Author Topic: A10 break down, analysis  (Read 1628 times)

Offline BSAnders52

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A10 break down, analysis
« on: 26.05. 2017 22:49 »
Hi, Referring to my long introduction, if you read it I dont have to tell more abot the circumstances.
http://www.a7a10.net/forum/index.php?topic=11737.0

Symptoms and diagnosis, this is where i need some feed-back.

The bike started fine, or at least willingly. Oil was ouzing from the RH side of the rocker hous and spurting out of the crankhouse ventilation. Oil was pitch black, and even felt somewhat thicker than its original SAE 50. It appeared to have passed through the combustion and then down to the sump..
There was a distinct tick-tick for every turn (of the camshaft?) wich to me tells there is something snagging or bent, or..
We took off the outer  transmission cover, and took out the generator chain, to eleminate it as a source of the ticking. Ticking remained

 I used a screwdriver as a stethoscope to find out where the noise come from..

Digging deeper , removing the inner cover, the ticking was traced to the cam area.

Compression test reveiled the LH cylinder to be hold twice as much as the RH.

The oil pump feels like the culprit, not able to keep the flow or pressure.
Or maybe it is the other way around, the oil bypassing the valves, getting too thick and too full of carbon deposits, makes the oil pum to fail..

Anyhow, I have not yet had the time to remove the head and look further into this.

I hope the bronze main bearing is OK, it sounds like it is. All bearings seem to have escaped any dammage. So far..
I likewise hope all dammage is in the accessible parts - pushrods, lifter, valves.. and not on the camshaft. Is this just wishful thinking? Possibly.
I would like to not have to split the engine, but probably it is better to know everything is OK, and then close it, than to hope there are no hidden dammages in there.

I will order a new Oil Pump from SRM, they seem to he the most recommended.  I seem to have to leave allso the cylinder head to them for rebuild and modification to accept non-lead fuel.
Or is there any other workshop that can do this job, who hav all necessary tools and jigs, and the knowledge? Cosmo in Hastings?
The only remaining workshop in Sweden is due to close down, and he is unwilling to take on more jobs.. I might be able to talk him over..
There are a coupple other workshops, that only do Norton or Triumph, and claim making the tools for BSA would cost more than the rebuild itself..

Any opinions? Tips
I will be back with pics, when I have them, but I will be off to Holland for some time first..

Anders
Sweden



Online KiwiGF

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Re: A10 break down, analysis
« Reply #1 on: 27.05. 2017 00:13 »
Possibly put some oil down the bores and re do the compression test, if the pressure improves it most likely means valves are the problem, rather than pistons/rings.

Edit: if pressure improves it means Pistons or rings are most likely the problem not the valves. The oil will i improve the seal on the piston but not improve the valves if they are leaking.

Ref the oil pump, the operating pressure is (worryingly) low in these engines once the oil is hot, the pressure relief valve is designed to prevent "over" pressure only when the oil is cold, and does not open when the oil is hot. The standard pump is not often found to be worn, they last well.

if you are lucky the tapping noise might be a bent or stuck push rod  *lol* alloy ones in particular can get the end stuck in the rocker.

I think the jury is still out on modifying valve seats for unleaded, iron heads do not seem to need modifying, alloy heads maybe.

My guess is burnt valve, maybe partial seizure. Both can cause a tapping noise and low compression.
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, project missing parts, mission impossible?

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Online RichardL

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Re: A10 break down, analysis
« Reply #2 on: 27.05. 2017 04:27 »
Anders,

Oil blowing out the breather port is likely due to excess oil in the sump. This could be because the pump is not pumping it out or because it drained down ("wet sumped") while sitting. It would be nice to know if you saw oil returning to the tank while running. If you did, it is very unlikely the problem is the pump. While you can't go wrong with an SRM pump, you could hold off buying it until you reveal the tick-tick noise and cause of gushing oil. That noise is not the pump and pumps are easy to change later. Tick-tick could  be as simple as a loose valve adjuster (we wish).

As for the color of the oil, pitch black would not surprise me after a run the length of Sweden.

As for modifying the head for unleaded, regardless of the debate over it being an issue, using lead substitute should guarantee that it's not an issue and you could forego the seat replacement, maybe, forever.

KiwiGF,
Uh, is there a glitch in what you wrote or in my understanding? For more than 50 years (which doesn't mean I'm right), I have understood that valves are the problem if compression DOES NOT improve when oil is squirted in the cylinder, the oil sealing leaking rings but not leaking valves.

As always, I am warily expecting any correction which may come.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: A10 break down, analysis
« Reply #3 on: 27.05. 2017 05:19 »
Anders,
KiwiGF,
Uh, is there a glitch in what you wrote or in my understanding? For more than 50 years (which doesn't mean I'm right), I have understood that valves are the problem if compression DOES NOT improve when oil is squirted in the cylinder, the oil sealing leaking rings but not leaking valves.

As always, I am warily expecting any correction which may come.

Richard L.

Richard you are quite right even though I know the correct method I put it the wrong way round, senior moment eh  *problem* it's now edited ......hopefully clearly.
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, project missing parts, mission impossible?

