How I saved my Bridgeport Cylinders

I'm sure by now you know that I am a ATF/Acetone fan so here is my way of removing stuck cylinders.

I picked up a 1969 “early number” (00390) H1 500 which has Bridgeport cylinders. This bike had sat in an outside salvage yard for years. Due to the value of the original Bridgeport cylinders, I was going to do everything I could to not damage them. I have removed many sets of stuck cylinders from H1’s before and usually had to resort to the “Drill and tap” method to get them off. And, of course, I have had a few of the really bad cylinders break as I tried to get them off. I did NOT want to do that with this bike.

I put a front and rear wheel on the frame that had the engine in it so that I would be able to have some room “under” the engine to work – so, if your bike has the engine in the frame, leave it in the frame. I have a m/c lift so I put the bike on it and raised it to a good working height.

I removed all the engine covers and cases, the exhausts (which were rusted through and shot), the heads and the clutch, etc. so that all that was left was the primary gears and nut on the right side of the crankshaft. I tried to turn the crankshaft with a breaker bar on my ½” drive ratchet and it would not budge. I tried pounding on the pistons with a mall and a block of wood, they would not move. I tried to get the cylinders to move by putting a 1”x 2” piece of pine wood in the exhaust port and pounding up, they would not budge. I wasn’t too concerned about breaking the crank or the pistons as they will be replaced, but I did not want to hurt the cylinders.

I had heard of a good combination of fluids to use as penetrating oil – 50% ATF (Automatic Transmission Fluid) and 50% Acetone. I then bought a quart of each and mixed up a small batch in an 8 oz glass beaker. I then poured this mixture in a metal “pump style” oil can. I then shot this mixture down each of the cylinder stud holes until they were filled close to the top. I also shot this into each cylinder. Obviously the piston position was different for each cylinder and I was able to get some of the mixture down the transfer ports in addition to having some on top of the piston(s) in hopes it would seep down along the side of the pistons. I did this on a Saturday. On the following Monday, I took my small Propane torch and began to heat the mixture in the stud holes by aiming the torch at the base of each cylinder right at the stud position. I would heat it until the mixture in the stud hole began to “boil”. I noticed as I did that, that the mixture was turning a different color, it was getting mixed with the corrosion and turning “brownish” in color. At no time did the aluminum fins get “red” or indicate that they were in danger of “melting”. I did have some fins that needed straightening though, so I took the opportunity to carefully do that at the same time. I also noticed that the fins transferred the heat very well as even an adjacent “hole” would start to bubble also. I worked around each cylinder (all 4 holes) until each one “bubbled”. I then moved on to the next cylinder until the same thing happened. I also noticed that the pistons that I had put the mixture on top of now were cleaned and looked like new – with no scrubbing done on them at all. After I completed heating all 3 cylinders I thought I would try to get the crank to turn. I was shocked when it actually did. It creaked and was hard to turn, but it gradually got easier and the pistons were moving too.

On Wednesday, I repeated the same process as above. I noticed that the liquid level in a few of the holes had dropped, which I took as a sign the penetrating mixture was working down into the stud holes, or maybe was even getting down alongside the cylinder liners, which I’m sure were also corroded in the engine cases.

On Saturday, I repeated the process again, but this time, right after I had heated up the left cylinder, I took a 8” long piece of the 1”x2” pine board and put it in the exhaust port and began hitting it up. It actually began to move. I angled it as much as I could to drive it parallel to the studs rather than vertical. Once I had the front of the cylinder up about ¼”, the fluid ran out like crazy. Now, this mixture is not “highly” flammable, but it WILL burn, so just be aware of that. I then placed a cloth over the top of the engine cases right behind the cylinders so I wouldn’t mar the engine case. I then placed a ¼”x1” wide piece of “strap iron” on the cloth that was long enough to “bridge” across the entire width of the engine case. I then used a pry bar to try to lift up on the carb flange, again thinking I didn’t care if I ruined the carb flanges, as those are easy to replace. I was able to get the back to move also. I then just alternated beating up the front and prying up the back until it came off. I did the same procedure for the other 2 cylinders.

All 3 cylinders are now off and undamaged and it took 1 week. I think this mixture is a GREAT penetrating oil and that combined with the heat is what freed things up. I do think it is critical to try to get the cylinders to move when they have just been expanded by the heat. I MAY have been able to get them to budge even earlier, I just didn’t try until Saturday or after 2 previous “treatments”.

At this point, I will never use the “Drill and tap” method again as I am convinced the above is easier and less time consuming and the bonus is that your cylinders are still original and not damaged.