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Thread: 1959 AJS 650 oil problem

  1. #1
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    1st October 2005 - 23:01
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    1959 AJS 650 oil problem

    I am working on a 1959 AJS 650 for a friend, I had the crank reground and the rods resized in the big end and them put the engine back together, its filling the intake rocker boxes to the TOP with oil witch is coming UP the push rod tubes,

    I thought running the bike with the rocker covers off was causing the oil to be pushed up but I am now 100% sure its doing it with them on as I whipped one off and it was FULL to the top with oil,

    I also started the bike and watched the oil rise up and fill them up.


    This has got me stumped, I had everything apart and it had the restriction jets in the bottoms of the heads for the oil feeds, It has 1962 heads on a 1959 bottom end also.

  2. #2
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    13th June 2010 - 17:47
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    Scavenge pump not working ? Is oil going back to the tank ?

    Swarfie on here is the AMC twin guru - worth a PM.
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  3. #3
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    Interesting reading re: changes made to AJS Models here ... http://www.jampot.com/article_print.asp?id=20

    As to your problem ... crankcase pressure build-up .. ??? aren't the rockers oil supplied via external tubing and oil flow is supposed to be down the tubing... ?? or is my memory going (again) .. ???
    Sweat wipes off. Road-rash doesn't.

  4. #4
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    Return pump is working, and its not the oil feed to the rockers witch is the problem, I have run the bike with the sump plug out so that eliminates crankcase pressure and the scavenge pump.



    The intake cam tunnel is not draining or having too much oil pumped in.


    AJS 650 twins went through alot of changes to the oil system over a few years and this bike has mismatched parts, it did not have a pressure relieve valve, (not to be confused with the oil filter bypass valve or air bleed on the pump plate)

  5. #5
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    If it is mismatched parts - and it's hard to avoid nowadays - I'd suggest there's an oil gallery plug missing.
    It's pretty much the only way oil can get there in those quantities.

    It's an engine out and strip IMO.

    Many years back I saw a similar thing. Triumph TQ engine with a Rickman top end. The rocker boxes filled with high pressure oil to the point it lifted the cover and there was a sheet of oil spraying out....Bob Densem had put in one of his oil pumps and overestimated how much oil the top end needed....
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  6. #6
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    Its starting to look like an engine out and strip job, and like you say the more I study the parts books the mismatched crank case halves may be missing the brass oil metering jet thet the other half didnt use that year.


    There is one small window of hope but there is a very slim chance the cam oil level drain hole has not been drilled in the 1962 case half, alot of fixes for the AJS twin is to drill extra holes to drain oil.

  7. #7
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    Well, it took 3 people to work it out, It turns out because the RH crank case is a 1962 and the left is a 1959 the oil drains for the cam tunnels are in different sides.

    Anyway the intake cam has no drain hole on this bike in the RH side so I am guessing thats the problem, I will remove the intake cam gear and drill the fucker in place.

  8. #8
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    14th July 2006 - 21:39
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    Well spotted. The joys of keeping something on the road. Post some pictures of the bike.

  9. #9
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    Quote Originally Posted by rudolph View Post
    Well, it took 3 people to work it out, It turns out because the RH crank case is a 1962 and the left is a 1959 the oil drains for the cam tunnels are in different sides.

    Anyway the intake cam has no drain hole on this bike in the RH side so I am guessing thats the problem, I will remove the intake cam gear and drill the fucker in place.
    Nice piece of detective work there. And yeah, I'd like a few pics as well.
    . “No pleasure is worth giving up for two more years in a rest home.” Kingsley Amis

  10. #10
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    This forum wont let me post pictures from photo bucket, they dont show up.


    Yer I think the last guy gave up on the bike, I am not supersized as the work he had done was total shit, he had rebuilt the gearbox with a bent layshaft and he had jammed a set of A10 BSA bigend shells in the AJS rods and they had about 10 thou clearance, he had forgotten to put the gasket in the main oil gallery/filter compartment, and used liquid steal for case sealant witch took me 2 hours to clean off.


    AJS did say they don't fix the mechanical/ engineering problems with the bikes as the owner likes to tinker, there are a lot of AJS books about where to drill holes in the engine to fix problems.

  11. #11
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  12. #12
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    Awwww. Looks a bit like my old Matchy G9 which I couldn't wait to sell in order to get a Kawasaki trail bike. Would love to have it now.
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  13. #13
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    That's a cool looking ride. I quite like the natural patina it has developed over the years.

  14. #14
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    Quote Originally Posted by AllanB View Post
    That's a cool looking ride. I quite like the natural patina it has developed over the years.

    It was blue but wile the engine was out I sprayed it black with spray cans.

  15. #15
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    If you have the original papers I'll bet it was originally an MOT bike... A lot seemed to come in about that time

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