Why oh why...

[Darrell]

Another issue for the Hodaka Think Tank:

Some years ago I totally rebuilt the bottom end of a waterlogged 250SL with only 830 miles. That involved bearings and seal, so essentially I considered the engine as having basically zero miles.

Later, at around 4500 miles the countershaft completely sheared at the sprocket. I split the cases again and installed a new CS.

At about 6900 miles I replaced the stock 14T sprocket with a 15T, at which time the CS splines looked fine.

Lately the bike has been exhibiting the typical Hodaka loose CS nut leak seepage. On inspection the nut was slightly loose but the lockwasher tab would've kept it from turning after it was last torqued. However, as I was dreading to discover, the splines on the most recent countershaft are shearing -- at least halfway at this point.

Am I suffering alone with this problem? I haven't heard of any other 250 riders in the same boat.

There are no apparent conditions that would cause any unusual side loading to the sprocket. Could I be overtightening, or undertightening, the countershaft nut?

Anyway, this will be the fourth time I've had to split the cases: 1. Initial rebuild; 2. Melted and holed piston; 3 and 4: Countershaft replacement.

Thinking now about preventative maintenance while the engine is going to be completely in pieces: at 9,000 plus miles should I also replace crank seals (and anything else) pre-emptively?

Thanks Guys -- here's couple pics too.

[Joe Ormonde]

Incredible !!! What is happening here is a hardness problem. Can you get a new counter shaft and get it hardened so this wont happen? That depends on the metal it`s made of. This may be a problem that just can`t be fixed. Joe

[taber hodaka]

At 6500 miles the splines looked fine, At 9000 miles the nut is loose and the shaft is damaged. I have had the problem when assembling, the nut was tight but the sprocket was loose . The nut got hung up on the locking washer. The nut must be tight and stay tight. Once the splines are distorted there is no way to keep the nut tight, that is the same thing with the splines under the clutch. The manual's maintenance chart states, check all nuts and bolts every 500 miles --------- Clarence

[Joe Ormonde]

What I would do at this point is to find a used shaft that shows no signs of wear. I had this happen back in the day to my Super Rat clutch BUT the Crank shaft splines were Perfect. Sometimes a used part that has proven to be trouble free is the best option. Just my opinion. Joe.

[Darrell]

Thanks for your thoughts and ideas.

In my "quest for truth" as to why the splines are shearing I can clarify that the sprocket nut was just loose enough to weep some oil and the sprocket did not have any significant sideways play.

However, it comes to mind that Honda's countershaft sprocket design (sprocket loosely retained to the CS by two 10mm bolts holding a retainer plate) allows for significant designed-in looseness and play on the CS without consequence, so I'm not getting my head around how any slight play would cause shearing to the Hodaka splines.

Is it possible that metal fatigue sets in? Coincidentally, both shafts failed with around 4,500 miles.

As for hardening/tempering, both sheared shafts have blued ends, but perhaps they weren't properly quenched after heat treating. In this light I can see how a used/proven/veteran/experienced part would stand out amongst a batch of defective countershafts. Are there any metallurgists in the group that could offer an opinion?

[Darrell]

Okay, I referred back to a topic in Hodaka Chat that I started the last time this happened in September 2016: "Shear Agony..."

Consensus then, as now, is that the failure stems from a loosening countershaft nut and the vibrations that result.

It's beyond my abilities, and the projection of the countershaft, but the deficiency could be remediated with a sprocket that has a wider/thicker hub to increase contact area between the shaft and sprocket.

In any event, I don't remember but I must've been able to reassemble the control shaft without a special too. However, I do remember it being impossible while installing Space Age shifter springs in my Wombat; clips flying all over the place until using a homemade tool.

[olddogs]

You could try cutting the center out of a countershaft sprocket and welding it to the face of the regular sprocket. Kinda like a splined washer. This would spread the load on the spline. The splined washer may have to be shaved a little on a surface grinder to give you enough threads to keep the sprocket tight, but it appears the shaft end has enough length. Skip the lock tab and use red locktight on the nut. Clean the nut and shaft with carb cleaner to provide the red locktight a good bite. There is little side load on this nut and it will give you more exposed threads. The inner side cover and sprocket seal should clear the welded washer. You can use the old shaft to index the 2 sprockets for welding. Thats what i would try. Remember, fool me once shame on you. Fool me twice, shame on me.

[viclioce]

Just out of curiosity, are you folding a couple of the edges of the lock washer up around the nut? Most do. If you aren’t, then the lock washer isn’t working. You’re pics don’t show the sprocket mounted, so I had to ask… Victor

[Darrell]

Just out of curiosity, are you folding a couple of the edges of the lock washer up around the nut? Most do. If you aren’t, then the lock washer isn’t working. You’re pics don’t show the sprocket mounted, so I had to ask… Victor

Hi Victor, I have been remembering to fold the lock washer tabs.

