Wombat gearing

[Bill2001]

Wombat 94, stock final ratio is 56/14 or 4:1. For non-competitive trail-riding would a lower final ratio option be good?

I recall that overlay rear sprockets were common back in the day. Are they still available, and recommended for use?

[dirty_rat]

It's all a matter of preferences, but I find the stock gearing on the Wombat is fine off-road. As for the overlay sprockets, they were made to go over the "Road" sprocket (I believe it was a 36 tooth) on the Ace 100's to make it better off-road. The ones that came with the bike were 50 tooth. I don't think they made one that would fit a 56 tooth sprocket.

[matt glascock]

The Wombat is essentially a streetable enduro bike. I take mine trailing all the time and the gearing is great. You should try it with the stock gearing for your application before you change the ratios. You too will probably like it fine for trail riding as is. I have another M94 set up for VMX that has a 13 tooth countershaft sprocket to keep it in the powerband more easily but this is not essential for trail riding.

[hodakamax]

Hey Bill, I've got my Wombat 94A at 15/64T. I road a 38 mile cross country and it seemed perfect. There was everything from creep to roads. I rarely got into top gear. For what it's worth. As for overlay sprockets, I personally don't recommend them as it's another failure point in a high stress area.

Max

[Bill2001]

I've got worn chain and sprockets so as long as i'm replacing them I thought I'd look at options. The stock 15/56 "seems OK" but I don't have a lot.of seat time.
What I may try is a moderate 15/64 (4.26:1) ratio and swap back and forth between that and the 4:1 stock ratio to evaluate. Huge difference between the Hodaka 5-speed and the 4-speed on my BMW "tractor engine".

I was thinking overlay sprocket because the overlays used to have an on-hub carrier for the extra sprocket and it was easier to change. But doesn't seem available anymore.

[viclioce]

On my Wombat I'm at 13/56 and on the street it peaks out at fairly high rpm at 47 mph on the OEM speedo. So I would consider sticking with the 15/56 combo. The 13/56 also makes first gear virtually useless! It revs so quick you are shifting to second gear as soon as you start to move. It's one of the items I'll be changing for regular off road riding myself. Victor

[viclioce]

My Wombat has the current 13/56 final drive. As stated earlier, it peaks out on the street at about 47 mph at a high rpm in 5th gear. It's not not an original Model 03 motor. It's s Model 94 bottom end with a Model 95 cylinder & head with a 2 ring non-ported piston & a flanged Model 93 carb.

I want to change the counter shaft sprocket to either a 14 or 15. I'm not sure which to get. My grandson will be riding it off road and back & forth to school, about 3.5 miles each way, when he travels to school alone.

So I'm looking for what folks would think is a better counter shaft sprocket, a 15 or a 14? I'm assuming the 15 would be OK because that's what the original frame & wheels came with. But, how much difference and benefits would there be going to a 14 vs. 15 tooth countershaft, given this motor probably doesn't put out more power than an original Model 94 motor. No piston porting, no Reed valve.

So,which would you use? Maybe you all could tell me the drawbacks and benefits of each size countershaft sprocket. But I know the 13 is just too small. Thanks! Victor

[Bullfrog]

14X56 is the stock sprocket tooth count(s) for the toaster tank Wombat. For gravel roads and easy trails 14X56 is pretty good. For more "rustic" trails (creek crossings, steep creek banks, up-hill switch backs, gnarly rock picking, etc.) . . . 13X56 is better.
Ed

[viclioce]

What size wheels do the Model 94s have? Are they the same 18/21 like the Model 03, or different? Victor

[Bullfrog]

Yup, 18 and 21.
Ed

[Bill2001]

I checked my notes and see that my Wbat94 has a 14x58 (4.14:1) which is midway between the stock 14x56 (4.00:1) and Ed's rustic 13x56 (4.31:1). So it looks that I'm comfortably lower than stock. The next step lower with a countershaft sprocket would be an almost stump-pulling 13x58 (4.46:1).
Having figured all this, let me check SH and our other Hodaka suppliers and see what sprocks are readily available. But now we have an idea of what does what.

[hodakamax]

Looks like my 15/64 is in the area at 4.267:1. I prefer larger sprockets on the front as the chain doesn't have to bend so much. 12/13s eat up slightly more energy and produce more chain wear. Something to consider.

Max

[Bill2001]

I recall hearing the caution about a small front sprocket, especially with a cogged drive belt on newfangled bikes.

I envision possibly needing to ride the bike a long distance to a ride instead of trailering it. So in order to get the engine RPM down for a highway cruising speed I'd want a smaller rear sprocket. Anyone know what would be a good cruising RPM for a 125cc Hodie engine? On a four-stroke you try to cruise at or near the Torque Peak RPM.

[hodakamax]

If you are going to "ride it to the race" like we actually did in the last century, LOL, the stock 94 gearing isn't bad. You do have some easy countershaft options like 16-14-13T if you start with a 15T front. The 16T is always a little close on clearance but does work. All speculation but I'd get it going with what I had and make decisions from there. The wide power band and wide ratio transmission will fill a lot of situations. Torquey engines don't require much fine tuning on final gearing except on riding it there at reasonable speed and RPM. I think we all know this and I'm just reiterating about possibilities. Racing is a different story and different tracks can require different gearing for optimum performance. At this point it sounds like your importance is getting there at reasonable speed and RPM. Also, it's not a major issue to change countershaft sprockets when you arrive. You might even have to have another master link and extra chain links for your change. Just thinking out loud here, lots to discuss in gearing!

