Corroded 94 Crankcase

[AKwombat]

This crankcase came from a model 94 that sat outside for many years. Other than the heavy pitting in the crankshaft area, the case is low time and in good condition.

After bead blasting I could see several pits at the vertical split line that were all the way across the mating surface. You can see them in the picture. They are below the centerline of the crankshaft. They are not very deep, so I put a dab of JB Weld on them, and then carefully filed/stoned them flat. These little dabs of JB Weld will be captured by the case halves when the cases are assembled. The rest of the pitting is pretty rough but it doesn't look like it has compromised the strength of the case. The crankshaft seal areas have some pitting, but I think if I install the seals with #2 Permatex (or similar) the seals will stay in place and seal on the OD.

What do you guys think about using this crankcase?

I could TIG weld repair it, but I haven't looked closely at that yet.

Thanks,
Chris

[Dale]

Hey Chris, Happy New Year!
Your cases did take a beating! I have put together cases with some pitting but nothing like these. I am going to say that I am 51/49 on my vote. On one hand, I doubt that you would have any issues with using them. On the other hand, model 94 cases should be pretty easy to replace. I would go for it!
Dale

[Bullfrog]

I really like Dale's 51/49 comment. I'd use those cases . . . on the other hand, I might put 'em on a shelf to save for a time when there are no other choices (I hear they aren't making Hodaka crankcases any more) and go searching for a better set of Model 94/95 crankcases.
Ed

[viclioce]

I would think that any case sealant would take care of the mating edges. As long as the crank surface is clean, I think you’d be OK. But as Dale & Ed said, cases should still be easy to find. Victor

[AKwombat]

Gentlemen - Happy New Year and thanks for your input! I have been on the fence for about a year trying to decide whether to use this crankcase. The corrosion looks bad, but I can't really see where it will impact the serviceability of the case. All the bearing fits and other surfaces on the crankcase all look good, so I will probably use it. The motorcycle looked all original and didn't have many miles when I got it, but it had been sitting outside going through all those freeze/thaw cycles. When I disassembled the engine the piston was near the top of it's stroke, so the intake ports would have been open to the carburetor. The crankshaft and magneto were heavily corroded, and of course the piston was stuck. However, everything on the clutch side, primary gears, and transmission were all in perfect condition, and the trans oil looked good. Lucky I guess!
Thanks,
Chris

[viclioce]

Save this one!!! Victor

[dirty_rat]

If you are unsure on the case halves sealing well, take each one and lightly "lap" the sealing surfaces. Get a piece of thick plate glass (or a thick mirror even better) approx. 1 foot square. Pit some 400 wet and dry sanding paper on the glass and wet with soapy water or a light oil. Remove the case alignment pins and lightly sand each half in a figure 8 motion, keeping them flat against the sandpaper the entire time. And, to borrow an idea from Ed, mark the edges with a sharpie. Then any low spots will stand out as you sand as they will still have the sharpie ink showing. Just go slow and only continue until the cases look good.

[Bullfrog]

I suspect AKWombat has a "handle" on this, but just to be sure. There may be some spots on these cases which may not cleanup with a normal lapping procedure cuz they may just be too deep. But that's OK if a good plan is developed to fill those deep spots. Must assure long term adhesion, heat/fuel resistance, etc. Not talking anyone thru this though. It would be much better if the only folks who pursue such a repair are the ones who have the experience and "know-how" to pull it off successfully.
Ed

[AKwombat]

Dirty Rat & Ed - Thank you for your guidance. I blended those little JB Weld spots flat with a long flat fine file, being very careful not to get into the surrounding metal. Then very lightly checked them with a stone. I don't think further lapping is necessary. Other than those pits I filled, the mating surfaces look good and I hate to mess with them any further. The Yamabond 4 should fill any small imperfections. Appreciate the help and look forward to seeing you guys at Hodaka Days '23!
Chris