AJS & Matchless Owners Club

just been involved with investigating a tight engine, after complete engine strip I found roller main outer race was too wide and rubbing on crank bob weights have now ordered rls 12 1/2 , had loads of issues with oiling and very low o/p when hot, going to mod pump to seal spindles on h/p pump, also o ring seal oil way into center web. also going to fit lipped oil seal to crank on drive side. any body out there had similar problems

All sounds like a good idea. But, are you sure the old bearing was the wrong size or is the shoulder on the crank shaft that bears against the inner race ( of the main bearing ) missing or worn down! Just a thought.

I cannot believe you would have a bearing 'just a bit too wide'. They would not make one. Are you sure it is fully home in the cases? The other thing to examine is the centre bearing 'thrust washers', are they correct?
Most of the mods you propose are for combatting wet sumping, I don't think they'll improve low oil pressure when warm. These engines will show low oil pressure when hot, that's why they no longer fit gauges, stops people worrying themselves.

thanks for reply , been all round houses on this one.have miced and measured thrusts and faces on crank all good there! bearing outers do protrude some what from crank case bearing housing and are only held in by 3 nibs, not very good for security, the bearings I removed where CR1 11 a nandge wider, may be using bearing fit and grinding 20 thou from outer race will help. any body ever built twin with straight ball bearings instead of rollers?

Brian

The crank thrusts on the centre web hence the use of rollers that can self adjust, I do not think that ball bearings could accommodate that unless they were a loose fit in the shafts which would not be healthy for the engine.

i am still not happy about security of outer race in crank case, any thoughts on improving this?

As an option, you could drill and bolt through the crankcase if you wish.

I haven't done this myself but seen it and I have attached a picture to show you. The bolts appear to have a particular form on the internal face... a circular thin flat face. I don't know what they are but the bearings also need grinding to provide the same shaped register for the bolt to hold it and stop lateral and circular movement.

This would mean modification of the chain case to accommodate the bolt on the drive side bearing... and I suspect some case on seal to avoid oil leaks on both. I have no idea whether this is a common modification or even desirable and make no recommendation... others can comment.

thanks for that john, what I did in the end was to grind outer race down to 16 mm wide so when it was put into the crank case I could get a decent stake on it in three places. this also fixed the problem of outer rubbing on crank. am I right in thinking that matched crank cases had the same colour paint blob on the under side? also as far as lining up center web, I don't see how this is possible because out side diameter of web fits case snugley and stud holes are a close fit. my guess is in production the web and cases where assembled and then line bored. any thoughts out there on this one?

Matched crankcase halves. I have asked that question and nobody has come up with a definite answer. BSA Triumph etc. stamped (letter/number) each half so you could tell. Paint is NOT a good idea as it will be erased by now, fifty or so years later.
I've just checked my 1960 Spares book AND much to my surprise, it states that crankcase halves could be bought separately. That now puts ‘matched' pairs in a different light: they were NOT matched! AMC machining was that precise, you could mix ‘n' match! Likewise with the centre web. SO NO, they were not line bored!
I personally would bolt the two cases together without the crank and clock the centre web bearing bore.
I don't know why the outer races are causing a problem. There are no side thrusts so they should stay put. It's different with a ballrace that has to control end-float. That's a bad idea that BSA Triumph etc. use. Because the bearing that is supposed to check end float is not held securely in all 4 sideways directions. The inner is clamped in both directions by the crank web and the timing pinion, BUT the outer is only checked by the lip in the crankcase, nothing on the inside. May be why they had to fit a single lipped roller on the drive side. The AMC twin does not have that problem as crank float is controlled by the centre main ‘thrust washers'.
There must be something wrong if you have had to grind 1.5mm approx. from the face of the outer roller bearings.

i agree there must be some thing wrong! any way with all me mods engine is good kicks over cold and starts with out heating crank case ,what I am going to do now is modify oil feed to top end to over come over oiling.one thought ,did they mod crank shaft outer webs at all, becuause this one has an extra 3 mm wideflange on out side and is this that rubbed on bearing outers. even with bearing reduced in width the rollers still run on the track ok! this engine also has wellworthy alufin barrels.