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c.cito
Joined: 12 May 2008
Posts: 15
Location: South-central Pennsylvania
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 Posted: Thu Aug 21, 2008 8:57 pm Post subject: Mk3 Oil pump check value issue |
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I have been working on my 75 MK3 oil pump to reduce wet sumping and
have run across a bit of a problem. The plunger for the check valve
is getting stuck in the timing side housing. I had to drill out the
old plunger it was stuck so badly, and the new plunger got hung up
almost immediately while I was checking its movement. I deburred the
new plunger but was afraid to mess with the timing side cover for fear
of making the plunger seat out-of-round. Has anyone else run into this
problem? How loose a fit can the check valve have before oil leaks
past it? Thanks, this board has been a life saver more than once...
-paul |
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cash
Joined: 10 Nov 2006
Posts: 448
Location: west cumbria
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| Posted: Thu Aug 21, 2008 11:58 pm Post subject: |
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You're going to have to have a close look at the hole, sounds like it's tapered or burred. If you haven't the equipment perhaps you could take it to a small engineering firm and they could measure it and advise. A little extra clearance shouldn't cause a problem if the pump is in good nick.
Cash |
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79x100
Joined: 19 May 2006
Posts: 706
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| Posted: Fri Aug 22, 2008 6:52 am Post subject: |
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My impression has always been that they tend to stick open because of the small oil bleed hole behind allowing thick oil to cause a suction.
The seal is made between the top of the plunger and the oil pump rubber so I can't see any objection to a slightly loose fit, assuming the plunger stays the right way up. I polished my plunger and this seems to have helped.
The plunger should be free to move with just the slightest finger pressure. |
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Jason Curtiss
Joined: 14 Jun 2003
Posts: 667
Location: HOUSTON, TEXAS
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| Posted: Fri Aug 22, 2008 8:58 am Post subject: |
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| Unfortunately, the check valve was a failed attempt to prevent the wet sumping problem. |
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c.cito
Joined: 12 May 2008
Posts: 15
Location: South-central Pennsylvania
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| Posted: Fri Aug 22, 2008 9:46 am Post subject: |
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| The plunger will work fine with slight finger pressure for several pushes, then gets hung up, usually when I push it all the way to the bottom of the seat. I rigged up a "honing" device (a dowel wrapped with emery paper chucked in my drill) and will try to loosen things up there a bit. I just finished work on the oil pump so maybe that will help with the wet sumping. Thanks again for the advice. |
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cash
Joined: 10 Nov 2006
Posts: 448
Location: west cumbria
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| Posted: Fri Aug 22, 2008 10:46 pm Post subject: |
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Don't do it that way. If you do for goodness sake be careful you could quite easily remove way too much metal and and put more taper in the bore. I would be inclined to get the bore measured first. The problem might not be the bore, the vent hole could be too far forward??
If it is the bore a lead in on the piston skirt might help, or perhaps a machinist could turn you up a broach. The material wouldn't need to be anything but mild steel or a 8.8 bolt shank.
Cash
Ps
Never had a wet sumping problem with my Mk3 |
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c.cito
Joined: 12 May 2008
Posts: 15
Location: South-central Pennsylvania
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| Posted: Sun Aug 24, 2008 7:07 am Post subject: |
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I checked the plunger (just purchased) and it isn't completely round. Soooo I ordered a few more of them, and just hope one will be correct. If that fails I will take it to the local machine shop and have them make one. One little check valve has kept this bike off the road for a few weeks now, waiting for parts... I should probably start hoarding little bits and pieces so this doesn't happen so often. Thanks again.
-paul |
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Norton Commando Forum by Corporate Pages Web hosting using phpbb
The Unapproachable Norton Commando
At the end of 1967 the Norton Commando was announced.
The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.
It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.
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It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.
The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.
