The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: MB-Transits on 12.12. 2011 21:11

Title: a10 plunger smoking
Post by: MB-Transits on 12.12. 2011 21:11
help  I have an a10 plunger which smokes its had the bottom end done rebored new pistons & rings
valves & guides but its still smoking when I take the top off the oil tank it stops
any one got any suggestions how to cure it
Title: Re: a10 plunger smoking
Post by: bsa-bill on 12.12. 2011 21:32
Sounds like the tank breather is restricted.
Return side of the pump has more capacity than feed side so pumps back oil and air to the tank, the air/oil mixture is more than the oil sucked out so the tank has to be able to breathe to let pressure out.
Is there a pipe attached to the breather - perhaps it's kinked
Title: Re: a10 plunger smoking
Post by: wilko on 12.12. 2011 22:31
That's a new one on me? Must try that on a mates bike which has smoked for 15 years. It,s a hard habit to kick!
Title: Re: a10 plunger smoking
Post by: chilblayth on 13.12. 2011 00:07
unlikely , but !  when it was stripped and rebuilt doesent the breather have to be timed ?  its hard to remember now as its about 30+ years since i rebuilt a10 engine  *conf*--------     i know the cork washer had to locate on the peg and i vaguely recall it also had to be timed or it didnt function  *ex*   
i also recall a plunger flash that pumped its oil out of the breather but that was a stuck ball valve on the sump/return pipe  *smiley4*
Title: Re: a10 plunger smoking
Post by: trevinoz on 13.12. 2011 00:34
It is timed when the peg engages the rotor. Nothing more to do.
Trev.
Title: Re: a10 plunger smoking
Post by: beezermacc on 13.12. 2011 08:41
The timed breather only affects bottom end pressure, releases bottom end gases into the atmosphere. The tank breather releases pressure from the tank (obviously!). I agree with the tank breather theory. Excess pressure in the tank  is most likely to work its way up to the valve gear, down the push rod tunnel creating an overflow into the crankcases. Easy enough to check; if its not that we'll have to think again!
Title: Re: a10 plunger smoking
Post by: Gavin on 13.12. 2011 10:25
Very interested in this post... I have exactly the same problem... great compression, great to ride, but man she fills the street with smoke on a cold startup... only a few puff's after a warm start, and fine elsewhere....
Bill, how can I check that the oil tank breather is clear? I would rather do that as a next step than check the rings... Just done the valve guides and that didn't help. Rings have done less than 2000 mile.
Title: Re: a10 plunger smoking
Post by: bsa-bill on 13.12. 2011 11:02
Hi Gavin
As I don't own one I'm presuming plunger tanks have a similar arrangement to Swinging arm for oil tank.

