Partial seizure

[ben]

Hi Guys

Bike is an RGS replica, de-tuned, ie no high lift cam or 9-1 pistons. Rebuilt several years ago.

Taking my bike out the other day after nearly a year, I did a very silly thing, or rather, I didn't do the sensible thing.
The motor started first kick (believe it!) and I roared gently away, After about 5 miles I stopped to get some petrol. All well. Riding back, I passed through some fantastic Belgium countryside, rolling downhill at no more than 50 mph I suddenly felt the engine tighten up, radically, like a seizure. I pulled in the clutch and coasted. It was a baking hot day of about 35C. After 10 seconds I let the clutch go and she started up again. This time I ran at tick over (just get me home) and just put putted along. Suddenly I realised the true horror of the situation. The oil feed tap that I'd carefully fitted 20 years ago was off! I'd forgotten to turn it on! Oh wo is me! I turned it on and the bike continued forward, gently. I carried on for another 10 miles, problem free and got home ok.
After things had cooled down there was still plenty of compression and no disturbing noises.
I contemplated the folly of my ways and don't know quite what to do.
Any ideas, drain the sump, maybe? If poss I'd rather not strip the whole thing (again).
Greetings
Ben

[Greybeard]

Oh dear!   
Nice looking bike by the way. I reckon that one or both pistons have picked up in the bore; the damage may later cause a seizure at high speed and we don't want you to have that do we.  A top-end strip would be a good idea.
I'm amazed that you got so far before you had a problem.
Your story makes a strong case against oil cut-off valves and also why we should always check for a return oil flow when starting the engine.

[bsa-bill]

Sorry to hear of your predicament Ben.

Not at all unknown to experience a partial seizure, certainly after a rebuild and perhaps after a long stand.
a friend had one after a rebuild, once it cooled down was able to ride it home, had the barrels honed, new pistons and rings and is riding it regularly now  (although he was very nervous for a week or two).
Possibly he could have got away with tidying up the pistons.

 the tap and your memory (guess which one is the most reliable). although many will disagree I would never ever fit a tap, I have used a non return valve without any problems at all, took it off after rebuilding the engine as it no longer wet sumps.
All our bikes were built for men to get to work and back with not much more than the BSA toolkit a hammer and a large adjustable wrench, all wielded after Sunday dinner and a mug of tea, half a century and more later they are still going (some lavished with care , some left as is/was).
The moral is don't trust that thing on your shoulders, it's wonderful but in noway fallible (it's losing cc s every day) - dump the valve

[orabanda]

I have had 3 A10's seize when using JP pistons at the original clearances (0.0035 - 0.004")". They stopped nipping up after honing more out of the bores (0.007 - 0.008" seems to work).

I realise however,  that the reason for your seizure was the unfortunate lack of oil.

In most of the occasions, the bores would clean up with a hone. The pistons were re-used after carefully removing the high spots, and fitting new rings.

HTH,
Richard

[Topdad]

Hi Ben, thats a PITA, agree with Bill ,my memory is shocking whilst dealing with the bike, must be a relaxation thing 'cos that is one of the reasons I've got the bike. One thing I always always do is check the return but even that might not have helped .Does yours wet sump a bit ?, if so you'd see areturn ( i think even without a supply ) until the sump emptied, that also could be why you got away (almost ) with it , a bit of old splash oiling . Dump the valve unless you hook it up to mag earth? . Think you've got to look at the head barrels and pistons ,fingers very tightly crossed, best of luck BobH  just as an aside didn't know Belgium had any hills ! thought it was all flat? 

[muskrat]

G'day Ben,  .
 
The poor thing wouldn't have had the benefit of wet sumping over the year 
I agree you may get away with a hone and new rings. But I'd be using a dial gauge on the crank to check for T/S bush wear and end float as well as big end movement.
So now I'd say you'll live with wet sumping and ditch the valve.
I had my '51 A7 nip up a year ago at 80 mph. A quick hone, clean up piston, new rings and swapped sides. Good piston in bad bore and bad piston in good bore. Done about 5000 miles with no smoke but limit it to 70 mph now.
Cheers

[ben]

Hi Graybeard,

thanks for your advice. Sounds good. Honing the barrels and fitting new rings is very do-able.
I also agree with dumping the oil cut-off tap. It was one of those " it'll never happen to me" things.
I have fitted an SRM pressure release valve which should reduce wet sumping. But, as you say, one should always check to see if oil is returning. This was probably the first time ever that I'd failed to do so....Titanic thing.

Cheers
Ben

[ben]

Hello BSA Bill,

your wise words ring true, thankyou. Indeed, the cult of the BSA began with the get-work-ethic. I had a  C15 in the mid-seventies which I lavished with a total rebuild, tuning and making it lighter. It got me to school and college every single day for 3-4 years and always ran. The A10 I also view as a workhorse.
The memory thing, or lack of, is sad for me and the bike. I shall remove the tap, though I really don't want wet sumping, a big drag when the bike is left for a long time.

Cheers
Ben 

[ben]

Hi Topdad,

Yes, memory probs. My A10 and I share the same age, (55) this makes the bike more pretigious and me more pathetic. But I guess one just has to live with it and try to build in more idiot proof devices to prevent this kind of thing from happening. But I've learned my lesson. I shall follow all of your and your fellows' advice; do the bore and rings, check the big ends for play and float, and dump the oil tap.

Thanks

Ben

[ben]

By the way, Belgium is mountainous, think of the Ardennes. Holland is also very hilly where I am - in the south of Limburg, amazing bike country.

Ben

[bsa-bill]

though I really don't want wet sumping

no it's a pain right enough, ideally starting it up once or twice  a week is enough, (advice I fail to follow I might add)

[muskrat]

Fit a sump with a drain plug. Only takes a couple of minutes to dump what's in the sump and top up the tank. Too easy.
Cheers

[morris]

just as an aside didn't know Belgium had any hills ! thought it was all flat? 

How dare you say that Bob! Our highest mountain is 694 whole metres high! How about that...

Hi Ben, welcome to the forum. As you already must have noticed, lots of great help and friendly advice here.
Where are you located (more or less)? Me and my wife often go to the south of Holland. We have some friends living in Geleen.
Sad to hear about your oil tap problem. I'd go with the majority here and dump it. Then try to run the bike at least once a week, and if the sump really fills up to much after a longer standstill, go for the drain plug solution.

[chaterlea25]

Hi Ben,
Tough luck 

Ok, so my take may be a little different to others,
A partial seizure or nip up on my brothers SR led to the two piece main bush siezing to the crank and then parting from the steel backing bush 
It seemed to run ok after the partial seizure but a couple of hundred miles later a conrod made a bid for freedom through the cases

The root cause of all these problems turned out to be a porus oil pump body

I would remove the timing cover and check for any play at the crank end and if that is ok the crank bush is not turning with the crank

A little oil in the cases will keep the pistons lubed but the bigends rely on continuous high pressure oil to work

THe PRV has nothing to do with wet sumpiing

HTH
John

[Topdad]

Ben, Thats me corrected can't even remember flags now!! I forgot all about the Ardennes ,(must be a english thing after all they forgot about it in 1940 and 1944 with nearly disastarous results ) Thanks for taking as ever as was intended ,just a pun, best wishes Bob