A misunderstanding not a gearing question
- Thread starter Deoodles
- Start date
Here's a few pix. I was unable to get the camera to focus on the gear (dammit) so you'll have to use a little imagination to sharpen the blurry images.
Look at the sheer size of that ridge and the huge sawtooth toward the tip. The metal was heated close to its melting point. The $64 question is what produced that kind of sustained lateral loading?
Those formerly molten blobs of metal can be seen clearly here...as can the contact inside the "horseshoe". Again, the money question is what generated the sustained torsional loading? Also note the heat-discolored reverse side of the "smiley face". Best guess, this metal saw ~1400F, minimum(!).
Note the total lack of wear marks on the opposite sides of the fork tips.
Those bands on the gear should be shiny-smooth, not textured. Chances are that's residual metal, transfered from the shift fork. But, how would one go about having those surfaces refinished? A: no way that is, at present, cost-effective.
Look at the sheer size of that ridge and the huge sawtooth toward the tip. The metal was heated close to its melting point. The $64 question is what produced that kind of sustained lateral loading?
Those formerly molten blobs of metal can be seen clearly here...as can the contact inside the "horseshoe". Again, the money question is what generated the sustained torsional loading? Also note the heat-discolored reverse side of the "smiley face". Best guess, this metal saw ~1400F, minimum(!).
Note the total lack of wear marks on the opposite sides of the fork tips.
Those bands on the gear should be shiny-smooth, not textured. Chances are that's residual metal, transfered from the shift fork. But, how would one go about having those surfaces refinished? A: no way that is, at present, cost-effective.
Thanks for a great summary. I went over each associated part last night with Pat and we did not find any reason for this failure. Only fishing at this point. Shift drum, shift drum mounting bolt, are what we keep coming back to. The Cases are being replaced so with the drum being the only part left.... I’m not a throw parts at it guy but here is where I have to make the tough call. Build a 124 with an AHP 4speed trans or replace the drum and cross my fingers.
It occurred to me that the shift fork was acting like a disc brake pad. That would explain the non-contact area (inside the horseshoe) wear. Intuitively, it seems like the damage would occur only when this gear is delivering the power, the drive dogs providing the lateral locking force necessary to hold the interference fit. That said, it's a non-spinning (splined) gear that sees full engine torque, regardless of which gear is delivering power to the C/S. Thus, the altercation could occur in 1,2,3, or 4.
As was suggested earlier, lateral misalignment may be the issue. Unfortunately, the fork-to-gear tolerances are so precise I don't know how one could measure them, in 1,2,3 & 4, with the motor assembled. Case gasket vs no gasket, thrust washer(s) vs none might point you in the right direction. However, going by the wear I measured, I dunno how anyone could see what's going on...we're talking about a lot less than the thickness of a case gasket, or a thrust washer. I can easily see how this tranny was still shifting normally. It also looks like a few thousandths of an inch could make all the difference.
Rather than yet another longwinded dissertation, how about going back to basics. With two pairs of hands, it's possible to apply rotation and a little torque to both the M/S and C/S...while shifting gears (either via the shift lever, or fixing bolt). Leave the gear and new shift fork clean & dry, so as not to diminish any braking action. With as much heat-discoloration as the old fork developed, you may be able to feel when the fork is being forced against the gear. Alternatively, or additionally, Dykem or a Sharpie, could be used to mark the fork tips. You'd then spin the tranny, in a given gear (4th seems the most likely position to have created the problem), pull the drum assembly and look for signs of contact. Plan on at least a half-dozen repetitions, on the bench. Hopefully, you get some answer(s) with which you are comfortable before you feel like Charlie Chaplin in "Modern Times".
As was suggested earlier, lateral misalignment may be the issue. Unfortunately, the fork-to-gear tolerances are so precise I don't know how one could measure them, in 1,2,3 & 4, with the motor assembled. Case gasket vs no gasket, thrust washer(s) vs none might point you in the right direction. However, going by the wear I measured, I dunno how anyone could see what's going on...we're talking about a lot less than the thickness of a case gasket, or a thrust washer. I can easily see how this tranny was still shifting normally. It also looks like a few thousandths of an inch could make all the difference.
