The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Zander on 14.05. 2017 07:28

Title: Crankshaft End Float
Post by: Zander on 14.05. 2017 07:28
Having got the bike up and running, and relatively oil tight, during the course of attending to primary chain alignment I noticed that there is a fairly significant amount of end play on the crankshaft.  I seem to recall reading somewhere that there should only be a few thou movement, and mine is in excess of that.  I don't intend to pull it apart as I want to ride it, and as I've mentioned before, the previous owner had done a lot of work on this bike - the piston heads are squeaky clean etc., and I can't imagine him putting it together without addressing this aspect of the engine, so rightly or wrongly I'm going to assume it's ok.  Unless, of course, the collective thinks otherwise!
Title: Re: Crankshaft End Float
Post by: beezermacc on 14.05. 2017 08:07
When building a new engine most people aim for a maximum of 0.002", ideally 0.001". The problem is that, as the engine settles in, it is likely that the endfloat will increase slightly due to highspots wearing off various surfaces. I don't think I've ever come across an engine, which has been used, where the endfloat hasn't become quite excessive. In my opinion you're probably OK up to about 0.010", but beyond this there is undesirable twist on the conrods which will cause the big end shells to wear on their outer edges and the bike will start to sound a bit rattly downstairs. I'm sure there are lots of A10's riding round with endfloat beyond 0.010". A couple of things to check....... 1) Check there is no debris in the sump - it wouldn't be the first time somebody found their distance shims in there! and 2) check the primary side crankshaft nut is really tight so that the inner race of the bearing can't spin on the crankshaft axle. Maybe a winter rebuild should be considered.
Title: Re: Crankshaft End Float
Post by: duTch on 14.05. 2017 08:23

  ^^ What B-macc says, but also;
Quote
.....Unless, of course, the collective thinks otherwise! 

 Be prepared to face a reasonably sized collective   *eek*

 Did you actually measure it? Even a very small float can give the impression of being much larger than it is- but don't let that be encouragement to neglect it I say measure it as best you can, and report back, and be prepared  *fight*  *smile*
Title: Re: Crankshaft End Float
Post by: bsa-bill on 14.05. 2017 09:03
Quote
The problem is that, as the engine settles in, it is likely that the endfloat will increase slightly due to highspots wearing off various surfaces.

correct of course (as I'd expect from beezermacc) what we perhaps forget or dismiss is that BSA would be well aware of this and would not have expected an engine to need stripped down every time crankshaft end float increased a thou or tree.
Maybe we should give those old guys a bit of credit now and then
Title: Re: Crankshaft End Float
Post by: muskrat on 14.05. 2017 12:29
I agree ^^^ but 5 thou would be my limit before addressing it.
Cheers
Title: Re: Crankshaft End Float
Post by: jachenbach on 14.05. 2017 13:23
BSA specified allowable endfloat while Ducati and Velocette are built with a few thou pre-load. I've seen pictures of Velo engines with the crank bearing boss broken right out of the case, presumably due to excessive sideplay of the crank hammering it out. I wonder if the endfloat is allowed in order to make up for variations in crankshaft big end journal/conrod placement/spacing? Side clearance on conrods and a bit of play in the piston to conrod plus endplay in the crankshaft would, I suppose, allow for a little self-centering of things to help prevent seizing. Darn, this is too much thinking for my first cup of coffee! *smiley4*
Title: Re: Crankshaft End Float
Post by: RichardL on 14.05. 2017 15:05
A couple of things to check....... 1) Check there is no debris in the sump - it wouldn't be the first time somebody found their distance shims in there! and 2)

Apologies if this is an unnecessary clarification, but there has been misunderstanding on this before. Here, in case you have a sump plate with removable drain plug, Andrew (beezermacc) is advising to remove the whole sump plate and check on top of the screen, not just the plug.

I think it is almost certain you will find shim bits in the sump if float is greater than 0.010". I am not confident enough to suggest continuing to ride with excessive float. Taking what Andrew says, that would be 0.010". However, if I find shim bits in the sump (it's happened to me twice now) I go for the fix regardless of what the measured float is.

Responding to jachenbach, end float is recommended as the minimum to let the crank spin. No excess is spec'd as far as I can tell. Zero float means no spin. I know jachenbach knows this.

Richard L.
Title: Re: Crankshaft End Float
Post by: muskrat on 14.05. 2017 20:52
To add to RichardL's post.
Naturally end float is measured cold (just like revenge). At hot endfloat will be more as the cases expand a lot more than the crank. 5 thou cold could mean as much as 10 thou when hot. Not enough clearance will wear the thrust side of the main bush when cold and too much can wear it by hammering if there's a difference of compression between the two cylinders. That happened to my race motor, foolishly built with too much, thinking it would spin better  *pull hair out*
Cheers 
Title: Re: Crankshaft End Float
Post by: beezermacc on 14.05. 2017 23:52
With regard to Richard's comment, shim parts will only appear in the sump if the primary side crank nut has been allowed to come loose because the shims should be trapped between the inner race and the flywheel when the nut is tightened properly (solidly). If there are shim parts in the sump it can indicate that the nut has previously come loose and an owner might have retightened the nut without realising the shims had been lost causing the increased endfloat..... which is why I was suggesting to check for shim parts in the sump.
Title: Re: Crankshaft End Float
Post by: jachenbach on 15.05. 2017 01:29
From Richard:
"Responding to jachenbach, end float is recommended as the minimum to let the crank spin. No excess is spec'd as far as I can tell. Zero float means no spin. I know jachenbach knows this."

