Thanks for the input. I hate to show my ignorance but I don’t understand. I didn’t realize there was more to installing the shift drum. I thought it was put in place and tighten the mounting bolt. I replaced the gear and fork. This is now going into a new set of cases. I just hope the tolerances are good and I don’t see this again.
A misunderstanding not a gearing question
- Thread starter Deoodles
- Start date
Roy Chambers
Member
Let me try to refine this a little more.
We are definitely not going to Re - Machine anything!!!
I would disregard what the books say on the Shims.
I would rather check my end plays and Shim the Shafts accordingly.
I just wet out and checked 2 CT70 at random, that run, and on the Counter Shafts, one had .045 tho and the other had .048 tho End Play!
I think that this could be brought down to .008 to .012 tho, SO, if you needed to move a shaft over some to keep the fork from constantly riding up against the side of a Gear, you could.
AND, don't just think, that if the shaft has a lot of end play, that parts can just move over where they need to on there own! Them Gears have Extreme Pressure on them, and depending on how they have worn together, they may tend to ride over to one side. The Forks are NOT designed to hold the Gear in place.
So, if you can limit them from being aloud to move, you don't have to wonder if they are, you know that they can't.
I would buy several of the Shims to have on hand. I have measured several of the ones that have the Spline, and got .005 tho difference. As for the Counter Shaft goes, I don't see one for the Left side, but that doesn't mean you can't find some. I think it's 17 MM
I guess what my point is, check things the best that you are capable of doing.
Go back and read my post of what to look for.
Swap Forks around, Shim the Shaft over, ( if you need to) see if makes any difference .
I would also buy 2 or 3 Gaskets, of the same brand! use Grease on the test gasket, when your happy with the checking then use new gasket for the final assembly.
Not trying to re invent the wheel, I just try to shoot for the best, in case there is some error it will fall on the acceptable side.
Thanks Roy
Roy Chambers
Member
You did not do anything wrong! The way you put it together is the correct way! It's just that back in the day the parts were a dime a dozen, and I don't think that Honda knew that the bikes would last as long as they did. Your pushing a lot more power now. Another thing is the Gasket thickness the same as it was when it was New? Just for them two reasons alone is why it does not hurt to check things.
Thanks Roy.
Actually, it's the drive dogs that keep the gears torque-locked in place and they have to be fully engaged. Once the gear pairs are torque-locked, the shift forks should have virtually zero side load on the contact pads...unless something is seriously amiss. When those tapers no longer fit properly, the transmissions tend to jump out of gear...with a good chance of parts carnage beyond worn shift forks, that seem to be the first "domino" in what can turn into a cascading parts failure.
FYI, I'm not arguing. We're having an intelligent discussion here. That's a good way to spread knowledge. I agree with nearly all of your assertions, here, especially when it comes to differences in gasket thickness. That said, I've run across more worn shift pins, broken gear teeth and bent shift shafts than excessive endplay due to shims that were worn or of the wrong thickness. That's not surprising, when you consider the lack of worn bronze bushings (non-load bearing side) in the case halves...they're not being asked to do much. I like your approach, however, regardless of how my wording may or may not be interpreted, once I hit "post reply". Written comunication is a little tricky, at times, since there's no way to add voice inflections. FWIW, I test-fit lower ends, sans center gasket, before assembling them for real. More times than not, one or both tranny cluster will bind or have too little endplay. IMHO, it's one of those crude-but-effective little "tricks"one learns, over the decades.
FYI, I'm not arguing. We're having an intelligent discussion here. That's a good way to spread knowledge. I agree with nearly all of your assertions, here, especially when it comes to differences in gasket thickness. That said, I've run across more worn shift pins, broken gear teeth and bent shift shafts than excessive endplay due to shims that were worn or of the wrong thickness. That's not surprising, when you consider the lack of worn bronze bushings (non-load bearing side) in the case halves...they're not being asked to do much. I like your approach, however, regardless of how my wording may or may not be interpreted, once I hit "post reply". Written comunication is a little tricky, at times, since there's no way to add voice inflections. FWIW, I test-fit lower ends, sans center gasket, before assembling them for real. More times than not, one or both tranny cluster will bind or have too little endplay. IMHO, it's one of those crude-but-effective little "tricks"one learns, over the decades.
