Kawasaki Motorcycle Forums banner

Status
Not open for further replies.
1 - 6 of 6 Posts

·
Registered
Joined
·
76 Posts
Discussion Starter #1
I was one of the original posers of the "636 tranny problems" topic earlier this summer. Back then my transmission was brand new with only at the most 500 miles. The only problem I experienced at that time was; under hard acceleration the bike jumps out of 2nd, 3rd, or 4th gear "occasionally". Maybe once or twice a week. I took it to the nearest kawasaki dealer and they told me that since they couldn't duplicate my problem, I would need to just continue proper break in and maybe it will just "go away"[V]. Well it continued with the same problem throughout the summer. I ride hard everyday. to work, the store, just cruising, or just whatever.

Now to the problem:

I now have about 7,000 miles on my 636. Everything is just fine, except for one major problem. Now instead of "jumping out of gear" when I go from 1st to 2nd the bike jurks like something in the tranny slipping as if it is going to jump out of second, but it never does. but as soon as I go from 2nd to 3rd it rides like normal.

What does this sound like?
 

·
Registered
Joined
·
202 Posts
1st to 2nd on all bike is a little funky.Have you tryed to adjust the foot shifter? sometimes you might not have it in gear al the way, it sounds stupid but start with the simple stuff first. You might have a shift dog or shift fork problem.If it under warrenty and your not happy and they wont do anything ,just rip it through the gears and make sure it brakes,then they'll have to fix it
 

·
Registered
Joined
·
335 Posts
My dirt bike did something very similar before the bottom end went. I had rounded off part of the gears from powershifting and had to have them replaced. Dont know if that is the issue, but that is what happened to me.
 

·
Registered
Joined
·
132 Posts
“Jerks” under load, eh? Two possibilities come to mind, in order of severity: 1) clutch 2) transmission. I offer only ideas: draw your own conclusions based on the symptoms. You’re there, I’m not.

Slipping clutches go something like this: accelerate hard, the engine revs and the bike leaps forward as expected. At some point, the engine keeps spinning but the drivetrain feels a step behind. Then the transmission seems to “catch up” (via the clutch) and things resynchronize.

Cures include scuffing the metal clutch plates and/or replacing with another clutch. Fortunately that’s a simple and inexpensive affair.

Damaged transmissions usually mean damaged collars and dog teeth plus damage to the gears themselves. Very bad news, usually.

The symptom: accelerate hard, the engine revs and the bike leaps forward as expected. While under load in a lower gear (often 2nd), the drivetrain jerks suddenly, then reengages and acceleration continues. The “jerks” take a half-second or less, but definitely suggest something’s amiss below decks.

The behavior may occur in multiple gears or just one. 2nd’s often the culprit. I had a bike do it in both second and third gears, my 1984 Yamaha FJ1100.

Transmissions and soft valves seats were known weak points of these bikes: metallurgy, CAD/CAM design, and CNC milling hadn’t quite caught up with engine advances, leading to self-destruction. 101 rwhp was big news in those days, too.

With a lot of sleuthing and a wise mentor, I puzzled it out. Something about sport motorcycling doesn’t exactly draw the brightest folks into the repair business: there are seldom straight answers from mechanics, especially those with anything to gain (or lose) from supplying the correct diagnosis. Keep that in mind.

Here’s an interesting discussion of modern transmissions:

http://howstuffworks.lycoszone.com/transmission.htm/printable

Many features shown in the diagrams are common to motorcycle transmissions: shift forks, gears, collars, dog teeth, spline shafts, e.g.

Here’s a telling quote from the page:

“When you make a mistake while shifting and hear a horrible grinding sound, you are not hearing the sound of gear teeth mis-meshing. As you can see in these diagrams, all gear teeth are all fully meshed at all times. The grinding is the sound of the dog teeth trying unsuccessfully to engage the holes in the side of a blue gear.”

And there’s your problem: under extreme load, the collars can’t synchronize quickly enough and the dog teeth mate with the gears violently or incompletely. The “jerk” you’re feeling is the collar disengaging then reengaging the gear: the dog teeth and/or gear holes are rounding off, forming a less-precise engagement which can’t take the load. They’ll wear over time.

With my FJ tranny apart, many gears and collars showed damage. I also replaced two shift forks, as I recall, since they too looked tired. The wear on the gears and collars was obvious, on inspection. On reassembly, no more transmission trouble.

This job was difficult for amateur mechanics with other day jobs, though fortunately we had great tools and plenty of workspace. Essentially we completely stripped the engine. All gaskets needed replacement, a major ass-raping on most any engine job. Materials cost was roughly six hundred bucks, 1991-dollars, including other items destroyed on the way in or out (clutch basket, broken head stud, etc.) If you have more time than money, great organization skills, efficient work habits, and plenty of tools (including a real bike lift), by all means tackle the job. Two guys make it go quicker.

(In all fairness, trained mechanics can have an engine out and stripped in a day or two, tops, but they don’t exactly work pro bono.)

If that’s your conclusion for what’s occurring, the next steps won’t be easy. Options as I see them include: 1) swap the engine 2) fix the transmission yourself 3) drop off at Kawasaki and have them fix it on your dime or (preferably) theirs. Paying for the work turnkey will not be cheap, if they tear down the engine completely. I’d balance that very carefully against a new (used) engine: engine swaps are comparatively easy.

Every engine’s different. Some engine designs facilitate transmission removal without complete engine teardown. I don’t have a shop manual for my ’03, so I dunno.

If you tear down the engine on your dime, gear backcutting would probably be a good idea, in addition to other performance work. I’d call Motoman or Kyle Racing Engines. No way in hell would I pay some dealer to rebuild an engine, when there are hugely better options out there. Expect to pay extra, but consider what you’ll gain.

More importantly, I think you were glad-handled about the problem early on. What they meant was, “this is a major problem we don’t want to deal with, so we’ll deny everything.” I go through that bullshit in the software industry all the time: “nope: problem doesn’t repro on my machine; must be YOUR fault!” In fairness, the symptoms might have been too vague for the dealer and they don’t usually go on fishing expeditions to find problems, especially warranty issues: they aren’t reimbursed much for claims, as I understand.

Regardless, this particular issue worsens over time. So it went from bad to worse, now it’s broken. If you can’t obtain satisfaction with the dealer, I’d take it up with Kawasaki in detail. Kawasaki may (or may not) be persuaded to see the error of their ways and help with costs, or better yet fix the issue gratis.

Good luck.

-=DRB=-
 

·
Registered
Joined
·
76 Posts
Discussion Starter #6
Originally posted by Squidly
My dirt bike did something very similar before the bottom end went. I had rounded off part of the gears from powershifting and had to have them replaced. Dont know if that is the issue, but that is what happened to me.
Did this happen on your '03 636?
 
1 - 6 of 6 Posts
Status
Not open for further replies.
Top