Not necessarily. As I said, Ducati, Velocette, and possibly others are built with preload (no endfloat). From memory, I think it's about .003" preload. I guess you could think of it as negative endfloat? With ball and roller bearings, they still spin. As aluminum expansion coefficient is much greater than iron and steel alloys, they loosen as they warm up. It seemed strange to me when I went to Ducati school, but it works!
Title: Re: Crankshaft End Float
Post by: Zander on 15.05. 2017 08:29
Hmmm.... after getting it all back together putting oil in the prim. Ch case I'm reluctant to pull it all down again to measure the end float,  however, when I ride it I've noticed the bottom end sounds a bit " hammery" .  I put this down to the fact that I've not had a BSA before and as it goes well maybe it's a case of "they're all like that, mate".
Now I'm not so sure.  When I first got the bike, I removed sump plate and filter and checked for crap in the bottom of the case, but apart from a few bits of minor detritus, it was clear - certainly no shim fragments.  Looks like the sensible option is prim case off and do the necessary.  Bummer!
Title: Re: Crankshaft End Float
Post by: muskrat on 15.05. 2017 09:08
G'day Zander.
You can measure it from the timing side. Tap the shaft in with a hide mallet, set up the dial gauge and prise the shaft back out with a screw driver.
Cheers
Title: Re: Crankshaft End Float
Post by: orabanda on 15.05. 2017 09:17
To check that the shaft is all the way back towards the drive shaft bearings, the crankshaft can be rotated until the RH bobweight can be seen through a hole in the RH crankcase casting (about 20mm diam), and a drift inserted (soft; aluminium) and a careful blow with a hammer will ensure that the crankshaft is all the way across (to the drive side); wonder if the assembly foreman at BSA requested the hole for this purpose?
Title: Re: Crankshaft End Float
Post by: Zander on 16.05. 2017 09:40
Thanks to one and all for the guidance and info.  This morning I measured the end float (cold engine) at 0.016".  *cry* Removed SRM sump plate and found bits of what looks like fibre washer fragments but no metal on the mesh filter.
Title: Re: Crankshaft End Float
Post by: muskrat on 16.05. 2017 13:03
Bugga. So you'll be eating/sleeping in the shed for a while. *sad*
Cheers
Title: Re: Crankshaft End Float
Post by: Greybeard on 16.05. 2017 15:06
...looks like fibre washer fragments...
Excess red sealant maybe?
Title: Re: Crankshaft End Float
Post by: Zander on 16.05. 2017 16:00
Could be! I removed a small amount of what looked like sealant when I removed the sump plate the first time.  I take it that, due to the excessive end float it won't be sensible to use the bike til it's corrected?
Title: Re: Crankshaft End Float
Post by: mugwump on 16.05. 2017 16:54
Sent you a pm.
John
Title: Re: Crankshaft End Float
Post by: Zander on 20.05. 2017 13:24
Update:  engine is out on bench and  stripped. Crankcase are clean, no crap anywhere.
No sign of red hermetite so red bits on sump filter must have been fibre washer fragments - don't ask me where from!  I've got one, possibly two holes to helicoil - one for the timing case cover which is stripped, and the one by the mag. Which, although the thread is good it seems to be at an angle, which prevents proper assembly of the crank case halves.
There's no indication that crankshaft shims were ever fitted, which is good and bad I suppose.  Spoke to Roger at Cake Street re crankshaft balancing, but he doesn't do it, so undecided at the moment. Heads will need new valve guides, and am contemplating new valves too, also considering oil seals for the new guides.  Springs will be renewed.  Bores seem fine, pistons look new so won't be doing a rebore.
When I took the clutch apart, I found I'd made a mistake when I assembled it; I loctited the centre nut and had to resort to shock tactics do undo it. Am currently attempting to confirm the 0.016 end float by measuring the crank case internally, then measuring the crank shaft.  Not sure if this will work out, but I'll give it a go.  I was surprised how difficult it was to get the head bolts undone.  They were so tight I thought I was going to break my socket.
Title: Re: Crankshaft End Float
Post by: RichardL on 20.05. 2017 14:33
Zander,

With no shims present, I'm thinking you're going to find more than 0.016" float. The first time I tried to measure float I did what you are planning, that is, measuring across the inside of the case and across the crank. I only had a telescoping gauge for the inside and, really, nothing for the crank. Telescoping gauges are tricky enough to use, but inside the crankcase was a pain. For the crank, I found a friendly local machine shop with a micrometer big enough for the reach. When I built a shim stack based on these measurements, the result was a crank that would not turn. I ended up using the method of measuring off the drive side bearing boss (with a spanning block across the diameter of the boss) while pushing the crank back and forth within the case. This has been successful a few times.