Thank you both for the cliff note version. I can visualize what’s being said and somewhat understand it. I dont know the correct way to measure end play in the shaft. On the original assembly I replaced the shift drum pins and clips. Also all of the spacers and clips on the clusters as well as correct part number thrust washers. This being ATC70 cases I used a thrust washer on one side of each shaft. Next time reassembly will be more technical and I will look for and attempt to adjust tolerances.
cjpayne
Well-Known Member
This stuff has gone way over my head, but was just thinking that maybe, if possible, that some of the needle bearings may be damaged or worn. I've never seen the insides of the ATC cases before and dont even know what the needles look like, but if they're anything like automotive U-joints, I've seen plenty of those needles damaged, broke, and worn. Just my .02.
The jury is still out. The needles are in good shape. After much listening and some learning I’m beginning to think a thrust washer on that gear shaft is the culprit. It makes some sense to me. End play and measuring it could be what I missed. I’ll let you know. I plan on having the parts inspected soon.
FWIW, some of it went over my head, as well. A transmission is a deceptively complex piece of engineering...and it's high-precision engineering. That said, you're on the right track, imho. With a complex system and unknown problem, usually the best approach is to begin with the simplest possibility(ies)...in this instance, what is different/unusual/changed. The obvious answer is those GB4 (needle bearing) cases. That introduces a number of variables, not found in the old 6v style (bronze) plain bearing cases. The pockets might be machined a little differently, the bearings may not all be pressed in to the same depth and the bearings themselves could vary in overall length from one batch to another - all of which would make shims a crucial item to verify. Should be relatively simple to measure the width between the needle bearings, case halves assembled. OTOH, measuring the effective, installed, bearing heights and then comparing them to 6v cases would require precision jigging...stuff that's beyond just about anyone who isn't a journeyman machinist, or an experienced tranny specialist.
The one thing that captures, more accurately demands, my attention is the asymmetric wear. Shift forks should, and usually do, wear evenly. The $64 question here is why one contact pad, alone, was almost completely obliterated, the other nearly untouched.
Roy Chambers
Member
Well it's like this.
Looking a the engine from the Right side with the Crankcase split, you see the Counter Shaft, the Main Shaft, and the Shift Drum with it's Forks.
Now, picture in your mind a Triangle line (Delta) connecting all 3 parts.
You will notice, that the Burned up part of the Fork, more in center of that Triangle then the other side of the Fork.
In fact, it's to the Right side of the Gear.
When you apply Torque by means of the Throttle, the Counter Shaft goes Forward towards the front wheel on the Right Side. Now, over at the Sprocket end of the Shaft, it's headed towards the Rear Wheel, thus cocking the Shaft.
Now, you have Clearance on the part of the Fork that was not hurt. On the other hand, the other side is being rubbed severely. Note, the looser the Bearings are, the worse it gets.
Thanks Roy.
That seems clear enough...excessive radial runout, due to sloppy bearing/shaft tolerances. Are you saying that what caused the asymmetric wear and suggesting the use of precise-thickness thrust washers (shims) to limit lateral movement (of the transmission shafts) and with it, radial movement under load? Perhaps new needle bearings are in order?
Needle bearing cases are one of my largest blind spots. I've lost count of the number of engines I've rebuilt, over the decades. The overwhelming majority of them have been 6v type, with plain bearings on the non-thrust ends of the shaft assemblies. I've rarely seen appreciable wear of those integrally-cast bronze inserts. The ones that were loose were also visibly scarred. I always liked the idea of needle bearings, since they are replaceable; a dead, or dying, bearing would not require a new case half. You're giving the impression that the needle bearing setup may leave a little to be desired; FYI, Honda went to ball bearings with the new-gen motors (Wave, Nice, Innova, MSX125/Grom) in the late `90s.
