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Thread Like Summary
Adrian C W, NickL
Total Likes: 6
Original Post (Thread Starter)
by Adrian C W
Adrian C W
Hi all,

I recently acquired what I thought was a 71 Lightning, and am trying (unsuccessfully) to strip the engine down. After being left outside with no spark plugs in, the pistons are well and truly seized in the barrels...

After trying to unseize for a while (a week now - lots of heat treatment, gentle but persuasive hammering, penetrating lubricant's, and even a dose of Phosphoric acid...) I am thinking maybe I cut my losses,,,

I should just strip down what I can, get another used set of barrels, and then re-sleeve or re-bore that one with new matching pistons...

According to my parts book the barrels are part # 71-1464. When I look at the actual seized barrels, they appear to be Part # 71-1033.

The engine VIN on the case is XE 02985 A65L, which I think would be a December 1971.

My question is - what do I look for? The Part # in the book, the Part # on the bike, or will any barrels from an A65 fit??? Thanks Adrian
Liked Replies
by MarcB
MarcB
The part number and the number cast into the part are not often the same. The difference between the barrels off one year and the other may only be in machining, which would generate a new part number but keep the same casting.

Here is some good info: https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=719649
1 member likes this
by Allan G
Allan G
With anything cast, look for the part number (casting number) from the bike.
1 member likes this
by gunner
gunner
Quote
a week now - lots of heat treatment, gentle but persuasive hammering, penetrating lubricant's, and even a dose of Phosphoric acid

In terms of freeing seized pistons, week is not that long to wait, I would keep cycling the heat penetrating oil etc. for a while longer, eventually something will give.

If it came to the worst, don't forget that pistons are easy and cheap to come by whilst barrels are not, so it may be easier to sacrifice the pistons by drilling some holes around the edge of the crown which should relieve the pressure and help free them.
1 member likes this
by Jon W. Whitley
Jon W. Whitley
Originally Posted by Adrian C W
I am thinking maybe I cut my losses
Adrian


No man,

Suck out whatever liquid is in the cylinders and refill with kerosene and expect to let it sit for at least a few weeks or maybe a little more. That doesn't mean you can't try and nudge it along periodically. My first ever BSA was freed that way as well as my 1974 Honda CB750.

When trying to break it loose, you can try to nudge it using the kick start, you can put it in gear and try and rock it loose by turning the rear wheel (chain must be installed) or you can remove the primary cover and put a breaker bar on the crankshaft nut (most preferred method for maximum torque).
1 member likes this
by chaterlea25
chaterlea25
Hi Adrian,
If the pistons are partway down the cylinder I would unbolt the cylinder from the cases, split the cases and undo the big end bearings
Now that the cylinder is off the engine it is a lot easier to work on and apply pressure to the pistons
This way it is also easier to get the cylinder mounted in a mill or large pillar drill to attack the pistons
Be very careful to support the cylinder properly if trying to push the pistons out !! If there is rust /crap in the bores below the rings when the piston is pushed down it can split the cylinder below the base flange

John
1 member likes this
by Stuart Kirk
Stuart Kirk
Originally Posted by Adrian C W
.... I will start from the "bottom-up".....
One little word of warning.
There is a nut inside the crankcases that has to be undone to split the cases. It may be hard to get to with an end wrench if the cylinder is in the way and the head sometimes hasn't enough side clearance to use a socket on it.
1 member likes this
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