Crank end float?

[sprint]

What is the acceptable limits for the crank end float on a Super Rocket?

Thanks

[Billybream]

Hi.
The maximum permissible crankshaft end float is 0.003". This is all to do with the main bearing type used, and end float controlled by shim,s.
Correct measurement procedure is important, suggested methods are by using dial Indicator or feeler gauges.
Upon engine reassembly target would be 0.001" end float, but never easy to obtain accurate measurement.
Search topic,s regarding end float to learn inspection methods

[sprint]

Thanks for the reply.

What are the implications of having more than 0.003"?

Since the crank is effectively sprung loaded on the drive side via the shock absorber spring is the drive side bearing of the split roller or a ball type? Either way the crank is free to move slightly under the tension of the spring?

[a10 gf]

Hi, try these searches (from the forum welcome page, or in A7 & A10 Engine or from http://www.a7a10.net/forum/index.php?action=search):

crank end float
end play
crank shim

see http://www.a7a10.net/forum/index.php?topic=1352.0 for search tips.

[Briz]

What are the implications of having more than 0.003"?

Since the crank is effectively sprung loaded on the drive side via the shock absorber spring is the drive side bearing of the split roller or a ball type? Either way the crank is free to move slightly under the tension of the spring?

Well, nothing really terrible is going to happen with -say- .010" end float. PITA to do as you have to drag the bearing off the crank to correct it.

The spring loading of the shock-absorber is only applied to the sprocket. Its self-contained to the sprocket shaft assembly. Has no effect on the crank as a whole.

[sprint]

What are the implications of having more than 0.003"?

Since the crank is effectively sprung loaded on the drive side via the shock absorber spring is the drive side bearing of the split roller or a ball type? Either way the crank is free to move slightly under the tension of the spring?

Well, nothing really terrible is going to happen with -say- .010" end float. PITA to do as you have to drag the bearing off the crank to correct it.

The spring loading of the shock-absorber is only applied to the sprocket. Its self-contained to the sprocket shaft assembly. Has no effect on the crank as a whole.

Thanks for the reply.

That is a bit more confidence for me as 0.010" is what it currently measures with a dial gauge. It looks like the guy who re-built it put the shim between the bearing and the oil seal distance piece and not between the crank and the bearing? I m loathed to have to do a complete engine strip unless it is absolutely critical/necessary?  

Is it a ball or two part roller bearing that is fitted to the drive side?

However, it is my understanding that there is a sliding bush on the M/S that the E/S, cam, and spring are attached to with only the crank nut being directly connected to the shaft so the crank will be free to move on this sliding bush the extent of what ever free play there is under the S/A spring tension alone?  Or have I got it wrong?

[Briz]

Yeah, I see what you're saying. Its been about 30 years since I worked on a A10 cush-drive! I cant remember if the nut tightens up on something solid or just tensions the spring.
But for this to allow crank movement, the inner bearing would have to be a sliding fit on the crank. Which it isn't.

The main bearing is a roller, so this allows end float.

[chaterlea25]

Hi Andy,
The crank nut MUST tighten against the sleeve solidly this forces the sleeve against the seal spacer, then the bearing +any shims aginst the crank, when its all tighened up theres no spring effect on the crank.
The main bearing is a single lipped roller

HTH
John

[Colsbeeza]

I have just joined the Forum today, and ask you sainted members for an opinion on the crank end float. I have re-commenced the final stages of getting my 1960 A10 Golden Flash up and running, having purchased this bike from England in 1985. Most work was done from 1987-1989 (Yes it has been a while). I was starting to panic, as my knees are starting to weaken ( I am 64)and I want to get to kick-start and ride this machine.
I had assembled the motor in 1989, but thought I should now dismantle and re-assemble due to the time interval. This time, I am getting the help of a more experienced British bike restorer, but this is his first A-model. I fitted an NF206 drive side bearing. This seems to be the most-often specified bearing, and it allows the outer race to remain in the housing whilst the inner race can slide out of the housing still attached to the crank. The bloke helping me (Phil) is puzzled by the timing side bush, which is a typical steel outer with bronze insert. The steel face bears against the end of the T/S crank is also steel. I had set the end float to 0.0015" using shims behind the D/S bearing as per the BSA Service Sheets. There is nothing to prevent the crankshaft from wearing up against the T/S bush. He was expecting to see the steel outer of the bush to have a bearing metal such as white-metal or bronze, and I must say that it has always seemed odd to me. I know there should be no shims on the T/S end, so is it correct to use the NF206 bearing and the usual T/S bush.?

[RichardL]

Col,

Welcome to the forum. That's a pretty good intro. Looking forward to some photos.

The simple answer is, yes the steel face of the bush is designed to ride up against the crankshaft web in a world of oil. I think the forces there are not great, being only the result of the cush spring force and incidental side-to-side bumpimg, which you have gone a long way to avoid by getting the play to 0.0015". One thing to be careful of is any looseness in the inner drive-side race on the crank. If you have doubt, some Loctite 641 bearing-hold juice might be the answer. If the race spins, conventional shims get shredded. Some folks here have gone with a one-piece  shim which has been ground to fit.

Richard L.

[chaterlea25]

Hi, Col & Welcome
If your T/S bush is two piece make sure the two pieces are pinned/pegged together
There are several posts here on the merits/ and arguments of different bush types
What is certain is that after this many years a lot of bushes are not a good fit in the crankcase causing loss of oil pressure to the bearings
It would seem that a trued up case and custom one piece bush is the way to go (other than needle roller conversion)
Make sure the crank sludge traps are cleaned
Check oil pump and pressure release valve or fit new ones

The main bearing you have is the correct type

I think the forces there are not great, being only the result of the cush spring force and incidental side-to-side bumpimg,

Richard,
Cush drive spring and assembly are captive on the drive side and do not affect crank bearings or shimming

HTH
John

[RichardL]

Thanks for the reminder. John. Definitely not pulled (or pushed) toward the timing side bush, so, no forces on that face due to the spring. I knew that at one time but you made me refresh my memory (and accuracy).

Richard L.

[Colsbeeza]

Thanks Richard & John,
Can I then assume that the only way to prevent the inner D/S bearing from spinning and shredding shims is to ensure it is a fairly tight fit, using Locktite if needed.? There seems to be no other means of ensuring that the shims remain firmly trapped behind the bearing.
Cheers
Colin
Here is a recent shot as I lowered it from my mezzanine.

[East_Coast_BSA]

Thanks Richard & John,
Can I then assume that the only way to prevent the inner D/S bearing from spinning and shredding shims is to ensure it is a fairly tight fit, using Locktite if needed.? There seems to be no other means of ensuring that the shims remain firmly trapped behind the bearing.
Cheers
Colin
Here is a recent shot as I lowered it from my mezzanine.

I used loctite on mine because it spun and ate the shims, but I believe that the root cause was the cush-nut being loose.  That nut tightens up the entire stack of components (outer spring retainer/nut, splined sleeve, shim and inner bearing race).  This is what prevents the inner race from spinning on the crank.  I think the spec. is around 65 ft/lbs.  That will hold it in place, I just used the loctite because I happen to have some in the garage.

[Colsbeeza]

Hi East Coast BSA,
I thought that only applied to early A7 models. ie. tightening up the cush drive pulls the crank up tight. BSA Service Sheet 208 says that this does not apply to the A10. (See Attachment) However, there appears to be no mechanism to pull up on the bearing other than tapping up the bearing against the shims using Loctite to tighten everything up before assembly in the crankcase.
So for the later A10's, is this all that prevents the shims coming loose.?
Cheers
Colin