Rather than yet another longwinded dissertation, how about going back to basics. With two pairs of hands, it's possible to apply rotation and a little torque to both the M/S and C/S...while shifting gears (either via the shift lever, or fixing bolt). Leave the gear and new shift fork clean & dry, so as not to diminish any braking action. With as much heat-discoloration as the old fork developed, you may be able to feel when the fork is being forced against the gear. Alternatively, or additionally, Dykem or a Sharpie, could be used to mark the fork tips. You'd then spin the tranny, in a given gear (4th seems the most likely position to have created the problem), pull the drum assembly and look for signs of contact. Plan on at least a half-dozen repetitions, on the bench. Hopefully, you get some answer(s) with which you are comfortable before you feel like Charlie Chaplin in "Modern Times".
kirrbby
Well-Known Member
That fork is worn out on only one side of one...side of the fork. It seems to me that something HAD to have been cocked...out of straight/parallel/perpendicular. If the fork was bent, in a twist, it seems the opposite "corner" of the fork would have similar wear. Could the gear have been cocked? Is there slop/wear inside of the gear...splined area? Eneven wear on the teeth of the gear?
If it were the gear that was cocked, I'd think it would show some wear to prove it.
I'm thinking the fork had to be bent, or cocked.
Maybe one tine bent..?
If it were the gear that was cocked, I'd think it would show some wear to prove it.
I'm thinking the fork had to be bent, or cocked.
Maybe one tine bent..?
I don't think that it's possible to gauge the straightness of the fork by eye. As long as the contact pads, at the tips, are flat and in the same plane, it doesn't matter if the "blade" section of the fork is angled, relative to the centerline of the fork bore. And that could easily result in the <visibly> angled wear pattern seen here, once the smaller tip has worn flush, or beyond. It could very well be that Honda engineered a certain amount of spring-action into the fork design, using a slight deviation from 90-degrees. Without more info, it's all just wild speculation.
All of that having been said, a little bit of dye and dry-fitted testing/R&R is likely the best we can do. It could be very telling. As for the repeated assembly & teardown, that's just part of the deal, kinda like building a tight-spec/"blueprinted" race motor and yes, it's usually a lot of painstaking effort.
All of that having been said, a little bit of dye and dry-fitted testing/R&R is likely the best we can do. It could be very telling. As for the repeated assembly & teardown, that's just part of the deal, kinda like building a tight-spec/"blueprinted" race motor and yes, it's usually a lot of painstaking effort.
The testing has begun. First up was back into the cases with both thrush washers. There was no binding but also noted was no “seat of the fingers” lateral movement of the counter shaft. Case gasket used. Also no binding in any gear. 2nd was with the thrush washer removed from the counter shaft. Again a nice shift but this time lateral movement of both shafts. Next was to add some case screws. Things tightened up more than I expected. It is noticeably harder to spin the shafts. I’m going to have to investigate. Also wondering what should there be? Lateral movement and an easy spin through the gears with case screws installed would be my guess. I will never really know what pre disassembly was.
My XR70 motor was delivered today. I got it because it had good splines, was a GB4 case and had the ignition. The post office threw it on my porch and the thud announced delivery. The shift shaft is now bent. USPS sux. I compared lateral movement to my 4speed and it’s about the same. Some but not a lot. Still leaning to a bad fork. As bad as the pictures of the fork are; there was more metal on the damaged side that grinded and melted away. That would have meant a bent tine on 1 side of the fork.
The cases on the new motor are in very nice condition. No damaged threads and no prior oil leaks noted. What I really like are the possibilities. I now have a CDI and flywheel for a 3speed crank. Thanks to Kirrbby I’m just about ready to bore the cases. If it goes well I may bore the 108 cases and put a 54mm on it as well.
The cases on the new motor are in very nice condition. No damaged threads and no prior oil leaks noted. What I really like are the possibilities. I now have a CDI and flywheel for a 3speed crank. Thanks to Kirrbby I’m just about ready to bore the cases. If it goes well I may bore the 108 cases and put a 54mm on it as well.
