The Hodaka Project

NOTE: All of the Hodakas were "excessed" in late 2005 when I had a big clear-out of "projects that were too far down the priority list to be likely to ever be started".

As with many of my projects, I really didn't plan on starting it - honest!

When I was in college back in Albuquerque NM I bought a used Ace 100B Hodaka from the local Yamaha dealer, with the thought of setting it up for MX or trials. When I got it home and pulled off the tank I found a DPO (dreaded prior owner) had arc welded some chunks of wrought iron where the frame spine had broken, and the interior of the engine wasn't in much better condition than that. I got the various tuning guides from PABATCO, bought some used Ceriani lightweight MX forks, and made a half-hearted start on the trials conversion, but since by then I had a new 1974 350 Bultaco Sherpa T the Hodaka didn't get very far before it was consigned to the back of the garage. The bike ended up being sold when I got out of school and moved off to my first job.

That was pretty much it for my Hodaka involvement until a few years ago. That was when I met Byron Woodruff at an AHRMA vintage trial. Byron was spectating on his neat Hodaka trials special built from an Ace 100B. I got Byron's contact info and corresponded with him - giving him tips on trials bike geometry and setup, some parts sources, etc.

Byron worked away on the bike, making a lot of custom parts for it, while trying to make minimal irreversable modifications to the bike so it could be converted back to stock at a later date.

Last fall I got a note from Byron that he was in a bind - he was moving to the east coast and didn't have room for the Hodaka! I offered to put it in my storage unit and try and sell it for him - he really didn't want it to go into the dumpster (and neither did I). What with winter coming on, and not having a truck for 9 months, I wasn't able to schlep the bike around to any of the trials to try and find a new owner for it. This spring I got another note from Byron in which he made me an offer I could have refused, but didn't (and how many of us can pass up those good deals, even on bikes we weren't looking to buy?). Suddenly, I was a Hodaka owner again.

Since I'm always coming up with new projects (though I'm not so good at getting them finished) I decided to use Byron's bike as a starting place for a custom-framed trials Hodaka. When you figure that the bike weighs under 145 pounds with the stock frame, and the stock frame and swing arm are heavy (28 pounds) and not too wonderfully designed for trials use, a custom framed bike could readily end up in the 135 pound range.


Some of the stuff Byron did was very useful for trials. He had Bob Ginder at B&J Racing make a heavy flywheel weight for the bike which greatly increased the tractability when chugging around at an idle. He did the PABATCO reed valve porting mods to the engine and made his own reed valve assy that he was going to control electronically. That reed assy wasn't a high-flow part, even for trials use, so I got a NOS reed block assembly from Paul Stannard at

I'll start with the stock 20mm carburetor that is on the bike since it is there and handy. The PABATCO sheet recommends a 24mm Super Rat carb. I've been told that this may work better more because of a better metering circuit, rather than the increase in venturi size. Currently, new Mikuni VM carbs are available in 22 or 26mm, and not in the 24mm Super Rat size - I'll evaluate carb changes after I get some time on the bike.

Byron modified a modern MX aluminum silencer to go on a copy of a stock head pipe (I'm not sure about the copy - it may be a stocker, but I don't have the bike close to me to check it). I'll redo this to incorporate a longer and smaller diameter headpipe which should help move the power down in the RPM range.

The Ace 100 has a cast iron cylinder, which isn't the lightest of items. I've purchased a 100cc Road Toad engine, which not only has an aluminum cylinder and reed valve, but also has bigger fins on the cylinder and head than the Ace engine. The engine isn't going to be putting out huge horsepower, but then it doesn't have a lot of air whistling through the fins at trials speeds. I'll have to get that apart, cleaned up, and checked to see what parts I need to order. The Road Toad does have oil injection which I'll be deleting (I run premix in my Kawasaki KT250 trials bike and want to use the same fuel in both) and a fancy tucked away kick start lever.


Since Byron was trying to not chop the stock bike the rearset footpegs he made ended up a lot higher than I think is best. He did make some adapters that move the front axle forward on the stock forks to reduce the trail, but the stock forks aren't the greatest in the world, so I've got plans to install either some 35mm Bultaco or Betor forks, both of which fall readily to hand.

The plan is to make a complete new frame and swing arm that will probably have somewhat less ground clearance than the bike has now. If you look at the photos, the engine rides quite a bit above the lower frame tubes. The engine could be lowered, the lower frame tubes eliminated, and an aluminum bash plate installed as is common on many trials bikes. This would lower the center of gravity and still give good ground clearance - I'm planning on 11-12" which is plenty for vintage trials sections. The stock seat ends up pretty high when the back of the bike is jacked up with the new upper damper mounts, so lowering that is also in the plan.

I want to end up with a fairly standard 52ish inch wheelbase - a stock Hodaka is about 49-50". With a light bike like this it will still be easy to loft the front wheel with the longer wheelbase and the engine moved forward to put a little more weight on the front wheel to help it to steer.


Photos - you can find some photos of Byron's bike at the top of the dirt bike section on my graphics pages. You can also find some photos and an article on the site.

For OEM parts or things like the brass flywheel check out and B&J Racing at I've bought parts for different projects from both Paul and Bob and recommend them.

My friend Craig Hanson at Hanson Racing Technology (530-342-8049) in Chico CA is working on a 125 Wombat trials conversion for his friend Hayden Campbell that will have a heavily modified stock frame and plenty of engine modifications, so you might check with Craig to see what Hodaka services he can provide.

There is a hallowed PABATCO tradition of oddball names for the Hodakas. I suppose I should have a traditional name for this bike. How about Trials Terrapin? Terrapins are very sure-footed, slow, and like the terrapin I'll probably need help to get upright if I end up pinned on my back under the bike.

Here are some scans of exploded diagrams of the 5 speed Hodaka transmission and shifting mechanism:

Hodaka 5 speed transmission 75K gif file

Hodaka 5 speed transmission shifter mechanism operation 65K gif file

Hodaka 5 speed transmission magneto cover/shifter assy 71K gif file

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© 1996-2007 Michael Moore, last update for this page 01 May 2007

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