Oil pressure 1951 g9

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Charles.
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Posts: 93
Joined: Wed Oct 12, 2005 10:45 pm
Location: CORNWALL UK

Oil pressure 1951 g9

Post by Charles. »

After total botom end rebuild eg center web big ends new cam bushes new distributer bush main bearings refaced oil pump end plates
oil pressure when cold 130 to 140 lbs when ridden approx 30 mls oil pressure gradually reduces to 18 to 20 lbs at 40 mph nil pressure at tick over
can any one help with what oil pump clearances should be
should i fit a 4 th oil restrictor in the head why did they fit 4 in 1953
Eric
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Joined: Fri Jan 01, 1993 12:00 am
Location: WEST MIDLANDS UK

Oil pressure 1951 g9

Post by Eric »

You dont mention what oil you are using this can have a big influence upon oil pressure when cold & hot. But I have to say your pressures do seem low, both cold & hot, lets assume that everything in the bottom end is OK for now, you have had the oil pump end plates ground back to remove side clearance, but how many miles do you think the bike may have done? The bit that I am getting to is that if the oil pump gears are worn you will not pump enough oil to generate higher pressures. When cold its possible to exceed 200 psi on some bikes, dropping back to more modest 20 to 60 psi when idling and running while hot. Also what is the range of the oil pressure gauge you are using, if its able to cover up to 250 psi it may not be very accurate at the lower end of the range.
Charles.
Deceased
Posts: 93
Joined: Wed Oct 12, 2005 10:45 pm
Location: CORNWALL UK

Oil pressure 1951 g9

Post by Charles. »

oil type pennzoil 50 grade
Being the second owner of this machine i know its history
the machine has covered some 140,000 miles
one hickup being a fractured nearside rod last November sense rebuild suffers low pressure i suspect has been for a long time
oil pressure gauge reads to 145 psi point taken from distributor end cap
is there any info regarding oil pump clearances
are new gears available
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