E: Engine Main bearing outer race width

[oexing]

So I guess these were the socialist bearings you had to change. One cannot compare these with the actual modern bearings with glass fibre reinforced PA66 from FAG, SKF and the like. But then, in case of a two stroke, well, with modern gasoline - which is basically a lot of different thinners, alcohol is nothing that matters in this respect (!!!) - I am not quite so sure what that does to PA66. That might soften the plastics possibly, I don´t know.
I should add to my post above, BMW had early polyamide cages one time in the sixties but there was some trouble with them I was told. I was not overly happy with bronce cages as well, did not prove to be as long lasting as the ridiculous price suggested. I will sell my old stock of these at max price for those who believe in them.

Vic

 

[BigEd]

I am no expert on bearings or materials but after reading the posts mentioning cage materials I'm amazed that original bottom ends on Vincent machines were able to do those huge mileages without replacement.

 

[Phil Arundel]

Surely it's only Drive side that has narrow outer track ?.
If you have not had the bearings out before, They do sometimes "Walkout a bit " Because of a bad crank ? and could be pushed back, With heating the cases.
They should both be flush with the cases.
Also you can use the wide outer track bearing on the drive side ,With a modified Alloy spacer, Which is more narrow , Where the outer track touches it, And is sold by the Club Shop.
Good Luck, Bill.

Thanks Bill,
It's not only the drive side which needs a narrow track - proved by the fact that the flywheel interferes with the wide bearing preventing the cases closing fully.
My crankcase are new so have never had bearing fitted. The problem has been solved by fitting narrow races to both sides.
Incidentally when fitting the crank into the French manufactured cases I found that the outer diameter of the flywheels interfered with the cases. Consequently I had to have them machined to accept the flywheels - the flywheels interfered with the oil scraper element of the crankcas.
For information purposes I had the machining carried out by Barry Dawson at Sherrif Hutton near York - a great guy with stacks of skilled expertise.

 

[Bill Thomas]

Thank's Phil, As I was putting the post on , My head was banging , That's why I put a Question mark !.
I have been doing these bikes for too long now, They put a plate in my head in 1970, That's all I can blame !.
Interesting you have new cases, Shame they still need work.
When I was racing my Twin, I often took the cases apart, And found the outer track had come out and was touching the bigend nuts.
I had the cases redone by an expert, But they still did it, If the crank has too much runout, They what we call walked out, But the poor old bike was thrashed to bits, Sprinting is very hard on an engine, With 12 to 1 pistons on petrol.
Good Luck, Keep us posted. Cheers Bill.

 

[Peter Holmes]

Years ago I had my engine rebuilt by a very well respected Vincent engineer, sadly no longer with us, the crankcases were bored and sleeved back to standard, new bearings fitted and the flywheels aligned with new big ends fitted, the whole works really on the entire engine. The next time the engine was pulled down the main bearings had walked again, a bit perplexing to say the least, the next well respected Vincent engineer, now retired, refitted the bearing with loctite and also ground three little recesses in the outer bearing, drilled and tapped 3 small holes very close to the edge of the bearing housing and retained the outer bearing with the overlapping countersink screws. The engine has not been down since, but I do use a magnetic sump plug, if the bearing does walk and grind itself against the big end nuts I am hoping that I will notice metallic dust on the magnet, as yet nothing has shown up. It did seem to me a fairly crude method of bearing retention, any comments from anyone?

 

[bmetcalf]

Rip Tragle in the US, now retired, but had a good reputation, used that technique.

 

[timetraveller]

I also used that method on my sprint and road bikes. I used two, rather than three large headed screws and sunk their heads below the surface of the crank case housing.

 

[greg brillus]

When fitting oversize sleeves in the main bearing tunnels, some use alloy, brass........I prefer to use steel sleeves that have a small hat section as well. We give them 0.003" interference, and afterward the new bearings press in cold. We have done several engines this way with no problems so far, and this was going off advice from my machinist who is now a good friend of mine, a fellow Kiwi with many years of experience and who loves all things motorcycle related.

 

[Garth Robinson]

I also used that method on my sprint and road bikes. I used two, rather than three large headed screws and sunk their heads below the surface of the crank case housing.

The late Doug Hollis also used and recommended that method.

 

[Robert Watson]

I have just done the job today. I used the two c/sunk screws method. That has been done in all my engines with never a hint of anything coming loose.
When the fit of the bearing is lost the local method is to grind down the bearing outer race a few thou and then build up with hard chrome, grinding back to the required .002 interference. Of course a mandrel and some blanking plates are required. And a friendly hard chrome guy.