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gunner Offline OP
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I'm just starting the rebuild of my 72 Combat Commando engine which was stripped because of low oil pressure. The issue seemed to be because of worn crank journals and shells.

The crank has now been reground -030 undersized and Kommando kindly supplied a set of NOS shells. I've fitted new FAG mains with bronze cages and a new S2 profile cam from Newman cams is being fitted together with re-profiled followers, new +20 Hepolite pistons.

I've cleaned and reassembled the crank with new nuts & bolts and am now at the stage of checking crank and cam side clearances with the cases bolted up.

The side clearances are surprisingly large with the crank clearance being 1.5mm and cam 3.5mm. I'm aware that you can get shims to take up play but which side are they fitted? What clearances should I be looking to get?

There is already a shim on the cam at the timing side but none on the crank, so which side should be shimmed?

The new cam has wider lobes than the old so I guess its important to ensure the lobes are centralized with the followers, but how is this done?

All info welcome.

Last edited by gunner; 10/17/21 1:33 pm.

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200000 series is the first engine family of the small diameter bushes. This continued to the end of NHT.
The original 06-2600/01 components should be avoided at all cost.

The early 300000 bushes are the preferable upgrade. Which provide correct cam positioning, spacing and clearance.
The 325000 (mk3) bush pair will work, but found to be less desirable due to more noticeable aggressive wear pattern.

The end clearance measurement you declare do not seem correct for an original unbutchered set of cases?
Describe each set of hardware that you are using to measure. CAM & CRANKSHAFT
[Linked Image]

nortonfam.jpg
Last edited by Dave Comeau; 10/17/21 2:12 pm.

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Originally Posted by gunner
The side clearances are surprisingly large with the crank clearance being 1.5mm and cam 3.5mm.

There is already a shim on the cam at the timing side

What do you mean by "a shim"?
There would normally be a chamfered steel thrust washer against the camshaft...
https://andover-norton.co.uk/en/shop-details/15521/thrust-washer-camshaft

...and for a Combat, a bronze thrust washer (remove the tab) against the T/S case)...
https://andover-norton.co.uk/en/shop-details/15903/thrust-washer

Last edited by L.A.B.; 10/17/21 2:35 pm.
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Why not tell him the "camshaft thrust washer" is 06-1086 is .125" thick and no other shims are factory components? It's use started with the 20M3S NHT family.

He has already been advised the 2600 components are detrimental plus FYI combat thrust washers are bronze faced steel, no good can come to the cases to have them rotate on the cases.

"Newman cams"
"The new cam has wider lobes than the old so I guess its important to ensure the lobes are centralized with the followers, but how is this done?"

I will tell him how to check the cam once he replys.

Gunner do you have a shop manual and parts book?


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gunner Offline OP
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Hi Dave,

the cases are numbered in the 220*** series and have the breather located on the back and low down, the sump plug is the small screw in type. I believe these are late 72 or early 73 Commando cases.

The pictures show the new and old cams, the journal diameter is 7/8 on both ends.

I've fitted the crank bearing inner journals to the crank, and looking at the shims available I may have to pull them off and fit shims behind, luckily I didn't use loctite to secure them. Looks like a shim can also be fitted behind the TS main bearing but the shims are only 3 thou and it apparently unwise to shim any further.

For info the old bearings were SKF NJ306 ECP with a fiber cage, there were no shims previously fitted and the new bearings seem dimensionally the same.

Looks like I will have to pull off the bearing journal from the crank cheek, not sure which way is best but probably a sharp chisel to get behind the journal and crank cheek and then some kind of puller.

For the cam, I don't think a shim can be fitted to the drive side cam journal, however movement is limited by the depth of the drive side cam bearing, so perhaps a shim can be added internally at the base of the cam journal.

The picture of the cam shows the old one at the bottom and new on top. As can be seen the lobes are wider on the new cam but the lobe nearest the drive side doesn't doesn't touch the cases as it bottoms in the cam bearing before this can happen.

20211017_153849.jpg 20211017_153914.jpg 20211017_154114.jpg 20211017_154153.jpg
Last edited by gunner; 10/17/21 3:21 pm.

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Quote
What do you mean by "a shim"?

I have the chamfered steel washer not the combat type in the link.

Quote
Gunner do you have a shop Manual and parts book?

I'm using various online parts lists such as the one on Andover Norton which seems accurate.

For a shop manuals again I'm using online versions, there is a factory workshop manual on the CBS site Here, then there is the Norton Commando service notes Here.

I've also watched the Mighty Garage Commando rebuild series on YouTube so I don't think I'm short of info.


