for those of you with the AMR timing cover mod

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acadian

acadian

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A bit of forward thinking advice for those of you with the AMR mod:

I think I may have discovered a possible reason for my less than optimal results with the AMR timing cover mod. While my first season with the modified timing cover in place was positive, with subsequent removal/reinstallations the effectiveness of the spring/ball/oring combo seemed to diminish, and now I think I know why.

When replacing the o ring (the AMR modification does away with the tapered seal), make sure you get the o ring sized just right, and this will vary depending on the thickness of the oil pump/cover gasket combo. When I pulled the cover the other week, I discovered that the o ring I last used had been over compressed to the point of preventing the ball bearing from fully seating on the pump spigot. I suspect this owed to my having used too thick of an o ring for the gasket combo... it allowed too much "crush".

I cut out my own replacement pump and cover gaskets using 1/8" thick gasket material and, prior to reassembly, made sure to measure the gap between the pump spigot flange and the cover surface. A little bit of math and I was able to determine the correct o ring size to allow the right amount of crush.

p.s. I suggest you also avoid using a metal implement (rod, wire etc..) to retain the ball/spring when reinstalling the cover, as when you withdraw it you may end up scoring the pump spigot. I used a plastic zip tie this time around.
 
A better idea is the Comstock crankcase breather. It's main job is to pump all the oil from the crankcase up to the oil tank in two or three kicks. Spendy at $230 but you can get around the wet sumping problem PERMANENTLY.
 
acadian said:
A bit of forward thinking advice for those of you with the AMR mod:

I think I may have discovered a possible reason for my less than optimal results with the AMR timing cover mod. While my first season with the modified timing cover in place was positive, with subsequent removal/reinstallations the effectiveness of the spring/ball/oring combo seemed to diminish, and now I think I know why.

When replacing the o ring (the AMR modification does away with the tapered seal), make sure you get the o ring sized just right, and this will vary depending on the thickness of the oil pump/cover gasket combo. When I pulled the cover the other week, I discovered that the o ring I last used had been over compressed to the point of preventing the ball bearing from fully seating on the pump spigot. I suspect this owed to my having used too thick of an o ring for the gasket combo... it allowed too much "crush".

I cut out my own replacement pump and cover gaskets using 1/8" thick gasket material and, prior to reassembly, made sure to measure the gap between the pump spigot flange and the cover surface. A little bit of math and I was able to determine the correct o ring size to allow the right amount of crush.

p.s. I suggest you also avoid using a metal implement (rod, wire etc..) to retail the ball/spring when reinstalling the cover, as when you withdraw it you may end up scoring the pump spigot. I used a plastic zip tie this time around.
Click to expand...

I have found the same effect. When I first installed the timing cover with the AMR mod, the wet sumping stopped. There was ZERO leak down. Then suddenly the entire volume of the oil tank leaked down in a few days. I found the O ring to be over crushed.

Thanks for the zip tie trick.

Slick
 
seattle##gs said:
A better idea is the Comstock crankcase breather. It's main job is to pump all the oil from the crankcase up to the oil tank in two or three kicks. Spendy at $230 but you can get around the wet sumping problem PERMANENTLY.
Click to expand...

I have the comstock breather, but it doesn't eliminate wet sumping, it just provides for faster evacuation of oil that's made it into the crankcase
 
you are right, it doesn't stop the wet sumping, we are stuck with the oil pump Norton provided. The breather gets around the problem in a really good efficient way and also functions as a breather. I think it's the best solution. It's a twofer.
 
acadian said:
A bit of forward thinking advice for those of you with the AMR mod:

I cut out my own replacement pump and cover gaskets using 1/8" thick gasket material and, prior to reassembly, made sure to measure the gap between the pump spigot flange and the cover surface. A little bit of math and I was able to determine the correct o ring size to allow the right amount of crush.
Click to expand...

@acadian. Would you elaborate more on this. I read you are using 1/8 " thick gasket material for the pump gasket, and for the timing cover gasket. The pump gasket is that between the pump and timing case .... is that correct? If so, would not a 1/8" gasket shift the pump worm in relation to the drive gear?

I see how similar thickness gaskets on both the pump and timing cover will preserve the spatial relationship of the pump spigot to the timing cover. Why are you resorting to 1/8" gaskets to deal with the O ring crush Problem?

In my own case, I have not yet decided how to deal with the O ring crush.

Slick
 
texasSlick said:
acadian said:
A bit of forward thinking advice for those of you with the AMR mod:

I cut out my own replacement pump and cover gaskets using 1/8" thick gasket material and, prior to reassembly, made sure to measure the gap between the pump spigot flange and the cover surface. A little bit of math and I was able to determine the correct o ring size to allow the right amount of crush.
Click to expand...

@acadian. Would you elaborate more on this. I read you are using 1/8 " thick gasket material for the pump gasket, and for the timing cover gasket. The pump gasket is that between the pump and timing case .... is that correct? If so, would not a 1/8" gasket shift the pump worm in relation to the drive gear?

I see how similar thickness gaskets on both the pump and timing cover will preserve the spatial relationship of the pump spigot to the timing cover. Why are you resorting to 1/8" gaskets to deal with the O ring crush Problem?

