stripped the engine down today and removed the crank, found some really dodgy stuff.

After removing the clutch and then the engine cover i found a washer and dowel in the bottom of the gearbox, had a look where the dowel could of come from and it shows one in the clutch basket, which is still there and two others behind the oil pump drive gear, except there is no oil pump drive gear??? there is nothing there. i have looked a million times on the exploded diagram of the dry clutch assembly, and the whole drive gear assembly is not present, it shows a gear with two orings and two dowels behind it, has any one come across this before? in addition the clutch is only running on one needle bearing and there is no ball bearing present in the clutch push rod assembly.

i'm beginning to think i'm going mad, i thought the oil pump worked off the same shaft as the water pump, which is driven by the primary gear??



I cant work out what the

Sounds like it's been converted to run pre-mix...
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hi dave, no nothing to do with tghe 2 stroke oil system, this is the drive gear that moves the gearbox oil around, not something you'd easily miss refitting just wondered if for any crazy reason people left them off?

and if not does anyone have one spare, the steel washer in the gearbox was just plain scary though!

The gear box oil pump runs off the back of the clutch basket.

Not good its missing. You will need to strip the box down and make sure its ok. I think I have a few spares of them kicking around though.

There should also be 2 needle roller bearings in the clutch hub. That won't of been doing anything any good if one of them was missing. I'm sure I have a few of them kicking around too!

Yes there should be a ball bearing on the end of the clutch shaft, under the top hat.

There are also dowls behind the transmission plate. If I recall 2. These locate the plate into the crank cases. It might well be one of them.
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If I have to take the carbs off once more...

What's the ball at the ned of the clutch shaft do?

It reduces the friction of the spinning clutch pressure plate/top hat onto the clutch push rod.

If you dont run one the rod ends up welding its self into the top hat. Go on. Ask me how I know
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If I have to take the carbs off once more...

I think I'll be in for a beating if I ask!

Does the ball need any lubricant on it?

The balls should always be well lubricated!
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nxrsr20 wrote: I think I'll be in for a beating if I ask!

Does the ball need any lubricant on it?

The ball gets gear box oil from up the center of the input shaft where the clutch push rod runs. The shaft is then sealed with the O ring(s) on the top hat to stop the oil getting onto the plates (dry clutch).

And yes, lubed balls is the way to go!
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If I have to take the carbs off once more...

o o


Last edited by DifferentStrokes on Mon Sep 28, 2009 11:05 pm; edited 1 time in total

ok time for the next installment of name that gearbox bit and the everpopular why is that part not fitted.

Thanks to stephen i now have a pump drive gear, cheers again stephen.

in the bottom of gearbox as prev mentioned was a steel washer (the dowel turned out to be one from aforementioned unfitted drive pump), the washer has 15mm inside diameter and 25mm outside, any ideas where this little bugger can of from?? other than assuming its a foreign visitor. i've checked the manual and cant see any washer that could easily find it way there?

Next thing, the water pump shim / washer, is it plastic and grey in colour and a bit over size, cause this one is and i cant quite make out the picture in the rebuild section

just a couple more.....

as i took the gearbox out, the end cog on the main shaft fell off, after checking the manual it looks like there should be a special washer fitted between it and the bearing in the case, does the washer just act as a spacer or does it hold the cog captive to the shaft? i've ordered one from lings but am interested to know.

And finally the plate seal is missing from the gearbox plate, (its like a shielding piece) does anyone have any spare or could confirm if it is safe or not to run without it??

Sorry for all the questions, its difficult when what you start with is not right, to know how things should be.

The washer you might well be the shim from the water pump gear.

I have a gear box sheild if you need one.

The washer on the end of the gear box shaft is just that, it does not retain the gear.
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If I have to take the carbs off once more...

Washer may be off kickstart mechanism.

yeah there is on on the back of the kick start mechanism and it is present, there is also one on the front held in place by a circlip which is also present, this one wouldn;t even fit over the shaft anyhow,

So i'm left with two washers, a steel one and a plastic one, and only one visible place that needs one (water pump shim)

going off the manual, neither are the correct size, allthough i do think the plastic one had been used as the shim.

I'm removing them both anyhow.

After more looking and cleaning last night I also saw the 8x18mm gearbox plate locating dowel was missing, no biggie but makes life easier with it, discontinued part now so i'll make my own using the end of an 8mm drill bit.

Top end kit is now sat in the garage thanks Matt.

just for an update stephen, the new gearbox washer I ordered arrived today.

It has two raised portions on it so you have to gently force it down the shaft until it sits into a little groove and does retain the gear, that fell of when i removed the gearbox.