I have a 1985 K100rs and I've had problems downshifting for awhile.

1. The bike shifts up and down smoothly and the start of a ride, but once I get some time on the bike suddenly down shifting become clunky. I'll pull the clutch in and try and down shift and the foot lever wont budge. I'll release the clutch and try again and the bike usually will down shift as it should. Sometimes it won't and I'll have to repeat the process until it shifts down.

2. I've found that if I pull the clutch in and rev the throttle then downshift it won't stick, but I don't understand why that allows it to downshift easier.

3. When the bike is cool at the start of the ride, moving it from 1st gear into neutral is easy, but after 10 minutes riding the bike won't go into neutral from first gear - it either is stuck in 1st and won't shift up or it shifts directly from 1st to 2nd gear, and skips neutral. If I turn the bike off I can immediately slip it into neutral with no issues.

I've broken my gear shift rod a half dozen times because of this issue. I've gotten really good at getting home in 3rd gear.

Anyone else run into this or have a solution?

Thanks so much,

Thomas

The first thing to check is that you don't have too much free play on your clutch cable, then it won't be releasing enough after you pull the clutch in. Hopefully you only have to adjust the clutch cable.

Difficult downshifting is also a typical sign that the splines need to be lubed.

Revving before down shifting means less work for the gear box. If you get good at knowing which revs to change at, you can change gears without using the clutch, so you can get home in fifth gear until you fix it.

Gear shift rod? do you mean the clutch actuating rod down the centre of the main input shaft?

After all above, did in some service the oil of the gearbox and final drive ever been replaced?
Gearbox; 0.8 liter
Final; 0.3 liter
Try synthetic gear oil 75W140

Arlina wrote:After all above, did in some service the oil of the gearbox and final drive ever been replaced?
Gearbox; 0.8 liter
Final; 0.3 liter
Try synthetic gear oil 75W140

Arlina's suggestion is something often neglected. When were the transmission input shaft splines and the clutch disc hub splines last lubricated? Dry splines on those components can cause exactly what you're describing. Breaking either the shifter or the clutch actuating rod multiple times is quite a feat. 

Sounds like it's time to order a tube of honda moly 77 to me....... Dry clutch spline and while your there do the bevel splines too. More expensive than gold but worth it's weight.

UPDATE #1:

I should have mentioned that my K100 is a custom cafe bike now so it has a shift rod connected to the shifter and that's what I keep breaking.

Because I have after-market levers I know my clutch is not set to specs - I can't find a proper clutch lever that will receive the K100 clutch cable properly, so I've had to drill out a large area in the AM lever I have for the end of the clutch to fit, bit it's a shit-show for sure and I need a better solution - any suggestions on where to find an AM clutch lever that's specific to the K-bikes clutch cable?

I'd like to replace the gearbox and final drive oil, but don't have any experience doing that - can anyone point me to a DYI video?

I've had the splines lubed and that did not fix the issue.

tjh1985 wrote:Because I have after-market levers I know my clutch is not set to specs 

Are you indicating that your aftermarket clutch lever has no freeplay adjustment at the lever? That seems unlikely. Tell us the brand and model of the lever. The cable connection to the clutch lever at the transmission is adjusted by means of a lock-bolt arrangement.

With using a non OEM lever you might not be getting enough travel on the clutch cable. This would definitely cause shifting problems. Check to see if you are fully activating the clutch.
Regards Martin.

MartinW wrote:With using a non OEM lever you might not be getting enough travel on the clutch cable. 

Martin has nailed it. Thanks for the info.
 
To compound the problem, you chose a short lever configuration which was likely designed to work with a hydraulic clutch setup. There are a couple of levers out there that work, from what I've read. To find them you'll need to sift through the Customization archives of this site and Motobrick, to name just a couple of resources. If you find some examples, send the customizer a personal message asking for details if the threads you find don't have enough. The 2V Bricks are basic mechanical clutches that need enough leverage to go the distance. They are useful for building grip strength. 

