two 500 engines have been apart subsequently (which is very rarely) I have refitted the rods and the rest of it just using new nuts and following the 'book' for torque settings. Very, very reliable & long-lasting motors in my experience - which is why I have kept the same bike for 47 years, even if it looks pretty horrible, and is why use it more than any other. Best £75 I ever spent!