AJS & Matchless Owners Club

Hi,

A friend of mine has recently bought a 1960 alternator Model 31. It's partially stripped down now, to fit new clutch rubbers, and tidy up a couple of things, but a couple of earlier test rides showed that it is pumping oil into the chaincase. Oil was also seen to be returning to the oil tank, but obviously not all of it. There was no sign of it smoking.as mine does when starting up with oil in the sump, and it felt OK (I took it on a quick test).

The chap who's been helping him (my mate is new to British classics) isn't able to complete the work for personal reasons, so the bike will be coming up to my garage soon. Any thoughts on what I should be looking for? Is there a breather on the end of an alternator crankshaft, as there is on my magneto version? We've washed out and dried the crankcase oil filter, but that's all.

All thoughts welcome.

Cheers,

Malc

Yes there's a breather in the nut holding the alternator on. Check that first. I'd reassemble , drain the sump and see how it goes. This 'pumping into the chaincase' is often down to topping the oiltank up before starting. The excess oil in the sump through leaving the bike standing can't be cleared quickly enough and it's forced through the breather. This never happens when the bikes are used regularly. Other causes might be worn piston rings/ pistons/bores/ oilpump return.
Dave

dave16mct wrote:Yes there's a breather in the nut holding the alternator on. Check that first. I'd reassemble , drain the sump and see how it goes. This 'pumping into the chaincase' is often down to topping the oiltank up before starting. The excess oil in the sump through leaving the bike standing can't be cleared quickly enough and it's forced through the breather. This never happens when the bikes are used regularly. Other causes might be worn piston rings/ pistons/bores/ oilpump return.
Dave

Thanks Dave

I'll check that first, then as you suggest reassemble everything and see what happens. Looking at it as it stands, reassembly should be a couple of evening's work, max. Of course, that won't be the case, it never is...

Malc

If its been doing it since purchase how about pump bodies being reversed, the larger one should be the return. Easy enough to check.

clive wrote:If its been doing it since purchase how about pump bodies being reversed, the larger one should be the return. Easy enough to check.

Thanks Clive, good point. He doesn't know the history of the bike so it's worth a look.

Malc

Thought I'd post a quick update on this.

The drive side was removed, which of course meant removing the crankshaft breather. The oil filter, the felt covered type, was also removed and was very mucky. That resided in a petrol bath for some considerable time, then left to dry out fully. Nothing, as far as I know, was done to clean or check the breather.

The whole thing is back together now, and checking after a 50 mile test ride showed the oil level in the chaincase to be unchanged, so that seems to be fixed.

Unfortunately it isn't charging though. There is output from the alternator but the rectifier, a small square bridge rectifier (I think) seems to have failed, as there seems to be AC at the battery. Mind you a thought has just occurred to me. If he's plugged the alternator wires back into the loom incorrectly, would that cause it?

Malc

MalcW wrote:If he's plugged the alternator wires back into the loom incorrectly, would that cause it?

Hi

Possibly but unlikely. Best bet is to investigate the out put from the rectifier, if you're seeing AC at the DC terminals then the rectifier is toast, get a new one or go down the A-Reg one route.

If it's a standard Lucas rectifier the AC terminals are the two outer spades, DC positive is the mounting stud, DC negative is the centre spade.

Regards Mick

Mick D wrote:
Possibly but unlikely. Best bet is to investigate the out put from the rectifier, if you're seeing AC at the DC terminals then the rectifier is toast, get a new one or go down the A-Reg one route.

If it's a standard Lucas rectifier the AC terminals are the two outer spades, DC positive is the mounting stud, DC negative is the centre spade.

Thanks Mick. Now we're allowed to do such things I'll try and take a socially distanced look at it down at his place tomorrow. I've bought an analogue multimeter so I'll take that and try it out. Easier than trying to make sense of digital output jumping all over the place.

Malc