In my own case, I have not yet decided how to deal with the O ring crush.

Slick
Click to expand...

The material isn't quite 1/8", perhaps a 32 or so thinner, it does compress slightly as well. I used this simply because it's what I had on the shelf, and have purchased similar thickness pre cut gaskets from norvil etc...
 
Maybe someone with the AMR mod can enlighten me. Am I correct in thinking the mod is the same as the MK3 cover? and if it is I cant see how
a pre MK3 cover could be modified as the MK3 cover has a lump on the outside to allow for enough depth of drilling for the piston and spring.
You could only increase the depth of the hole on a pre MK3 cover by about 1/16" or so before making a hole thru the cover.
Or am I missing something?
 
madass140 said:
Maybe someone with the AMR mod can enlighten me. Am I correct in thinking the mod is the same as the MK3 cover? and if it is I cant see how
a pre MK3 cover could be modified as the MK3 cover has a lump on the outside to allow for enough depth of drilling for the piston and spring.
You could only increase the depth of the hole on a pre MK3 cover by about 1/16" or so before making a hole thru the cover.
Or am I missing something?
Click to expand...

The AMR mod. uses a ball instead of the Mk3's piston/plunger.
 
Just did the AMR mod to a timing cover yesterday, you can measure on the outside of the timing cover the depth of the hole that would break out of the cover by measuring the width of the flange for the pressure release valve, this is 1.45" on one Commando timing cover I have and 1.38" on an earlier Dominator cover. The timing cover continues to get a bit thicker as it moves towards the oil pump galley so I was happy to bore down so the hole was a flat bottomed 5/16" hole of 1.35" depth from the gasket surface and it did not breakout. The resulting chamber is small and I doubt the ball is pushed down far enough to get out of the way completely so I was pondering if a dia of 8.5mm or 9mm may be better for the hole down to the cross hole to allow enough space for the oil to get around the 1/4" ball, I may still do that.
 
Thanks Kommando and L.A.B all much clearer now, 2 things
The spring must be very short and or be able to compress enough so the ball is clear of the cross drilling
The change to an o'ring on the oil pump spigot is to allow the ball to seat on the spigot and not the original rubber seal ?
Don
 
Yes the ball is pressed against the spigot, but my previous trials with non return valves showed a rubber seat will seal better than a steel seat. Once my O rings arrive I can check to see where the seal is, if it is on the spigot maybe lapping the ball into it will improve the seal. The spring needs to be long enough to press the ball against the spigot to hold back an 18" column of oil plus a contingency, a thin wired spring will compress the most, I will use a MK3 spring and see how far the ball can be pushed back but like you I think the ball will not completely get out of the way.
 
the MK3 spring is .270" inside diameter, and the MK3 spring is .250" long when fully compressed. its way to big.
Don/
 
That has saved me £0.69 ;)

I can get 7mm od springs 1mm thick wire so 5mm id so will try one of these.
 
I have a spring maker here on next island who makes all my springs so if we can determine the specs, I can get a bunch made
 
Will be out in the workshop later, I will measure the surface area of the outlet from the pump and then calculate the surface area of the gap between the ball and housing and see how they compare. It maybe the ball just needs to be lifted from the seat and does not need to be pushed all the way back, I will look at the non return on a Unit Single inner timing cover and see if the ball on that disappears or stays in the oil flow.

On the pump I have the size of the oil pump outlet is 7.22 mm2, the size of the gap around the 1/4" ball bearing is 17.6 mm2 so the ball does not need to drop below the x hole to not restrict the flow. This is confirmed when I look at the Unit single, the ball in the non return valve in the inner timing cover cannot get out of the flow completely either.
 
kommando said:
Yes the ball is pressed against the spigot, but my previous trials with non return valves showed a rubber seat will seal better than a steel seat. Once my O rings arrive I can check to see where the seal is, if it is on the spigot maybe lapping the ball into it will improve the seal. The spring needs to be long enough to press the ball against the spigot to hold back an 18" column of oil plus a contingency, a thin wired spring will compress the most, I will use a MK3 spring and see how far the ball can be pushed back but like you I think the ball will not completely get out of the way.
Click to expand...

Kommando,

Have you considered a synthetic ball instead of a steel one?
Pete
 
No had not, but will now ;)

I tested a Unit Single non return valve spring, it may be a bit long but I was able to compress the ball and spring far enough to get a zip tie through the X hole to keep it all in place before mounting the cover. The spring is 0.24" OD 0.55" long 8 turns of 0.015 wire with flat ends and was used with a 1/4" ball.
 
kommando said:
Yes the ball is pressed against the spigot, but my previous trials with non return valves showed a rubber seat will seal better than a steel seat. Once my O rings arrive I can check to see where the seal is, if it is on the spigot maybe lapping the ball into it will improve the seal. The spring needs to be long enough to press the ball against the spigot to hold back an 18" column of oil plus a contingency, a thin wired spring will compress the most, I will use a MK3 spring and see how far the ball can be pushed back but like you I think the ball will not completely get out of the way.
Click to expand...


Has anyone bothered to ask Mike @ AMR what size O-ring he uses? You also need to make sure they are made of the correct material to avoid them breaking down due to chemical incompatibility.

John in Texas
 
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