Worn oil pump worm gear

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Picture you see here shows return hole just above pump and the inlet valve drain, when 2 bar clean compressed air was blown into this hole, oil poured from the rocker feed pipe you can see at the bottom of the picture, so that route is clear..

Alignment all looks pretty similar to me.
Worn oil pump worm gear
 

I proceeded with 5 more tests on each gear -on the gear tooth -and had an average difference of RC 8.5


Just one test from the edge.
 
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Thanks Jim.

Gets to the root of it I think!

Did you test pump gears?
 
Brooking 850 said:
...............

It turns out there could be difference in hardness levels on the oil pump gear set depending on manufacturer.
Worth looking into.

Regards Mike
Click to expand...

Yes but.....and looking at Jim's RC hardness tests this may well be the source of the wear, but surely the only supplier is AN?
 
SteveA said:
Thanks Jim.

Gets to the root of it I think!

Did you test pump gears?
Click to expand...

Yes,
I tested two old original gears at an average of RC 53 for one gear [1969] and RC 56 for the second [1974]

I only had one new mfg gear and it averaged RC 42.

Now for some good news.

Old stock pinion gear [the kind that tends to loose teeth occasionally] RC 46

New pinion gear RC 56

These were all 5 dent averages from the side of the tooth.
 
Thanks Jim, excellent call and tests
The first piece you tested had exactly the same wear marks as mine.
My pump was a brand new item when I first built the race motor 5 years ago.
Looks like I can discount the oil being too thick based on others results.
Regards Mike
 
Well for what it's worth I have 3 motors that have never shown any real wear to the worm gears as this post discusses. So something is amiss , maybe the newer is softer ?
Dunno.
 
Torontonian said:
Well for what it's worth I have 3 motors that have never shown any real wear to the worm gears as this post discusses. So something is amiss , maybe the newer is softer ?
Dunno.
Click to expand...


Well, A few years ago when I built the replacement motor for my bike I put in new oil pump gears.
The old ones had a lot of miles and a little wear -but the new ones had a lot of wear after just a summer [~8000 miles] of riding.

I put the old gears back in. They are still there and had not changed much last time I looked.
 
Thanks Jim for the feed back, the new worm drive nut was also difficult to get on the crank once half way down the thread.
Tested two other nuts and a different crank timing side, the new one was difficult no matter which crank, the old ones went all the way on by hand on both cranks tested.
What about ideal alignment worm drive nut to pump gear, right on centre of just off as there is room to move the the pump gear either way?
Steve A's pic show the offset rearwards.
Regards Mike
 
Brooking 850 said:
Thanks Jim for the feed back, the new worm drive nut was also difficult to get on the crank once half way down the thread.
Tested two other nuts and a different crank timing side, the new one was difficult no matter which crank, the old ones went all the way on by hand on both cranks tested.
What about ideal alignment worm drive nut to pump gear, right on centre of just off as there is room to move the the pump gear either way?
Steve A's pic show the offset rearwards.
Regards Mike
Click to expand...

I don't think the alignment will make any difference.
 
Thanks Jim, the wear on the pump gear shows 5/8's engagement , just thought if the gear was centred to the crank and worm nut, this might give more centred engagement on the pump gear, reason I asked
Regards Mike
 
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Brooking 850 said:
Thanks Jim for the feed back, the new worm drive nut was also difficult to get on the crank once half way down the thread.
Tested two other nuts and a different crank timing side, the new one was difficult no matter which crank, the old ones went all the way on by hand on both cranks tested.
What about ideal alignment worm drive nut to pump gear, right on centre of just off as there is room to move the the pump gear either way?
Steve A's pic show the offset rearwards.
Regards Mike
Click to expand...

Yep the gear I sent back would not run down the left hand thread, but also looked bad.

Just purchased a NOS worm from ebay. Looks like I should look for a pump gear as well!
 
An air-cooled engine will necessarily produce more sludge (blowby combustion products) than a watercooled engine. Apart from trapping shavings, using an oil filter and not using synthetic oil, I believe frequent cleansing of the oil tank is the best precaution of premature oil pump wear.

The peculiarity with worm (helical) gear is the high shear forces occuring, in contrast to straight cut gears. If the oil isn't clean, abrasive wear will be more pronounced. Hence, using a worm-drive for the oil pump wasn't the best choice of design made by Bert Hopwood. However, abrasion can be mitigated by said actions.

-Knut
 
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Knut, I have clean oil and change it regularly as its a race bike, even though the oil may not be up to its use by date.
Have an oil filter system and the tank gets vacc'ed then wiped out every oil and filter change , new filter every time the oil is changed.
Have just checked after buttoning up the cases and timing gear, 0.017" end float with the crank and no backlash on the oil pump gear no matter what position of crank rotation or side position within the 0.017" sideways movement.
I use full synthetic oil 10W50 Joe Gibbs (Driven)
Regards Mike
 
Mike is ahead of me on tank cleanliness mainly because I have an Oil in Frame set up......sloshing stuff around isn't that easy!

I change oil and filter every two race meetings. Going to stick with synthetics.

I may need to say that I am not really a novice at this stuff! I certainly don't know everything and this is a great place to get more info.

Stripped and rebuild my road motor to go production racing in early '75 and then built my first full spec Norton race motor from a pile of parts including some significant parts from the Thruxton race shop in late '75! Made mistakes sure, still do, but I have finished a few races since then.

The problem discussed in this thread is wear in the pump drive gears. I am changing the pump to allow me to check the fitted item. It may be worn, but I don't know that yet. I will strip it and if needed do a basic fettle on the faceplate. Pumps aren't cheap, but they are cheaper than a lot of other parts.
 
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I thought the oil pump design inits 3 start guise predates Bert Hopwood..The one on my ES2 has probably been round the clock twice.and is fine.6 start may add all sorts of problems especially under racing conditions. But this was not an issue with the domiracer ? was it?
 
oldmikew said:
I thought the oil pump design inits 3 start guise predates Bert Hopwood..The one on my ES2 has probably been round the clock twice.and is fine.6 start may add all sorts of problems especially under racing conditions. But this was not an issue with the domiracer ? was it?
Click to expand...
Never had an issue in my '75 built 850 MkIII cased motor! Jim has illustrated the issue well.
 
SteveA said:
Never had an issue in my '75 built 850 MkIII cased motor! Jim has illustrated the issue well.
Click to expand...

I am wondering if there might be dimensional differences in different batches as well as hardess issues. Any way I shall take my existing gear and worm from my 71 cases known to be good for my Maney cases and crank and try new for the 71. They will have an easier life possibly helped by Ball location of crank
 
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