Road Toad third gear failure

[BrianZ]

In the new Resonator Revisited (Oct 2014), I contributed an article on my experiences racing a Road Toad. I've been waiting for the article to be published before posting here so that some of you could get a chance to read the article and maybe offer some suggestions on how I can resolve my problem. To put things in a nutshell, what has happened is that I have destroyed third gear twice on this bike. The teeth break off the mainshaft and then the mating cog on the countershaft is destroyed as well. The engine is fairly modified with what amounts to a Super Rat top end and an HT3 pipe so it makes a few ponies more than a stock Toad. Ideally I would like to use a cushioned primary drive, but that option is not available as the Super Combat/Super Rat parts will not fit the Toad motor.

Does anyone have any ideas on how to prevent third gear from failing?

Brian

[olddogs]

You could send your next set of gears out for case hardening but that gets costly. Running to large a rear tire will also put to much stress on that little transmission. Are you dead set on using a primary kick oil injected motor. If you love the handling and size but want more power, a Combat motor will bolt right in with the use of a model 97 or 98 kicker to clear the frame. We race a red tank Dirt Squirt with this combo. Makes a nice small, compact bike with good power. Your pipe will bolt right up. You could probably make this change for the price of having the gears done.

[dcooke007]

Hey Brian,
I was surprised to see the mix of countershaft gears used on the Road Toad....94,95 and 97 model gears. Since you are having repeat failure of the same gear I am not sure going to an earlier engine with out primary kick would help since they use the same gear. Just sounds like an issue with too much horse power for the original gears to me. May be add in a little too much throttle????

I have noticed the 03 Wombat gear teeth on the main shaft and countershaft are WIDER than the other models. I would assume that was done to strengthen the gears. Although the gear teeth are wider the over all length of the main shaft and stacked countershaft gears are the same as the Road Toad.

03 Wombat main shaft and counter shaft gears can be installed in the Road Toad cases with a little work. The Road Toad uses a bushing on the left end of the main shaft and the 03 Wombat uses a caged needle bearing. You would have to remove the main shaft bushing from the left Road Toad case and bore it for the 03 needle bearing. There is another possibility that "MAY" work. Look at the 03 Wombat main shaft illustration part #2. It is called the main shaft inner race and appears to be pressed on. If the inner race could be removed from the 03 main shaft with out damage it looks like the end of the main shaft would fit the Road Toad bushing.

I am sure using the 03 tranny would result in a slightly higher first gear and second gear ratio. I "THINK" 3rd through 5th is the same. You would need to do some research to confirm my thoughts as I am working from memory. Also there was a change in the 03 Wombat tranny...there was an early production and later production set of gears. The early production engine had a first and second gear ratio that was too close and is coveted by the trials competition folks. The later production gears spaced 1st and 2cnd ratios further apart and should be the gears that could be appropriate for your use.

Any way it seems the 03 Wombat gears are a little beefier and if the ratios will work might be worth trying. I have a set of Road Toad gears as well as the late production 03 gears if you would like to explore this option. I just need to find them in my stash and compare ratios .

Danny Cooke

[BrianZ]

Thanks for the advice folks!

I have thought about swapping the motor for a Combat (or late model Rat) motor. I have a Combat Wombat motor, but the trouble is that I also have the rest of the Combat Wombat, and I figured this may make a better woods bike than the Toad. Plus, in my mind anyway, it seems a shame to part out my Combat Wombat to keep my Toad racing.

One thing I did notice is that the the Toad mainshaft has 2nd and 3rd gears pressed onto the shaft. These two gears are one piece and the Wombat and Combat Wombat use the very same part. Now if this part is failing on my Toad, why wouldn't it fail on the Combat Wombat? I am wondering if the Wombat and Combat Wombat part had better hardening, or perhaps the hardening process went awry when the Toads were being manufactured. Regardless, I had my buddy Paul at Sasquatch Vintage Racing press apart the Toad mainshaft and press on a 2nd and 3rd gear cluster from a donor Wombat mainshaft. I'm a little reluctant to try the engine with the rebuilt mainshaft as I am not sure if it is a solution or not. Has anyone had third gear fail on a Wombat or Combat Wombat?