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So yes 2 X X X X X NHT family.
You would do well to measure.
Starting with cam: add cam bevel thrust washer, install chain drive gear and torque down Measure the shaft length. 1.135" is typical
Cases: Measure the thickness of the case cam bore (no bush/bearing). .88" is typical.
Cam bushes are longer than the case thickness but shorter than the cam shaft-shaft. This is your end play.
Due to the 20M3S-on having the internal tach drive, the cam always is driven toward the right making the internal bush face as the orienting surface and cam end play is generally irrelevant.
It is generally unheard of, to not have cam lobes be on the lifters.


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Suggest 73-74 06-3020 cam bush.
Anyone who recommends the 06-2600 series is not your friend!


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Thanks for the info, I think LAB may be correct, although I have the chamfered washer on the cam it may be that I need the combat type with the tab.

Looking at my cases there is a small hole next to the TS cam bush, which presumably is for locating the tab? If the combat type washer is 0.125 then this would take up most of the end float.

I suspect a previous owner has fitted the wrong cam washer, hence the excessive end float, I'm going to try a combat type washer and measure again.

Last edited by gunner; 10/17/21 4:23 pm.

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Using the 2601 washers is insane. Breaking off the tabs will, yes, prevent them going up the oil pump passage and destroying the pump and possibly locking up or blowing up the engine.
Running the neutered 2601 washers will however potentially cause wear on the case face as they rotate. There is no filter on this series of engine so don't miss the opportunity to put the upgraded 850 bushing. The 2600 bush plus 2 2601 washers was original and if there was only one, than it shows an extremely bad rebuild. You do not have to change the drive side bush..

Years ago I had locked up a norton motor doing 105MPH(indicated) and lived to tell. Don't invite problems.

Each 2601 washer is .0625" and did make the fit up length correct length with 06-1086 bevel washer.
Using the 2600 components would, to me, make the bike worth at least $2000 less.


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Originally Posted by Dave Comeau
Why not tell him the "camshaft thrust washer" is 06-1086 is .125" thick and no other shims are factory components? It's use started with the 20M3S NHT family.


I assume that was a reply to me (although you replied to gunner) plus there was a link to the 06-1086 camshaft thrust washer in my post.


Originally Posted by Dave Comeau
He has already been advised the 2600 components are detrimental plus FYI combat thrust washers are bronze faced steel, no good can come to the cases to have them rotate on the cases.

Ok, bronze faced steel. My reply was intended to point out what would normally be fitted and to identify which items could be missing and not to contradict anything you said regarding upgrading the bush.

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Ok I will try the 06-3020 TS cam bush, I can see that its flanged so this should take up most of the end float, is this sufficient by itself of do I need anything else?


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The cam bush will be all that is needed as .040-.050" will stick out into the timing chest area. They are a little shy of .990" OAL plus .125" bevel washer, and the camshaft is around 1.135". End float is usually small with correct components.


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Thanks for the info, just wondering whether the bush would need to be line reamed with the drive side bush or is it sufficient to just ream the TS bush. I guess that if the cam still turns freely after fitting and reaming the TS bush then that's sufficient?


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Now there is a difficult question. It would seem that for the last 30+ years, I have never had to ream new Commando cam bushes. On the last job I did for a local guy (200000 cases) where he supplied Andover Noton bushes, when the cases were bolted up solid the cam was slightly dragging. I actually had an "expandable" 7/8 reamer and lightly relieved the drag.
By individual size I thought they would have worked. It may have been the alignment between the two half cases? NHT cam bushes usually last over 100,000 miles.
Raw new bushes run about 3 thou over =.878"ID before installation


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The other thing I've now noted from reading various forums is that VW air-cooled crank shims can be used behind the main bearings and crankcases.

The shims come in various sizes from around 0.25mm to 0.32mm thick and 71mm od & 53.6mm id,

In my case, I think it would be easier to to use 2 shims 0.32mm thick behind each of the mains bearings. This should reduce the end float from 1.5mm to around 0.22mm (8.6 thou) which is within limits.

I'm a bit uncomfortable having the main bearings stick out by 0.64mm on each side, however, this approach seems a lot easier than trying to get the inner journals off the crank which will probably get butchered in the process.

My riding style is fairly sedate with only occasional high-speed blasts, so hopefully, it will all hold together for another 50 years or so.

There is an oil filter fitted and I've read the detailed "best oil for a Norton Commando" analysis, I will be using Morris conventional V twin 20w50 which comes out well in the tests.