As for the head bolts, unless some  of sign  rust or other corrosion is the obvious reason for being so hard to remove, I think you should carefully determine that thread types match.

Richard L
Title: Re: Crankshaft End Float
Post by: Greybeard on 20.05. 2017 15:04
If you have a look at this video you will see some pictures, (at 2:36) of how I measured my crank endfloat
https://youtu.be/nrOfq1O-gV8 (https://youtu.be/nrOfq1O-gV8)

Confession time: Because I was misreading the guage divisions as thou of an inch but being a metric guage it was reading microns(?) I managed to end up with almost no endfloat. I understand that that is ok.
Title: Re: Crankshaft End Float
Post by: Zander on 20.05. 2017 15:55
Excellent video - thank you. Excellent music too - sounded like Jeff Lynne and ELO👍
 I gave up on trying to measure crank case and crankshaft.
Too messy and I wouldn't have relied on any  measurements.  I'll do the same as RichardL, so, again, thanks for the guidance and sharing of experience.
Title: Re: Crankshaft End Float
Post by: RichardL on 20.05. 2017 16:21
Shot a picture to clarify what I was describing. I used the method shown by Greybeard when measuring in the bike. I am not sure the dial indicator method would work well on the bench because you have to jostle the crank and crankcase around to shift the crank from side to side.

Richard L.
Title: Re: Crankshaft End Float
Post by: RichardL on 20.05. 2017 16:29
P.S. Always keep your block in the same place and measure at the same place on the end of the crank.
Title: Re: Crankshaft End Float
Post by: Greybeard on 20.05. 2017 17:16
Shot a picture to clarify what I was describing. I used the method shown by Greybeard when measuring in the bike. I am not sure the dial indicator method would work well on the bench because you have to jostle the crank and crankcase around to shift the crank from side to side.
I did mine on the bench.
Title: Re: Crankshaft End Float
Post by: RichardL on 20.05. 2017 17:31
True. The bracket(s) you used to stabilize the case probably made it practical.

Richard L.
Title: Re: Crankshaft End Float
Post by: Zander on 21.05. 2017 16:47
Time was that when you wanted a spare, you had to physically locate a shop that had it in stock, then go and get it. The make of the part rarely featured - it was generally a relief to just get that part.  Today I've been assessing what I need, starting at the cyl. Head, and have been surprised at the variety of valves and guides available.  Talk about confusing!  Bronze or cast iron guides; where to buy them; which type is best?  On and on it goes.  eBay have a few complete sets of valves and guides at competitive  prices, but who makes them, and are they decent quality?  Pays yer money and makes yer choice!
Title: Re: Crankshaft End Float
Post by: Greybeard on 21.05. 2017 18:49
...Talk about confusing!  Bronze or cast iron guides; where to buy them; which type is best?  On and on it goes.  eBay have a few complete sets of valves and guides at competitive  prices, but who makes them, and are they decent quality?  Pays yer money and makes yer choice!

Just ask here ;)
Title: Re: Crankshaft End Float
Post by: terryg on 21.05. 2017 19:10
Zander - a shortcut for you could be to speak to Andrew at Priory Magnetos (member beezermacc on this forum).
Title: Re: Crankshaft End Float
Post by: Zander on 21.05. 2017 19:17
Thanks, terryg.  I had a look at Andrews site earlier but didn't find valves etc., but after your post I did another search and found the engine parts. *thanks*
Title: Re: Crankshaft End Float
Post by: chaterlea25 on 21.05. 2017 19:53
Hi All,
I bolt a piece of flat steel to some convenient place on the crankcase and stick the magnetic DTI base to that
Now worries about error then
(Bl**dy Indian Cheif engine is giving me problems with gearbox mainshaft endfloat at the moment *problem* )
Thrust washers have to come from USA, more delays  *sad2*

John
Title: Re: Crankshaft End Float
Post by: Zander on 22.05. 2017 09:50
Thanks to one and all for the advice and comments - vitally important to a newby BSA owner.  This morning I checked the end float using a DTI and am content that the resultant figure of 0.019" end play is accurate. I then removed the main bearing and found a ragged 0.002"shim sticking out, part of which must have gone elsewhere, together with a 0.010" shim in situ so the total shimming needs to be in the order of 0.030.  I'm going to see if I can make a one piece spacer so that I can eliminate the need for multiple shims.  Valves etc are on my list of "things to order" today!
Title: Re: Crankshaft End Float
Post by: Zander on 27.05. 2017 07:08
I won't bore you all with what I'm getting up to with this engine, but I feel I should post a HUGE vote of thanks to Andrew of Priory Magnetoes for outstanding service and advice. Much appreciated.   *thanks*