Needle bearing cases are one of my largest blind spots. I've lost count of the number of engines I've rebuilt, over the decades. The overwhelming majority of them have been 6v type, with plain bearings on the non-thrust ends of the shaft assemblies. I've rarely seen appreciable wear of those integrally-cast bronze inserts. The ones that were loose were also visibly scarred. I always liked the idea of needle bearings, since they are replaceable; a dead, or dying, bearing would not require a new case half. You're giving the impression that the needle bearing setup may leave a little to be desired; FYI, Honda went to ball bearings with the new-gen motors (Wave, Nice, Innova, MSX125/Grom) in the late `90s.
Roy Chambers
Member
I never have been a big fan of Needle Bearings, especially them Timken ones with the sheet metal cage, like a B108 and such. Plain Bronze Bushing, usually work great in all kinds of application. The Ball Bearing on the Sprocket side, should be replaced at minimum, with a Hi quality one, like a OEM Honda one, or a NOS Bearing. And when i say NOS, I mean an OLD USA or JAPAN made bearing that you have had on your shelf before 1980 or so. Stay away from third world country Bearings.
Thanks Roy.
Roy Chambers
Member
I hate to bring more bad news to the discussion, but i noticed something the same day the picture was posted but held off till now to bring it up! It look's like the Transmission part of this post is winding down now, so let me tell you what i see.
Another thing that I've noticed about Deoodles Engine is: On page 4, the 10th comment down.
The picture of the Cylinder Head: What i see in the Combustion Chamber is a lot of Deposits for 2000 miles.
It look's like OIL build up to me, but seeing in person i cant be positive .
If that's what it is, maybe the Rings did not seat or Valve Guide or Valve Seal issue.
Does that Engine have one of them HP Oil pumps on it ?
Thanks Roy
I use nothing but high-line made in Japan NTN ball bearings. I reckon that KOYO and Nachi would be on par, if they had the same kind of availability. I've installed FAG wheel bearings, no problems; but, as you say, once they were no longer made in Germany...time to say Auf Wiedersehen. We are deep into the era of everything being a pale substitute. Not many choices outside of adapting as best one can or dropping out altogether.
You may be onto something regarding the use of needle bearings in transmissions. The only worn out new-style shift fork I've seen, so far, was in a 1982 CT70 tranny. Can't recall if that had needle bearings, or bronze plain bearings. With the current generation Honda engines, I've yet to see a worn out shift fork; they have 4 ball bearings in their transmissions. I wouldn't be surprised if the changeover to ball bearings was done as a real product improvement.
Still, the needle-bearing GB4-era trannies haven't been noted for premature/rapid wear. Across the pond, these were sourced preferentially over the 6v/plain bearing cases, a good 10-15 years before the small bike scene matured here in the US. Some of those riders put serious mileage on their bikes.
You may be onto something regarding the use of needle bearings in transmissions. The only worn out new-style shift fork I've seen, so far, was in a 1982 CT70 tranny. Can't recall if that had needle bearings, or bronze plain bearings. With the current generation Honda engines, I've yet to see a worn out shift fork; they have 4 ball bearings in their transmissions. I wouldn't be surprised if the changeover to ball bearings was done as a real product improvement.
Still, the needle-bearing GB4-era trannies haven't been noted for premature/rapid wear. Across the pond, these were sourced preferentially over the 6v/plain bearing cases, a good 10-15 years before the small bike scene matured here in the US. Some of those riders put serious mileage on their bikes.
Good observation Roy there is excessive oil in there and it does have a high volume oil pump but that’s not the reason I recently put fogging oil in this engine and put it into storage and what you’re seeing is disassembly without running the engine to clear out the oil I put in it for storage
The posts here are all sequentially numbered. It's far easier to avoid confusion by using the post number, within a given thread.
