H motor rebuild

[djdesantis]

I am rebuilding an H motor I inherited when I bought a Super Combat last year with the wrong engine for the bike. Upon opening up the motor, I can see it is somewhat of a Frankenstein set up. Has the CW or SC head, iron cylinder that is set up to run a reeded intake. Looks like a model 94 cylinder. A SC piston and single dykes ring. Also was running the SC pointless ignition. I want to configure this motor to go in a 94 Wombat, for the dirt and street. Where do I start? I want to keep the cylinder and reed intake. But question using the SC piston with one ring. What other type piston can I use? To run with a reed valve, does the piston need to have all of the SC cut outs in it? Uncharted territory for me. Bottom end is stock H motor set up and I know I will need to change ignition to run lights, etc. Any input is appreciated.

[BrianZ]

Quite the dogs breakfast you have. You will need a piston with holes to take advantage of the reed setup. If the cylinder has been modified to run with a SC or CW head, the exhaust port will have been raised. I don't know of a two ring piston that will work in your motor unless you want to add holes to a Wombat piston, but the single ring piston should work fine. The nice thing about the dykes ring is that it offers better port timing, as the ring runs to the top of the piston. The two ring Wombat piston allows the ring to clear the exhaust port before the piston, so there is leakage of exhaust gases earlier that with the dykes ring. I'm not sure if this makes sense, and even if it does I have no idea as to the differences in performance.

Brian

[djdesantis]

Here are photos of the cylinder. Who knows what the standard bore is on these? I want to see how much over this cylinder is. Ques, did Hodaka make a model that used this cylinder stock, or is this a modification that had to be done to a non reeded cylinder? Or is this a parts purchase from Hodaka?

cylinder.jpg (3.35 KiB) Viewed 1146 times

cylinder 2.jpg (4.19 KiB) Viewed 1146 times

cyl 4.jpg (3.3 KiB) Viewed 1146 times

cyl 3.jpg (3.79 KiB) Viewed 1146 times

[BrianZ]

Your pictures are too small to make out much detail, but it certainly looks like a model 94 Wombat cylinder. In the last picture I cannot see any holes to complete the reed modification. The 94 was not reeded from the factory, but it was a popular modification back in the day.

I should also mention one other thing about Hodaka pistons. The Super Combat was the first Hodaka that came from the factory with a reed valve (there was a factory Hodaka reed valve kit for the Combat Wombat), and when they designed the piston, in addition to adding holes in the skirt they also made the skirt thicker. This makes the SC piston less likely to fracture.

Brian