engine noise

[David Tinsley]

1955 A10 S/A GF

I finally got the bike legal and took it out for its first short run, maybe 2 miles.
It pulls extremely well, gears a bit difficult to engage every now and again, but OK
What does concern me is engine noise, it seemed a bit clattery to me when I rolled on the power. bit not having ridden an A10 before I dont know if that is normal. I did not strip the engine down so wondering if I have issues that need to fix.
There is a leak from the rocker box, as can be seen on the video, hence the smoke, but that is an easy fix.
Here is a link to a video I just took right after the run, hoping someone with more experience than me might be able let me know if I have a problem or not
https://youtu.be/kATFVp8Ucmg

Another video I took last year as well of me actually riding it
https://www.youtube.com/watch?v=Ky6p57RytGU
Thanks in advance for any ideas or tips.
Dave

[Greybeard]

Video shot from a phone often has poor sound quality. The engine sounds quite noisy to me. It might be loose tappets but I worry about slack in the pistons, so called piston-slap*. I would be keen to strip the engine down and check everything and most importantly, if you have not done it already, clean out the sludge trap.

* I was told that rattle under load indicates worn pistons. Rattle with no load indicates worn big ends.

[limeyrob]

Not sure what's going on there.  It is primary chain noise?

[David Tinsley]

Video shot from a phone often has poor sound quality. The engine sounds quite noisy to me. It might be loose tappets but I worry about slack in the pistons, so called piston-slap*. I would be keen to strip the engine down and check everything and most importantly, if you have not done it already, clean out the sludge trap.

* I was told that rattle under load indicates worn pistons. Rattle with no load indicates worn big ends.

Thanks for the reply.
Much as I did not want to I am going to have to strip the engine down and yes, the sludge trap will be done at that time as well. I just  checked compression and it is 90/60 so apart it is.

[David Tinsley]

Not sure what's going on there.  It is primary chain noise?

I dont think it is primary chain noise, I did adjust that to within spec. The engine is coming apart though so I will have another look when the primary cover is off.

[Greybeard]

I just  checked compression and it is 90/60 so apart it is.

So possibly losing compression down the side of a damaged piston.
Just for shits-n-giggles you can pump oil into the plug hole just before you check the compressions. If you get better compression you might assume that the oil has temporarily sealed a dodgy piston.

[David Tinsley]

Well, that was an interesting afternoon. I got the head and barrels off. right hand piston looks as though it has been overheating, or something fell down there sometime and melted. pulled the barrel, the bores look good, but have not measured yet. Left piston has too much play, can feel it with my hand. The pistons have a slightly concave crown which I have never seen before on later BSA models, is this normal? No BSA part # in the crowns either.

Biggest issue is the right hand big end has way too much play, I suspect it would have have been too long before it let go, so glad I am stripping it down. I should have done this at the start, but you live and learn. I will doubtless be asking more questions as I did deeper.

[Swarfcut]

 Slightly dished pistons are the low compression variant, cam used with these is the 334.  For more vigour, use flat top pistons with a 356 cam. Easy to do at this stage as the crank will be coming out. Cam identity is stamped on the blind bush end. If you find it is already a 356 cam, the motor has certainly been played with.

 Cleanliness and attention to detail will pay dividend in building up a motor. Arrange finance now. Good that the cause has been identified. Expect someone's mis-guided efforts as you dig deeper, may not even be matching pistons........con rods the wrong way round is also a common mistake.

 Gear engagement problems, clutch drag common, first goes in with a clunk, under way stiffness or difficulty in changing gear is   a symptom of the cam plate adjuster being set a bit too tight. Too loose, it drops out of gear. Try for a mid-way setting.

  Swarfy.

[Macbeth]

1955 A10 S/A GF

I finally got the bike legal and took it out for its first short run, maybe 2 miles.
It pulls extremely well, gears a bit difficult to engage every now and again, but OK
What does concern me is engine noise, it seemed a bit clattery to me when I rolled on the power. bit not having ridden an A10 before I dont know if that is normal. I did not strip the engine down so wondering if I have issues that need to fix.
There is a leak from the rocker box, as can be seen on the video, hence the smoke, but that is an easy fix.
Here is a link to a video I just took right after the run, hoping someone with more experience than me might be able let me know if I have a problem or not
https://youtu.be/kATFVp8Ucmg

Another video I took last year as well of me actually riding it
https://www.youtube.com/watch?v=Ky6p57RytGU
Thanks in advance for any ideas or tips.
Dave

My story.. new to BSA (well any older bike but old BM’s really). Rode it a bit, great power & starting etc etc. I didn’t really like the sound the engine made & put it down to an old pommie bike & my unfamiliarity. Changed the oil & the crank shim came out in 17.6 pieces. Did an exploratory & found the gudgeon pin clip was out as incorrect one had been fitted & the wrist pin was happily chewing into the barrel. Long story short it ended up a long long wait & the GDP of a small pacific nation to sort with a full build

All good as I kinda expected a build buying an old unknown bike & now I’m sort of forced to keep it & ride it forever re cost into it which suits me fine

[JulianS]

The concave crown pistons are 6.5:1

You will probably find a casting number on the inside edge, 11016 if Hepolite.

[Greybeard]

DT, sideways movement of the pistons or bigends is not necessarily bad. Check for up and down slack in the BE's

[limeyrob]

I had a 55 or 6 standard GF back in the late 70s.  Bought it as a combo for £65 rode it thought the winter then took the chair off.  It was very standard, full mudguards, low comp pistons, soft cam. It had done a huge mileage and sounded like a bag of nails but it was lovely to ride, like sitting on an old sofa, it just bumbled along and did everything you asked except go fast . One day we tried to see how many people it could carry, we got 7 adults on it and rode round the (pub - that explains it) car park.  We had one on the rear light, one on each mudguard, another on the tank and 3 on the seat. Nothing bent.  I seem to recall it was 6.5 or 7:1, the tappet adjuster nuts were under(!) the rockers as the valves were so pocketed.

[David Tinsley]

DT, sideways movement of the pistons or bigends is not necessarily bad. Check for up and down slack in the BE's

It is up and down movement on this BE and a lot of it on the timing side. I would estimate a good 50+ plus thou! Dodged a bullet here I think

[David Tinsley]

Slightly dished pistons are the low compression variant, cam used with these is the 334.  For more vigour, use flat top pistons with a 356 cam. Easy to do at this stage as the crank will be coming out. Cam identity is stamped on the blind bush end. If you find it is already a 356 cam, the motor has certainly been played with.

 Cleanliness and attention to detail will pay dividend in building up a motor. Arrange finance now. Good that the cause has been identified. Expect someone's mis-guided efforts as you dig deeper, may not even be matching pistons........con rods the wrong way round is also a common mistake.

 Gear engagement problems, clutch drag common, first goes in with a clunk, under way stiffness or difficulty in changing gear is   a symptom of the cam plate adjuster being set a bit too tight. Too loose, it drops out of gear. Try for a mid-way setting.

  Swarfy.

Not sure what you mean by camplate adjuster? I set the operating arm angle at the gearbox end as per book and advice off here and adjusted the 6 clutch nuts on the drive side. What else affects clutch operation and gear selection?

[rocker21]

oh you have the old six spring clutch, they are well known for being troublesome, they can drag and slip at the same time!!! replace it with the later 4 spring clutch much better. there is a cam plate adjuster on the gearbox which is hidden from view which adjusts the tension and the amount of effort needed to move the gear lever, to little and it might come out of gear to much will make it hard to change.