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

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.
 

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oexing

Well Known and Active Forum 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 . . . .

Vic
drive side with seal in between:
P1070623.JPG


timing side with scroll:
P1070655.JPG


gearbox rollers:
P1070657.JPG


inner races drive side:
P1070540.JPG
 

Bill Thomas

Well Known and Active Forum 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.
 

Cyborg

Well Known and Active Forum Website User
VOC Member
More on crank centring….. math test anyone?
NOS crankcase just resting on the mill bed, crank held in the quill with a collet to keep it vertical and prevent it from rocking in the drive side ball bearing. A section of liner and cut down piston was used as a reference point.
1DAE12E3-390D-4AED-97AA-FAD58D369CFD.jpeg


Results are as follows:

DA1F71DD-41E2-45BF-95FF-CD4C761A1ECB.jpeg


So front rod needs to go towards the drive side by .0195” and the rear rod needs to go towards the timing side by .0065”
So the question is…how unusual is it that instead of shimming, one has to remove material from the ET77?
 

royrobertson

Well Known and Active Forum Website User
VOC Member
Try turning the cases up the usual way and pull the crankshaft over the the drive side with either the shock absorber or a spacer and nut. The rods have side clearance on the pin and the spacer and by laying the cases on their side you just may be getting false readings. The spacer should be accurately ground for the offset between the cylinders and by the look of it you have new Carrillo rods so having the difference you measured is very odd. If not new can the rods be bent? Have your cases been machined on the split line thus reducing the offset?
Roy
 

Cyborg

Well Known and Active Forum Website User
VOC Member
Thanks for the reply. As far as I know the cases haven’t been altered on the split line. The cases are NOS, so who knows what transpired at the factory. When I measured, I took the rod side play into account. When measuring the gap on the drive side, I made sure the rod was all the way towards the timing side and vice versa. The total gap ( both sides of the rods) is equal on both cylinders. Not sure what that tells me other than my measurements may be in the ballpark. I tried several ways of measuring… calipers, snap gauge, bore gauge and couldn’t get consistent results, so opted for the old liner/piston setup and feeler gauges. I’m reasonably sure the crank was sitting all the way home against the E91 bearing. I put some downward pressure on the quill and locked it in place. They are new Carrillo rods, so should be straight.

ps… I took a new pin and it will slide through both small end bushings (at the same time) very smoothly. That indicates to me that the rods are straight. If one or both of the rods were bent, I would assume the pin would make a fuss going through there.
 
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Cyborg

Well Known and Active Forum Website User
VOC Member
Rather unscientific method, but if I measure the width across both rods at the small end and subtract the width of one rod, I come up with 1.248” so pretty close to the cylinder offset.
I used a Mitutoyo caliper… frowned on by some, but the thing never ceases to amaze me how often it agrees with a micrometer. I measured the distance with the rods moved apart all the way and again with them as close together as they would go. From that I calculated the mid point and subtracted the width of the rod. Lots of room for error measuring that way… including assembly grease, but nothing to indicate anything amiss with the spacer.
 

royrobertson

Well Known and Active Forum Website User
VOC Member
Hi again. Yes the new Carrillo rods should be straight. so is the spacer the right width? I see you have a pressed in pin. Who made the flywheels?
From bitter experience over many years I have learned to suspect everything in these sort of cases if Something is not right. Check the offset of the bores in the cases. Check the offset of the rods match the cases. Sorry its 20 years since I built my racers bottom end and I just can't remember what the spacer width should be.
Again may I suggest you try measuring again with the cases in the normal orientation as the spacer being a just a slide fit may stick on the pin and give you false readings. Also the rods may stick if the bearings are new and the rods trying to tilt sideways. I would just use a slip to measure the gap between the top of the rod and the piston casting. Or any piece of flat metal if slips are not available. Near enough is good enough.
 

Cyborg

Well Known and Active Forum Website User
VOC Member
I will measure again as you suggest. The flywheels are from Maughan. I am always suspicious of NOS parts as they may be OS for a reason. I’ve quickly learned to become suspicious of new parts as well. Some crap out there. Good reason to have sufficient tools for measuring because it seems the end user must fulfil the QC Department’s duties in some situations. Beware the term CNC, it doesn’t necessarily translate into quality. Anyway… enough ranting.

Measuring cylinder offset with a caliper seemed a road laced with land mines. I bolted the drive side case half to the bed, attached an indicator to the quill, zeroed the DRO on the Z axis (quill) and then raised the knee to zero the indicator on the liner clamped in the rear bore. Then moved the liner to the front and lowered the quill until the indicator zeroed again. The reading on the DRO was 1.2295”, so off by 0.0205”.…. which begs the question what is “ normal” assuming there is one.
I’ll take a stab at measuring the spacer and remeasure the clearance between the rod and piston.

5FB09066-F02B-4F55-AB3A-133993894800.jpeg
F3B21E80-1801-481D-9E79-BC8C8CA6156B.jpeg
 

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