Possible FIX for Triumph TF transmissions

lowmass wrote:

Wasn’t expecting to get to this for at least a week or so but had time today and went for it. This will be a bit...

Wasn’t expecting to get to this for at least a week or so but had time today and went for it. This will be a bit long……

 I found 2 obvious problems and some other lesser but likely useful stuff. FORTUNATLY ALL ARE FIXABLE! It does not look like we have a design problem here, just some bad parts. This has been a consistent theme with these bikes. 

Anyway, armed with the following info I have confidence based on past experience that anyone good with their hands can make their Triumph shift well, avoid the death sentence of false neutrals, and maybe even overcome a good portion of the notchy stiffness many are experiencing. Will have to wait till spring to test it all but based on what I see I believe this mess is salvageable. Yes Mr. Fakebook worrior, I admit what I found here is nothing new so no need to chime in with all the negative comments 😉. 

I can see now why Some people are reporting their bikes are working OK while others are reporting serious issues. Most of what I found were simply subpar finishes on surfaces critical to shifting in ALL similar designs. Those who have bikes that are working ok likely just got lucky with some parts that didn’t have serious flaws. BUT imo even those bikes would likely benefit from this info as they too likely have at least some of the flaws. 

 So lets see if I can put this into words with some pics and make sense of it all…..

FALSE NEUTRALS- First off understand this, ALL constant mesh transmissions (most motorcycles) have a “neutral” between each gear. As you shift your sliding a gear out of engagement with the gear on its left, and into engagement with the gear on its right. Mid way through this move there is no engagement and everything free wheels as if you’re in neutral. This is necessary in all constant mesh designs and not specific to Triumph.  If all is well everything moves right past this mid position and completes the gear change. However, if it hangs up mid-way, you get a false neutral.  In truth ALL constant mesh transmission hang up mid-way through a gear change for a split second. How? When a gear is moved out of the gear on its left into the gear on its right, they usually contact first at the “end faces” of the “dogs”. When the surfaces of those end faces are smooth and well finished, the dogs just slide over top of each other until they fall into place and lock in. When those surfaces are rough enough it won’t slide and the gear hangs up mid-way. 

Take a look at pic# 1. The arrow points to the “end face” of a dog. If that surface is not smooth it can grip the surface of the gear it lands on (see pic #2).  If these surfaces are not smooth and flat they will grip each other and the dog will not fall down into its pocket completing the shift move (see pic #3). This holds the gear in a “mid position false neutral”. You feel this at the lever as a jam mid-way through the stroke. Normally these surfaces slide right past each other and the dogs can fall into place locking the gears together in a completed shift but when these surfaces are rough enough they can hold position and foul the shift.

What I found on MY TF450-RCheezburger addition  was very rough surfaces on these faces. And making it even worse (the pics don’t show this well) the edges of the pockets the dogs need to fall into ( see pic # 3) had large machining Burrs that literally stopped the dog from sliding into its pocket even with excessive force!! 

On the track my bikes 1st to 2nd shifts were so so, notchy and stiff but no false neutrals. 2-3 was a bit stiffer and notchy and would occasionally give a false neutral, 3-4 and 4-5 were even worse. BTW I don’t power shift. I’m easy on bikes yet this condition had me on egg shells at jump faces. Anyway, sure enough, bench tests show similar performance AND close inspection revealed that the surfaces involved in 1st to 2nd shifts were not great but they were the smoothest of them all, 2-3 were rough and felt gritty spinning gears by hand, and the surfaces on 3-4, 4-5 shifts were really ugly gritty feel and even a Galling like feel at times. This is very hard metal so generally Galling is out BUT in this case the large Burrs left over from machining the pockets were causing a galling like feel.

 This find is consistent with the performance on track and consistent with other reports in the field giving some confidence that this is likely the cause of the false neutrals. It’s an easy fix with some emery cloth on a flat stone if your good at that kind thing. I suppose you could even polish from there. 

STIFF NOTCHY SHIFTING- After visual inspection of all transmission parts and direct compare and feel too newer KTM transmissions I believe the cause of the notchy stiffness in the Triumph is related to a combination of a few things all adding up. 

       1, Unpolished dogs (not the faces but the sides) see pic # 4. These surfaces have to slide apart at beginning of a shift so smooth here helps. The Triumph dogs look like hammered dog meat. A completely unfinished surface Ug. The KTM dogs look like jewelry. Highly polish smooth perfection. I suppose a vibratory polish may help here BUT won’t be same as the KTM dogs that are machined and polished. A machine shop could grind smooth but it would be expensive AND such a mod here would likely only be a big deal to racers who are shifting under full load.

