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check valve

Classic Norton Commando Motorcycles.

Re: check valve

Postby worntorn » Sat Apr 08, 2017 7:47 am

There are other methods that work just fine, however a MK3 should be quite continent all on it's own.

The ball and spring supply line check valves are a much proven bad idea, not sure why they are still being manufactured and installed.

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Re: check valve

Postby seattle##gs » Mon Apr 10, 2017 1:21 pm

I replaced the feed line and check valve with a single piece of hose. Oil in the tank looked pristine. I drained the crankcase, it had about a 1/2 cup of dark goo but no metal bits. Pumped about a cup of oil over the rockers and cam. Started it and oil flowed immediately through the motor and back into the oil tank. I cracked the rocker banjo and oil flowed easily from it. The noise in the top end really lowered in volume but occasionally there was the metallic clack. Drove it 4 blocks. All seems well but the owner still wants to tear it down for an inspection. he also complained of acute vibration going down the road. First place to look was the isos and they were locked up tight. I did a quick .010 clearance front and rear and the thing smoothed out like a Norton should. I'm sure other surprises are ahead.

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Re: check valve

Postby gortnipper » Mon Apr 10, 2017 7:45 pm

One can only hope that the valve was operational, and only locked up after sitting idle for a while while being sold.
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Re: check valve

Postby seattle##gs » Tue Apr 18, 2017 11:01 pm

I pulled the motor apart today and it was very fortunate that I did. The STD pistons were badly scored along with the cylinder. Oddly enough there was no damage to the cam and lifters. When the rods came off the bearing shells STD fell out of the rods. They were down to the copper with only a trace here and there of the original bearing material. The steel cap on the right side rod showed discoloration from heat. Is that rod still usable? The crank rod journals have scoring and they taper .002.

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Re: check valve

Postby JimNH » Wed Apr 19, 2017 3:18 am

Sad that an unneeded accessory ruined the engine. A MKIII will wet sump but only after a long period.

Was the original factory valve and spring still in the timing cover?

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Re: check valve

Postby seattle##gs » Wed Apr 19, 2017 1:16 pm

The original MK3 check plunger is still in the timing cover

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Re: check valve

Postby Nater_Potater » Wed Apr 19, 2017 2:01 pm

seattle##gs wrote:The steel cap on the right side rod showed discoloration from heat. Is that rod still usable?

I would say no, especially in light of what else you found. Besides, the engine is apart; why chance it for the price of a rod? Steel begins to yellow at ~420'F, going full, deep blue by around 590'F. Aluminum is "aged" around 400'F, so, with any color noticed in the attached steel cap, the aluminum is well past its hardening temp, and resulting strength is in question.

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Re: check valve

Postby htown16 » Wed Apr 19, 2017 2:57 pm

The trouble with the oil-line check valves is that they are on the wrong side of the pump. BSA's, Tridents and Mark III Commando's all have the check valve or ball on the pump output. If the pump works the ball has to come off the seat by pump pressure. AMR does a similar mod for the non Mark III Commandos. I've had them do 3 Commandos. They also do a mod on the pump to eliminate leakage between the inlet and outlet sides.
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Re: check valve

Postby kommando » Thu Apr 20, 2017 12:08 am

If the pump works the ball has to come off the seat by pump pressure.


My one failure with check valves is on a C15 with the valve after the pump, it stuck shut and the pump would not force it open although it was primed. I caught it before it caused any damage as I was using clear oil line on a reassembled engine and was looking at the flow as a check. As the engine started oil flowed into the engine, then it slowed and next went into reverse followed by lots of air, only a new check ball and spring and seat refurb fixed it. Changing oil pumps had no effect and oil lines were all clear.

I know these are positive displacement pumps and the theory is they produce highest pressure when the exit is restricted but you can never beat seeing the result of a post pump blockage, instead of pumping oil out when it met resistance it must have got air in through a mating surface and that forced the oil back out the inlet.
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Re: check valve

Postby JimNH » Thu Apr 20, 2017 3:56 am

kommando wrote:
If the pump works the ball has to come off the seat by pump pressure.




I know these are positive displacement pumps and the theory is they produce highest pressure when the exit is restricted but you can never beat seeing the result of a post pump blockage, instead of pumping oil out when it met resistance it must have got air in through a mating surface and that forced the oil back out the inlet.


That's quite amazing as generally a positive displacement pump, gear, gerotor, pumping a liquid, will build pressure until something moves, blows, or breaks. Is there a relief or regulator valve in that circuit somewhere? A 1/2" ball with 200PSI pushing is almost 40lb of force, quite likely a lot more than one needs to push the ball off its seat by hand and that's at only 200PSI.

What was the condition of the valve when you removed it?

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Re: check valve

Postby kommando » Thu Apr 20, 2017 5:21 am

It was 20 years odd ago but still got the engine which still runs and the oil flow is fine, there was a slight black ring on the ball, but spring and seat were fine. Not enough to suggest anything but after the 3rd complete strip down I could find nothing else to change so went for it and it cured the problem. Its in the same position as on an A10, after the pump but only accessible by splitting the crankcases and just under the timing side bush. It was the oil flowing and then reversing with mainly air coming back out that suggested to me there was a blockage, without seeing it I would not have believed it as the positive displacement pump should in theory have built up pressure enough to clear any blockage. There is a relief valve and I did not change that but did clean it up, when you look at a gear pump on BSA's they all are made up from 3 parts and the A65 ones especially can leak out oil between the joints, so it equally could allow air in.
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