AJS & Matchless Owners Club

Thanks Spriddler. That is very helpful. I will go for a 3 to 4 thou clearance.

The flywheel / crankshaft has just been assembled with the new big end bearing and using no shims each side of the conrod. The end float of the con rod eye on the crank pin is about 0.020" which seems excessive. The army technical manual says that float should be less than 0.008". I notice that engines before mine (1954) had a spacer / shim each side of the conrod. I am now wondering if I have to fit these. If so does anyone know what material the are?

The flywheel / crankshaft has just been assembled with the new big end bearing and using no shims each side of the conrod. The end float of the con rod eye on the crank pin is about 0.020" which seems excessive. The army technical manual says that float should be less than 0.008". I notice that engines before mine (1954) had a spacer / shim each side of the conrod. I am now wondering if I have to fit these. If so does anyone know what material the are?

Hi Eddie, the trust washers were Bronze(?) up to around 1948 then they went to steel, I just measured the thickness of the ones below (I think they are AMC) and one is 67thou and the other 64thou, these are worn dimensions but obviously when combined far greater than your 20 thou.

EddieDay wrote: ↑Fri Mar 22, 2024 11:23 am The army technical manual says that float should be less than 0.008".

I can't decide if it's relevant (my brain is still thawing out from the bitterly cold Ardingly show so pls forgive my idle musings) but up to 1947 the t/s axle had a roller bearing. This was discontinued in '47 and replaced with a lengthened bush. Maybe the tightly fitting inner and outer races of the roller bearing (as opposed to a 'sliding' bush) limited the end float of the whole c/shaft assembly and de facto the lateral movement of the crankpin relative to the cylinder centre line such that a smaller clearance between the big end eye and flywheel inner cheeks was possible/practicable.
I've never measured the big end to flywheel gap on my singles but from memory 20 thou (i.e. 10 thou either side) doesn't seem a lot to me bearing in mind that the t/s bush will allow a lateral shift of the whole flywheel/crankshaft/crankpin assembly.
According to the Archives, Quote: 'The washers/spacers were discontinued in 1951 and the flywheels altered'.

Thanks Spriddler. Owing to the guidance in the army technical manual - max end float of the conrod on the crankpin 0.008" - I have acquired two of the bronze thrust washers shown in your photo and asked the machine shop to recess the inner cheeks of the flywheel to give a 0.004" to 0.005" clearance. I am making this up as I go along to a certain extent.

An update on the engine rebuild. The barrel was in a poor state with some broken fins and a rusty bore. The fins were repaired with fins cut from a donor iron head and brazed in place. The liner, which was standard, was bored to +0/020" to suit a +0.020" piston. Then a coat of hight temp paint was applied.

(My thanks to webmaster Eamonn who worked out why I could not upload some of my photos. The file extension (.jpg) has to be in lower case.)

Just started rebuilding the forks after new seals and bushes received from the Club spares shop. These are the sliders undergoing a leak test after fitting the damper tubes and drain bolts with new fibre washers. I thought this might be a good idea before going too much further. Just poured some oil in to see if any comes out.
A friend here had a universal engine stand so I copied it.

Nice job with the barrel Eddie. Following your project with interest.