Your choice is unlikely to fill the bill.

Is that a 6mm thread and 10mm nut where it has broken? From what I can see it is so send it back and get a refund because it is unfit for purpose the way it has been welded and the size and considering it is stainless. The angle it works at is another cause.
You probably paid heaps for it too.

+1 on what Rick has stated. It looks poorly designed and executed. More pictures might clarify the setup.
Regards Martin.

Appreciate the input and suggestions here. I'll work to get more images of the rats nest that is this issue ASAP.

Thomas

MartinW wrote:With using a non OEM lever you might not be getting enough travel on the clutch cable. This would definitely cause shifting problems. Check to see if you are fully activating the clutch.
Regards Martin.

down shifting issues are usually associated with dry splines on the clutch plate - input shaft to the gearbox 

can make a fair bit of difference

Might wanna take a book how to work on tour K

https://mega.nz/folder/PmYCESAD#C1e0ijnsfDwqzH_evEOK2Q

UPDATE 4:

Well I found a shift linkage rod that has enough (maybe a little too much) curve in it to work for my custom rearset, but I'm having some trouble setting it properly so that when I shift up or down it shifts properly. I am finding that when it's all assembled the lowest gear I can get to is 2nd and the highest gear I can get to is 3rd. Not sure what I'm doing wrong. Any insights?

Thomas

I will send pics in a little bit

Thomas

Jezz now you got me stuffed. I always thought the gear shift lever returns to the same neutral position after a gear change (wether up or down). So I'm confussed about you not getting 1st,4th & 5th. Maybe your problems are a bit deeper. Martin is a fountain of knowledge so his insites are worth investigating. I'll go with Charlie Regards Poddy

I would put the stock shift leaver on at this point and try that.
 When you described the problem originally , that sounded like dry input shaft splines. I have had that issue before.

tjh1985 wrote:UPDATE 4:

Well I found a shift linkage rod that has enough (maybe a little too much) curve in it to work for my custom rearset, but I'm having some trouble setting it properly so that when I shift up or down it shifts properly. I am finding that when it's all assembled the lowest gear I can get to is 2nd and the highest gear I can get to is 3rd. Not sure what I'm doing wrong. Any insights?

Thomas

I will send pics in a little bit

Thomas

hmm '

sounds like the paul (sp?) that pulls and pushes the gear selector drum isnt moving far enough in either direction to engage the next change ,  but you did turn the input shaft whilst trying to change gears ?   other wise the gears them selves wont mesh on the dogs correctly allowing the next change 

alternatively you have the old selector drum cam issue , where the cam is moving on the selector drum due to a broken - worn locating pin making the selector drum pins that catch the paul out of reach for the next action 
 seen that a few times

pawl

charlie99 wrote:. . . but you did turn the input shaft whilst trying to change gears ?   other wise the gears them selves wont mesh on the dogs correctly allowing the next change 

Until the shifter and peg plate setup is returned to stock configuration as Rick G suggested in one of the other threads you've created about this hanging alabatross, and the clutch is adjusted using the correct sequence of steps afterwards, sorting the condition of the transmission/clutch interaction is likely to be stalled.

Dai wrote:pawl

cheers Dai , figured it out long after the post ,,   sorry, my spelling is less than accurate, at times .

Appreciate everyone's willingness to throw in on my troubles - somewhere in all of this is 'the best it's going to get' given I'm not using the original parts. This all falls into the category of shit you don't think about when you have a custom bike built.

I had same issue a long time ago after I put rear sets on my Honda CB500-4. Getting them and the rear brake set up took a lot of headache. At the time I had access to lots of threaded rod and bottle screws from my boat parts box to get it fine tuned and it made it easier.

Seems to me that the plates that the threaded rod goes into are not equal or are at different angles, needs to be longer at the foot end or shorter at the gear box end to increase the amount of travel on the gear shift to drive each gear fully home. Currently it does not seem to have enough travel.