However, I'm wondering if I've been applying too much torque applied to the countershaft nut and might be compressing the countershaft bushing behind the sprocket. That might stretch things out over time and eventually create a thou or two of play (How's that for overthinking? ). Torque value for that nut is unknown as no shop manual was made for the 250s. On the other hand my Wombat gives me no grief in this regard.

If more owners had this issue then Old Dogs solution of building out a sprocket hub would be especially viable for a fabricator to make small-scale production run of several hundred to market. The 250's also had defective kickstart shafts and Paul/Strictly Hodaka had a few hundred redesigned (3/4" longer) KS Shafts produced, plus kick levers. I bought one and expect they're all sold out now.

You know, I would weld the sprocket to the shaft, BUT the Hodaka sprocket and CS bushing interface is steel to steel, so it has to be under constant compression to keep transmission oil from weeping between the bushing and the sprocket.

Darrell

[viclioce]

Well Darrell, I personally haven’t worked with a 250 yet. The lock washer was my first thought. I don’t see any torque listings for the CS nut.

It looks, at first glance, at your photo, that the threads almost appear to be brass? Say it’s just discoloration in the photo, I really don’t know.

With my 125’s I just tighten with a 26mm socket until it’s snug against the bushing. Then I tap up the lock washer. I haven’t seen one work lose on the 125/100 bikes I work on.

This will be interesting to follow. My plan is to purchase an ED to restore come Hodaka Days. Victor

[Darrell]

Well Darrell, I personally haven’t worked with a 250 yet. The lock washer was my first thought. I don’t see any torque listings for the CS nut.

It looks, at first glance, at your photo, that the threads almost appear to be brass? Say it’s just discoloration in the photo, I really don’t know.

With my 125’s I just tighten with a 26mm socket until it’s snug against the bushing. Then I tap up the lock washer. I haven’t seen one work lose on the 125/100 bikes I work on.

This will be interesting to follow. My plan is to purchase an ED to restore come Hodaka Days. Victor

Not brass -- but it seems as soft. Did I mention that the sprocket splines show no wear or damage?

Anyway, I hope I haven't used up all the spare shafts by the time you need one for your ED

[dirty_rat]

Are you sure that the countershaft sprocket is the right one? There are 4 different c/s sprockets that will fit on the countershaft, but only one is the correct size. The sizes of the 4 are as follows:
diameter of the inside of the splines: 16mm, 17mm, 17.5mm and 18mm.
diameter of the widest opening of the splines: 20mm
spline thickness: 4 mm

All 4 would fit on a countershaft made for a 16x20x4 sprocket, but the ones with an inner diameter of 17mm, 17.5mm and 18mm would not have as much contact with the shaft as the 16mm one. If this was the case, it could easily result in excessive wear on the countershaft splines.

To see an example of these go to jtsprockets.com and look up JTF413.15, JTF266.15and JTF 259.15

[viclioce]

Anyway, I hope I haven't used up all the spare shafts by the time you need one for your ED

Well that’s a need I hope I won’t have. Hope you get it figured out!

Just as a thought… any chance your chain isn’t tracking as straight as it needs to be? Just scratching my head thinking on this one… Victor

[Darrell]

Are you sure that the countershaft sprocket is the right one? There are 4 different c/s sprockets that will fit on the countershaft, but only one is the correct size. The sizes of the 4 are as follows:
diameter of the inside of the splines: 16mm, 17mm, 17.5mm and 18mm.
diameter of the widest opening of the splines: 20mm
spline thickness: 4 mm

All 4 would fit on a countershaft made for a 16x20x4 sprocket, but the ones with an inner diameter of 17mm, 17.5mm and 18mm would not have as much contact with the shaft as the 16mm one. If this was the case, it could easily result in excessive wear on the countershaft splines.

To see an example of these go to jtsprockets.com and look up JTF413.15, JTF266.15and JTF 259.15

Yep, I checked JT specs and all dimensions and the new 15T I put on measures up to exactly what it should be. The first shearing incident occurred with the original factory sprocket and countershaft.
The sprockets must be much harder than the countershafts as the sprockets come through these catastrophes with no measurable wear on their splines .

[Darrell]

Anyway, I hope I haven't used up all the spare shafts by the time you need one for your ED

Well that’s a need I hope I won’t have. Hope you get it figured out!

Just as a thought… any chance your chain isn’t tracking as straight as it needs to be? Just scratching my head thinking on this one… Victor

Chain tracking checks out as straight.
Naturally the cush drive rubbers won't be a pliable as they were in 1977 -- but that might be going off on too wild and unlikely of a tangent.

[taber hodaka]

Dumb question but do you use the clutch all the time? I would guess you ride very hard, lots of miles on the hodak. ------ Clarence

[Darrell]

I use the clutch, but I ride with other bikes at least 30 years newer. I guess some of the riders are a few years younger than me too.

