transmission pops out of 4th

So, last summer, coming into time for a rally in Vermont, I picked up this wonderful 1983 kz1100 ltd with full vetters and low, low miles. Requisite carb cleaning and fluids done. Progressive 440's on the rear, regulator/rectifier, Taylor wires, and minor tuning then it ran better than expected. Only thing was...well, uh...hanging in 4th for more than a minute or two (no difference under load/accel/no load) it'll pop out of 4th to somewhere in the middle. With the power of the machine and gear ratios I decreased rally risk by using 4th as a brief stop hop between 3rd and 5th. No issue, no pops, smooth.

As we get to the ride this year there is do much more prep time and this must be addressed. The trip will be much longer (MA to AR) and the bike another year older. Did the research here, elsewhere, and now I'm coming back to resident experts for your thoughts.

So far I'm hearing for bikes that have been torqued hard, popping out of 1st or 2nd can arise. 4th seems to be a question of "fork, lever, or spring is tired." Mechanic is about to drop the pan, look for metal, and check the shift forks...I am looking at used fork and tranny assemblies and thinking I might as well go all-in on the full pile o' parts and keep what is extra on hand.

Looking for crew guidance here on the likeliness of fault to be efficient in repair- shift fork, washers, linkage, bearings? Also, left the FSM with the installer, so can I get confirm/deny my memory serves in that the '82 and '83 kz1100 transmissions are identical?

(Other trip prep dreams pending this cost: already bought the Progressive front fork springs..those seals are old and should be done too. Hoping to go HID/daytime led to save wattage and heat...exhaust is 4-2 but older and not stock, loud and lean-blued so probably need 2x on main jets with the MAC 4-1..love this ride though)

I should add: Motor Head had some suggestions last year

"well the Manual has a section to cover the trans Issues of course...Could just be weak springs, detents are easy to change, and then the selector shaft spring is also pretty easy. the fork of course would be a teardown."

Springs, fluids and find out...or is there another thought?

Doesn't sound good, although with 7k original miles the bike WAS running and shifting fine other than the 'drift out of 4th.' Had it to the mech; he figured shift fork.

Guy (FSM in hand) couldn't find anything off with shift forks, drum, pawl. Suspects trans ate a washer, popped a circlip..but can't see it. Said he tried to shift it & wouldn't go into third. Unwashed pan was surprisingly pretty clean, only had two small pieces of flat, slightly raised in center, dark orange-ish, half-pinky-nail sized wafers which look like some kind of flaked rigid ceramic or sealant to me...and few small pieces of a thin, narrow plasticky tape of sort, almost something from the build. No grindings, chunks, anything else. Probably never been dropped before. Whether that orange stuff was cam guide or not I wouldn't know.

Sigh. Soon I will be picking up the rolling chassis: shift forks, drum, pawl, whatever else came out of her in a box. With the help of KZR I will try to work some magic here, as other wheeling prospects are distant to say the least.

I've got the exact same bike, including full vetters fairing, side bags and trunk. I also have the exact same symptom of popping out of 4th gear. What was the problem and solution?

Could be the shifting dogs are worn. To have two with the same problem suggests a problem with the heat treating. You can look in there and inspect them or split the cases. The dogs are what fit into the gear next to it and if the edges are rounded, that's the problem
Steve

Thank you Steve, how would I inspect them without splitting the cases? I'm following what you mean about the dogs and needing a square edge (not rounded off). Pablo from the KZ650 site suggested the same possibility, but pointed me over here for more expertise on the bigger bikes.

You can drop the pan but to fix it you need to split the cases. On my bike 2nd gear goes first. That's the power gear. I back cut the dogs in 13 when I got the bike back on the road. I didn't do the ones on the input shaft next to the clutch basket. It lasted a year but started popping out again. I won a low mile tranny and back cut all the dogs. Works great. When I hit second gear you can hear them lock. Another thing, the Z1's had the main fork that was rather wimpy. The KZ 1000's had a thicker one. I bought the whole Magila, drum, shift forks detent and put them in. I've gone through three rear tires, about 15,000 miles, no problems.
Damn, I'm riding the piss out of it. :evil:
Steve

I ride spirited but I don't normally turn the tires, just short. I too like crackin' the throttle, tach'ing it up and grabbing the next gear so I want them to be tough. KZ1000 shaft drops straight in, same gear ratios? I thought they used the KZ1100 in police bikes up through 1995 and they were crazy strong throughout the drive train. Maybe not so much.

Granted, this is an older post. However I can tell the rest of the story. First, don't bring your bike to the shop I brought mine to initially (which should be easy if you aren't near Worcester, MA). I do not know they could actually read the factory service manual.

I did a lot of research and folks were did a lot of stuff like sending drag transmission gears out for expensive machining, etc. I took the gamble that at 7k and light throttle the gearing should be good.

Inspected the gears without splitting cases (yes, time on back, with light and magnifying glass). The issue wasn't there: teeth and valleys were tight and right and what little wear pattern was where it ought to be.

inspected shift forks (which I think were referred to as dogs above). One fork was slightly different from a same-sized other and a potential replacement: maybe 0.010-0,.020" off in casting, heat treating, or machining. It just didn't sit the same for measurement on the granite block.

Put almost 1,000 miles on it, first bit of it testing "grip in 4th" with zero issue. Would suspect that a particular short run of the '83 KZ1100 run included a barely out of specification shift fork or forks. That is, if miles are low and not beat or hammered on.

Also, the fork or dog can be changed without splitting cases. The pins slide out. But before spending the money do inspect: gears, pins, dogs.

The forks are what their called, forks. Dogs are the blocks on the sides of the gears that fit against the dogs of the next gear. They are straight cut. no rounding should be apparent. Normally back cutting shouldn't be necessary. Under high stress, it is possible for them to separate. Once this occurs the edges of the dogs become damaged thus making it easier for them to "pop out" again and so on. Sloppy manufacturing tolerances, worn bearings, defective heat treating, bent forks can cause this to happen also. Back cutting is to be done so the treated surface is not ground away. A slight angle carefully mated to the next dog is essential. If done correctly, the gears are expected to last as long as a in a new tranny.
Steve

Mark, thanks so much for circling back to close out on the resolution. So replacing the fork is what you believe resolved your problem. I'm clear you didn't have to split the engine case, but you had to pull the engine so you could remove the bottom cover, right?
Steve, I'm following, instead of restoring the leading, rounded edge of the dogs to a flat 90 degrees, I'll cut it at a very slight angle in the opposite direction of the rounding.

Yes. It doesn't take much. Most of us can drop the pan with the pipes off. I'm not home or I'd show a pic of bossie lying on her left side on blocks while I poked around in there. The shaft for the two small forks comes out from under the transmission cover. I've never tried to replace them this way but I'm sure it will be a BTCH trying to get the new ones back in. The main one can only be removed by splitting the cases. :dry:
BTW, it took me two days to do it. I had to, it's my RIDE :whistle:
Steve