Crank end float - best guess?

[muskrat]

 
Way too much. It will allow oil to escape instead of going to the big ends. as the motor warms up that gap will get bigger! 3 thou is so it's not tight when cold.
Cheers

[limeyrob]

Agreed. You will see its done under 200 miles since a rebuild (not by him) so perhaps it was never set correctly in the first place.  Lots of expensive parts but some basics not right.

[BagONails]

I'm thinking before I put my top end all back together I should check the crank end float as a precaution. I'll whip the primary cover off and check it out. It'll give me a chance to see how everything is settling down in there too, done about 2.5k km since new everything was fitted.

Last time I checked it was 0.008" and I was prepared to let that go while keeping a careful eye on what came out in the old oil etc. so far so good but reading these threads can make you paranoid. I figured majority of older rebuilds would be running more than 0.003" after a few years so I shouldn't worry too much but then... 

[limeyrob]

0.008 after 2.5 k miles doesn't sound too bad and could be fine, I'm sure many run more.  But the bike in the video is 020 at under 200 miles which is not a good sign.

[berger]

it could be worse it could be worty's that had about half a mile and the oil seal ring on the wrong way round

[Worty]

Bergs, just remind these good folks what mine actually was.  I do remember posting some Youtube video pulling and pushing the crank in and out and thinking that couldn't be good.  The crank didn't give a gentle clunk, you could actually see the movement quite clearly.  Having said that, the motor still ran reasonably well and never blew up.

https://www.youtube.com/watch?v=XWoB5zr5sEY&ab_channel=MarkPhillips

[muskrat]

G'day BON.
The main reason the old girl got a re-build was because the end float was 0.008" cold, hot more like 10-12. I was running 40/75 oil to keep it going. End float (gap between crank and bush) is a place oil can escape hence the quoted 0.002.
Cheers

[BagONails]

Thanks Musky, Its a dilemma isn't it. By that I mean do you know how many miles you ran with excess E/F before you discovered the problem and rectified it and it never failed?  That's not to say it wouldn't fail at some point and I know you like to get the best out of your machines but it could have been happy running like this for years?  Or had you checked it regularly and you had a slow wear-out condition going on with gradually increasing clearance and presumably more and more oil being lost into the crankcase. 

Thing is maybe you can get away with a more generous end float if the diametral fit on the bush and crank journal is still within specs?  Perhaps the ones that go bang are the ones that have a worn journal AND big end float. Equally the oil is free to escape on the outside of the bush isn't it, into the timing case? So even with 002' E/F the oil can just pee out the other side or have I got this wrong?

Not sure any of us really know the answer to this.  My feeling is the state of the bearing journal is more of an issue than slightly generous E/F but that's just my guess!

[berger]

mine had shred it's shims without me knowing years ago and i don't hang about regarding revs and it survived , i was told by a chap at a big bike shop shop in derby the crank would  find it's own place BUT i got scared and put it right

[limeyrob]

I had a bog standard very clapped out Golden Flash that had hauled sidecars most of its life. Low comp, low geared and lovely. You could pootle about at 50 all day long.  I've no doubt it had a ton of end float but it lived with it.  My RR has high comp pistons, higher gearing (23t) and will be working much harder so I sweated the end float and stripped the bottom end twice before I got it right.
There is no exact answer and its horses for courses but on the bike in the video I'd be pulling that bottom end out, enough else is badly assembled I would not feel happy.

[Swarfcut]

 Bagga... These engines will still continue give reliable service even when worn to the limit. Sure, rattles, clanks, blowing smoke are all niggles, but back in the day they got dad to work and back. So I would not worry JUST about a small amount of float, it is a lot of work for perfection.

 In any event, the sideways reaction of the oil pump drive scroll keeps the crank more or less pushed towards one side, my reckoning is to the drive side, but if you have the bits to hand, have a consider.

  With an engine that performs well otherwise, pull another beer, check the basics and ride until something more pressing shows up.

 The ones that go bang are the ones with a blocked sludge trap, and to clear this the motor has to come apart anyway, so you takes your choice.

 But the bike in question here has more of RM about it and is best sorted sooner.

 Swarfy.

[muskrat]

G'day BON.
Mine ran for a couple of years (5K Km) like that and had a bit (5 thou) of up and down movement hence the use of thicker oil (with Nulon). I don't have an oil pressure gauge on the A7 so I was starting to worry. As soon as I had the wherewithal to do the job it was done.
You are correct about leakage on the timing side but two holes in a bucket empties quicker!
I agree with Rob & Swarfy in that these motors are very robust but if you have the chance (like now) to fix it do it.
Cheers

[BagONails]

Thanks all for your sage advice, for which I am grateful as ever.

I agree the bike in question on YouTube is looking very suspect, the telltale signs are there everywhere you look. I mean how does a cush nut come loose in just a few hundred miles, unless it was never done up in the first place!  I think Paul is going to have an interesting journey and will learn a lot about the A10/A7 world. I think the bulk of his experience is with old Enfields and later 60'/70's Brit machines.

With my one I've decided, to whip off the primary cover and recheck the E/F.  I did this the last time I had the timing side off for the broken dynamo chain and although there was 008" E/F I could not detect any appreciable movement up and down to indicate bush/journal wear. I also know the bike's history through piecing together the threads on here (yes the PO was a forum member and a member of our local BSAOC so I've had a lot of the history!) Once I realised who he was I spent many hours piecing together all the problems and struggles he had, some of his own making I believe but not all.  He was a decent guy and fortunately had the bottom end rebuilt by a reputable person so I can have some faith in it. (I hope!) At least it's been fine so far unlike the rest of it...and yes the sludge trap was definitely done! 

If nothing has changed then I'll complete the current top end rebuild and the old girl will ride again, mostly on fairly sedate club runs and never thrashed, mainly because the brakes don't fill me with confidence.  It'll do about 2000km a year and get fresh oil once a year with a screen clean and oil tank scrape out each time. Meanwhile I can concentrate on getting the A65 Spitfire finished, start riding that around and at some point maybe think about taking the A10 apart but then there's the 49 Longstroke to get into... I'm trying to avoid having two bikes in bits at the same time as things are getting pretty hectic as it is.  Cheers. 

[bikerboy]

Hi Limey

Why are you changing crankcases anyway?????

[limeyrob]

I had to change the cases on my A10 because the engine had been built by (insert word here...) who had used mismatched cases with a step under the barrel concealed by a 1/8 compression plate.  In the box with it was the matching number set of cases for the bike!  Made no sense!