The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: TimK on 15.03. 2020 08:37
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Hi Everyone
Since I fitted a new barrel and JP pistons the right hand cylinder has been smoking on start up. It clears after a mile or two so I'm tempted to give it a damn good ignoring - am I courting disaster or should I just keep on riding?
Cheers
Tim
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I've had no joy with JP rings. I rode a B44 for a thousand miles and it never bedded in. Ended up fitting new rings of a different brand and they never puffed a wiff of smoke. My feeling is that if they don't seal straight away they are never going to. Check to see if your oil is black in no time. If it is you have blow by and it will never behave properly.
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Get some miles on it, a possible cause is the oil which accumulates in the sump on standing being scavenged, hence exhaust clears after a short distance. Try leaning the bike to the left on start up, left cylinder may also start to smoke. No noise or other symptoms? Oil returning as it should in a stream and gulp on idle? All OK? Ride like you stole it to break the bore glaze, yes, a DAMN GOOD IGNORING.
Modern oils, our fastidious cleanliness and pussyfoot break in procedures often result in the scenario outlined by Slymo. I go for the cheapest oil, the "suitable for older engines plain wrapper Supermarket Own Brand cheapo crap" for the first fill. The lubricating properties are adequate, but at this price it does not contain the exotic ant-wear, anti oxidant and other additives that contribute to this initial problem of poor ring sealing.
Swarfy.
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JP use rings that are way way too hard.
Despite regular request to supply the piston bare he insists on sending them with his duff rings.
If you fitted the piston with the supplied rings, it will smoke and probably get a lot worse before they finally bed in and we are talking around 500 to 1000 miles .
If you go the ignore route, just remember to keep an eye on the oil.
A member rode his C10 fited with the JP rings ( against everyones advice ) from Croydon to Warragamba to see me ( Sydney of course )
When he got here it had stopped smoking.
There was no oil left in the tank
HE used another 2L to get back home , went to Trojan, bought & fitted some Hastings rings ( dry ) and has not a problem with the rings since.
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Hi Tim,
My Golden Flash smoked badly on the LHS cylinder, After replacing the rings, no change. I pulled it down again and discovered that the LHS piston was tilted L to R by 10 thou. I have had the small end bushes replaced and reamed square. Only point I can add to the other advice is to check that both pistons are level within a thou or two if you have to pull the cylinders, obviously before you pull the cylinders.
Colin
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Thanks everyone,
I think I can cope with putting some miles on it (whilst keeping an eye on the oil level) to see if it clears. As I said it clears very quickly once I set off so I'm pretty sure it's not a broken/incorrectly gapped ring or valve guide problem. I'll let you know if (when) it clears up.
Cheers
Tim
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G'day Tim.
How many miles has she done? Can you do a compression test cold then again hot? Hold throttle wide open and give 10 kicks as quickly as you can.
Cheers
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G'day Tim.
How many miles has she done? Can you do a compression test cold then again hot? Hold throttle wide open and give 10 kicks as quickly as you can.
Cheers
Hi Musky
The valves were reground about 500 miles ago and she's only done about 50 miles on the rebore/new pistons. I havent done a compression test but the effort needed to kick her over doesn't seem to change much hot or cold.
Cheers
Tim
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G'day Tim.
After 50 miles the rings should have bed in.
Is she wet sumping at all? Try dropping the sump plate to drain the sump before the ext cold start just to eliminate that.
Cheers
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This tendency for the oil to exit the oil tank into the sump explains the popularity of the aftermarket sump plates with a handy single drain plug. One of the best, cost effective and convenient upgrades that fits all models from a '47 Longstroke to the last A70. Saves the hassle of shearing those pesky little studs or pulling the threads in the alloy cases.
Swarfy.
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G'day Tim.
Bugga, I had a spare one you could've had. *sad*
Cheers
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G'day Tim.
After 50 miles the rings should have bed in.
Is she wet sumping at all? Try dropping the sump plate to drain the sump before the ext cold start just to eliminate that.
Cheers
Hi Musky
She used to wet sump - my own fault, I'm not riding her regularly enough - but I've fitted one of 'the magneto guys' oil taps with magneto cut out so that's not the issue.