"Reading" combustion chamber & plug coloration has become very difficult, since about 10 years ago. That's when new pump gas regs went into effect. First differences I noticed were a sudden rash of carbs that needed rejetting...and...the disappearance of the "highway grey" exhaust. Agreed, it does look a bit sootier than one might expect, especially those of us who've been building & rebuilding engines for decades. This doesn't look very different from what I've seen in known healthy engines, some with even lower mileage. If my memory isn't too faulty, this is a low-mileage TB head. That's a part with a lengthy field service history of reliability.
With anything beyond 88cc, a high-volume oil pump is required. FYI, these engines cannot generate much oil pressure.
Transmission parts arrived I replaced the 2nd gear on the countershaft and the shift fork both NOS. Assembled they look like a perfect fit. The jury is still out on root cause but my gut says I probably installed a NOS bent fork. I do have an important to me question to ask. Is it acceptable to build a 108 from bronze cast Honda 50 cases? I have a set and would drop in an aftermarket 4speed gear set. I haven’t picked up cases for my 124 build. I may build both motors and a 3speed lower end could come into play and help with parts for both motors.
They're all 49cc cases, everything from the Z50 up to the non-US spec C90 flavor, upon which those motors are constructed. Roy Chambers expressed concerns over the reliability/durability/consistency of needle bearings. FWIW, I've since run across information/case studies of recent-vintage Harley Davidson motors experiencing catastrophic failure(s) due to excessive "walk" in...you guessed it...needle bearings. Those are non-replaceable, DOA bearing means DOA case casting, unlike 49cc Honda cases.
Cutting to the chase...for a nice change...I wouldn't worry about either pre, or post, GB4 style cases. I'm taking RC's input seriously but, for me, the jury is still out and may be for years/decades to come. Those non-thrust ends of the transmission shaft assemblies have a relatively light mechanical load to support. Haven't seen many failed needle bearings, other than a few early Lifans...even fewer problems with the bronze bushings. Bearing tolerances are easy enough to check.
FWIW, a couplathree years ago I went through an "ebay special rebuild". IOW, this was an engine cobbled-together from used parts and Chinese service parts. Even the primary gears had mismatched tooth counts. The C/S ball bearing was so rusted and loose, I couldn't believe that the tranny hadn't grenaded. Everything else, including the needle bearings and shift forks were fine. With new ball bearings & shift pins installed, the thing shifted as one would expect a Honda to do. Capiche?...
Cutting to the chase...for a nice change...I wouldn't worry about either pre, or post, GB4 style cases. I'm taking RC's input seriously but, for me, the jury is still out and may be for years/decades to come. Those non-thrust ends of the transmission shaft assemblies have a relatively light mechanical load to support. Haven't seen many failed needle bearings, other than a few early Lifans...even fewer problems with the bronze bushings. Bearing tolerances are easy enough to check.
FWIW, a couplathree years ago I went through an "ebay special rebuild". IOW, this was an engine cobbled-together from used parts and Chinese service parts. Even the primary gears had mismatched tooth counts. The C/S ball bearing was so rusted and loose, I couldn't believe that the tranny hadn't grenaded. Everything else, including the needle bearings and shift forks were fine. With new ball bearings & shift pins installed, the thing shifted as one would expect a Honda to do. Capiche?...
I autopsied the gear & burnt shift fork. The results, seen firsthand, are anything but as-expected. The metal ran hot...smoking hot...for a long time. There's heat discoloration like I've not seen in a very long time, on the side opposite the huge "smile", almost resembles heat-treating(!). Additionally, the gear shows significant galling on the associated face, plus the cylindrical portion, which locates the fork. The fork, itself, has a major wire edge...and...unusually, heavy wear just below the tip, inside the "horseshoe". Consider the fact that the opposite side of the fork and inside face of the gear appear completely untouched.
