Normal wear?

Wow, this is hard work.


Item 8 / part number 06.7569

As you can see with a new picture with an original main bearing from my Mk2a 850 for size comparison and the same part number 06.7569 on the unopened AN shim bag it is a small diameter shim unlike the ones that go in the engine case (which AN do not make or ever have)

I seem to remember I bought these shims based off the same muppet AN picture only to have these arrive to be of no use, as posted before, free to a good home.



I won't ask how a shim the size of the inner races shoulder hard pressed against the crankshaft was removed without moving the inner itself.

What JC has said in the past is. (and there might be other posts)

"Because when the end float is less than about .010 on a stock motor or .015 on a high revving race motor you will start to see damage on the ends of the superblend rollers and the thrust surface of the races.
The crank actually gets longer as the revs increase."

With Wellseal I have around 0.013" + on a stock engine which I deem close enough.
I would be surprised if the cases did not grow as they get hot.

If the means to adjust the float or someone could not be bothered it would all be a moot point.

Not having a lathe I stuck some shimstock with contact adhesive onto a piece of ply and with two sizes of hole saws cut them out. After picking the better size shim thickness I then stuck it back on the ply to dress it smooth.
The picture shows two sizes "roughed" out with the saws.

Time Warp said:

Wow, this is hard work.

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Item 8 / part number 06.7569

As you can see with a new picture with an original main bearing from my Mk2a 850 for size comparison and the same part number 06.7569 on the unopened AN shim bag it is a small diameter shim unlike the ones that go in the engine case (which AN do not make or ever have)

I seem to remember I bought these shims based off the same muppet AN picture only to have these arrive to be of no use, as posted before, free to a good home.

View attachment 20205

I won't ask how a shim the size of the inner races shoulder hard pressed against the crankshaft was removed without moving the inner itself.

What JC has said in the past is. (and there might be other posts)

"Because when the end float is less than about .010 on a stock motor or .015 on a high revving race motor you will start to see damage on the ends of the superblend rollers and the thrust surface of the races.
The crank actually gets longer as the revs increase."

With Wellseal I have around 0.013" + on a stock engine which I deem close enough.
I would be surprised if the cases did not grow as they get hot.

If the means to adjust the float or someone could not be bothered it would all be a moot point.

Click to expand...

I don’t believe anyone is disputing that AN definitely sent you the wrong shims. Still worth an email from FF though to see whether or not AN have ‘corrected’ what they supply to match what they show IMHO.

You‘re right about JC saying 0.010”-0.015” was the minimum, he explained in another thread that going below that can turn the ends of the rollers blue. Which would also stress the cases.

He also discussed upper limits thus (which I have amended my earlier post to reflect correctly):

“I would not worry about shimming the crank unless the end play ended up being over .035 in or so. None were shimmed from the factory with Superblends.If you decide to install shims the install them between the bearing and the case.You may be able to get by with a shim between the timing side bearing and the crank but if you install a shim between the drive side bearing and the crank it will usually come out sooner or later and cause much damage. There is nothing to keep it pinched tightly between the bearing and crank like there is on the timing side. Jim”

Personally, although the ramifications of running tighter than lower limit seem clear, I’m not sure what the ramifications of running greater than the upper limit are. In theory, you‘d reach a point whereby you got thrust issues on the big and / or small ends, but that level of float isn’t realistic.

I was not worried about the shims sent which were as the part number so were the correct shim as per that number (The actual placement location of them is not stated but assumed (incorrectly)
I am lucky to have the option of simply making what I wanted.

FF could also ask them why they reduced the diameter on the con rod bolt heads then increased the head offset to the point contact in the rod counterbore was reduced at the rod beam side. (lol <)
There will be no answer only smoke and mirrors baloney like the young guy got.

Fast Eddie said:

I don’t believe anyone is disputing that AN definitely sent you the wrong shims. Still worth an email from FF though to see whether or not AN have ‘corrected’ what they supply to march what they show IMHO.

You‘re right about JC saying 0.010”-0.015” was the minimum, he explained in another thread that going below that can turn the ends of the rollers blue. Which would also stress the cases.

He also discussed upper limits thus (which I have amended my earlier post to reflect correctly):

“I would not worry about shimming the crank unless the end play ended up being over .035 in or so. None were shimmed from the factory with Superblends.If you decide to install shims the install them between the bearing and the case.You may be able to get by with a shim between the timing side bearing and the crank but if you install a shim between the drive side bearing and the crank it will usually come out sooner or later and cause much damage. There is nothing to keep it pinched tightly between the bearing and crank like there is on the timing side. Jim”

Personally, although the ramifications of running tighter than lower limit seem clear, I’m not sure what the ramifications of running greater than the upper limit are. In theory, you‘d reach a point whereby you got thrust issues on the big and / or small ends, but that level of float isn’t realistic.

Click to expand...

The rods probably have around 0.100" axial float in the pistons so it might take some radical crank shimming to upset that.
The reality is a lot of people do not have the means (measuring equipment etc) or inclination to alter the axial float and as proven plenty still ran fine with large clearances (0.032" / 0.029" on the original crank) in my case.

What does the oil pump gear really do as far as thrust I do not know.

I had read about the 0.010/0.015" somewhere so went for that on the looser side. I also have the option of milling the tops off the original (after comparison to the NOS AE's) AE pistons to see how the rods sit in them but with equal crank shimming side to side it should be OK but of course do not know it for a fact without checking and checking is what real engine building is about including long term peace of mind.

The thing for me with British bikes is some of the unreliability myths were/are just that and in many cases careful assembly can avoid it these days.

Time Warp said:

The thing for me with British bikes is some of the unreliability myths were/are just that and in many cases careful assembly can avoid it these days.

Click to expand...

I wholeheartedly agree !

The only reason I posted about the limits here is that some people do get sucked into the ‘less is more’ with regards to tolerances, especially when they start comparing to modern engines. Even some pro machine shops are guilty of this too (I had to have a strong discussion with one local machine shop to ensure I got the clearances I wanted with a rebore, and I know of two old Brits bored by him that suffered piston seizures)!

We just have to remember that in some areas (crank end float and piston to bore clearance for example) old bikes do need to be treated differently to new ‘uns.

My old mk2a had 24 thou float on the crank from memory
That bike covered a lot of miles in my ownership and the float was never a problem
In fact nothing on the bottom end was,I never split the crankcases