Oiling Problem

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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Oiling Problem

Postby itma » Fri Jun 19, 2009 7:44 pm

It veru much sounds to me as though you are nipping up the piston[s]
either not running in properly or too tight on the bore


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Oiling Problem

Postby freddie 136 » Fri Jun 19, 2009 8:38 pm

Thanks for you reply, the bike has done about forty mile since the rebuild, bike has not done more than 35/40 mph during this time, i wouldn't have thought this was to much for a 600cc,any way thanks for your help cheers Fred

p.s.would the pistons getting tight in the barrels stop the oil from getting to the tappets, cheers.

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Oiling Problem

Postby Groily » Fri Jun 19, 2009 10:24 pm

I'm interested how you can be sure there's 'no oil flow to the tappets'. I guess if you take a rocker cover off with the engine running you might see something in the way of slime, but I'd have thought the only proof of the pudding would be to take a rocker shaft out and see how oily it was. Because of the metering jets in the underside of the heads, there isn't going to be (or meant to be) gallons of oil floating about up there.
Dry rockers might be a bit noisy but probably couldn't force a sudden halt nor, I think, produce a 'loud knock'. I think it's more likely there's a piston/bore problem, despite best efforts.
Other possibilities are altogether too dismal to add, just hope the bottom end is OK, the oil filter and relief valve arrangements are the correct ones for the year and model, etc. There are a lot of thing to beware of with these beasts, which many far more knowledgeable people than I will be able to help with if you find you have a case of major post-rebuild blues.

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Oiling Problem

Postby wilko » Sat Jun 20, 2009 1:04 am

That spring and ball is just a check valve to stop wetsumping (which it doesn't) The pressure relief valve is incorporated at the opposite end behind the timing cover. I hope that it is installed properly or you'll have buggerall pressure!Unscrew the checkvalve and screw in an oil pressure guage to make sure you have adequate pressure. I have a permanent guage mounted with the checkvalve behind it.

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Oiling Problem

Postby TommoT » Sat Jun 20, 2009 10:02 am

Make sure your friend has used the correct piston to bore tolerance. Always use the piston makers recommendation, they will have all the data on expansion rate, which is crucial to avoid seizures. If haven't got this right you will continue to experience, seizures or near-seizures for thousands of miles. Just ask around in this forum, I remember a few reports to that effect.
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Oiling Problem

Postby itma » Sat Jun 20, 2009 10:46 am

engine capacity, road speed, has little bearing on correct way to run in an engine.
Tommot is on the nail.
It is no good referring to an out of date manual for piston tolerances.

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Oiling Problem

Postby Eric » Sat Jun 20, 2009 11:23 am

Assuming the screw you describe for the pressure relief valve is on the nearside of the bike next to it will be a large hex head cover for the oil distributor. The distributor is a rotary valve driven from the end of the exhaust camshaft that controls how much oil is allowed to go up to the top of the engine. It could be worth removing the cover and withdrawing the the distributor to see if everything looks normal. Sometimes these seize up because the thick copper washer that should be underneath the head of the cover is not fitted and the clearances for the distributor become compromised particularly when the engine is hot. This was discussed sometime ago in the forum have a search around you may find it.

I agree with everything that has been said about piston clearances what may have been OK for an original piston may not be suitable for a different replacement. And using a modern rule of thumb for modern water cooled engines will definitely not work on air cooled engines that can and do run much hotter and require greater clearances when everything is cold.

Edited by - Eric on 20 Jun 2009 11:27:47 AM

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Oiling Problem

Postby freddie 136 » Sat Jun 20, 2009 2:50 pm

Hi, thanks for all your replays,The reason i know that oil is not getting to the tappets after a run is that when i got the bike back home i filled the carb with petrol then took the tank and rocker covers off and started the engine with the engine still hot there was no oil being delivered to the tappets, as there was before i went on the run, you see i took the rocker covers off one a time to make sure oil was getting through.
Regards running in, i rode the bike nice and steady not more than 35/40,MPH not letting the bike labor in any gear [lot's of nice long country lanes round where i live] and i have run a bike in be for as i have been biking for quite some time,although not with a Matchless.
I Had a 20thou re bore and bought piston and rings from Jampot spares that were [+20 though]could this be the reason for my trouble ?, if any one as any info i would appreciate there input,cheers Fred.

Edited by - freddie 136 on 20 Jun 2009 3:04:46 PM

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Oiling Problem

Postby petert120r » Sat Jun 20, 2009 5:07 pm

As has been stated previously, a reputable engineering shop will want to bore the barrels to the pistons. Both should be taken to the shop, along with the piston specifications which should have been supplied.

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Oiling Problem

Postby Don Madden » Sat Jun 20, 2009 5:10 pm

Oil is delivered from the pump to the filter chamber. From there a drillway passes the oil to the oil distributor. The distributor has a hole or a flat, depending on year, that lines up it another drillway once per cam revolution. That drillway leads to the case clamping bolt above it. The bore for this bolt is used a an oilway to connect to the pocket formed by a machined channel between the crankcase halves. From there drillways angle to align with the drillways in the cylinders & thence up to the heads. The heads usually had oil restrictors pressed in, but in some cases not fitted. Early restrictors were drilled & later had a flat.

After 50yrs, you may have any combination of these variations. Pull the heads & check for blockage of the oilways. The oil holes in the rockers do not line up with those in the bushes so hard to determine if clear. You can blow air up the heads from the bottom to see if it escapes from the outlet in the rocker supports. Restrictors can be forced out by dropping in bearing balls to fill the drillway & tapping on the topmost. If your distributor is the type with a hole, check for blockage. You can probe most crankcase drillings with a stiff wire.

ALWAYS give year & model with requests for help. The twins, especially, changed something in the oiling system every year, sometime reverting back to prior versions.

Read up on it in the service manual & articles in Christian's Archives.

That will keep you out of trouble for awhile. Cheers, Don.

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