Stuck piston in BSA B21 (like a B31 sort of)

[KiwiGF]

I use my log splitter to press in bearings and do jobs like freeing up stuck pistons. I agree with previous entry, soak in diesel for a long time.

Thanks, I think I read somewhere diesel is as good as any expensive “penetrant” wonder chemical!

[RDfella]

Are you sure the rod is still in there, or did it disappear through that hole?

[berger]

I've got a home made ten tin press, but I'm hoping to not resort to that as it will damage the piston for sure, but as a last resort I'll use it. is the ten tin press for destroying ten 1970's skodas in one go

[KiwiGF]

Are you sure the rod is still in there, or did it disappear through that hole?

That is what I’m trying to find out! All will revealed soon, I tried some more heat and oil this evening but there is no signs of piston movement yet when using the clamp to apply pressure, so given all the advice here I reckon I should next split the cases and have a look inside.

I can put the cases back together if the lower part of the barrel is not too rusty and there’s a chance I can move the piston without using a press or dissolving it, and if it’s easier to handle assembled, and there is also the suggestion of splitting the crank to think about, assuming the big end looks rusty, which it almost certainly will do.

 There was oil On the piston top, and in the rocker area, and not too much rust elsewhere eg the cam followers had surface rust but pressed out quite easily through the brass bushes, so there is still a faint hope it comes apart “normally”.

[ironhead]

Well that’s good news on the piston availability, I assumed a piston and/or rings would be hard to source, I’m assuming there is no chance of saving the rings, and only a remote chance of avoiding a rebore and subsequent oversized piston, which company sells the pistons please? (It’s a 1937 B21 deluxe), 250cc).

C10 /C11.  From any company you choose.

[KiwiGF]

Well I tried my home made press (20 tonne jack) but chickened out after after putting a fair pressure on the piston, it didn’t move at all, I’m thinking the cases would give way before the Piston.

Muskrat was right and I could not split the cases as the through bolts fouled by just 3mm and hence just stopped me pulling the cases apart. I could try to melt the bronze holding the centre nuts on the through bolts in place and slide them down the 3mm, but decided to leave them alone for now.

So the engine (barrel and piston) is currently sitting in diesel as per prior suggestion, I’ll report back in a month after it’s been soaking a bit. Oddly the piston is under size, and the barrel sleeved slightly under sized. I suspect it has a Nissan car piston.

I’m still not sure if I’ll take this project on rather than sell it, but it’s becoming an “affair of honour”  .

I’ve spent a couple of hours on google looking at pics, and it looks like not many of these early pre war “B” series bikes (B20 through to B26) are original, so maybe it may be viable to get this one back on the road, wrong tank and all  it would involve making lots of parts (stand, gear change etc etc). Random pics of a complete one below (not 5he basket case I have)


 

[RichardL]

You say, "barrel and piston" in diesel. Is the bore in diesel below the piston? In other words, is the whole engine submerged?

Richard L.

[Greybeard]

... It could be the stone jar of mercury that I used to empty out and play with when I was a young en...

I also know what mercury feels like, running through my fingers.   

[KiwiGF]

You say, "barrel and piston" in diesel. Is the bore in diesel below the piston? In other words, is the whole engine submerged?

Richard L.

It’s upside down in 10l of diesel, it’s covering the base gasket area by 15mm so diesel can get into the barrel and fill the under piston area (cases are split, with 3mm gap). I also put the diesel in by pouring it through the sump opening, onto the Conrod, so that should also have made sure the barrel was filled.

Fingers crossed this works, it’s going to be messy 

[Rocket Racer]

You might also like to put an ad in the Southern Star, those motors and their 350 counterparts the B26 are about. At one stage I had several K & YB26 motors.
Try and source a spare motor or parts...
All the prewar 250 and 350 B series had fragile cases and rolling chassis compared to the post war B's but  as they are so light go very well.
Sounds like the piston and bore are going to be pretty stuffed, but barrels are getting scarce so if in doubt sacrifice that piston. Its toast anyway.
How hot have you got that barrel? More heat...

[RDfella]

I reckon a few ounces of Blue Dot would shift it.

[KiwiGF]

You might also like to put an ad in the Southern Star, those motors and their 350 counterparts the B26 are about. At one stage I had several K & YB26 motors.
Try and source a spare motor or parts...
All the prewar 250 and 350 B series had fragile cases and rolling chassis compared to the post war B's but  as they are so light go very well.
Sounds like the piston and bore are going to be pretty stuffed, but barrels are getting scarce so if in doubt sacrifice that piston. Its toast anyway.
How hot have you got that barrel? More heat...

Hi Tim, all good advice thanks, i’m Still in two minds on whether to keep the b21 project, so I’ll wait a few more weeks to see if the diesel works on freeing it up, my brothers asked if he can dunk his seized Kawasaki kt250 barn find in the bucket of diesel after I’ve finished with it 

[RDfella]

I'd heat that piston as hot as I dared without melting it, let it cool and then put as much pressure on it as I could (much more than a G clamp) and leave the pressure on. Sometimes when something is obstinate, leaving the pressure on for an hour or overnight does the trick. Remember, as the piston is at TDC putting pressure between piston and crankcase will achieve nothing (assuming the conrod is still in there - if the barrel won't lift off it must be).

[olev]

So, how did we go. The suspense is unbearable.
cheers

[KiwiGF]

So, how did we go. The suspense is unbearable.
cheers

It’s still soaking in the diesel  other bikes are in the way of getting on with it.

I’ve actually just been working on my A10, the stand I bought didn’t have the “extension” piece to hook your foot on, i’m used to finding it with my foot but it’s not easy, I’m lending it to a mate for a day long Rally, so I thought I’d better weld on a short length of bar to make It easier for him.

I was SO pleased to find the stand spring installation tool I made years ago works so well  I was going to weld it in situ but was concerned the DVR2 might get fried, so I took the stand off, I wasn’t looking forward to doing that, which is why I’ve put off doing the job for years, in the end it only took 30 mins