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ET: Engine (Twin) Installing ET92 Inner Roller Set on Mainshaft


Well Known and Active Website User
VOC Member
What is the best method of installing these inner roller bearing sets ET92 on the mainshaft?
I appears to be a 0.0015 interference fit.

greg brillus

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VOC Member
Vic, my machinist is a fellow Kiwi like me......... Not much older than me, and he is from Bert Munro territory.........Pretty clever chap........His shop is quite small really........with his son and an apprentice there......They have both manual plus CNC machines........lathe and Mill........He loves doing bike work being a bike rider himself, but the small jobs don't pay like the production run stuff.........He is always doing stuff for me..........Some of the repairs he has done for me have been amazing........We always seem to work out a plan to fix these old bikes.........but it does take some head scratching at times........Cheers.

Bill Thomas

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VOC Member
Having had " Walking Mains ", All my life !, Plus other problems :) ,
Maybe 17 years Racing not helped ?,
Enough is Enough,
These Beggers Cannot walk !,
You have to make sure there is enough side clearance, And I will have to grind the outers to 5/8 ",
It was in MPH many years ago, By a respected Racer.

Think how much faster I could have been , If they had stayed in place ?, Just Dreaming !.
Cheers Bill.


  • IMG_20211130_074608.jpg
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Well Known and Active Website User
VOC Member
Bill, that looks good to have faith in it, is it drive side ? Why grind it to 5/8 , no space there ? I´d rather grind other items next to the bearings for getting more space.
Nevertheless I like the rollers in the outer race and the modern high load types, count the rollers in photos. The 62/30/20 mm type got 13 rollers, the old style just 9 . One snag in the timing side is you have to drop the oil pump scroll in before fitting the main bearing as it would not pass the rollers, At least with first engine it was no deal to assemble the timing half of engine through bearings and scroll , no string trick involved here. Thinking it all over I am no longer sure about the small outer timing side bearing. I had a plain inner race pushed in later from crank end. So there is some risk of outer walking into the scroll as no lip prevents this. So for the second engine I´ll need an idea for securing the outer race with rollers. Hmmm . . . .

drive side with seal in between:

timing side with scroll:

gearbox rollers:

inner races drive side:

Bill Thomas

Well Known and Active Website User
VOC Member
Yes Vic, That's the trouble with going too NON Standard,
If down the line , Someone else strips your engine, He's in for a Shock !.

My lipped ones are for both sides,
I have a narrow spacer with the scroll, In stock !, Drive side,
But can't use it, Or the lip will be too far away and and won't stop the bearing from walking inwards,
An 1/8".

Comets being More narrow, Don't walk very often ?,
But as you can see from mine, It's had a hard life !,
I think it was used in the 1970 TT as a 624 cc Sidecar Racer ?.

Not sure I am up for the job, In my head I am keen , But can't get my BUM in the Garage !!,
Must give myself a good talking to :) .
Cheers Bill.

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