The Hodaka Club Forum

I recently acquired an ACE 100 with frozen engine. The engine is now on the bench with head, ignition and clutch removed. Piston is stuck at mid-stroke & looks okay from what I can see through the ports and top. The base gasket must have been glued on with super something as the cylinder won't come off. I've soaked penetrating oil down around piston but hesitate to whack on things too vigorously. Any suggestions?

I'm partial to the patience, hot/cold cycles and penetrating oil method.

Propane torch to bring cylinder up to "spit/sizzle" temp. Squirt penetrating oil on the crown of the piston to wet the piston/cylinder joint. Let cool to ambient air temp (preferably in a cold shop). Check to see if piston is free in the morning. Repeat as necessary. 5 or 6 cycles of this often works without brute force efforts.

Ed

Thanks, Bullfrog, I'll try this. When I put penetrating oil on the piston crown it eventually soaked down earlier.

That's good that the penetrating oil soaked in. The hot/cold cycles stress the "marriage bonds" which have formed over the years between the piston and cylinder (or piston ring and cylinder) and weaken them - much more than penetrating oil alone.
Ed

It seems like two problems. The piston won't go up & down and the cylinder is stuck to the cases.

I think your crank is froze up, as is the piston cylinder. I would not think the cylinder is stuck to the cases. ------------Clarence

. . . so add the base gasket area to the penetrating oil treatment. The hot/cold cycles we've talked about will already be "doing their thing" in that area. A little Copper Coat on both sides of the base gasket, torque down, let set half a century or so . . . yeah the cylinder could be "stuck" to the cases. But it'll come loose. It could well be that the crank is "frozen" and can't turn at all, but you should be able to see a hint of crank rotation by grabbing the flywheel or clutch by hand and twisting if it isn't "frozen".
Ed

Just a quick reminder to never to use the kick starter to try and free up a stuck piston. Serious damage to the kick starters moving parts can occur.
Use a strap wrench on the flywheel or clutch.

I purchased a couple boat anchors from the local Boneyard and, as expected, both of them had stuck pistons... After removing the head I wasn't able to get the cylinder to budge either. After lots of penetrating oil, heating and cooling, it still wouldn't budge. Did some reading and found this tool.
I proceeded to remove the cylinder studs with this tool which allowed me to split the case without removing the cylinder. On both engines, the cases split easily and the transmissions were in great shape but the crank was toast; rebuildable, but toast. I used a hydraulic press with 1 1/2" thick steel to support the cylinder and pressed the pistons out.

Just offering a suggestion. But obviously, this only works with engines that have the cylinder studs protruding from the top.

$0.02

Roger

And a previous mechanic might have used a hardening gasket compound. Copious heat at the cyl-case junction might work.

Kroil seems to be the best commercial pene. oil. The very best stuff is a 50:50 mix of ATF and Acetone.

All good ideas. I'll keep working at it and report any progress.

Progress report. Several heat, cool cycles haven't done the job. It is now in the deepfreeze following the last 'spit-sizzle' torching. I've considered dry ice on the piston crown. Using utility knife blades as wedges I have raised the cylinder about 1 mm and have cooked out the base gasket and freed the cylinder from the base. It seems both crank and piston are seized. Acetone/ATF solvent soaks slowly around piston. I've ordered a stud remover and may go to rikarren's procedure. Could a wrist pin keeper jam into a transfer port?

A word of caution. Don't get too impatient forcing the cylinder out of the cases. Make sure the cylinder comes straight out of the cases. The skirts on the cylinder are pretty fragile. Don't ask......

The cylinder finally surrendered the piston after considerable resistance. The DPO had apparently forgotten that the sparkplug should be in place when a bike is left in the rain for decades. Lower end is trashed. Clutch, tranny, etc look quite pristine. A real shame as the entire bike (wiring, seat, tank, paint and fenders) are in very nice shape. Dang!
Now what?

When you say the lower end is trashed, are you referring to the crank, etc., or the cases? I figure it must be one of those as you said the transmission and clutch parts are all good. If that is the case, you can usually find another set of used but good cases from one of the parts suppliers (Strictly Hodaka for one). If none available there, then on-line. Same for a new or refurbished crank.

I think he is saying the crank is bad?? ----Clarence

The cases survived, the crank is bad. I found another in my archives and have hopes of getting the old girl back on the trail.

There have been times I have either made an offer to provide a "spare part" or thought about making the offer. But with the way parts are going these days, I may be saving more & more of what I have left over IN CASE the grandsons are a little tough on the bikes! Good luck with your find now that you can move forward on it! Victor