 2, the pins in the shift forks that ride in the shift drum grooves do not spin under load. They are designed to spin BUT when there is a load on them, they don’t. It’s a similar design on the KTM but for some reason theirs do spin under load. Not sure why this is and likely nothing we can do about it. The Triumph pins are nicely polished but this is a high friction area and there would likely be a noticeable difference in shift force if they spun properly. Oh well I wonder if the KTM forks fit ha.

3, The finish on the shift fork shafts are a bit rough and even a little force on the shift fork that’s not perfectly square to the shafts axis results in a noticeable drag and even a stiction action. Possibly a finer finish on these shafts with some 2000 grit or maybe a polish would overcome that? I will play with that eventually and report what I find. That said if ya do the mod in #4 this problem may go away because its unlevel fork fingers that would put a strange force on this part. If everything else is good this may not be a problem but I would try a polish anyway.

4, I found the shift forks are far from perfect as far as how the fingers push the gears. The fork fingers are not putting an even and square to shaft force on the gears as they are moved( See Pic #5). You can see wear in one small spot on only one finger, AND, easy to miss, look at the shinny wear on the top of the “A3” mark molded into fork. Hard to see in pic but that molded in marking is raised and it was pushing on the gear. If ya look closely, you can see it’s a bit shiny at the tops of the letters. It was dug in quite a bit by the gear groove! The problem is, when you push on splined gears that ride on a splined shaft you have to push the gear evenly with both fork  fingers OR the gear will be tilted slightly on its shaft. A splined shaft with a splined hub is a perfect engine for a stiction if ya tilt the gear even a little bit. I found this same issue on two KTMs in the past that had stiff shifting feel. They have a similar fork design where the fingers are not machined, just a coating over the rough forging and if the forks weren’t level finger to finger it would cause hard shifting feel due to the gear being tilted slightly on its splined shaft.. This too is fixable. Just grind those molded in letters off, and with a granite stone, some V blocks, and some emery cloth, you can level the surfaces of the fingers so they push evenly on the gears.  Of course, any machine shop can do it for ya too. 

So That’s it. I know it was long BUT the devil is in the details and wording things to make sense is difficult. In the next week or so (If my equipment shows up ha), I will post pics of how to sand this stuff down. It’s not that hard to do but of course a lot of work to get at everything. Hope this helps. 

 

neverwas wrote:

I don'   own a Triumph, but cool Info. Thanks.

 

lowmass wrote:

Wasn’t expecting to get to this for at least a week or so but had time today and went for it. This will be a bit...

Wasn’t expecting to get to this for at least a week or so but had time today and went for it. This will be a bit long……

 I found 2 obvious problems and some other lesser but likely useful stuff. FORTUNATLY ALL ARE FIXABLE! It does not look like we have a design problem here, just some bad parts. This has been a consistent theme with these bikes. 

Anyway, armed with the following info I have confidence based on past experience that anyone good with their hands can make their Triumph shift well, avoid the death sentence of false neutrals, and maybe even overcome a good portion of the notchy stiffness many are experiencing. Will have to wait till spring to test it all but based on what I see I believe this mess is salvageable. Yes Mr. Fakebook worrior, I admit what I found here is nothing new so no need to chime in with all the negative comments 😉. 

I can see now why Some people are reporting their bikes are working OK while others are reporting serious issues. Most of what I found were simply subpar finishes on surfaces critical to shifting in ALL similar designs. Those who have bikes that are working ok likely just got lucky with some parts that didn’t have serious flaws. BUT imo even those bikes would likely benefit from this info as they too likely have at least some of the flaws. 

 So lets see if I can put this into words with some pics and make sense of it all…..

FALSE NEUTRALS- First off understand this, ALL constant mesh transmissions (most motorcycles) have a “neutral” between each gear. As you shift your sliding a gear out of engagement with the gear on its left, and into engagement with the gear on its right. Mid way through this move there is no engagement and everything free wheels as if you’re in neutral. This is necessary in all constant mesh designs and not specific to Triumph.  If all is well everything moves right past this mid position and completes the gear change. However, if it hangs up mid-way, you get a false neutral.  In truth ALL constant mesh transmission hang up mid-way through a gear change for a split second. How? When a gear is moved out of the gear on its left into the gear on its right, they usually contact first at the “end faces” of the “dogs”. When the surfaces of those end faces are smooth and well finished, the dogs just slide over top of each other until they fall into place and lock in. When those surfaces are rough enough it won’t slide and the gear hangs up mid-way. 

