The Hodaka Club Forum

I bought this gear set in 2008 because I thought it was unusual and it was reasonably priced. It has the number 91 hand engraved on it. The description on the packing list says: "Close Ratio Gear Set for All Early Hodaka's from the Ace 90 to the 125"

I have my Ace 100 engine apart to replace the connecting rod.

While it's open I intend to put this gear set in.

If I don't like it, I'll take it back out.

Is there any additional information available about how and why this gear set was offered back-in-the-day?

I street ride my B+. It has the complete reed valve super rat top end, super rat expansion chamber and the super rat primary gears.

Thanks

The 91 gear set originally came out as a racing option for Ace 90s which were 4 speeds. They required some machining of the crankcases. I ordered the set for my 90 racer about 1966.(a close guess). There was a bulletin on it from that time and someone posted it on the Forum quite awhile back during a discussion of the close-ratio 5-speed.

The early ones for 90s came with a countershaft with a snap ring for the sprocket requiring a different sprocket collar with an o-ring to prevent oil leakage. I always thought that the splined main shaft was way cool.

Max

Thanks for the picture and information. What you show is what I have.
I'll put the gear set in and give it a try.

From your description of your build, it should be like riding an MX bike on the street. Could be fun but would depend on final gearing. Are you looking for around town zip or do you ride back roads and such? Just curious. I would expect with close ratio you would have to avoid gearing too low or too high, depending on your preferred ride style. Does anyone know the ratios for this gear set? Or the tooth count?

I think the splined shaft would be worth the effort in any case.

I'm also somewhat curious how this will work out on the street. I have only driven the CR on tracks, keep us posted! AZ, I'll try to count them soon. (It is the Christmas season!) Maybe I can Just lay them out in a picture.

Maxie

OK, while waiting for Santa I had a few moments to shoot one for you to analyze.

Max,

Are you sure your gears are close ratio? The tooth count as shown on the counter shaft is: 24/26/27/30/34. Seems like a wide ratio spread. The main shaft gears I am not sure. Are the stickies the tooth count for the three gears starting with the machined spur?

If so I get 21/20/18/15/11 as the associated counts. Trans ratios would be: 3.09:1, 2.0:1, 1.5:1, 1.3:1, 1.14:1. Maybe close and wide are relative terms. These also sound really tall. Is this a dirt track gear set? Or road race?

AZ, I only raced these short track. Harry Taylor recommended them for road racing also. This is not the set that I raced but they are marked 91. In road racing 4 and 5 need to be really close because you are geared so tall. As I remember low is taller in the CR than the WR. I bought this set last year to replace the set in my short tracker that disappeared between the time I sold it and found it decades later. I really hadn't looked at these until I shot the picture. We'll figure it out, I'm off to Christmas dinner!

Maxie

The numbers seem to me what you said, tall on the bottom, close on top (or reasonably close). Which would make them a pain for street use. Guy I worked with back in '75 had a Yamaha 350 (TZ?) road racer we took to the 1/8 mile drags. Took forever to get the clutch all the way out but then it was a beast. But, in an 1/8 mile I beat his time with my stock RD350. Quarter mile would have been a different story. I topped at 110 in sixth. He went much faster. At an 1/8 mile I was 90 mph at the top of third hitting fourth, but he was just topping second gear. I was about out of poop. He was just getting to OMG speed. I wouldn't know how to make the road race gears work on the street.

Before reed valve modifications our race engines were extremely "pipey''. Worse yet we were working with a 4 speed really wide ratio transmission. The CR 5-speed was the answer to our prayers as you could keep the engine ''on the pipe''. It wasn't as important with reed valve engines as they had a broader power band but still was useful in that you could build a more radical engine which usually resulted in a narrower power band. In a short track you gear to top out at the end of the fastest part of the track. If the two fastest parts of the track weren't the same the close ratio was useful in that you had two close selections to choose from. In road racing you are geared so high that the engine might not be able to pull top gear without being really close to the next lower gear. As for use on the street, I don't know. Low might be rather tall when geared for the road. It might be fun to try but you might have to lower the overall gearing which would limit your top end speed.

