Gearbox problem? Bent shift fork?

[sherco12345]

I have a 125cc 2007 Sherco. I can move the gear lever all the way up and down without finding any gears, if i acually find a gear and try to give it some throttle it will immediately slip into neutral. So to access the gearbox and the gear lever mechanism, do i need to split the motor?

Mabye a bent shift fork?

Thanks! 

Edited July 4, 2017 by sherco12345

[tony27]

Could be something as simple as the spring in the selector mechanism.

Remove the clutch & primary cover to check the condition of the spring fitted inside the mechanism on the end of the gearchange shaft, part number is M111.

The other spring to check is the 1 that keeps pressure on the indexing cam, part number M117

Both of these parts are outside of the gearbox & easy to check once the clutch is off, both are only a couple of quid

Sherco gearchange shafts have a weak point built into them that lets them break rather than damage internal parts so I'd be pretty confident that a full motor split will not be required

Have a look at this diagram & both springs I mention are on the left

http://www.splatshop.co.uk/Parts-Finder/Sherco/2009/290/Gear-Selector/

[sherco12345]

Thanks for the reply! 

How do i proceed to remove the shift shaft? 

[tony27]

Remove the primary cover, slide the spring loaded piece back so it clears the drum & it slides out.

From what I can see both springs I mentioned are still in place but I would still be checking everything in that area. Make sure all the pins on the end of the drum are still good & the capscrew is tight

[tony27]

If I can find the parts I'll show you where the engineered in weak spot is, basically the mechanism that grabs the pins on the end of the drum is only welded on the 1 side & the shaft is turned down quite a bit.  

I snapped the shaft on my first Bultaco branded Sherco & have twisted at least 1 other. When you twist the shaft at the weak point the lever hits the bashplate so getting first gear is a problem, can't remember if it affected changing down but I expect so, haven't had a problem since I fitted the short type lever 

[sherco12345]

Thanks for the help, but it doesn't seem like this was the problem.

I guess the next step would be to check the gearbox?

[tony27]

The photos of the broken selector, does anything look different to your's?

Before getting further into the motor I would be refitting the gear change shaft & operating the lever while watching what goes on at the indexing plate, you will probably need to spin the rear wheel or fit the clutch holding nut to the end of the shaft & use it to turn the gearbox 

If the shifting side is working properly you will see the spring loaded roller drop into the next recess around

I guess it is possible that the pin in the end of the selector drum has broken so the cam isn't moving it properly, easy to check by removing the capscrew in the centre of the indexing plate & taking off the plate. Have a look at the photo of the selector drum in the link above by clicking it & you'll see what the end looks like

I was hoping 1 of the guys from Splatshop may have been in here by now, they're definitely worth asking what they think is the problem 

[sherco12345]

I was on vacation this week so i havent done anything more to the bike. But i was out in the garage today and i think i have found the problem. The weld on the shift shaft seem to be broken, allowing the gear lever to be moved freely without changing gears.

What oil do people use in the clutch house?

Thanks for helping!

Edited July 13, 2017 by sherco12345

[tony27]

Simple fix then, a lot cheaper than needing to strip motor down