Converting to 12 volt and cdi

[007Calvin.C.]

New here I'm working on a 73wombat 125
The stator windings are shot and the mag is in rough shape just wondering if any one has done these conversions

[dirty_rat]

I don't know about converting to one from another brand/model, but there are CDI's available for the bike. If you want to keep it street legal, or just keep lights on it, Strictly Hodaka sells a Power Dynamo bolt on external magneto CDI system that is 12 volt. It is Product Code: 40349 and list price is about $575.

If all you want is a CDI (no lighting coil), then the CDI off of the Super Combat will bolt right on (as will one off a 1976-78 Honda CR 125 I have been told).

[007Calvin.C.]

Thank you very much for the information I was not sure if it could be done and yes getting the bike back to street legal is the goal
I had never seen these bikes before other than a bit on the jay leno you tube page
untill this fall when one was brought to my shop

[007Calvin.C.]

I have a funny triangle with an h in the centre stamped on the top of the cylinder along with a +7
No one seems to know what they mean

[matt glascock]

Do you mean piston or cylinder? The +7 refers to the 7th overbore over stock.

[olddogs]

I believe the +7 was just a manufacturing spec used to match up standard pistons with standard bores on new castings as engines were assembled on the production line. You see them on most cylinders.

You would find over sizes stamped on the piston, seldom on the cylinder, and in milimeters or thousands of an inch.

[matt glascock]

That's why I was wondering if it was the piston with the marking. That one I'm familiar with. Thanks for the clarification. So, does this other number represent series of piston/cylinder sets matched to spec tolerances a la a +7 piston goes with a +7 cylinder and a +2 piston goes with a +2 cylinder, etc?

[Hydraulic Jack]

As mentioned, the numeric reference on the cylinder is a manufacturing reference, so that on the assembly line, parts can be matched for building the engine. I don't know of a seventh oversize piston. Don't think there were that many sizes over standard. The reference is to manufacturing tolerances, which vary. Cylinders and pistons were measured with reference to a standard, and marked according to how far from standard each part was. Once marked by the manufacturer of the part, the builder on the line need not measure each part, he need only match numbers.

So the engine builder would place a +7 piston into a +7 cylinder. Once the engine left the manufacturer, that reference is largely pointless. Any overbore would be based on actual piston in hand.

The triangle H was a registered trademark of Hodaka Industries.

[matt glascock]

I will have to look into this a bit more. My Road Toad, which was a basket case when I bought it, supposedly had been overbored 8, that's right, 8 times. That might explain why the piston melted the first time I rode it. The cylinder must have been about the thickness of a pop can.

[Dale]

Matt,
For the bore, +8 (.080") is the maximum oversize. From standard it goes in .010" steps from +1 to +8. Not to be confused with anything stamped on the cylinders as has been stated.

[matt glascock]

Thanks Dale. My knowledge of this subject begins with a pressure check when the bike doesn't snap and ends when I bolt on a freshly bored cylinder and matching piston/ring set after it comes back from the machine shop. Does my experience with the +8 overbore make sense with the overheating issue? I would assume that the heat dispersing properties of a cylinder bored that many times would be compromised.

[Dale]

I have no personal experience beyond +.050. I know that walls are getting pretty thin at +.080 but I haven't heard of it creating heating problems. If I were faced with going to that large of bore I would choose to have the cylinder Nikasil'd.

[Bullfrog]

Matt, it is far more likely that a "standard" fault killed your .080" over size engine. There are a fair number of "eighty over" cylinders out there which are running sweet as pie.

"Standard" faults being things like (but not limited to) . . . excessive compression, advanced timing, plugged pilot jet, air leak, broken blue points wire, (you can fill in the rest of the list from here - it should only take 15 or 20 minutes to type out an exhaustive list . . .)

Ed
PS: Hydraulic Jack's description of the use of the stamped number on the cylinder was precisely correct.

[007Calvin.C.]

The piston is 30thou over bore stamped right on the piston the cylinder has a plus 7 marking on it
Stamped on the machined surface of the cylinder where the head gasket sits

[Bullfrog]

Cal, yeah we zoomed off into other territory there for a while. But I think you do know now that 1) there are options for CDI and lights on your machine and 2) the little "7" stamped on your cylinder has absolutely no utility now. (see Hydraulic Jack's response)

Ed

[007Calvin.C.]

Ok thanks everyone
Any kind of information always helps

[matt glascock]

Indeed. As always, thanks fellas!