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife

Online RichardL

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Re: A10 break down, analysis
« Reply #4 on: 27.05. 2017 05:48 »
I honestly thought you just glitched in the way you wrote it and figured you were well familiar with this old trick.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: A10 break down, analysis
« Reply #5 on: 27.05. 2017 07:20 »
The drastic loss of compression on the right hand cylinder is either valve or piston problems.
With black oil pouring out of breathers etc. I would strongly suspect a failed piston.
I would not go messing about with oil pumps at this stage. The oil pump is not the problem.
Off with its head!
Once the head is off, it should be obvious where the problem lies. Pouring paraffin down the ports will show immediately if a valve is not sealing properly. In any case, with the head off I would take the valves out and do the normal clean and lap in anyway.
If the valves are OK lift the barrels. There will be a problem with the RH piston or rings. Place a rag over the crankcase mouth as you lift the barrels in case any pieces of piston or ring try and leap into the crankcases.
The screwdriver stethoscope is notoriously inaccurate. Sound can propagate wonderously through engines. What sounds like a cam may well be a piston.
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Offline duTch

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Re: A10 break down, analysis
« Reply #6 on: 27.05. 2017 09:01 »

 Richard & Kiwi I thought the same ^^^, when I read it earlier  *shh*...thanks for easing my mind
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
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Offline BSAnders52

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Re: A10 break down, analysis
« Reply #7 on: 27.05. 2017 13:40 »
Thanks a lot for thoughts.
I too am open to find the cause elsewhere than in the oil pump. Lifting the top will reveil the truth, but I am not sure I will have the time until a few weeks ahead..

As I dont have handbooks at hand, is there any special I must think of, any procedure I must follow when I lift the head? I simply cant remember, too long since last time..

This is how it looked then, 1978-ish .
How do I use the "INSERT IMAGE" button? It is boring to have all pictures at the end, after the written text..

I will definetely come with more pics and questions.

Anders
Sweden


Online RichardL

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Re: A10 break down, analysis
« Reply #8 on: 27.05. 2017 13:50 »
Nore: Anders posted just before me, so please take that into account.




The drastic loss of compression on the right hand cylinder is either valve or piston problems.
With black oil pouring out of breathers etc. I would strongly suspect a failed piston.
I would not go messing about with oil pumps at this stage. The oil pump is not the problem.
Off with its head!
Once the head is off, it should be obvious where the problem lies. Pouring paraffin down the ports will show immediately if a valve is not sealing properly. In any case, with the head off I would take the valves out and do the normal clean and lap in anyway.
If the valves are OK lift the barrels. There will be a problem with the RH piston or rings. Place a rag over the crankcase mouth as you lift the barrels in case any pieces of piston or ring try and leap into the crankcases.
The screwdriver stethoscope is notoriously inaccurate. Sound can propagate wonderously through engines. What sounds like a cam may well be a piston.

Black Sheep,

First, would you mind sharing your first name? I'd rather not start abbreviating  your name as "BS", because it would NOT apply.

I think your diagnosis is probably right on, but I have a couple of questions/points. I know I have done compression tests where the cylinders vary widely, only to come back (rested maybe) and run another test where everything is fine. Therefore, maybe we can't rule out a faulty test. If the piston has a hole in the top I would expect no compression as opposed to half, but maybe other modes of failure apply.. Then, about the rag covering the crankcase, I would have thought that piston pieces falling off was a sign the whole thing needs to come apart. Needed or not, if it was mine I'd have to do it for peace of mind.

Richard L.

Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: A10 break down, analysis
« Reply #9 on: 27.05. 2017 14:01 »
How do I use the "INSERT IMAGE" button? It is boring to have all pictures at the end, after the written text..

Ha! True confessions: After over 3000 posts here I still haven't bothered to figure it out.

Not sure about special  tricks when removing plunger head. For my swingarm, it helps a little to remove the top-rear center valve cover stud to ease rocker box removal. You might want to loosen the valve adjusters before loosening the rocker box. Not mandatory, though.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline BSAnders52

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Re: A10 break down, analysis
« Reply #10 on: 27.05. 2017 14:18 »
Ah, yes, that rings a bell..to remove one of the studs to be able to free the rockerhouse off the upper frame tube.
Thanks

I will analyse everything before I start ordering parts.

Anders
Sweden

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Re: A10 break down, analysis
« Reply #11 on: 27.05. 2017 15:02 »
Pouring paraffin down the ports will show immediately if a valve is not sealing properly.

I had to stop for a minute and think about this before I realized that Black Sheep was speaking British and not English. I then figured out he was referring to kerosene and not candle wax.   *conf2*  *smile*
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Re: A10 break down, analysis
« Reply #12 on: 27.05. 2017 20:55 »
Casting aside my anonymity, my name is Gordon and I'm a bagpipe playing Scotsman. A Cracked piston may still give some compression. Pistons can fail in a number of interesting ways. I have a number contributed by my Norton over a number of years. 
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Offline duTch

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Re: A10 break down, analysis
« Reply #13 on: 27.05. 2017 22:37 »
  Hi Anders, You'll get to the bottome of it.....

   
Quote
Quote from: BSAnders52 on May 27, 2017, 23:40:21

    How do I use the "INSERT IMAGE" button? It is boring to have all pictures at the end, after the written text..


Ha! True confessions: After over 3000 posts here I still haven't bothered to figure it out.

        Well I thought I'd have a go, so clicked on it and copied a pic from my docs and pasted it in.....>
   
       .........< there twice, but it did nothing. *dunno*

 (it looked like this>
         
Quote
           
                 
            <,in the 'reply' pane-without the 'quote' )...  and when I come back to modify it, the 'insert 'stuff is still all there.......*dunno*  all a bit ghostly I say, but maybe best to leave it for another place...

 IMG_20160828_23676.jpg
   NB- ^^edit/Edit/Edit   ^^


   B.Sheep-  I think the first Monty Python I ever saw was the Big marauding Scotsman episode


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 duTch

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Re: A10 break down, analysis
« Reply #14 on: 27.05. 2017 22:56 »

 I just finished playing further with no result ... *bash*
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