What goes in this hole then?

[Rusty nuts]

In my humble opinion that's a partial seizure, no question.
That & or a broken/stuck ring will give you clouds of white smoke.

I had a Triumph way back that I used as a dispatch bike in London weekdays &  thrashed down the A3 to Sussex everyweekend & on several occassions it produced more smoke than the whole Red Arrows team put together!
cleaned up pistons fitted new rings & thrashed again!

If it was mine I would remove piston & check it & barrels for ovality.
If you're not confident about determining this, take piston & barrells to local rebore shop & have them check.
In that first pic it looks as if there may be a small nick out of the bottom of the skirt?
If all OK, i.e not too bad, put it back together.

I would fit new rings regardless, there is too much "blow by" between first & second ring & also between piston crown & first ring.
Hard to tell from photo how deep piston scoring is but looks salvageable.
 Bore should not have suffered so much as harder material.
If it's light, dress with fine grade wet & dry.
You may want to consider giving barrels a light hone to aid new rings bedding in either DIY with wet &dry or get your local rebore shop to do it.

Clean piston crowns, ring grooves
Remember to gap your rings correctly, ensure new ring gaps are not all in line about 120 degrees apart ideally.

Chuck it back together & go for a ride while the weathers still reasonable.
Speaking of which.................

Rusty
The Artful Bodger

[RichardL]

a broken/stuck ring will give you clouds of white smoke.

...and that top ring is certainly looking like it might be stuck or too stiff in the gap, considering the blowby path. Perhaps the partial siezure has damaged the ring lands and that is keeping the ring(s) from taking to the cylinder walls.

The good news is, you didn't disassemble for nothing.

Richard L.

[olev]

Cus, A while back I mentioned the local Vincent yahoos used 3 piece oil rings from some sort of mitsubshi in their engines. At the time I was hoping someone in the forum would leap in with a direct replacement for an A7.
While i'm terrified these rings would destroy the unique character of the engine, I'm prepared to take a chance that despite the lack of smoke, misfiring and compression it will still seem like a BSA.
Please tell me about your rings.
cheers

[beezalex]

If it was mine I would remove piston & check it & barrels for ovality.

I would certainly hope that the piston is oval...

[Rusty nuts]

If it was mine I would remove piston & check it & barrels for ovality.

I would certainly hope that the piston is oval...

Oops yes, but not the barrel! Distortion is probably a better word. Wriggle wriggle!!!!!! 

[cus]

G'day Olev,
I had already purchased new rings, but my mechanic said he wasn't happy to fit the one peice oil ring. He had a contact in Melbourne, Victoria,
that can supply rings for anything, so I called him up, great guy & very informative, sent down my new Hepolite pistons, he has to alter the ring rebate
slightly on the pistons, did a beautiful job. He is called Pacific Engine Parts.

Cus

[chaterlea25]

Hi All,
regarding 3 piece oil rings,a source of these is,

Cords Duaflex

Mayphil Industrial Estate, Goatmill Road, Dowlais, Merthyr Tydfil., Mid Glamorgan CF48 3TF

p: 01685 353240  f: 01685 353241

http://www.cordsduaflex.com

Email Cords Duaflex

There are various reports on the benefits of fitting this type of rings to old engines,
satisfy yourselves!!!
I fitted a set to a Commando a long time ago and its still going strong!
Cheers
John O R

[Mosin]

Hi,

I have just returned home after working away for a couple of weeks and ben met with the site of my poor A7 in pieces standing in the dining room. It seems like the next step is to try and establish the size of the pistons so that I can obtain some new rings. Is there an easy way to do this or is it just down to measuring?

I don't think that there is a rebore shop within about 100 miles of where I am, so it might be a bit of a struggle getting the barrels checked unless I send them off somewhere.

Also, I have heard some talk of "honing" can anyone expand on this for me a little?

Sorry to be a pain, but I really want to crack on with this, partly because it will be nice to have my bike back, but also because I don't want to risk loosing interest in the project and it sitting there indefinately - although I suspect that my wife and the imminent arrival of my second child in the next three weeks would prevent this from happening!

[a10 gf]

Sorry to be a pain

No pain, such posts + questions with following answers are the reason for the forum's existence !

[RichardL]

Simon,

Here is a video that I think decently shows DIY cylinder honing (or, if you will, deglazing) http://www.youtube.com/watch?v=82OMO1ArSkk .   Here in the states, the tool that's shown is available at about every retail auto parts store. For laughs, I tried to figure out where you might buy one in Cumbria, but Halfords does not seem to have them, though you might try.

As for the piston size, it should be stamped in the top of the pistons if they are any oversize at all. Nevertheless, you could hardly expect to do this project without owning or having the use of a decent quality dial or digital caliper like the one in the picture for about 30 GBP. For the bore diameter, a cheap set of telescopic gauges could do it, where you use the gauge to fit the I.D. of the cylinder then measure that with your caliper.

