Mk3 Timing Cover, for Pre- Mk3 applications (2017)

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RoadScholar said:
My experience, which is not nearly as global as some on this forum, leads me to believe that fitting (almost) any part to a Norton requires some fettling or at least close inspection.
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Yes, so all it would appear to need to correct the problem is for a comparatively small amount of metal to be removed from the face of the intermediate gear boss and just one of those 'fettling jobs' we encounter from time to time.

grandpaul said:
Mk3 Timing Cover, for Pre- Mk3 applications (2017)
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RoadScholar said:
I have gathered, from this discussion, that, as long as the oil galleries are completely drilled the swap should go as stated by AN, although timing cover gaskets also vary in thickness, I'll come up with some method for measuring the free play of the intermediate gear to insure that it is not binding when the cover fasteners are at set torque.
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No, with a Mk3 cover, the return oil gallery in the timing side case DOES NOT need to be there at all, because it isn't used, that's why DD suggests blanking it off.
 
L.A.B. said:
Fast Eddie said:
The bigger question IMO is the oil feed machining differences as mentioned by DD. Was this mentioned in the instructions provided with the AN kit? Is the 'kit' timing cover already modified accordingly?
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There's no actual machining difference between the pre-Mk3 and Mk3 timing side case in that position, as the Mk3 T/S case still has the OPRV return gallery same as pre-Mk3 T/S cases. The difference is in the cover, as the Mk3 timing cover blanks off the gallery because the Mk3 cover vents oil from the OPRV directly into the timing chest unlike pre-Mk3 where it's sent back to the feed pump inlet, so although it can be beneficial to blank off the return gallery as DD suggested, it isn't absolutely necessary and wasn't done on the Mk3 model.
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Thanks LAB, I get it now (although I'll need to look at a cover properly with my own eyes before it's fully sinks in to the grey matter)!
 
Fast Eddie said:
Thanks LAB, I get it now (although I'll need to look at a cover properly with my own eyes before it's fully sinks in to the grey matter)!
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Compare this pre-Mk3 cover, below, with the previous Mk3 type above.

The Mk3 cover doesn't (normally) have the drilling where the '12' is, as the OPRV oil blows off directly into the timing chest, not sent back to the pump feed inlet.

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Images deleted as they are no longer available.
 
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RoadScholar said:
I have gathered, from this discussion, that, as long as the oil galleries are completely drilled the swap should go as stated by AN, although timing cover gaskets also vary in thickness, I'll come up with some method for measuring the free play of the intermediate gear to insure that it is not binding when the cover fasteners are at set torque.
Click to expand...

Bill,
This might be something you might want to try to measure the free play.

http://www.plastigaugeusa.com/

Pete
 
With a 12" machinist scale across the intermediate gear/cases it shows the gear about .005" proud of the cases.....which is why it locks up the gear with no gasket installed....with the gasket (.0315/.0325") there is .025" freeplay. All you need is regular feeler gauges like when you adjust the valves. :idea:
 
Deets55 said:
RoadScholar said:
I have gathered, from this discussion, that, as long as the oil galleries are completely drilled the swap should go as stated by AN, although timing cover gaskets also vary in thickness, I'll come up with some method for measuring the free play of the intermediate gear to insure that it is not binding when the cover fasteners are at set torque.
Click to expand...

Bill,
This might be something you might want to try to measure the free play.

http://www.plastigaugeusa.com/

Pete
Click to expand...

Plastigauge is a good idea, my local NAPA stocks it and I will give it a try, however, I thought that I would build up the intermediate gear with shims (washers) until the timing cover was proud of the engine case, measure the shim stack, subtract the cover clearance and the difference should be the intermediate gear clearance/interference without gasket; having two ways is much better than one, hopefully both methods would agree.
 
dynodave said:
With a 12" machinist scale across the intermediate gear/cases it shows the gear about .005" proud of the cases.....which is why it locks up the gear with no gasket installed....with the gasket (.0315/.0325") there is .025" freeplay. All you need is regular feeler gauges like when you adjust the valves. :idea:
Click to expand...

Sorry I missed your post, and thanks for doing the measurements. So a .025 running clearance sounds good, any sense of what happens to that clearance when the engine gets to operating temp?

' Am I correct in observing that the Mk3 timing cover dumps over pressure oil into the timing chest and that the pre-Mk3 covers route the oil into the sump? You had suggested plugging the over pressure gallery in the pre-Mk3 engine case , or suggesting that the gasket might serve the same purpose??
 
RoadScholar said:
Am I correct in observing that the Mk3 timing cover dumps over pressure oil into the timing chest
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Yes.


RoadScholar said:
and that the pre-Mk3 covers route the oil into the sump?
Click to expand...

No, it is sent back to the feed pump inlet.
 
L.A.B. said:
RoadScholar said:
Am I correct in observing that the Mk3 timing cover dumps over pressure oil into the timing chest
Click to expand...

Yes.


RoadScholar said:
and that the pre-Mk3 covers route the oil into the sump?
Click to expand...

No, it is sent back to the feed pump inlet.
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Feed pump inlet...

Unless it is sealed perfectly, is there not a risk of cavitation in that case?
 
Fast Eddie said:
Feed pump inlet...

Unless it is sealed perfectly, is there not a risk of cavitation in that case?
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I couldn't say, but then again, was it ever known to cause problems as Commandos had it from '68 to '74.
 
