Norvil Main Bearings?

Wow Nick,

I have some experience here. As a cheapscape Yorkshire Norton owner I asked my local bearing supplier if they had anything that I could use for a lightweight. A roller bearing of the type you photograph was supplied and I duly ground the inner race to suit.

In service the outer race trough catches any and all wear debris. No amount of oil mist in the crankcase ever washes the dirt and debris from the outer race. When standing, the dirty oil sits in the bottom of the outer race trough.

Contrast this with the normal design for Norton's. The outer race is L-shaped, not U-shaped. Oil splash and mist is constantly cleaning and removing any wear particles or dirt from the outer race.

After 5,000 mile my drive side bearing was shot. I should have been more careful and less penny pinching. The replacement, of proper automotive design, which I should have bought in the first place, is fine. 

I had already told Phil Hannam and Andy Sochanik about this issue, so it is a bit Deja-vu. Disappointing to see these bearings being sold for Lightweights.

Best Regards

Peter

I fitted a set of those loose inner race bearings to my 650 and was horrified by the amount of pitting  plus a bad score mark evident on the rollers when I checked the bottom end 1,000 miles later. Possibly this is why C3 or 3 dot clearance is specified for them to help cope with the rubbish that the oil system carries around. I then fitted an external oil filter to my bike.

I know that fitting a cartridge oil filter to a Lightweight is not that easy but this would go some way to help sifting the muck out of the oil. 

Is it possible to drill the outer race to fabricate an oil drain?

Nick,

After learning my lesson, have

e bought main bearings from NOC in the past. Once heavyweight bearings and twice lightweight bearings. All looked up to the job with proper riveted cages per original design. I bought the heavyweight bearings because l/w out of stock and ground the internal radius myself.

Past performance is no guarantee of the future.

I think it unlikely the NOC would now sell a poorer type of bearing. Very much doubt any NOS bearings available in useable condition after 60 years.

Peter

Agree with above. Unless you can find a way of fitting a drain hole in the outer of the bearing & its seating to allow oil (& any foreign matter) to drain away, I would avoid this 'U' shaped outer bearing.

If clear of swarf & well lubed, I'm sure this is a capable bearing. Maybe its intended to work horizontally on a vertical shaft?

Hi Nick,

MRJA30 bearing will get you what you need for the Navigator. Henderson bearings? 

Try stabbing this into the search engine.

Should always be an outer race with one lip, inner race with two lips.

My Norton Twin manual agrees.

They never used to be that expensive. A regular clearance will be OK for your 20 HP.

Good hunting.

Peter

... on Simply Bearings show 2 versions - one RHP. https://simplybearings.co.uk/shop/advanced_search_result.php?search_in_description=1&keywords=MRJA30%20&

When I rebuilt my Jubilee in 1994 I fitted FAG roller bearings, as in the Commando. I just had them machined to match the radius on the crankshaft and that was it. They’re still there, never going to wear out. As the original ball bearings in the lightweights were the same size as in the Dominators, you’d think they’d be bullet proof, but they’re not for a couple of reasons. I figured that main bearings tough enough for a Commando 850 should last for ever though and it looks as if they are going to. Mine came from Norvil then, I don’t see any reason not to use them. 

Nicholas.......you have done well and your diligent research has paid off.......albeit nearly costing an arm and two legs.  Anna Dixon recommends this brand of bearings so extra brownie points for that.

This has been a very interesting thread with tankfuls of useful information being bandied to and fro. The Town Crier is often out and about with regards to fitting 'superblend' bearings on a 'twin'  crankshaft but as Peter Holland points out ........these can be a collecting trough for any debris washing around the engine.  Which makes me wonder how  Commando owners get away with fitting a pair of such bearings?

The first Model 7 engine had a sump plug but without a filter. Any junk material in the oil was washed around the inside of the engine before being sucked into the oil pump and then dumped into the oil tank. Where a coarse filter caught the bugs, leaves and road grit but then fed anything smaller back into the lubrication system.  Some of these early Dominator engines also had a 'non-return' ball valve fitted to the oil supply plumbing but this useful gear was soon to be an ex-item due to the dodgy oil causing the ball to stick either open or closed.