Take a look at pic# 1. The arrow points to the “end face” of a dog. If that surface is not smooth it can grip the surface of the gear it lands on (see pic #2).  If these surfaces are not smooth and flat they will grip each other and the dog will not fall down into its pocket completing the shift move (see pic #3). This holds the gear in a “mid position false neutral”. You feel this at the lever as a jam mid-way through the stroke. Normally these surfaces slide right past each other and the dogs can fall into place locking the gears together in a completed shift but when these surfaces are rough enough they can hold position and foul the shift.

What I found on MY TF450-RCheezburger addition  was very rough surfaces on these faces. And making it even worse (the pics don’t show this well) the edges of the pockets the dogs need to fall into ( see pic # 3) had large machining Burrs that literally stopped the dog from sliding into its pocket even with excessive force!! 

On the track my bikes 1st to 2nd shifts were so so, notchy and stiff but no false neutrals. 2-3 was a bit stiffer and notchy and would occasionally give a false neutral, 3-4 and 4-5 were even worse. BTW I don’t power shift. I’m easy on bikes yet this condition had me on egg shells at jump faces. Anyway, sure enough, bench tests show similar performance AND close inspection revealed that the surfaces involved in 1st to 2nd shifts were not great but they were the smoothest of them all, 2-3 were rough and felt gritty spinning gears by hand, and the surfaces on 3-4, 4-5 shifts were really ugly gritty feel and even a Galling like feel at times. This is very hard metal so generally Galling is out BUT in this case the large Burrs left over from machining the pockets were causing a galling like feel.

 This find is consistent with the performance on track and consistent with other reports in the field giving some confidence that this is likely the cause of the false neutrals. It’s an easy fix with some emery cloth on a flat stone if your good at that kind thing. I suppose you could even polish from there. 

STIFF NOTCHY SHIFTING- After visual inspection of all transmission parts and direct compare and feel too newer KTM transmissions I believe the cause of the notchy stiffness in the Triumph is related to a combination of a few things all adding up. 

       1, Unpolished dogs (not the faces but the sides) see pic # 4. These surfaces have to slide apart at beginning of a shift so smooth here helps. The Triumph dogs look like hammered dog meat. A completely unfinished surface Ug. The KTM dogs look like jewelry. Highly polish smooth perfection. I suppose a vibratory polish may help here BUT won’t be same as the KTM dogs that are machined and polished. A machine shop could grind smooth but it would be expensive AND such a mod here would likely only be a big deal to racers who are shifting under full load.

 2, the pins in the shift forks that ride in the shift drum grooves do not spin under load. They are designed to spin BUT when there is a load on them, they don’t. It’s a similar design on the KTM but for some reason theirs do spin under load. Not sure why this is and likely nothing we can do about it. The Triumph pins are nicely polished but this is a high friction area and there would likely be a noticeable difference in shift force if they spun properly. Oh well I wonder if the KTM forks fit ha.

3, The finish on the shift fork shafts are a bit rough and even a little force on the shift fork that’s not perfectly square to the shafts axis results in a noticeable drag and even a stiction action. Possibly a finer finish on these shafts with some 2000 grit or maybe a polish would overcome that? I will play with that eventually and report what I find. That said if ya do the mod in #4 this problem may go away because its unlevel fork fingers that would put a strange force on this part. If everything else is good this may not be a problem but I would try a polish anyway.

4, I found the shift forks are far from perfect as far as how the fingers push the gears. The fork fingers are not putting an even and square to shaft force on the gears as they are moved( See Pic #5). You can see wear in one small spot on only one finger, AND, easy to miss, look at the shinny wear on the top of the “A3” mark molded into fork. Hard to see in pic but that molded in marking is raised and it was pushing on the gear. If ya look closely, you can see it’s a bit shiny at the tops of the letters. It was dug in quite a bit by the gear groove! The problem is, when you push on splined gears that ride on a splined shaft you have to push the gear evenly with both fork  fingers OR the gear will be tilted slightly on its shaft. A splined shaft with a splined hub is a perfect engine for a stiction if ya tilt the gear even a little bit. I found this same issue on two KTMs in the past that had stiff shifting feel. They have a similar fork design where the fingers are not machined, just a coating over the rough forging and if the forks weren’t level finger to finger it would cause hard shifting feel due to the gear being tilted slightly on its splined shaft.. This too is fixable. Just grind those molded in letters off, and with a granite stone, some V blocks, and some emery cloth, you can level the surfaces of the fingers so they push evenly on the gears.  Of course, any machine shop can do it for ya too. 

So That’s it. I know it was long BUT the devil is in the details and wording things to make sense is difficult. In the next week or so (If my equipment shows up ha), I will post pics of how to sand this stuff down. It’s not that hard to do but of course a lot of work to get at everything. Hope this helps. 

 

lowmass wrote: