1998 Suzuki Quadrunner LT-F250 Will Not Shift 3rd, 4th, or 5th

[Parham]

Got engine issues sorted out...kinda.  Engine starts easy and idles smooth.  It had gasoline in the crankcase...lots of it.  Drained, changed, and fixed stuck float.  Now it won't shift into 3rd, 4th or 5th. Reverse works as it should.  1st and 2nd click easy and with no abnormal noise.  4WD, superlow, and LOCK all seem to work.  What should I check next?

[Mech]

Were you riding it when you were trying to change gears. If not, was the motor running at the time, and were you rocking the bike back and forwards as you tried to move the lever ? How did the lever feel, did it move but not change the gears, or did it just move a small distance and then come up solid ?

 

[Parham]

All of the above...I just got it.  It won't shift above 2nd running, not running, rocking...nothing.  1st and 2nd is a solid "click".  After that, nothing.  No matter how many times I pull up on the shifter or how hard, two clicks down and I'm back to neutral.

[Mech]

Ok, I'll presume then that the lever only moves a short distance when the problem is happening. It gets a full travel for first and second, and then after that it only moves half the distance ? If it's traveling full distance but not changing then it will be a different issue.

It probably just needs to have the output shaft turned more to align the higher gears.

Try jacking the back end up and turning the rear wheels as you try changing. You might have to rotate the wheel several turns before it will change up into each consecutive gear. Try turning, and turning backwards. It's pretty much standard for a stationary bike to need rocking to shift gears, and they need rocking further for the higher gears.

[Parham]

10 minutes ago, Mech said:

It probably just needs to have the output shaft turned more to align the higher gears.

Try jacking the back end up and turning the rear wheels as you try changing. You might have to rotate the wheel several turns before it will change up into each consecutive gear. Try turning, and turning backwards. It's pretty much standard for a stationary bike to need rocking to shift gears, and they need rocking further for the higher gears.

Are you saying de-couple the shift cable from the output shaft and rotate it to a new position and tighten back up? Forgive my ignorance...

It won't shift when running/rolling, not just stationary.

[Mech]

No the cable should be ok where it is.

I'm trying to figure whether it's a problem with the shift mechanism, or inside the gearbox, or no problem at all.

Did you jack the back wheels up and try as I suggested ?

Have you tried driving it at a proper speed for those higher gears while you are changing it ? And were you using the throttle to "unload" the torque on the gears as you shifted the lever ?

They are a long travel shifter and always a bit heavy and clunky. Gearboxes also don't shift if the gears have a load on them as you try to shift, or if the gears aren't rotating enough to allow them to slide together.

Have you ridden bikes before ? Was it two wheelers or four ? And are you familiar with the technique for doing clutchless changes on a two wheeler ?

It'd be a shame to pull the side case off if there's nothing wrong, let alone pulling the whole engine out and stripping it only to find it's technique that was the problem.

You could try pulling the oil filter out and seeing if there are signs of gear damage.. metal in the oil.. flakes or chunks of metal..

[Parham]

Never ridden two wheeler. Had a1983 Honda 3-wheeler for many years...similar "clutchless" shift.  I just got this one last week for cheap.  Trying to figure out the actual condition.  I rode it just a couple of times before starting work on it.  Crankcase was full of fuel...got that sorted out and cleaned the carb. Right now it's jacked up waiting on brake parts...cylinders blown in both wheels, right side didn't even have shoes!  Not worn out or broken...not even THERE!  While waiting, I thought I would try to figure out the shift issue.  Just for background, I'm 65 years old and road submarines for twenty years.  Former nuclear engineer...new to 4-wheeler maintenance 🙂

I certainly appreciate your help!

[Mech]

Well the gearboxes are pretty robust and it's not very likely to have a fault/damage with the gears if you haven't notices any sign of metal in the oil. That's why I suggested you look in the oil filter.

It's very likely that it just needs the two gearbox shafts to be rotated so the gear it's in(second), isn't under any load on the teeth when you try to move up, because that is required so it will come out of that second gear. Then as the shift lever moves further after moving out of second it needs to have the third gears lined up so they can slip together. To achieve both those two things you need to keep rocking or rotating the rear wheels I'm thinking. When we are riding the alignment part mostly works itself out, but it's always a good idea with any bike, two or four wheeled, to accelerate slightly and then throttle off smartly just as you change up. That takes the load off the gear you are in and lets it slip out of gear easily. If we don't use that technique, and especially when the clutch isn't adjusted or operating correctly, then we can get the problem you are describing. This I suspect is where your problem lays. But...

Inside the gearbox there is a ratcheting mechanism that notches around to select each consecutive gear. If that works in first and second then that should work in the higher gears too. There is one exception though, and that's why I asked you how the lever feels, how far it's traveling when it won't engage third. You haven't told me that yet.

 

Edited January 26, 2023 by Mech

[Parham]

7 minutes ago, Mech said:

Inside the gearbox there is a ratcheting mechanism that notches around to select each consecutive gear. If that works in first and second then that should work in the higher gears too. There is one exception though, and that's why I asked you how the lever feels, how far it's traveling when it won't engage third. You haven't told me that yet.

 

As soon as I get the front wheels back on so I can try the rocking thing, I'll get back to you.  Right now, stationary with engine off, 1st and 2nd make a distinct "click" when shifting.  Further "pulls"/toe-taps on the shifter feel like shorter travel against a "mushy" stop...if that makes sense.  No matter how many time I try shifting "up", two clicks down takes me back to neutral.  When I have more info about "rocking" or even riding results, I'll post again.  Thanks again for your help!

[Mech]

Put it in two wheel drive, high ratio, and try rotating the rear wheels..  While you have it up.

[Parham]

Operator error! With the rearend raised. it shifted through all gears while rotating the wheels! Thanks Mech!  Now I just need to learn how to ride it! 🙂

[Mech]

Onya.. Cheers.

[Mech]

Inside the guts of it there's a centrifugal clutch which is used at takeoff, and another clutch, a multi plate clutch, that's operated off the gear shift mechanism. The multi plate's there so when you change gears at a rev above the centrifugal clutches lock up speed, the  gears don't graunch or be hard to slip in and out. The shift mechanism slips the clutch before the gear's start to move in or out of gear. That clutch operating is probably that "mushy" feel you detected (just an incidental bit of info). You should check the adjustment of that multi plate clutch. It's on the right behind the rear wheel, behind a bung. If it's not slipping enough they are hard to shift.

The real secret to good changes though is in A: getting the torque load off the gears at the instant you move the lever, and B: synchronizing the speeds of the gears.

The process when changing up is , give it a little extra throttle(more than you had been) just before the lever gets moved, so the bike is accelerating, then throttle off just as you move the lever. That way the bike and the engine are both under a sort of float condition, both are neither accelerating or decelerating.  The process when changing down is throttle off till the revs are low enough to change down, then blip the throttle just at the instant you are moving the lever down a gear. The throttling on takes the load off the gears you are in, and then brings the revs on the lower gear shaft up to the speed of the other shaft and gears. Depending how fast you are going at the time and the gears being shifted you sometimes need to give it quite a rev, but at low speeds just a little rev. 

Edited January 27, 2023 by Mech