Author Topic: a10 plunger smoking  (Read 3095 times)

Offline MB-Transits

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a10 plunger smoking
« 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
bsa 1960 SUPER ROCKET
BSA 1960 RGS CLUBMAN REP

Online bsa-bill

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Re: a10 plunger smoking
« Reply #1 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
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline wilko

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Re: a10 plunger smoking
« Reply #2 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!

Offline chilblayth

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Re: a10 plunger smoking
« Reply #3 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*

Online trevinoz

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Re: a10 plunger smoking
« Reply #4 on: 13.12. 2011 00:34 »
It is timed when the peg engages the rotor. Nothing more to do.
Trev.

Online beezermacc

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Re: a10 plunger smoking
« Reply #5 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!
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline Gavin

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Re: a10 plunger smoking
« Reply #6 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.

Online bsa-bill

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Re: a10 plunger smoking
« Reply #7 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
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline chilblayth

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Re: a10 plunger smoking
« Reply #8 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  :!

Offline A10Boy

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Re: a10 plunger smoking
« Reply #9 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.
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline Gavin

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Re: a10 plunger smoking
« Reply #10 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??

Offline duTch

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Re: a10 plunger smoking
« Reply #11 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!!
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline cus

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Re: a10 plunger smoking
« Reply #12 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
56 G/Flash project

Offline Gavin

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Re: a10 plunger smoking
« Reply #13 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 !!

Online orabanda

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Re: a10 plunger smoking
« Reply #14 on: 15.12. 2011 19:03 »
Gavin,
Good news; suggest you buy a pipe, and keep the cleaners!
Richard