Slip a bit of pipe over the breather and see if you can suck air through it, blowing might be more hygienic but off the top of my head I can't recall if there is a non return element to the breather, I think it's just a sort of baffle so blowing should be OK, others please correct me here.
It's quite common for A's to smoke when first fired up, usually just one side or the other, could be just oil from guides getting into the ex pipes, it has been put down to a number of different things most of them not worrying. it clears after about a hundred yards or so
Title: Re: a10 plunger smoking
Post by: chilblayth on 13.12. 2011 12:23
try some seals over the valve guides  ????   i believe these are the most likely cause of the smoke with excessive clearance between stem and guide  :!
Title: Re: a10 plunger smoking
Post by: A10Boy on 13.12. 2011 12:51
Get an old oil tank cap, drill a suitable hole to push a length of petrol pipe tightly into the hole, screw it on the oil tank and blow. You will soon know it the breather is blocked.
Title: Re: a10 plunger smoking
Post by: Gavin on 13.12. 2011 13:42
Really appreciating the diagnostic ideas, keep them flowing..... Thanks... But are there any remedies on offer? How do I clean the breather if it is blocked??
Title: Re: a10 plunger smoking
Post by: duTch on 14.12. 2011 13:59
I'll go with Bills' idea too,'cos it makes sense,especially given the 'cap off' scenario, and the breather timing isn't all that ha?rd(?) and as I was planning to play with oil tank tomorrow,'cos it's all in bits- just had a head start. I blowed (blew) up the breather and it was a bit hard,(been sitting unattended for a while) but after poking a bit of wire up it came good. To do this in situ, (tank on), I would suggest blowing through the filler hole whilst poking wire up as it will purge gunk,(lizards, snakes,hornets,roadkill,maybe that other stuff you misplaced ) out downwards. Then it should all be sweet, and maybe add a vented old brake fluid bottle or similar at the bottom to catch oil vapour so it doesn't hit the road. cheers, good luck and have a nice day, duTch
Nb. For doing those tubie types of cleaning, you can use a pipe cleaner, like from a tobacco shop,or a gun cleaning brush -which come in a bunch of different gauges, but usually all short and need some ingenuity to extend them!!
Title: Re: a10 plunger smoking
Post by: cus on 14.12. 2011 20:51
Does it still do the smoking thing after a good run?
If you are starting it up after sitting for a while, it could be wet sumping.
Let us know.
If it still smokes after a run, I'd be looking at the rings again, maybe go
for a 3 piece oil ring this time, I've got the 3 piece on mine, never get any smoke
& don't have to top up between 1000 mile changes, 

regards, Cus
Title: Re: a10 plunger smoking
Post by: Gavin on 15.12. 2011 15:06
Decanted some oil out of the Tank. Took a handle bar grip with small hole in one end, sealed  the large opening over the mouth of the oil tank, gave a blow and felt the pressure build then heard a blockage move like glorious relief... as the tank pressure eased.... think you have got the idea.... and yep she be smoking far less.

Would now believe I need a long hot run to take care of the existing oil film inside the exhaust system, and I could have an acceptable smoking range on the old girl.

Thanks for the ideas on this post. It's a step I prefer to replacing rings. If I have to do that later... then so be it.

Have a pack of unopened pipe cleaners if anyone needs them !!
Title: Re: a10 plunger smoking
Post by: orabanda on 15.12. 2011 19:03
Gavin,
Good news; suggest you buy a pipe, and keep the cleaners!
Richard
Title: Re: a10 plunger smoking
Post by: bsa-bill on 15.12. 2011 20:42
well done Gavin
Quote
Good news; suggest you buy a pipe, and keep the cleaners!

Tenuous link to the subject but my dad used to smoke a pipe now and then, used Erinmore mixture, had a lovely smell, others I new used a strange stuff called "plug" I think, resembled a century old black pudding that they carved a slice off, stuffed it in their pipe and lit it, I seem to recall them using about twenty matches to a pipe full.
Any of you guys join your A10's in a smoke like that ? *smil*
Title: Re: a10 plunger smoking
Post by: beezermacc on 18.12. 2011 18:35
Ref Gavin's smoke on start up, sounds like typical wet sumping to me. Most A10's do that. I've just bought a Bri-Tie one way valve to cure mine.
Title: Re: a10 plunger smoking
Post by: wilko on 18.12. 2011 20:03
He said it stopped when the oil cap was released. Which wetsumping wouldn't do.
Title: Re: a10 plunger smoking
Post by: trevinoz on 18.12. 2011 20:07
Good luck with the one way valve when it becomes no way!
Title: Re: a10 plunger smoking
Post by: cus on 18.12. 2011 21:37
I think it could be a combination of wet sump & blocked tank breather,

Cus
Title: Re: a10 plunger smoking
Post by: kiwipom on 18.12. 2011 23:17
hi guys/Beezermacc, can`t make out the engine Beezermacc has got in that bike in his Avatar, is it an A10? cheers,Bob
Title: Re: a10 plunger smoking
Post by: bsa-bill on 19.12. 2011 09:16
Don't look like an A but beezermacc  might shed some light (there's a pun there if you can work it out)

Just had a look at his web site, wish he'd been here when I had all my Magneto problems, might send him my redundant one to sort out when time and sheckles allow
Title: Re: a10 plunger smoking
Post by: cus on 19.12. 2011 20:52
It looks a bit like a Harris Matchless engine?