Max

Az, your count on the teeth are correct and it is the close ratio transmission. Most of the parts were 91xxxxR except the control shaft parts. -------Clarence

"Close ratio" means many things to many people. Each of those definitions has some utility to the person adopting a particular definition. Problems arise when your definition does not match the definition another person holds dear. Perhaps the following information will be useful.

NOTE: Arizona posted ratios for the "close ratio" transmission under discussion, and Clarence has confirmed those ratios are correct -- so I'm going to run with 'em.

I like to use something I call the "ratio of the ratios" to be able to compare different transmissions. The "ratio of the ratios" can be used to answer the following question, "How big is the 'jump' between first and second (or first and fifth)?" And it allows me to compare that "jump" between gears with two different transmissions. Nifty. These relative "jumps" between gears will ALWAYS be the same with a given transmission - regardless of the sprockets installed.

Sooooo . . . The "ratio of the ratios" between 1st gear and 5th gear for the tranmission under discussion is 3.09/1.14=2.71. That tells me that at a given engine RPM, I'll be going 2.71 times faster in 5th gear than I would be in 1st gear. In this case, if 10,000RPM produced 80mph in 5th gear, then I could go 80/2.71=29.5mph in first gear --- so I could exceed residential speed limits in town (with lots of noise) in 1st gear, but pulling away from a stop sign would likely involve quite a bit of clutch slipping. NOTE: This transmission seems to me to meet a more-or-less techinical definition of "Close Ratio" because it does not have a w-i-d-e range of speed capablilities between 1st and 5th.

By comparison, the "ratio of the ratios" between 1st and 5th in a standard Wombat (94) transmission is 3.44/0.95=3.62. So, with the Wombat at any given engine speed, you'll be going 3.62 times faster in 5th gear than you were in 1st gear at that same engine speed. That is a considerably w-i-d-e-r range of speeds.

I hope this info is helpful to someone out there.
Ed

Good explanation Ed, I think that was what I was trying to say.

Maxie

All of which makes sense, and is why I suggested such a gear set might be a pain on the street. First isn't low enough to use without MX final gearing, and fifth will only get you to 40 if first is low enough to use.

I do like the splined shaft design, but for general, non-race use I would source a gear set from a 100B or similar, which will work on street as well as trail without burning clutches or screaming the engine.

Or, build this gear set into a land speed record replica. Watch Worlds Fastest Indian. The trouble he has getting rolling at Bonneville is how I see these gears working on the street.

To address the suggestion of the OP about putting these into a 100cc reeded engine for use on the street, I would say no. You won't like it. Ed's description of the speed spread between first and fifth tells us that if you gear low enough to use first, which means you will only go from zero to maybe ten mph in first, top speed will be a screaming 40 or so, which isn't enough to be useful. Plus, the clutch isn't strong enough to take daily slipping to get first going if you gear for a higher top speed. On the track, it's okay. You only get rolling once per heat, hopefully. But around town, the clutch will take a beating.

I would keep these gears for use in something for which they were designed, and put a normal wide ratio 100cc gear set in your bike.

Somewhere I read about a Hodaka running the Texas Mile which is a standing start mile run. He was having trouble pulling 5th gear. I wonder if he had a CR transmission. Anyone remember that? Edit: It's on the Forum under Hodaka on the Texas Mile post by Pep. I still think there's another article somewhere.

Max

PS--Hmm,Texas Miler, that might be a fun project and a good use for my transmission.

Check it out at texasmile.net

The 100B gears are the same as the first Ace 100's. I think the Super Combat has the closest ratio gear set of any.
Clarence

It appears to be time for a clever chart and/or graph from AZ comparing all the transmissions.

Maxie