I'm hoping that some of you might be able to give me some tips about unfreezing parts that have rusted together. I recently acquired a BSA ZB32 alloy barrel and cylinder head dating from around 1949-51 which I hope to fit to my iron engined B32. The barrel is in reasonable condition with a STD bore which although probably still serviceable would be best with a 0.5mm overbore. The head however, although it has no broken fins, has been stored in very poor conditions for many years. As a result the rockers are seized to the spindles and the spindles are siezed into the head. The biggest problem is going to be freeing the rockers first. So far it has spent 5 days in a 10% Deox-C solution which, although it dissolved all the external rust, didn't seem to penetrate into the tiny clearance between the rocker bores and the spindles. It has now been in a bath of diesel/acetone mix for a week and even after a fair bit of heat applied to the rockers they still don't want to move. I'll try every day and hope that they will eventually move. If the worst comes to the worst I will cut them out and try to source new spindles and rockers. Here are couple of pics.
I’ve had a fair degree of success with PlusGas Formula A on rusted tf bolts. At £10 a can, not cheap but if it does the job, money well spent. Andy
I'm happy to try anything Andy. The main trouble as I see it is that the rockers are about 75mm long and have quite a close clearance to the spindles. That's a long way to penetrate.
As I see it the trouble with using electrolysis is that it won't penetrate any better than the Deox-C and I think it would have a deleterious effect on the alloy head
I agree on the Plus Gas I used it many years ago to de rust an adjustable wrench it was more a sentimental thing than a need as the plus gas cost more than a new wrench
I don't have access to Dingbro but my local bike shop uses the Deblock Oil. I'll speak to him and see if he can get me the Deblock Ice. I like the idea of a thermal shock.
if you can i would advise having both. a good pre-soak with the XS. it really is that good. then maybe a quick spray with the ice immediately before any attempt to remove the shafts. mate, i know you know your stuff. but if they could be drawn out by making up spacers with a bolt of some kind i am gonna put money on them coming out.
I doubt if it will be as easy as that Fin. The cast rockers are seized to the steel spindles and the spindles are seized onto the alloy head at both ends. I think the first priority is to get the rockers free on the spindles. The spindles will hopefully then release from the head with the alternate application of releasing agents and heat
I'm confident. how will you be heating it? getting some localised heat in there might be an issue without bluing some of the components. oven?, gas mark something while already under tension from a drawing out tool then a good spray of the ice on the shafts? maybe? or maybe I'm taking it too far. chortle.
Unfortunately all oxides are 'bigger' than their parent metal and it sounds as if you have two materials' worth of oxide to deal with. IMO a few heat cycles would be a good starting point with, as above, some separation preload in place if possible. Bugger.
Got them out. After 4 days in Deox-C, a week in diesel/acetone mix and (thanks @finm), 3 days of applying DeBlock XS and a fair bit of heat most times I tried to get anything moving. On Tuesday I got some movement on the exhaust rocker, yesterday some movement albeit stiffly on the inlet. Today I got both rockers moving freely and after judicious application of a propane torch got the exhaust then the inlet components out. I think the most effective thing was to fill the oil ways in the spindles with DeBlock and plug the inlet so that it was contained and soaked it's way through to the bearing surfaces.
Meanwhile sales in DeBlock have just doubled... I've personally never heard of the stuff but I reckon I might be getting a can cus you never know when it might be needed. And are the rockers & spindles salvageable?
Yes, the DeBlock worked a treat. I was on the point of thinking I was going to have to cut through the spindles. The rockers are definitely salvageable, I managed to damage the thread on one of the spindle although bit would probably dress up. I bought a spare set of rockers though in case the worst came to the worst, so I'll probably use them. Next task is to find an exhaust valve and collets. They are rarer than hobby horse shit.
