61 M20 crankshaft non return / breather valve

Information relating to the Matchless G9 or AJS Model 20 500cc twin
bsazb34
Posts: 8
Joined: Sat Aug 19, 2017 10:14 pm
Location: SOMERSET UK

Re: 61 M20 crankshaft non return / breather valve

Post by bsazb34 »

I thought I'd got it right John but I will be having a look to check thanks.

Chris
bsazb34
Posts: 8
Joined: Sat Aug 19, 2017 10:14 pm
Location: SOMERSET UK

Re: 61 M20 crankshaft non return / breather valve

Post by bsazb34 »

I think when I built this pump a few years ago I did a silly thing when I didn't spot the difference in height of the gears, yes I got them the wrong way round with the longer scavenge rear on the right and the feed on the left. Now that could explain a lot.

thanks John I think you've just made an old lecturer in engineering very happy.

Chris
JimFitz
Posts: 663
Joined: Thu Feb 27, 2014 9:27 am
Location: Kent, England

Re: 61 M20 crankshaft non return / breather valve

Post by JimFitz »

bsazb34 wrote:I think when I built this pump a few years ago I did a silly thing when I didn't spot the difference in height of the gears, yes I got them the wrong way round with the longer scavenge rear on the right and the feed on the left. Now that could explain a lot.

thanks John I think you've just made an old lecturer in engineering very happy.

Chris
Good call John.

Glad you have found the problem Chris. I reckon that the lube system on the twins are really complicated resulting in many mods by the factory over the years and they probably never did get it right up to the end.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
rump
Posts: 30
Joined: Fri Jun 19, 2015 1:00 am
Location: NSW AUSTRALIA

G9 chain case filling with engine oil

Post by rump »

I had this trouble 2 years back i fitted a seal into the sump behind sprocket and in place of the thin spacer with the spiral groves as it was to loose in the sump to screw the oil back into sump a few people i know dont use the breather valve .I drilled the sump and fitted extra breathers but they only worked at idle, triumph did better with a positive driven disk like some prewar bikes. rump australia.
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