Cus
Title: Re: a10 plunger smoking
Post by: BSA_54A10 on 20.12. 2011 11:37
Depending upon where you live, beetles , bees & wasps an cause you grief with your oil tank breather.
We have a lot of case moths & wasps here who seem to love using oil breathers to metamorphose in or lay eggs in.
Had the tank off the M20 for a week earlier this year and a wasp decided to domocile in both of the fuel lines.
And didn't that give me some grief 240 km into a 300 km ride when they finally broke up and blocked the filter in the banjo.
So it is always a good idea to fit a long clear hose to the breather so you can see that it is clear.
Title: Re: a10 plunger smoking
Post by: Gavin on 20.12. 2011 12:14
After a great run Starting out with far less smoke and making the old girl work a bit down the highway keeping up with some pretty pacey traffic, I'd have to be pretty happy with how she is going.

Will play round with mixture settings to try and eliminate a damp exhaust.

Thanks for the advice in the post... will keep an eye out for insects. Most of the ones I collect are on the front of the bike or on my visor.

For the record I gave up smokin a pipe at 15. So the pipe cleaners may get twisted into a new "Rider" for the wooden model BSA on the Piano !!!
Title: Re: a10 plunger smoking
Post by: MB-Transits on 22.12. 2011 07:51
well I have cleaned out the pipes on the oil tank replaced the oil pressure valve & its still smoking
Title: Re: a10 plunger smoking
Post by: beezermacc on 26.12. 2011 07:52
It sounds like we have two distinct problems here. If we look at Gavin's original post there is no reference to removing the oil cap etc. so I still think Gavin's problem is wet sumping. Recent runs have started with less smoke because he has used the bike day by day, and it clears on a run. Whilst I wouldn't recommend a one way valve (as supplied by Bri-Tie in the UK) even though the proprietor has sold thousands of these, it has completely cured my wet sumping problem. Furthermore, starting a bike which has wet sumped can cause serious damage, believe me, I've seen it - blown oil seal and burst gaskets due to hydraulic lock in the bottom end, primary chaincase full of oil.

I would be interested to hear an update from Old-Bikes-Are-The-Best who has a different problem where the bike stops smoking when the filler cap is removed. If this genuinely solves the problem then riding round with the filler cap removed would presumably effect a cure, and no!, I'm not suggesting that as a serious permanent recommendation, just a pointer to where the problem lies, i.e tank breathing.
Title: Re: a10 plunger smoking
Post by: bsa-bill on 26.12. 2011 10:36
Quote
If we look at Gavin's original post there is no reference to removing the oil cap etc.

Gavin's original post
Quote
help  I have an a10 plunger which smokes its had the bottom end done rebored new pistons & rings
valves & guides but its still smoking when I take the top off the oil tank it stops
any one got any suggestions how to cure it

Too much sherry trifle beezamac *smiley4*


Title: Re: a10 plunger smoking
Post by: beezermacc on 26.12. 2011 13:07
Too much sherry trifle? Yuk? Don't touch the stuff, much prefer single malt. I think you'll find the original post was posted by 'old-bikes-are-the-best', where there was mention of removing the oil filler cap.  Gavin responded to the original post but went on to describe a slightly different problem of his own where there was no mention of removing the oil cap. It's a pity that two different problems have got tangled up in the same thread. Too many chocolate liquers BSA Bill  !!
Title: Re: a10 plunger smoking
Post by: bsa-bill on 26.12. 2011 13:27
Quote
Too many chocolate liquers BSA Bill  !!
OOPS sorry about that beezermacc, yep I was thinking of the original post

I'll put it down to yesterdays red wine, no Liqueurs for me though , too much sugar in them, but my last employer chucks a bottle of Grouse at me every Christmas so I'll sup a wee bit by way of apology  *beer*