Lots of work to disassemble. Had to drill out a stator plate and clutch screw. I am quite happy with the internals. Dirty but at least it had oil changes. A perfect 3speed and the new style kick shaft assy. I did a SN check and turns out to be a 2004 CRF70. Bearing cam in the head. I believe I’m the first person to pull the head and split the cases. It’s a great parts motor. One suprise was no neutral indicator hole in the case. I had to drill through and bigger to get the indicator assy installed.
CRF & XR engines are the same, mechanically. No surprise about the lack of a neutral switch, though. There's no lighting coils, either. These were offroad bikes.
I expect that you'll have better results this time around. It's just doubtful that we'll have a definite answer for the "WTF happened" question.
That may have been the issue, Ray. But, I'm not yet confident enough to bet the farm on it, let alone suggest that anyone else should do that...especially just on my say-so, that was based on an edumacated guess. It's the rigidity of the fork and the complete lack of any wear marks on the reverse side that have me thinking "hmmmmmmm???". I'd expect bending to result in non-parallel contact, which would leave a far smaller contact patch, at each tip...concentrating the PSI loading dramatically. Seems more likely that the thrust-load damage occurred over a long time, while riding and that's more consistent with incorrect lateral spacing. I'd feel a whole lot more confident if the contact patterns could be checked, in your engine/as-assembled, with Dykem.
I expect that you'll have better results this time around. It's just doubtful that we'll have a definite answer for the "WTF happened" question.
Roy Chambers
Member
I want get something straight for me and the others following the post!
On post #128 you said, testing has begun. Now on post #132 you say Good Spin.
Is this, (Good Spin) with all of the parts moved over to the New 2004 CRF70 Crankcases ?
Thanks Roy
For clarity. New NOS countershaft second gear. New NOS shift fork. Testing was done on the old cases and moved to the new cases with a gasket and screws to hold the cases together for final testing. There is lateral movement on both shafts and it is similar to the CRF70 before disassembly. The thrust washers in the final fit are exactly the same as they were in the original 108 build. I am confident that gear assemblies on both shafts are correct as I used a Micro fiche to verify.
And no: I didn’t get to give the delivery guy what he deserved. The shift shaft is junk. I’m going to need a new one if I ever want to use the trans.
And no: I didn’t get to give the delivery guy what he deserved. The shift shaft is junk. I’m going to need a new one if I ever want to use the trans.
WTF am I looking at??I noticed some what I thought was right case damage and thought just my luck. I went on eBay to look at some others and see the same thing. Can someone comment. I’m a little annoyed and I’m not sure if I should be. Look at the right upper case stud hole. The last picture is mine the others are off eBay
Roy Chambers
Member
IMHO, the heir-apparent to the "missing/broken" head casting...that notch below the exhaust port the instills panic in most owners, at some point in the owner/mechanic experience.
No doubt, this is done by the factory and is no accident. I've seen a lot of engines in which the stud in this location is oxidized right through the zinc plating and rusted. The tiny slot opens the stud passage to the crankcase, allowing it to "see" crankcase pressure and some oil mist. FYI, this is pure speculation on my part. Consider, however, that this is otherwise a sealed, blind, passage.
No doubt, this is done by the factory and is no accident. I've seen a lot of engines in which the stud in this location is oxidized right through the zinc plating and rusted. The tiny slot opens the stud passage to the crankcase, allowing it to "see" crankcase pressure and some oil mist. FYI, this is pure speculation on my part. Consider, however, that this is otherwise a sealed, blind, passage.
Cases are prepped. They are 12v GN4 and I see another hurdle to overcome. The top forward case bolt on the right side is installed when the clutch cover is installed. The one right up front on the top by the cyl. It is 80mm. It holds the clutch cover and also the case halves. There isn’t one on the left on this case design. By changing from auto to manual this screw isn’t long enough. It needs to be 95mm to properly secure the case halves. Anyone know where this can be bought?