Engine strip/rebuild

[Azubi]

Hi all,

I used my A 10 plunger (my first bike) without any significant issues for some years now. This spring on a sunny day the engine broke down - I think the pictures give a first impression. Now I would like to use this topic to aks for advice and help and  to inform about the progress.

I have to start a winter project to bring my bike back on the road. I already found a lot of information (just to mention "Musky's Plunger rebuilt").

• Do you agree that I should strip the engine down until I reach the sludge trap?
• I am not a machanic and own the usual hand tools (but no welding equipment/skills, lathe...): which steps could become difficult?  Or should I involve professional help (could be difficult in Austria)?
• At the moment the barrels should be a 67-1074 (have to verify). Is it possible to use a thick flange barrel on a plunger?
• Is it possible to use new liners BSA A10 Cylinder Liners/Pair and resleeve the barrels?
• At the moment the primary drive and cluch are untouched? Is there a good way do start detaching this parts (I already have a tool to remove the shock absorber nut)?

Appreciate your help and comments.

[muskrat]

G'day Azubi.
Ouch that looks nasty 
Is that the top half of the piston still in the bore?
* Yes a full strip down and rebuild.
* Depending on condition most of the work can be done with a modest set of tools. Crank grinding, boring of barrels & timing side bush will need to be sent       out to a reputable machine shop.
* Yes thick flange barrels will fit with longer studs. (I wouldn't reuse those barrels).
* See above. It would be possible BUT 
* Pretty straight forward removing the primary. Loosen the cush nut first (do not remove) Then the clutch center nut, back the chain adjuster right off (I remove it so it's not in the road but not necessary). Now remove the clutch plates and hub and the cush nut & spring. The sprocket and clutch chainwheel will come off together (with chain still attached).

I like to remove as much as possible (dynamo, magneto, timing gears etc) before removing the lump. Quite heavy with the gearbox attached. Reminds me of the first time I did it. With no book or internet (1982) I tried to remove the gearbox first 
Best of luck with it mate. Take your time and if in doubt of anything ask and you will get answers.
Cheers 

[sean]

those barrels are scrap you can put liners in the thick flange barrels but better if you can find a set that have a couple of rebores left in them......clean the sludge trap and put a return line filter on it .....pick up a copy of the service sheets and a parts book tag lots of pics and bag and tag everything ....goood luck

[Azubi]

Good morning,

thx for your valueable input. So next stesps should be clear.

@Musky: you yre right - you see the piston. I did not remove it until now.

[KiwiGF]

Any idea what caused the blow up? Failed piston? Failed oil pump?

[Swarfcut]

 Azubi,  As mechanical failures go that is not too bad. A conrod through the cases is more usual. More in the "Great Mechanical Disasters" thread. That later cylinder base gasket could mean it has already been apart more than once.

 The engine must be stripped right down to its basic parts to have any confidence the rebuild will be successful. Bent valves, cracked valve guides and bent pushrods for starters, then scrap con rods, cracked cases and a blocked up sludge trap. But all is not lost, the majority of the parts are available and these engines are relatively simple.

 BSA improved the design over the years and yes, a thick flange barrel will fit, but be expensive. The later wide fin barrel fits straight on and both need the later matching wide fin head. You can also fit a later big journal crank and rods.

 Don't overlook the oil tank. Give it a good wash out, there may be evidence inside of what caused the failure. When the sump plate comes off, prepare for a few surprises.

 We will all be interested to see what you find. As you dig deeper, some parts will be damaged as a consequence of a basic failure somewhere...that's the cause you are looking for.

 Swarfy.

[muskrat]

G'day Azubi.
Looking at how the piston broke I'd say either bad wrist pin or bent rod to stress the piston at that point.
That type of piston is weak in that area.
Cheers

[Azubi]

Hi,

thank you for your interest and your super feedback.

I always checked the oil circulaton when starting the bike.

In the first winter of my ownership I removed the barrel - I remember something was not 100% correct when installing the left gudgeon pin. I installed the gasket during rebuilding.

The magneto on the drain plug shows definitlly metal particles. I already drained the oil some time ago and  I didn't pay too much attention...

[RichardL]

I don't think that's particularly bad iron particle buildup on the sump plug. You're about to take it apart to the last screw, so why not start at the sump cover and see what falls out? Besides parts of the piston and barrel skirts, I'm guessing shards of crank shims.

Richard L.

[KiwiGF]

Out of interest (but I’m not suggesting this is a good or economic fix!)

https://www.youtube.com/watch?v=HhyBWK0pE8Y

[muskrat]

G'day Kiwi.
Good video but I think Azubie's barrels are past it 
Cheers

[Worty]

I don't think that's particularly bad iron particle buildup on the sump plug. You're about to take it apart to the last screw, so why not start at the sump cover and see what falls out? Besides parts of the piston and barrel skirts, I'm guessing shards of crank shims.

Richard L.

I'd agree with Richard, that's not a bad build up on the sump plug.  I whip off the sump cover at every opportunity to see what's collected there and to give advance warning of potential failures.

These engines are robust though, see my engine rebuild story by Bergs 'Worty's A10 Engine Refurb', to experience the horrors of a shocking 'professional' engine rebuild and the state of the motor which continued to run despite the issues.  Bergs has a story where he discovered a broken crank web after a ride out!!

You'll get every bit information you'll every require on the Forum mate, right down to the last screw, tolerance or ball bearing.

All the best with the rebuild.

[berger]

worty talking of ball bearings , remember that one stuck in your camshaft oil delivery hole , that was a great mystery.



 quote ----I whip off the sump cover at every opportunity to see what's collected there and to give advance warning of potential failures.

have you found the map i left in there that takes you to the buried treasure of the Brough yet
 

[Azubi]

Allright - found my second piston after removing the sump plate.

[trevinoz]

That barrel is repairable but would be expensive.
The barrel on my '55 Flash was worse than that, the cylinders were broken almost to the base. A mate made custom stepped liners from cast iron and they were fitted and bored to suit new pistons.
Never had any problems with them.