Maxie

[Bill2001]

Wouldn't ride it to a race-- were I racing I'd trailer it. Else it might be a looong walk back. I was thinking bike rallies or get togethers. Or something like the Barber Vintage Festival. I'm thinking distances of 50-100 miles on secondary roads. I don't think I'd be ballsy enough to do long Interstate highway runs. I'm thinking my W'bat does something like 5000rpm at 50mph. I'd loke to get something like 4000 rpm at 60-ish. I'll need to check my notes, but the engine did seem a tad buzzy at highway speed.

And starting to kick around the idea of that transcon run.

[Bullfrog]

I'd hazard a guess that the only way the Wombat engine will actually be able to maintain 60-ish mph at 4,000 rpm would involve, A) going down hill to your destination (AND down hill on the return trip), B) a good strong tail wind (both going out and returning home) C) "drafting" behind the car ahead of you. Although . . . small cross section full road tires and a fairing (and a diet? <-- sort of speaking for myself there ) might, possibly, maybe, get you there.
Ed

[Bill2001]

Hmm. I may be too conservative in the cruising rpm goal. I've not done a top speed hiway run in a few months, but I recall the engine feeling rsther topped out at 50-60-ish. I've got an engine hr/tach on the bike. I'll need tp check notes and specs. You're right, 125cc might not be able to maintain speed at higher gearing. My first car was a 36hp VW, and it taught humility.

[hodakamax]

VWs are for humility. I started with models above 36HP but later regressed to an early VW Rabbit Diesel. Weak. Passing even stationary vehicles required mandatory AC off. Noise level, off the legal standard, not from the exhaust, but the engine. What's that you say? Vibration? Top notch. Anything in the dash tray would be completely disassembled within ten miles or was it kilometers, I can't remember which. Ah, but the game was MPG. I was always after the elusive 50 MPG. Nope, 49.9 was the top. The wind could be your enemy or your friend in MPG contests with high gearing and low HP. How did you get me started on this? I thought this was about Model 94 gearing. Never mind.

Max

[taber hodaka]

Hi jack how could settle for a V W and 50 M/gallon? when a Loyd Wagon would get 60. The wombat speed range makes my speedy ace 90 look like a good deal.----------Clarence

[hodakamax]

We are on the edge of hi-jack here but one more story here now that you mention Ace 90s. They really never did seem to be slow. We had a stock Ace 90 in the shop that was just a trade-in and we used it as a spare for Sunday trail rides and such. When the new Ace 100s came out I took a new one for demo and rider. I put on a Webco head and some pipe of the day. Much to our dismay the 90 would out run, out drag any new Ace 100 including my slightly modified one. Obviously it was the efficient exhaust on the 90 or at least what we surmised that made it faster.

If you read my article in the new Resonator, It tells of a stock Ace 90, lights and all, winning a major cross-country Hare and Hound race both in class and overall.

Just some observations that much of the race was on gravel roads with throttle pinned. I think that was the day I saw the future of my motorcycle racing career and sold my intermittent running BSA at first offer.

Yet another tale, but shows that a broad power band can be advantageous making gearing not as critical. (I'm trying to stay on the subject!)

Max

[Bill2001]

I don't know what orifice I pulled thay 4000 rpm cruise engine speed-- that rpm is at 30mph in 5th which is practically lugging.

Found my notes and specs. HP peak is at 7500 rpm and torque peaks at 5900 rpm. Calculating road speed vs engine speed, 7500 rpm is 55mph and 6000 rpm is 44mph in 5th grear. To get 60mph at 6000 rpm, it would need some 73% reduction in overall gear ratio. I'll run the numbers later and see what final drive ratio this would be.

[Bill2001]

To get a reasonable engine speed at a useable road speed, the Wbat will need a 3.0:1 rear sprocket. This would range from a 14:42 set or a 16:48 set. And raising the final drive ratio to 3.5:1 would give more choices.

Just envelope-scribbling now.

[hodakamax]

I've been through this sprocket experiment through the years both racing and just to see how fast you can get a Hodaka to run. It always looks good on paper (or envelopes) but in the end reality sets in and no amount of gearing will make it go faster. A little wind, a little grade and you end up in the next lower gear or it might not even pull top gear on calm flat ground. All fun and that's how science works! Just watching your fun experiment and remembering mine.

A side note is that some of my top end testing was that I used a close-ratio transmission to close up the dreaded step of falling below the power curve. I still dream of some top end attempt and still have a close ratio 5-speed perhaps for that purpose. Just envelope scribbling also and I do need a project.

Maxie

PS--I should add that increasing horsepower and torque helps a lot.

[Bill2001]

I'm guilty. And was prolly guilty of this 40 years agp, too. I measured, ran the numbers, and tossed the idea around.

I'm impressed with the transmission ratios-- there is a nice big jump going into fifth, makes for a good "overdrive" for pavement travelling. I think that 20 mile paved road jaunts will be easily do-able. Longer trips more of a challenge.

Like I've said, if I want to do long trips to an offroad ride I can get a new DualSport bike.

[viclioce]

Bill. I checked the tooth number on the rear sprocket of the Red Toad today. It's a 62! I know that machine is going to high rev! May need to drop the rear to a 56 or 58 tooth! I believe this one has a 14 tooth countershaft, if I remember correctly. That would make it a 4.43 final drive. Should have counted when I had the shifter cover off today! Victor