AJS & Matchless Owners Club

The oil and debris in the chaincase cannot block the engine oilways, they are separate systems, although engine oil and its impurities can find its way into the chaincase. You will have to look elsewhere for the cause of the failure, more likely conrod bolts/nuts.
Rob C

robcurrie wrote:The oil and debris in the chaincase cannot block the engine oilways, they are separate systems, although engine oil and its impurities can find its way into the chaincase. You will have to look elsewhere for the cause of the failure, more likely conrod bolts/nuts.
Rob C

Thanks Rob, Well the left conrod is totally destroyed, I mean mangled, snapped into lots of pieces and generally gone to meet its maker. The big end bearings are folded flat and you wouldn't know what they were. The right hand conrod is complete, but I guess it would have failed within a few miles as well. There is lots of play and the bearing face has started to loose its plating. There are bits of sharp metal all through the engine, I have been cleaning it as I stripped it down, but it is still all over the place. If I can get the crank re-ground I will spend the waiting time cleaning and cleaning and, well you get the picture

Just a thought: if the alternator rotor has hit the stator, then perhaps the drive side main bearing packed up first?

It does sound like a lubrication failure. If the oil pressure drops then the drive side big end will usually go first, followed by the timing side one.
I don't know much about the twins, but I'd start by having a close look at the oil pump and pressure relief valve...

clanger9 wrote:Just a thought: if the alternator rotor has hit the stator, then perhaps the drive side main bearing packed up first?

It does sound like a lubrication failure. If the oil pressure drops then the drive side big end will usually go first, followed by the timing side one.
I don't know much about the twins, but I'd start by having a close look at the oil pump and pressure relief valve...

Thanks for the suggestions. I will check these parts out before I rebuild it. I have ordered a new rotor and stator, someone suggested that the engine overheated while I was waiting to do the TT parade lap, (we were kept waiting for ages on the grid and maybe the rotor expanded a bit?)

I have removed the oil pumps, but not stripped them yet. The main bearings look solid, but maybe I will change them while it is in bits. Peace of mind and all that eh?

Luckily, the crank looks like it hasn't been re-ground yet, so that gives a bit more leeway to remove the damage.

Thanks again.
Cliff

Clanger9, the AMC twins have the feature that oil is fed into the crankshaft in the centre, so big end bearings are equidistant from the feed.
Rob C

Cliff-1959 wrote: ".........Has anyone fitted 600 or 650 parts? I have heard that the bottom end is the same and I am just wondering what would be involved in increasing the engine size a bit. There also seems to be more parts available for the bigger engines.

The 500 and 600 had the same crank but different size barrels and pistons, not sure if the heads are different but you would probably need to change the carb jets. The 650 has a longer swept volume so the barrels are longer and not interchangeable, similarly the crank.

clive wrote:

Cliff-1959 wrote: ".........Has anyone fitted 600 or 650 parts? I have heard that the bottom end is the same and I am just wondering what would be involved in increasing the engine size a bit. There also seems to be more parts available for the bigger engines.

The 500 and 600 had the same crank but different size barrels and pistons, not sure if the heads are different but you would probably need to change the carb jets. The 650 has a longer swept volume so the barrels are longer and not interchangeable, similarly the crank.

Unless you just happen to know a man who has all the required bit in his shed! Advert, what advert?

robcurrie wrote:Clanger9, the AMC twins have the feature that oil is fed into the crankshaft in the centre, so big end bearings are equidistant from the feed.
Rob C

Thanks Rob! In that case the bid ends would be more likely to let go together if the oil supply dried up...
See, I said I knew nowt about twins.

ajscomboman wrote:

clive wrote:

Cliff-1959 wrote: ".........Has anyone fitted 600 or 650 parts? I have heard that the bottom end is the same and I am just wondering what would be involved in increasing the engine size a bit. There also seems to be more parts available for the bigger engines.

The 500 and 600 had the same crank but different size barrels and pistons, not sure if the heads are different but you would probably need to change the carb jets. The 650 has a longer swept volume so the barrels are longer and not interchangeable, similarly the crank.

Unless you just happen to know a man who has all the required bit in his shed! Advert, what advert?

Ha ha ha, well as I am a regular customer, I'm sure I will get a good rate
Can you send me an email with an idea of what you would be looking for please Rob?
I have got a few feelers out for a replacement barrel, but it would be nice to know that there is a Plan B available. (If you can stand the stress of the couriers again!)

Ohh those couriers!!!!!! What a blasted pain they were! I'll have a root around in the shed over the next few weeks and send you a e-mail as before.