Danny, thanks for the info regarding the 03 Wombat transmission. I had not considered the later transmission, mostly because I have never even seen an 03 Wombat here in Canada, much less transmission parts. Like you say, I will have to research this a little further. It sounds like it could have possibilities.

Brian

[olddogs]

I suggested the early model 100 or 125 because the cushioned primary in straight cut is still available at a reasonable price. I am very heavy, 275 with gear, so I always run a cushioned gear to give the tranny a fighting chance, With the interchange parts Hodaka loved to use, it sounds like quite a few options are are going to pop up. I am sure you checked you do not have to much slop/wear on the sprocket hub rubber cushions.

[BrianZ]

I have considered the rubber cushions in the hub. They are the original parts so I suspect that the rubber has hardened over the years, but they didn't seem to be worn or deformed in any way. There is some slop in the fit between the sprocket carrier and the rubber cushions, but this is present on all my Hodakas. I am running longer shocks (14.5"), which necessitates running more chain slack. This creates a situation where there is much more drive train lash than on the stock bike, and this added lash tends to make any slop in the hub cushions insignificant by comparison. Regardless, I am sure that the added chain slack makes things harder on the gears. Softer hub cushion rubbers would help the situation but I don't think that they would cure the problem completely.

Are softer hub cushion rubber available?

Brian

[taber hodaka]

Hi Brian Z. Brian are you one that uses the clutch to shift I know some do not, that would make a big difference. I think someone mentioned a smaller rear wheel or smaller tire. ---------------Clarence

[BrianZ]

Hi Clarence;

You've nailed one of my bad habits... I don't use the clutch when I up-shift. I quickly back off the throttle and snick (where have you heard that before?) it up a gear. I know it would be easier on the gear box if I used the clutch, but I've shifted this way for almost 40 years, and I'm getting too old to try to change now. I've tried to change but my brain is "programmed" and up-shifting without the clutch happens without consciously thinking about it.

I am running a 100/100 - 18" rear tire that is about 4.4" wide. It is an oddball brand Magnum SX, made in Vietnam.

Brian

[Bullfrog]

A few comments:

-- The urethane sprocket drive cushions available from Strictly Hodaka are better than the original rubber ones -- and I'd recommend that you install them. They will reduce shock loads in the drive train.
-- Harry Taylor was of the opinion that clutchless shifts were actually easier on the transmission, largely because there are usually no "hiccups" in making the shift. When properly "snicked" (where have I heard that before? ) , the ball receiver engages the "next" gear positively - with greatly reduced chance of stuttering even once before engaging. It was his feeling that the shock loads created by bunged-up shifts were harder on the transmission than the stresses created by clutchless shifting. (I talked with Harry about this very subject some years ago.)

Now comes the hard to believe comment . . . make sure there is no chance that you inadvertently apply the rear brake when landing from jumps . . . that seems to be hard on transmissions and is completely preventable. ALSO, check for evidence that the rear tire contacts the underside of the fender at full shock compression. If you find evidence of that, take steps to correct it immediately. Tire contact with the fender is a baaaaaad thing for transmissions.

Ed

[BrianZ]

Thanks for clarifying the clutchless shifting bit Ed, and I will try the urethane cushions before I give the mighty Toad another try. As for landing jumps with the rear brake, what's the mechanism for damaging the transmission? If the rear brake is applied, I don't see how it increases stress on the gearbox. Or is it applying the rear brake in the air, thus slowing the engine, and then the sudden acceleration to the engine/gearbox when the rear wheel touches the ground?

Another thing I am considering; would a lighter flywheel help? I am thinking this would reduce inertia in the engine and perhaps reduce the load on the gearbox. The trouble is that a reduction in flywheel effect would make the bike less "usable" in the woods.

Brian

[Bullfrog]

I just plain don't have an explanatory theory for the correlation between un-knowingly punching the brake on landing from a jump and transmission damage . . . but there IS a correlation between the two. In fact, I've stopped trying to develop an explanatory theory since several past "thought experiments" have been pretty much un-satisfactory. But I am convinced that I have seen a correlation between the two items.

Have you checked the underside of your rear fender for signs of tire contact? You are running a BIG tire. Tire/fender contact is really baaaaaad.

And that brings up the thought that a slightly smaller tire couldn't hurt. I'm partial to the Duro (HF355 I think it is). It is called out as a 4.00X18, but is very close to the same size as the old Cheng Shin 3.50X18. (NOTE: Dwight Rudder recommended the Duro to me back in 2005.)

Like you, I wouldn't want to go to lower flywheel effect for woods use --- that would the very last thing I'd try to help the situation. It might help, but I think it would be a considerably smaller effect than the new production urethane cushions for the rear hub. In fact, I think I'd look into having a cushioned primary gear fabbed up well before reducing flywheel weight (better addresses the problem, fewer negative side effects).

Ed

[admin]

Brian I was having problems years ago busting gears too. What I found out was seen in a photo at a race track. While racing and in the air I was inadvertently pushing down with my toes while on the pegs hence I was braking in the air. I did not mean to do it but clearly from the photos was doing it so I backed off my brake adjustment and this helped. We also found that even using brand new cushioned dampers from Hodaka that there was back and forth freeplay between the sprocket carrier and hub. We believed that if in the air and landing power on that this caused a whiplash effect and transferred the "shock" into the transmissions which was breaking gears. The idea we all came up with was to build bumps on the outside and the inside of the rubber dampers to take away this freeplay. It was also decided that we did need to keep pockets so that the rubber dampers did not completely fill the cavity of the hub. We experimented with different durometers of rubber and seem to have a winner. I stopped busting gears and the idea seemed to work well.
Paul

[BrianZ]

I checked the underside of the fender and there are no signs of tire contact. It's a painted plastic fender, so any tire contact would be obvious.

The first Toad gearbox failure occurred on a MX track. The track had lots of loose soil and jumps, definitely not "gearbox friendly" terrain, so I can see how the extra stress could lead to a failure.

The second failure occurred in a hare scramble. The race started with a lap around a MX track and then went into the woods where the conditions were a little on the slippery side with lots of rocks. Third gear let go well into the second lap, nowhere near any jumps, so this would not seem to have contributed to the failure.

One of the things that puzzles me is that I raced a Combat Wombat for a few seasons, and despite it having an extra 25cc, I never had a problem with the gearbox, keeping in mind that the Combat Wombat uses the same third gear. For this reason I was curious what the differences are between the two bikes. The CW should be putting down comparable power to my modified Toad and the weight difference should be negligible. The one difference I keep pondering over is the chain run. On the CW there is really nothing to be concerned with. On my Toad the chain runs over a roller on the top of the swingarm. When the suspension is fully extended this roller pushes up on the chain, taking up some of the slack (remember, I am running 14.5" shocks). You can see this in the picture in the Resonator. As the suspension is compressed, the chain gains some slack as the roller looses contact with the chain, but as the suspension compresses further the chain begins to tighten as the center points of the front sprocket, swingarm pivot and rear sprocket come into alignment. Perhaps this odd cycle of tight - loose - tight as the suspension compresses and rebounds could have something to do with the problem. I can't see how, but once again, this is the only real difference I can see between the "no problems" CW and the "two third gear failures" Toad.

While I am on the subject, has anyone had third gear fail in their Combat Wombat?

Anyway, I think my plan going forward is to get a set of the improved cush drive rubbers, and see if i can find a smaller rear tire. I'm also going to avoid using the Toad in MX events and stick to the woods. We'll see how it goes from there.

Once again, thanks for the input folks. Being able to bounce ideas off of others helps the thought process, and can sometimes lead in directions I hadn't considered.

Brian

[dcooke007]

Hey Brian,
Lots of good ideas shared here. I thought of one more thing to consider. I do not know if you can install the Road Toad countershaft gear/gears upside down and still assemble the cases with out binding but I have to wonder if that could be a possibility? If not installed properly you might not have proper gear teeth engagement. Kind of grabbing for straws but I have been around long enough to see stranger things happen.

Danny Cooke

[admin]

Brian I would not be afraid to take the Toad back on the track. My friend,neighbor and all around good guy Ivan Beattie has been NE 100cc expert champ a few years in a row now. He races for now a Road Toad and Ivan has not had any gear issues.You cannot turn the throttle much harder than Ivan does!
Paul

[BrianZ]

Danny, I always examine the gear engagement after I assemble the shafts into the cases to ensure that everything lines up, so I doubt that was the problem. It's certainly worth mentioning though.

Paul, thanks for the "inspirational" photo. I say now that I won't ride the Toad in any more MX events, but assuming I get everything back together and gain some confidence with the bike, I may give it another shot. I still want to get to Unadilla for the Vintage Rewind and race the Toad in the hare scramble, and if that works out well I may end up racing it in the MX. Time will tell.

Brian

[eichco1]

I have broken 3 sets of 3rd gear on 97/98 models. I think mine were mainly caused by the rear brake like Paul mentioned. I didn't keep much free play in my brake pedal. I now have a lot of free play, and use the hardened gear sets, so I don't know which made the difference. I would definitely go with a smaller tire like the Duro HF335 4.10x18 which is about the same width as a 3.50 cheng shin. Does your 100x100 clear the chain?

Concerning using an 03 gear set, I am pretty sure some machining needs to be done to the left case half of the 99/01/02 cases in order to use the 03 counter shaft gear set. Not positive, but I seem to remember some extra clearance in there.

Mark in Illinois
#492

[BrianZ]

Thanks for the advice Mark. My rear tire does clear the chain, but it's pretty close. Do you know the maximum width of the Duro tire? My tire is about 4.4".

An interesting observation concerning the front brake: When I was sitting on the line I noticed that I could pull my front brake lever all the way to the bar, so I tightened up the adjuster. Then during the race, once the front brake started to heat up the free play in the lever disappeared and the front brake started dragging. It's amazing how much the shoes "grow" when they get hot. Anyway, I wonder if the same thing was happening with the rear brake. I don't have as much "feel" for the rear brake when I have a pair of Alpine Star T6's on my feet, so it's difficult to tell if the free play is disappearing. I'll have to pay more attention to it when I'm riding.

Brian

[Bullfrog]

If your rear brake is set up close enough that heat/shoe growth/dragging might even remotely be a possibility . . . you have identified one of the contributing factors to your transmission problems.

Ed

[eichco1]

Never had the shoes grow that much to cause dragging. I have had vintage pads separate from vintage shoes.

I measured the Duro with a set of calipers. I came up with 3.940" on the widest part. You do have some extra chain room using the primary kick/injected motor. And of course, different brand tires might be different overall widths. When my 03 had a 100/100 tire, the right side knobbies were wearing into the rear brake backing plate stay arm when I rode it. The left side was wearing into the chain guard. I don't remember what brand tire that was though.

Mark in Illinois
#492

[BrianZ]

Thanks for the measurement on the Duro tire Mark. My tire measures just shy of 4.4" and it runs very close to the rear brake stay arm. It has rubbed against the brake arm once when the rear wheel alignment was out. I don't run a chain guard as there just isn't enough room.

I can't say for certain that the rear brake has been dragging, but the front definitely has. I can't imagine having the lining seperate from the shoes, that could certainly lead to a "pucker" moment.

Brian

[Bullfrog]

I think you'd like the Duro tire and (in my opinion) it would be a better match to the engine size . . . and might have some effect on slightly reducing shock loads in the drive train.

Finally, (in my opinion) running without a chain guard is like playing with matches at the gas station. Without a chain guard you have a very nice conveyor system for grunge (some of it large, hard and non-compressable) from the tire to the chain to the countershaft sprocket. I've been in attendance when a freshly re-built engine popped all three shifter case mount screws on a muddy track during it's first moto. Bummer.

Mud runners and cross country guys really ought to have a chain guard. My two-bits on the topic.

Ed