The real issue is, does the piston properly fit the bore? This could be checked with feeler gauges at the skirt of the piston 90 degrees from the line of the gudgeon. As a basis, this clearance should be between 0.003" and 0.006", the latter may be a bit loose, but probabaly not a real running problem.

Richard L.

EDIT: Here is a honing description. http://www.realclassic.co.uk/techfiles/tech05010600.html

[Mosin]

Cheers Richard. I've just cleaned up the top of my pistons and they are clearly stamped 11603 and +020 so I guess that clears that one up. I should be able to get a set of +020 rings easily enough.

I have also just ordered a digital calliper - I've been meaning to get one for ages so a long overdue purchase I think. I'm sure I'll not regret it!

One thing did occur to me though. If my problems stem from some sort of oil supply/circulation issue as most people seem to suspect, would this not have affected both cylinders simultaniously? As can be seen from my photos, the right hand cylinder appears to be pretty much fine.

Oh, and finally (but only for the time being no doubt) is there some sort of a 'knack' to removing and refitting the piston rings? I don't want to risk breaking anything or making matters worse than they are already.

Many thanks as always,


Simon

[RichardL]

Simon,

First, ring removal and replacement. A tool for this is cheap enough, probably as low as 8 GBP (and up). It can be done by hand, but brand-new broken rings are quite possible. In any case the tool must be used cautiously as well, only spreading the ring just as far as necessary to get over the piston diameter. When you put it back together, you will need two ring compressors, as in

http://cgi.ebay.co.uk/NEW-PISTON-RING-COMPRESSOR-65-70mm-BSA-TRIUMPH-AJSARIEL_W0QQitemZ140333943763QQcmdZViewItemQQptZUK_Motorcycle_Parts?hash=item20ac8e0bd3&_trksid=p3286.c0.m14

Regarding oil, the left side is most likely to starve first for a variety of possibilities: bad pump; low oil supply in tank; clogged flexible lines; clogged oil pickup tube in sump; bad right-side main bearing; bad pressure relief valve; clogged sludge trap (in later models, a tube through the crankshaft that separates heavier particles from oil by centrifugal force); dirt, metal or other large particles in oil; too loose right side rod bearing; clogged pressure equalizing hole in left side piston rod (maybe, controversial herein as to its potential guilt). The first four of these, I think, probably would have resulted in siezing on both sides. [Gents-at-large, please fill in causes I may have missed, after all, much of what I know I owe to you (or, if I were in the South, which I am not, "y'all")].

Before blaming oil completely, I think you should determine, to a certainty, that piston clearance on the two cylinders was the same before the failure and that that clearance was enough, for openers, let's asy 0.003". If just the left was too small, it may not have been an oil issue. If it turns out to be oil, and the chances for that are pretty good, you are in for a much bigger engine rebuiding job. If you don't already have it, get a copy of the Haynes shop manual. There is some not perfect information in there, but, for a beginner with an A7 or A10, I think it is a must. If you want to find references in this forum as to Haynes' inaccuracies, use the search tab, above, and search for "haynes".

I think that must be it from me, for now.

Richard L.

[a10 gf]

Good advices from Richard. Here is another twist, pieces of hard cardboard, plastic or thin metal

If you do not have some books, get them, you'll find tons of small and big tips to get things done the best way and in the right order, + lists of clearances, gaps etc etc, see books.

[nigeldtr]

Hello Simon,

Just read this thread and sounds like what I had happen to me, you may have seen the thread "Advice needed engine tightening up". A bit heart breaking when this happens. Have a look at the good comments from the guys on the problems I have encountered and I hope you find the cause.

Regards

Nigel

[Mosin]

Finally, a glimmer of hope!

I have just (and I should stress, not for the first time) had another look at the sump plate area, as it seemed to me that the engine was pretty much "drowning" in oil, despite the fact that the oil appeared to be returning to the tank last time I had the engine running. I took a length of stiff wire and had a good rummage about in the end of the pipe which drops down through the gauze into the sump plate (The scavenger pipe I think this is). After a good bit of delving about, I finally managed to release a lump of instant gasket which was about 2mm across and 3mm long! It must have been virtually bloking the scavenger pipe altogether. How I missed it the first couple of times, I have absolutely no idea! Anyway, it's out now and I am cautiously optimistic that I may have finally got to the bottom of my woes...

My current hypothesis is:

Oil pump pumping oil into the engine faster than it was being returned to the tank - engine gradually filling with oil - engine overheating - oil finally being blown up past the piston rings, past the valves and out of the hole that I first started with! (or perhaps just out of the rocker cover and cylinder head gaskets).

Does this sound at all like a plausable possibility?

Simon