L.A.B. said:
Fast Eddie said:
Feed pump inlet...

Unless it is sealed perfectly, is there not a risk of cavitation in that case?
Click to expand...

I couldn't say, but then again, was it ever known to cause problems as Commandos had it from '68 to '74.
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There should be no cavitation for this reason. Once the oil comes from the tank (with no entrained air) the 'tank head pressure' oil goes through the pump and becomes under 'system pressure'. No atmospheric air gets into the pressured oil system. The ORV threads might leak into the chest, but any system oil OPV flow is immediatly back down to 'tank head pressure' once out the exit hole by the OPV piston...
Now recirc oil is back in the oil pump feed again with the tank oil and both are at tank feed head pressure.

IMO only hugely bad pump shafts may include air into the system from the scavenge side. Sorry I haven't tried it yet.
 
Just to be clear, I'm referring to the oil way drilling in the crank case, and what might happen when fitting a MKIII timing cover is fitted to pre MKIII cases, and IF that oil way drilling is not sealed properly, could the pump not draw in air there, from within the timing cover, and induce cavitation?

Seems to me that plugging the oil way properly makes sense due to the above.

Well, maybe...!
 
Fast Eddie said:
Just to be clear, I'm referring to the oil way drilling in the crank case, and what might happen when fitting a MKIII timing cover is fitted to pre MKIII cases, and IF that oil way drilling is not sealed properly, could the pump not draw in air there, from within the timing cover, and induce cavitation?
Seems to me that plugging the oil way properly makes sense due to the above.
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It applies to Mk3s as well, not just when fitting a Mk3 cover to pre-Mk3 cases.

But, yes, I think air could potentially be drawn into the feed from a leak at the timing cover joint (damaged gasket etc.) although again, I'm not entirely sure it would cause any significant harm as there would still be the pressure head of oil from the tank feeding the pump inlet unless an 'automatic anti-drain valve' happened to be fitted in which case the lack of vacuum resulting from an air leak 'downstream' of the valve could cause it to shut down.
 
Fast Eddie said:
Just to be clear, I'm referring to the oil way drilling in the crank case, and what might happen when fitting a MKIII timing cover is fitted to pre MKIII cases, and IF that oil way drilling is not sealed properly, could the pump not draw in air there, from within the timing cover, and induce cavitation?

Seems to me that plugging the oil way properly makes sense due to the above.

Well, maybe...!
Click to expand...

under those conditions cavitation maybe yes... IF you can get the bike started... since all the oil tank oil will probably be in the sump...
I can attest to a good pump making vacuum. On my oil pump test rig, the good pumps will collapse the inlet rubber line until I open the ball valve to let oil in from the tank.
Yes put a 1/4-20 set screw and wicking loctite. Then the tank won't drain on the floor if you pull the cover off. :lol:
 
I don't know if this will help, but I have had the same MKIII timing cover and oil pump on three different engines ('70, '71, and '73 850) for nearly 29 years, and 150,00 miles without any problems. Any chance the problem is with your customer?

MIKE B
 
Hi all,

I'm rebuilding a 72 engine with combat specs,
at the moment I'm machining the cases with modification suggested by andover on the site
http://www.nortonmotors.de/ANIL/SI Combat.htm

I will fit its standard pre MKIII cover,
referring to the oil way drilling in the crank case, you're assuming that the oil way drilling in the crank case should be fully opened,
my cases have the oil way not drilled!

Do I need to machine the case to open it?
Mk3 Timing Cover, for Pre- Mk3 applications (2017)

what kind of problem could cause a not drilled oil way?
Please advise

Mario
 
Thomasdunstall said:
I will fit its standard pre MKIII cover,
referring to the oil way drilling in the crank case, you're assuming that the oil way drilling in the crank case should be fully opened,
my cases have the oil way not drilled!

Do I need to machine the case to open it?
Mk3 Timing Cover, for Pre- Mk3 applications (2017)
Click to expand...

The oilway is here.....:
Mk3 Timing Cover, for Pre- Mk3 applications (2017)


......And should line up with a drilling in your pre-Mk3 timing cover.
 
Thomasdunstall said:
but what about the extra treaded hole close to a cover fixing hole?
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I don't know. It seems to be a '72 - '73 crankcase oddity. :wink:


Here's an image from dynodave's website which shows the same drilling in a '73 case, but it isn't there in earlier and later crankcases. :?
http://atlanticgreen.com/engcases.htm
Mk3 Timing Cover, for Pre- Mk3 applications (2017)



Perhaps one of our other members will know.
 
The mk3 cover is offered as oem replacement. No gear interference. I just did this on my bike to get rid of feed line valve. 74 commando, I made a plug to block OPV feed line return in crankcase as it's no longer needed and makes for an overall much tidier timing cover removal job as oil doesn't pour out of that threaded hole before using a cover screw to temporarily plug. Just make sure anti-sump plunger and timing cover pressure side receiving port that this slides into are de-burred and super silly smooth action is achieved as sometimes valve can get hung up on milling artifacts. Also make sure u put in New different sized rubber oil pump rubber seal and seal grommet as seen in pic, required for the right fit.

See post and notes from AN and my favorite norton whisperer, oldbritts

https://www.oldbritts.com/11_066161.html
 
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