Cheers
Tim
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Mine was apparently wet sumping but I discovered that the oil pump was leaking from the gasket. A careful flat file to face off the back of the pump and a new gasket with a re tightening after a few miles sorted that. I would get the best part of 1/2 a pint of oil out of the timing cover after the bike had been sitting a while now there is no more than a couple of tablespoons in there. I reiterate though if they are JP rings and they havent sealed straight away they probably never will. I put Gandini rings in mine and gave the bore a light hone before assembling it dry. It has never made a puff of smoke since and after an 800 mile journey over two days the oil was not noticeably down and was still clean as a whistle.
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gandinis swear by them - I do not own the company, I have had trouble with rings from firms that you would say are well known for BSA spares and many waste of time arguments, Gandinis sorted the job very impressed with them
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gandinis swear by them - I do not own the company, I have had trouble with rings from firms that you would say are well known for BSA spares and many waste of time arguments, Gandinis sorted the job very impressed with them
Mine was apparently wet sumping but I discovered that the oil pump was leaking from the gasket. A careful flat file to face off the back of the pump and a new gasket with a re tightening after a few miles sorted that. I would get the best part of 1/2 a pint of oil out of the timing cover after the bike had been sitting a while now there is no more than a couple of tablespoons in there. I reiterate though if they are JP rings and they havent sealed straight away they probably never will. I put Gandini rings in mine and gave the bore a light hone before assembling it dry. It has never made a puff of smoke since and after an 800 mile journey over two days the oil was not noticeably down and was still clean as a whistle.
Thanks Guys
Gandinis do seem to get consistently good reviews on the forum. I'm going to give her a couple of hundred miles to settle down, but if that doesn't do it I think Gandinis will be the go. The current smoking isn't a problem when I'm riding as it clears rapidly, but the smoke when I start her up might upset the neighbours if it continues too much longer.
Cheers
Tim
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Hi Everyone
Since I fitted a new barrel and JP pistons the right hand cylinder has been smoking on start up. It clears after a mile or two so I'm tempted to give it a damn good ignoring - am I courting disaster or should I just keep on riding?
Cheers
Tim
Check with the supplier and see if the rings are chrome plated. If they are, you need to run them in hard. If you go easy on them they will glaze the bore and you get blowby and smoking for a couple of miles until everything warms up.
Beware of the pistons. Check the specs on them and that there able to take brisk running while bedding in. I know some suppliers in the US are using Italian pistons and fitting US chrome plated rings claiming they are better made. Yes, they are. However, the rings have to have brisk running in but the problem is the Italian pistons (made using traditional materials) pick up under load.
Check your oil consumption regularly as well. If you're using more than normal its could be a symptom of blowby.
I hope the above is of help. regards Fergus.
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Clouds of smoke on start up sounds like you should maybe check your oil pump. I took the timing cover off mine and saw a steady stream of oil leaking out the join between the pump and the crankcase. The horrible mazac bodied pumps tend to grow out of shape and may need some fettling to fit properly. The wet sumping will also stop the rings from bedding in as they are constantly having to deal with excess oil. Take the cover off and leave it over night with a drip tray underneath you'll soon spot if its leaking.
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Thanks for your advice everyone, I'm hoping it's just the rings need a bit of bedding in. I'll let you know if it settles down.
Cheers
Tim
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Clouds of smoke on start up sounds like you should maybe check your oil pump. I took the timing cover off mine and saw a steady stream of oil leaking out the join between the pump and the crankcase. The horrible mazac bodied pumps tend to grow out of shape and may need some fettling to fit properly. The wet sumping will also stop the rings from bedding in as they are constantly having to deal with excess oil. Take the cover off and leave it over night with a drip tray underneath you'll soon spot if its leaking.
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Clouds of smoke on start up sounds like you should maybe check your oil pump. I took the timing cover off mine and saw a steady stream of oil leaking out the join between the pump and the crankcase. The horrible mazac bodied pumps tend to grow out of shape and may need some fettling to fit properly. The wet sumping will also stop the rings from bedding in as they are constantly having to deal with excess oil. Take the cover off and leave it over night with a drip tray underneath you'll soon spot if its leaking.
Thank Slymo - another option to try if it doesn't sort itself out.
Cheers
Tim
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Hi Tim,
Did you settle it down yet, or are you locked down like me due to COVID.?
Colin
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Hi Tim,
Did you settle it down yet, or are you locked down like me due to COVID.?
Colin
It's definitely decreasing - it cleared by the time I got to the end of the street last time I took her out (200m ish), but opportunities to ride are limited at the moment.