no oil returning to the tank

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Re: no oil returning to the tank

Postby spookefoote1956 » Thu Oct 18, 2018 8:25 pm

What year is it? I have a spare timing axle for a 47 model 18. This would obviously require a 47 pump which I sold and is a unique year.
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Re: no oil returning to the tank

Postby Andy51 » Thu Oct 18, 2018 8:37 pm

Hi Ian, re Pharisee's comment about possible damage to the pump bore, I had trouble with my G80 wet sumping, down to a worn bore. I spoke to a local engineer about the factory cure - sleeve and rebore - he said it would not be economically practical. However, I found that the pump worked OK and draining off excess oil in the sump was not too much of a chore (I do not trust myself to turn on a tap in the system!) so you can live with any reasonable damage here. Andy

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Re: no oil returning to the tank

Postby willowbedone » Fri Oct 19, 2018 1:33 pm

Thanks for all replies .Yes it looks bad and possibly will be I'll strip it down completely and asses what needs to be done to sort it Does anyone know where I can get a new big end ( if required ) And who could fit it to the crankshaft .I'll keep this thread updated as to my progress with the repair As I'll need quite a bit of help rebuilding the engine
Thanks Ian

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Re: no oil returning to the tank

Postby willowbedone » Fri Oct 19, 2018 7:12 pm

Hi
Is the worm gear on the crankshaft replaceable ? Can anyone recommend a firm to replace big end bearing ?

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Re: no oil returning to the tank

Postby Duncan » Fri Oct 19, 2018 10:11 pm

The worm gear is part of the timing side axle.

T&L come highly recommended but are a fair jaunt from Sussex, the Sussex section should be able to advise of more local options.

One option may be: Owlesbury Crankshaft Service, Unit 12 Winnall Valley Road, Winnall, Winchester, SO23 8LU. I know they can grind and balance Twin cranks.

Be prepared for making some decisions these engines will run quite happily even when outside of tolerances, once you open it up the sensible (and expensive) thing to do is address the all bushes and bearings, the drive side axle may also be worn, if you do not intend circumnavigating the globe any time soon the wear could still be acceptable.

All the usual AJS&M spares suspects can normally source big ends.

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Re: no oil returning to the tank

Postby Pharisee » Sat Oct 20, 2018 7:52 am

willowbedone wrote:Hi
Is the worm gear on the crankshaft replaceable ? Can anyone recommend a firm to replace big end bearing ?


I recently had a crankshaft rebuilt at T&L Engineering. The big end assembly came from the AMOC Spares and the new drive side axle I obtained from Andrew Engineering.
Andrew Engineering have stopped making spares now i believe but they are still selling what they have in stock. They list a timing side axle (part no. 021247) at £57.60 but you'll have to phone them to see if they actually have one left.
Just checked on the AMOC Spares web site and they have one available at £67.50

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Re: no oil returning to the tank

Postby ajscomboman » Sat Oct 20, 2018 7:57 am

Duncan wrote:The worm gear is part of the timing side axle.

T&L come highly recommended but are a fair jaunt from Sussex, the Sussex section should be able to advise of more local options.

One option may be: Owlesbury Crankshaft Service, Unit 12 Winnall Valley Road, Winnall, Winchester, SO23 8LU. I know they can grind and balance Twin cranks.

Be prepared for making some decisions these engines will run quite happily even when outside of tolerances, once you open it up the sensible (and expensive) thing to do is address the all bushes and bearings, the drive side axle may also be worn, if you do not intend circumnavigating the globe any time soon the wear could still be acceptable.

All the usual AJS&M spares suspects can normally source big ends.


I can confirm that Owlesbury Crankshaft Services are more than able to machine and fully reassemble single crank assemblies, they recently did a mates (yes Duncan I DO have some! :rofl: :rofl: ) 500 CS bottom end and a quality job it was too. Just give them plenty of time to turn things around though as they're always up to there neck work wise.

Alternatively you could ship the whole lot to Ken De Groome and let him do the complete motor or bottom end.

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Re: no oil returning to the tank

Postby clanger9 » Sat Oct 20, 2018 8:17 am

As a minimum, you'll need a new oil pump plunger, timing side axle and timing side bush (the bits from the stripped teeth will have chewed the bearing...). [Edit: oh, and of course a new oil pump drive pin!]
Fingers crossed that the oil pump bore isn't too scored.
There will be bits *everywhere*, so it'll need a very thorough strip down and clean of all oil ways.
The big end may well be fine. Hope you have some better luck!
Last edited by clanger9 on Sun Oct 21, 2018 1:35 pm, edited 1 time in total.
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Re: no oil returning to the tank

Postby willowbedone » Sun Oct 21, 2018 1:06 pm

Thanks to all who have replied .As yet I have not stripped the engine ,but I will post what's damaged on the here when I have done so What could be the causes for this to happen ? It has always wet dumped since I bought the bike but ran great. I have done around a thousand miles on it and changed the oil for 50 sae at 500 miles

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Re: no oil returning to the tank

Postby clanger9 » Sun Oct 21, 2018 1:31 pm

I don't know the definite cause, but I think wear in the timing side bush might play a part. The crank hops up & down and eventually wears through the oil pump teeth. Look how thin the teeth were on my Lightweight oil pump (compared to the new one, behind):
IMG_1708.jpg
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