Looks to me like the gear was held tightly, as in "interference fit" against the gear...as if the shift fork was not fully & properly "seated", by the detent assembly. Instead, the wear patterns (and the extent of the wear) are what I'd expect to result from the fork being held tightly to the gear if one were to "ride the shifter"...kinda like riding the brake, or clutch...if that was even possible. I doubt that it is possible, with this transmission. Once the gear change has progressed over-the-top of the detent, the shift linkage should (ostensibly) lose contact as the rotational forces of the spinning gears and detent rotates, then positively locates, the shift drum and with it, the fork. Judging by the condition of the gear teeth and drive dogs (both pristine), the gear locked-into the adjoining gear as it should. Hard to imagine the gears being misaligned but I can't say that's impossible without more detailed information.
IDK about the bent fork theory. It's certainly possible. And, there's definitely taper to both tips. The more heavily-eroded side ranges from 4.86mm at the very tip to 4.61mm at the base of the contact pad. The larger, less-eroded, pad varies from 4.71mm at the base up to 4.86mm at the tip. That's a lot of variation, in two planes. By comparison, I measured a new service replacement 4-speed fork and got 4.86mm at both tips, 4.85mm at both bases.
Wild-assed theory...it's like the fork was being kept under tension by the channel, in the drum. That's the only thing I can imagine that could apply both rotational AND lateral force, sustained. Hopefully, this will make more sense once I can get some pix taken & posted. Unfortunately, without serious measuring equipment and a skill set way beyond mine an easy answer won't be possible. I'm hoping that between a few of us here we can at least come up with a workable, if not definitive, answer...and solution. Stay tuned...
Looks to me like the gear was held tightly, as in "interference fit" against the gear...as if the shift fork was not fully & properly "seated", by the detent assembly. Instead, the wear patterns (and the extent of the wear) are what I'd expect to result from the fork being held tightly to the gear if one were to "ride the shifter"...kinda like riding the brake, or clutch...if that was even possible. I doubt that it is possible, with this transmission. Once the gear change has progressed over-the-top of the detent, the shift linkage should (ostensibly) lose contact as the rotational forces of the spinning gears and detent rotates, then positively locates, the shift drum and with it, the fork. Judging by the condition of the gear teeth and drive dogs (both pristine), the gear locked-into the adjoining gear as it should. Hard to imagine the gears being misaligned but I can't say that's impossible without more detailed information.
IDK about the bent fork theory. It's certainly possible. And, there's definitely taper to both tips. The more heavily-eroded side ranges from 4.86mm at the very tip to 4.61mm at the base of the contact pad. The larger, less-eroded, pad varies from 4.71mm at the base up to 4.86mm at the tip. That's a lot of variation, in two planes. By comparison, I measured a new service replacement 4-speed fork and got 4.86mm at both tips, 4.85mm at both bases.
Wild-assed theory...it's like the fork was being kept under tension by the channel, in the drum. That's the only thing I can imagine that could apply both rotational AND lateral force, sustained. Hopefully, this will make more sense once I can get some pix taken & posted. Unfortunately, without serious measuring equipment and a skill set way beyond mine an easy answer won't be possible. I'm hoping that between a few of us here we can at least come up with a workable, if not definitive, answer...and solution. Stay tuned...
Well..... that’s a heck of a lot more than I saw LOL. I have no idea what galling looks like and I’m glad I didn’t cheap out and try to reuse the gear. To my untrained eye it was probably okay. I kind of get what your describing. I have had the bike out on many 100 mile plus rides and was clueless. I thought it shifted great and never popped out of or missed a gear. I’m starting to get concerned about other parts. My shift drum seems fine..... I put the new fork on it today. Dry fit the gears in a case and looked for clearance on both sides of the interface. Based on your findings should I be looking for damage on the shift drum under the fork??? BTW. Thanks for the damage assessment