Suzuki 2 Strokes

How much backlash is there supposed to be in the transmission gears? When turning the clutch hub is the countershaft supposed to turn immediately?

Smokie, what you're asking is "how high is the sky" ??!!??
When a tranny is new, yes, the c/s should start turning immediately when you start turning the main shaft......assuming it's in any gear.
As a tranny gets worn over the miles, you will get small amounts of clearance/backlash between the various gear faces. You will also get worn shaft/gear interfaces, worn bearings (both in the gears that have them and on the ends of the shafts. All this wear will "stack up" to give you a certain amount of total overall "lost motion" as it is called. This lost motion is the difference between when you start turning the main shaft and when the counter shaft starts turning. It is impossible to quantify how much lost motion is too much. Let's just say that this is a case where "less is better".
I'd be making a WAG here but I'd say that more than 1 degree rotation of lost motion on the input shaft would be too much......but that's just a guess.
I'm sure the tranny engineers in Hamamatsu could tell you exactly what that figure should be but up to this point in time those engineers haven't shared this info with anyone that I'm aware of.
Let's here more on this from you physics and engineering majors out there.....

I think im just being picky, the gears operate smoothly and everything went back together as it should. The bike has about 25,000 miles on it.

smokie wrote:How much backlash is there supposed to be in the transmission gears? When turning the clutch hub is the countershaft supposed to turn immediately?

I think there's a bit of clarification required here...

When the input (clutch) shaft is turned, there will be (depending on the gear and the relative positions of the two shafts) a noticeable lag before the output (counter) shaft turns.

This is because of the distance between the dogs (the tabs that stick out on the gears) and their respective mating surfaces on adjacent gears.
This is designed into the gearbox from the factory and is essential to make the gearbox work properly.
If you had no backlash or clearance between the two, you'd never be able to mesh the two together - there wouldn't be enough 'play'.

And, this play can seem quite significant. I reckon on some gear sets it's as much as 20-30 degrees of shaft rotation (I haven't measured this so I can't be too sure).
The backlash isn't very noticeable when riding the bike however. If you change gears carefully and gently, you'll never discern it, give the 'box a hard time and the thumping and clonking into each gear will give it away as power is applied suddenly.

Now... on the other hand, if there is movement or backlash between the clutch hub and it's own shaft, well then you might have a wear issue between the two parts.
There should be NO major noticeable movement or backlash between two splined parts.


Cheers
Paul

I see, so the dogs need time and space to engage properly, this is the "backlash" im feeling. And no, theres no play anywhere in either shaft. I couldnt believe the condition of the tranny, it looked new. All bearings,gears,washers, clutch,etc. looked in great shape. Now all I hope is that I sealed the crankcase good enough, dont want to do this over! Also the crank seals appeared to be in great shape (bike was running fine before the "incident"). I DONT like how I decided to install the left outer crank seal (after cases sealed) because I ruined 2 of them trying to use PVC and a mallet because they started in crooked. It almost seems like Suzuki never intended them to be changed that way.

It almost seems like Suzuki never intended them to be changed that way.

Suzuki DIDN'T intend for them to be changed that way. It simply CAN be done.



Lane

rngdng wrote:

It almost seems like Suzuki never intended them to be changed that way.

Suzuki DIDN'T intend for them to be changed that way. It simply CAN be done.



Lane

CAN'T be done...?

You could install a non-outer lip type seal, but what a PITA that would be with the crank in the way.

Can you get a decent seal around the outside with a plain seal?


Cheers
Paul

After the 3rd try I got it to go in straight. Yes, I used a standard seal-car quest actually carries the right size!