But I don't think I'm abusing the bike though, and about half of the accumulated miles are street and highway.

The smaller and lighter drivetrain of my 94 Wombat would be more stressed under the same conditions but it hangs together regardless.

[Joe Ormonde]

If you think about how clutches would basically explode in some super high horsepower cars BUT the Input Splines on the Transmission were just fine, what does that tell you? I have however seen them twist but never wear out. The 250 Hodaka Counter Shaft may be surfaced hardened but past that point it`s probably soft. 500 or 600 Horsepower going through a old Muncie 4 Speed and the splines never wear out? Why? Joe.

[taber hodaka]

good point and the ace90 racing transmission did not have a nut on the sprocket it had a snapring. Clarence

[Joe Ormonde]

The bluish coloring looks like it may have been Induction Hardened. I do however believe that a 250 Counter Shaft can be found that wont wear out. Good point Clarence. The earlier Hodaka Counter Shafts were basically made from premium Tool Steel : Hard enough to not wear out BUT not so hard that it was brittle. Had Hodaka been in Business a little while longer I`m sure they would have made a better 250 Counter Shaft. Joe.

[Darrell]

The bluish coloring looks like it may have been Induction Hardened. I do however believe that a 250 Counter Shaft can be found that wont wear out. Good point Clarence. The earlier Hodaka Counter Shafts were basically made from premium Tool Steel : Hard enough to not wear out BUT not so hard that it was brittle. Had Hodaka been in Business a little while longer I`m sure they would have made a better 250 Counter Shaft. Joe.

Joe, you say "I do however believe that a 250 Counter Shaft can be found the won't wear out." Where would you look for this?

I think it's now a given that my last two counter shafts were incompletely tempered/too soft for the purpose.

I'm out of my depth here about how to make this right, but it might be reasonable to assume the next countershaft I get will also potentially be defective: What if I took the new CS to a machine shop for additional tempering? If perchance it was adequately tempered already then would repeating the process make the CS too brittle maybe? If so then the next failure could be catastrophic.

To quote the original Resonator sub-title here's seeking: “Whomping Wads of Wondrous Wisdom and Whizzing Waves of Wanton Wit” in order to identify and remediate this apparent deficiency.

Thanks Guys!

[taber hodaka]

If nobody else is having the same problem, then there should be many used ones that should work.?? guessing ----------- Clarence

[Bullfrog]

I've been reading this thread with considerable interest . . . but I have no experience/expertise to bring to bear on the issue. I have only questions and guesstimations. Have you done any "shade tree mechanic" hardness testing with a small file? It might be educational. If I were in your shoes, I'd try to compare your failed 250 shafts with a countershaft from a Hodaka 100 or 125. I'm also stumped about your bike seeming to be the only Hodaka 250 in the world (and in history?) to have the problem. We're missing something, but I'll be danged if I know what it is.(!) Hmmmm, if you go to see a good machinist, that comparative hardness testing information might be helpful..

Still stumped..
Ed

[Darrell]

I've been reading this thread with considerable interest . . . but I have no experience/expertise to bring to bear on the issue. I have only questions and guesstimations. Have you done any "shade tree mechanic" hardness testing with a small file? It might be educational. If I were in your shoes, I'd try to compare your failed 250 shafts with a countershaft from a Hodaka 100 or 125. I'm also stumped about your bike seeming to be the only Hodaka 250 in the world (and in history?) to have the problem. We're missing something, but I'll be danged if I know what it is.(!) Hmmmm, if you go to see a good machinist, that comparative hardness testing information might be helpful..

Still stumped..
Ed

Thanks Ed, I've since had opinions from a tool and die maker and a mechanical engineer in my local network.

They've opined that the shafts are too soft, likely surface hardened by a few thousands, and once that wears slightly then the splines are gone.

I will take the original and next (third) shaft I source to a machinist to check the hardness values (I'm told it should be: Rockwell C 55).

Still bummed,
Darrell

[Darrell]

If nobody else is having the same problem, then there should be many used ones that should work.?? guessing ----------- Clarence

Hi Clarence,

I checked and there are several used shafts on eBay. It's counter to usual thinking but in this situation I would like to confirm that it's a high-mileage used part. That would indicate that it's proven it's mettle.

There's only one used shaft that has a determinable mileage available: about 2,250 miles. My inner "Eeyore" says that's used up it's half-life already (both my countershafts sheared at 4,500 miles +/-).
###
On that note: I've been curious for a long time now why so many bikes from the '70s were tossed into the weeds with only about 2,000 miles, or so, on the odometer.

For instance, my Wombat emerged from under a pile of junk in an old barn: 1,399 miles.
My 250SL was hacked out of some bog at only 830 miles.

It's a mystery to me: Could the influence of Disco music make society mechanically inept to the point they could not handle basic maintenance and repairs ? It's one thought anyways .