Excessive crank end float

Hi, I have recently measured the crank end float of my 72' 750 Roadster at .42mm.
I know this is quite beyond the 5 thou to 15 thou (.13mm to .38mm) recommended by Norton ...

Is this something I should be overly worried about?
Since my rebuilt a long time ago, where obviously I missed this point, my bike has done 3,000 trouble free Km and feels great.
Could I be riding a time bomb?

Your thoughts are appreciated.
Regards
Aris

Is this end float with new bearings or the 42 year old OE bearings? The endplay you measured is very excessive; time for a hard look.

Bill.

.42 mm is about sixteen thou by my calculation. A friend has a running but tired MK 3 with fifty thou end play (at 110,000 miles, only ever had the head off!)
I think Jim Comstock mentioned recently that end play could be as high as forty thou and still be OK. I'm assuming that in the rebuild 3,000 miles ago, the mainbearings were replaced with the recommended type?

Glen

Found the post:

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

And this important bit

Not enough endfloat causes more problems that too much -from what I have seen. I have taken engines apart that were set at .005 and found the ends of the rollers turned blue. Jim

I found the above information very interesting because I plan to take my 650ss apart for crank balancing. I discussed my plans with the local dynamic balancer, who has a hotrodded Atlas. In addition to the balancing, he suggested shimming end float down to 2 to 3 thou on reassembly, as this is what he did with his Atlas. But it turns out that bike has only done a few hundred miles set up this way. It might be that the bearings have already turned blue!
So it looks like your sixteen thou of endfloat is a good amount to have, not too much, not too little.

Glen

worntorn said:

A friend has a running but tired MK 3 with fifty thou end play (at 110,000 miles, only ever had the head off!)

Click to expand...

Once opened up an engine with similar end play: the crankshaft worm gear and oil pump worm gear appeared considerably worn down :!:

Thanks for the insight on shifting crankshaft as wondered a long time if crank just self centered with pistons in bores or if the cam and oil drive sucked it to TS and then what? What mainly made me post though was to leave my mixed reaction to Nortonspeed's avatar ride > a mean naked bulldog cutie pie that could bite you hard in the joint and not want it to let go!

worntorn said:

Not enough endfloat causes more problems that too much -from what I have seen. I have taken engines apart that were set at .005 and found the ends of the rollers turned blue. Jim

I discussed my plans with the local dynamic balancer, who has a hotrodded Atlas. In addition to the balancing, he suggested shimming end float down to 2 to 3 thou on reassembly, as this is what he did with his Atlas. But it turns out that bike has only done a few hundred miles set up this way. It might be that the bearings have already turned blue!


Glen

Click to expand...

example:
Assuming you assemble and engine at 72 deg F .002-.003 clearance
I have run my norton at 25 deg F
difference 47

thermal coef of aluminum 12.3 x10-6/deg
thermal coef of steel 6.7 x 10-6/deg

length of material effected crank= 7.5"

case shrinks about .004
crank shrinks about .002
NET differential .002 shrinkage

on start up the 2 thou clearance is gone......ZERO

I aim to assemble my engines to .010 end play... if I do any adjustments.

Dyno you are one of the few that have considered temperture on assemblly to judge clearances and maybe fastener torque, other that the garden tractor puller builders. While topic hot, can ya fill us in on a TS ball bearing ability to set/hold crank centering? Is there any downside to TS ball other than somewhat shorter mileage and load tolerance? I had to cut my teeth on the late Mr. Hudson's video, he'd hand sand TS crank till the ball bearing would slip on/off easy, then senily chuckle at his seasoned refining touch... Was great inspiration for a Norton novice.

The engine was rebuilt back in 1997 using brand new superblends but cannot recall at all if I tried to control end float back then.
And 3,000 Km in almost 17 years is not a lot, but it is what it is. Plus all of these miles have been trouble free.
It was my first ever MC engine rebuild and it must have been beginners luck. But there you are.
Of course there are many tens of things I could improve upon if I decide or be driven to split the cases again and rebuild.
But for the occasional blast to the empty roads of the Peloponnese (southern Greece), and the annual mileage it does, it might be just fine.
Cheers, Aris

.005" or less end float can also lead to minor cracking around the DS oil seal due to crank flex at high revs.

Kool_Biker said:

Hi, I have recently measured the crank end float of my 72' 750 Roadster at .42mm.
I know this is quite beyond the 5 thou to 15 thou (.13mm to .38mm) recommended by Norton ...

Is this something I should be overly worried about?
Since my rebuilt a long time ago, where obviously I missed this point, my bike has done 3,000 trouble free Km and feels great.
Could I be riding a time bomb?

Your thoughts are appreciated.
Regards
Aris

Click to expand...

.42mm is definitely not excessive.
I would generally use that figure as a minimum when building a performance engine. Jim

comnoz said:

.42mm is definitely not excessive.
I would generally use that figure as a minimum when building a performance engine. Jim

Click to expand...

I am surprised to hear this. I used to shim my racing engines (500 Dominator, Nourish one piece crank, revs up to 8500 rpm) no more then .10mm Never gave me any trouble :!: I am aware of the extra flex of a build up crank but .42mm minimum seems rather extreme to me :?:

nortonspeed said:

comnoz said:

.42mm is definitely not excessive.
I would generally use that figure as a minimum when building a performance engine. Jim

Click to expand...

I am surprised to hear this. I used to shim my racing engines (500 Dominator, Nourish one piece crank, revs up to 8500 rpm) no more then .10mm Never gave me any trouble :!: I am aware of the extra flex of a build up crank but .42mm minimum seems rather extreme to me :?:

Click to expand...

On engines with bolt up cranks -the crank gets longer as the revs rise. I have seen distressed roller ends and a small loss of high end horsepower when the endplay was below about .015 in. That was on a 750 turning 8200.
The bearings seem to come out looking the best when the end play was around .020 when racing.
I have not tested this with a 1 piece crank although I still set them around .020 in. Jim

A length of steel stacked up whether bolted or welded or one piece affair will all thermally expand pretty much same amount. Btw Holes in alu and steel get bigger as well not swell up tighter inside. Wonder how many 1000's of Norton engines were taken out forever learning their quirks the hard ways.

hobot said:

A length of steel stacked up whether bolted or welded or one piece affair will all thermally expand pretty much same amount. Btw Holes in alu and steel get bigger as well not swell up tighter inside. Wonder how many 1000's of Norton engines were taken out forever learning their quirks the hard ways.

Click to expand...

It's not the thermal expansion that concerns me as much as the fact that the cheeks spread with the crank flex. Jim