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Originally Posted by gunner
In my case, I think it would be easier to to use 2 shims 0.32mm thick behind each of the mains bearings. This should reduce the end float from 1.5mm to around 0.22mm (8.6 thou) which is within limits.

https://www.accessnorton.com/NortonCommando/crankshaft-permissible-end-float.24835/

Edit: Note that when the factory began fitting two (pre-Superblend) crankshaft roller bearings the end float increased to 0.010" - 0.024" (Norton Service Release No.68), however, that information wasn't updated until the 850 Mk3 manual.

Last edited by L.A.B.; 10/17/21 9:38 pm.
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gunner
In this crankshaft situation, like the cam that gets pulled to the right from screw into the tach drive gear, the crankshaft also gets pulled to the right from screwing into the oil pump gear..
Just remember that you are setting end play at room temperature. The week end I blew up (at 105mph) the temp was 4 degrees F / -15C and the cases would have shrunk close to interference fit at start up. I would never build at room temp, a NHT engine with under .010".

With a quality small bearing puller you can easily pull off and then press on repeatedly with out damage.to the crank or bearing. This is for ball or moderrn fag superblends. The middle type with rollers on the inner race are more difficult if you want to reuse them. A special tool may be needed to hold the rollers and prevent damage to the brass cage. I have not bothered yet to make one..
My preference only...
Avoid shims if possible.
The original shims were on the crank despite the parts book pix showing large shims to go behind the races in the case. I would prefer to remove the crank bearing over the case races. I would also only put shims on the timing side that gets held together with a nut... there is nothing on the drive side except press fit...and "there are stories"of shims broken up and have come off and showed up inside the bottom end.


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Quote
With a quality small bearing puller you can easily pull off and then press

Agreed, I think I'm going to invest in a decent-bearing puller so I can get the inner race off the crank.

Does anyone have a recommendation for this? The main issue will be getting the puller to engage with the race where it butts against the crank cheek. I've seen some clamp-on types that might work, will investigate further.

Quote
Note that when the factory began fitting two (pre-Superblend) crankshaft roller bearings the end float increased to 0.010" - 0.024"

Thanks LAB, I'm going to try for end float within that range (0.010 - 0.024).

Last edited by gunner; 10/18/21 7:44 am.

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Originally Posted by gunner
Agreed, I think I'm going to invest in a decent-bearing puller so I can get the inner race off the crank.

Does anyone have a recommendation for this? The main issue will be getting the puller to engage with the race where it butts against the crank cheek. I've seen some clamp-on types that might work, will investigate further.

Personally, I'd be inclined to follow Jim Comstock's advice to shim between the bearing and the case
https://www.accessnorton.com/Norton...ings-to-early-commando.17806/post-263967
Edit +
https://www.accessnorton.com/NortonCommando/crankshaft-end-play.7841/post-101934

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And I've seen it said that once you pull the inner race off the shaft, it will stretch a shade and will never be as tight again.
I'd say these are wise words ... ?

In a past life as a farmer, we changed probably hundreds of bearings.
Although not the same ones as on a Norton crank, (obviously), they only seemed to have one life.
Disturb them, and they were best thrown away.

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"On the timing side the bearing is held tightly against the shim by the torque on the oil pump drive worm and I have not seen one come loose there. Jim,"

IF Jim says it that's OK but when I say it I'm wrong.

"If the shim is soft metal it will wear through the shim"

How man attempts to get the correct shim size and material and location installed? 2 or 3 times max in 150,000 miles?

Yes after 18 years there was a reason I am no longer publicly active on accessnorton.


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Bearing puller OTC 1122
I have used this puller since 1987, buy two and reserve one exclusively for crank bearings.


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Originally Posted by Dave Comeau
"On the timing side the bearing is held tightly against the shim by the torque on the oil pump drive worm and I have not seen one come loose there. Jim,"

IF Jim says it that's OK but when I say it I'm wrong.

Jim said it's ok as you did, but he also said "If you decide to install shims the[n] install them between the bearing and the case." and I said that personally, I agreed with in my opinion.

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I've ordered shims for both the inner race against the crank and the outer bearing against the crankcase.

Looking at the AN website drawings it shows that the shims between the bearing and case are 3 thou thick and can number anywhere between 0 to 8 depending on what clearance is needed, if all 8 are used this adds up to 24 thou (0.61mm).

The shims I've actually bought for this are the VW engine type and are 13 thou 0.34mm) so I would use 2 on the TS side and 1 on the drive side which would reduce the end float from 1.5mm to about 0.48mm (19 thou). Does this sound right, it's within the end float limits mentioned by LAB. Just slightly concerned about using too many shims between bearing and crankcase.

I think I would only try shimming the inner race if using 2 shims between the bearing and crankcase is too much.


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