TOPIC:

I think that my transmission might be slipping from 2nd gear back into neutral. Last week was pretty cold, and as a new rider I was blaming my inexperience as the reason for 'mis-shifting' a few times, but it happened again twice today and I don't think it's my fault.

From 1st gear I take off as usual, kick it up into a second, and around the time that I would shift into 3rd gear the transmission will slip down into neutral at a really high RPM and backfire (as well as making me look like an idiot rider).

What could be causing this? A sign of needing a rebuilt transmission? Expensive problem?

What kind of bike is this on?? How many miles? Does it do it while under heavy load at high rpm's?? It could be the dogs on the slider gears in the tranny. Over time they can round off/wear away, and not engage as well as they should. If you can do the work yourself, it's not too expensive, but extensive! It may also be a problem with the shift detent, but I don't know why it would fail. I'm a KZ newbie, so dunno their exact tendancies..

Your bike has three shift forks. The forks basically have paddle shaped tips that engage the gears and when they wear and flatten out, the bike can jump out of gear. This generally happens on 2nd gear initially. You can either replace the shift forks or get the transmissin gears undercut so the forks won't pop out. In either case, you will have to pull the engine out, take off the engine covers and split the cases. You don't need to remove the top end so the job can actually be done in a day or so.

While it is possible that the external shift mechanism is the culprit, it is about 80 percent that the problem is with the shift forks. Since getting to the external shift mechanism can be done without much fuss, do check it first. On the external shift mechanism are two pawls which grab pins on the shift drum. There is a spring that keeps these pawls returning towards each other. Check this spring. There are also two other springs that are used in the external shift mechanism. One is used for the shift detent... if that spring is tired, the detent will not engage and stay. This is the spring in the upper left corner as you view the shift drum. There is one more spring on the mechanism that returns the piece that holds the pins in the drum. I would remove the countershaft covers and look at the external shift mechanism first then consider how annoying the slipping is.

My 900 had that same problem, it turned out the dogs on the gear rounded and the recesses also. I back cut both with a dremel and now it stays in second gear. It was so bad i had to skip second gear, and when i shifted from 1st to second during a wheelie it'd pop out of second and in and out and in, it was like a record spun back and forth rapidly like a dj does, it was very quick and i swear the back tire locked and unlocked. It was scary. Make certain that you look closely at the forks too, this can be a compound problem. The inside diameter of the gear must be checked for play beetween it and the shaft. When a gear doesnt fit tightly on the shaft, it turns sideways under load and the new angle of force will be sideways. The gear will get pushed back out of mesh by the pressure.

Thank you for the advice. The bike is an 83 Kz550 with about 8,000 miles. I've only had it a few months and have ridden it nearly every day since getting the bike, plus one 200 mile trip. I have a manual for the bike but transmissions are way out of my league, so I'll look into the external shift mechanism for any problems.

I also have an issue with my throttle return that hasn't helped my shifting. Following the instructions for throttle adjustment hasn't fixed it yet but I'll spend more time trying to adjust it today. The bike is still needed for convenient transportation to work (bikes park for free) but I don't want to start disassembling the transmission yet if it could leave me without a ride.

Post edited by: Grebnaws Inc., at: 2006/10/18 12:08

Okay, I just put another 45 miles on the bike. The transmission slipping is definately limited to 2nd gear. It seems to slip back into neutral at random. It hasn't made any difference whether I put the engine under load or keep it steady, and it doesn't always slip. I had the best luck getting out of 2nd gear as quickly as possibly and giving it the least amount of time to slip. Unfortunately that just makes it worse when it does finally slip, because it makes me look like a really stupid rider

I was able to make a great deal of improvement to my throttle problem. It was not in the cable adjustments but in the throttle sleeve and engine shut-off housing. Cleaned it out, lubricated it, and smoothed out some spots where my grip was rubbing the bar. I think I lost some clearance at WOT though.....

Is it generally cheaper to get something like this repaired, or to find a tranny in good condition and make a swap? Replacing a tranny myself must be a lot easier than tearing through one in hopes of repairing it.

Getting it repaired means paying for labor and labor is high. Replacing just the worn part or parts is the way to go if you can do the work or know someone that can. It isnt very difficult just time consuming. Ebay and state wide junk yards may have the parts youll need. If they sell you the entire shaft, compare the price with the cost of a new part wether it's a gear or fork, and take it from there. Check the pins in the shift drum, the springs and such first, before going into the motor. It seems to be internal but check it out first.

I tend to agree with nads on this one. I buy used transmissions for this purpose. In the event I have a bad one, I yank the engine, take off the engine covers and scrape, scrape, scrape old gasket, remove the case bolts and pull the bottom off the engine while it is upside down. It takes about 5 mintutes to swap a transmission out and it is hard to do wrong. Problem is, this is for a 900/1000 and the 550 bits are probably harder to come by. Keep your eye on eBay and pick up a gasket set. Don't forget to remove the bottom and TOP bolts on the cases. I always chase all the thread and also clean the old bolt thread. I use blue Loctite on the outside bolts and red Loctite on those inside the cases and use a torque wrench. I use Hondabond HT to seal the cases. On a 900/1000 I can swap a transmission (pull engine, split cases, swap tranny and put it back together and back in the bike) in about 8 hours. If you haven't done it before it will take a tad longer and also have a transmission jack to hold the engine and lift it over the frame when all mounts are loose.