Thursday, 19 May 2016

Sherco 290 2002 - Head Bearing Replacement + Fork Seals Replacement

My poor little Sherco is having everything changed at the momet as it seems to be falling apart!

The head bearings were knackered so I did a bit of shopping around and bought the 'All Balls' bearing kit for this bike. It seems to have a better quality of bearing, something I have learned a bit about in the last two years with KTM's!

The kit comprises of two tapered bearings: (M32004) and the tapered washers for them to sit in, then there is also the rubber washers and a big thick washer. Ignore that thick washer, or you'll have to do what I did and remove a newly fitted bearing to get it off!

I had the forks out anyway to change the seals and oil on them too, the yoke and triple clamp were ready to be taken out.

I undid the retaining nut then took off the top yoke, a big mallet saw the bottom yoke out and the bearings exposed.

Pretty pitted head bearing rillers

The top one just lifts out, but the bottom one is a compression fit, meaning it's bloody tight as!

After removing the top one I inserted a long bar into the hole of the head stock and tapped out the tapered washers at either end. Then it was time to get onto the bottom bearing.

I prised the outer race of the bearing off with a screwdriver, then tried tapping the compression collar off with a chisel and a hammer, no luck, it was stuck solid, so I cut it off with a dremmel, being careful not to damage the main shaft.

Once this was off, I cleaned everything and applied a light smear of grease, then mounted the new bearing. A quick ratch around Youtube found out a method for me with the tools I had on hand. I slid the large washer on, then the rubber seal and finally the bearing, then inverted the bottom yoke and put it loosely into the vice, a few taps with a mallet and hey presto the bearing was in place.

One thing I did learn was to really coat the bearing in a waterproof grease, seems it's best if you pop a blob on the palm of your hand, then force it into the bearing all the way round, then fit it.

This all done, I started to rebuild it all after I had seated the replacement tapered washers into the head stock along with a load of grease. (NB: Remember to tap the bottom bearing cup up into the head, it doesn't sit flush with the bottom but is slightly recessed into the head tube).

Here's where I found out that the All Balls fat washer was crap, I ended up having to cut the bottom bearing back off and replace it as the yoke shaft was now too small to get the headstock nut onto it!

Hey ho..

Back to the rebuild... I refitted the forks, these also a bit more shiny on the inside and outside after their service.

When fitting the yokes back to the head stock, there is a sequence, as with all bikes... see the pic below, the locking nut then plastic dust cover,then the top yoke all held down by the small nut, which should sit flush to the top of the shaft.

Torque Settings can be found in the Sherco PDF's Manuals HERE

Fork Service consisted of a strip down of the forks from the top down. Once you've got the forks out of the yokes, it's then time to strip them down.

1. Remove the blue air seal plastic cap on the top of the fork leg
2. Remove the 22mm Allen head cap from the forks, (there is an O ring under this)
3. Remove the tiny drainage allen bolt from the bottom of the fork, then the 8mm sunken allen bolt and drain the oil.
4. Gently prise off the dust seal on the fork leg and remove the sping clip under this.
5. Drop out the fork internals - be careful here, don't drop, damage or lose any bits and note their position.
6. Pump the top stanchion very hard a few times to lift the fork seal from it's bed. (This can be a pig to do on old stuck seals)
7. Clean everything and drain last of oil.
8. Clean it all again!
9. Replace it all back together once you've checked for damaged or worn parts. You'll need a good tool to get the seal to sit flush and tapped into place, (a long piece of plumbers pipe will do it I found!).
10. Refill with 270ml or 330ml of 5w fork oil. (Use the higher figure if you have stripped it all down)
11. Refit the threaded 22mm cap loosely into the top of the fork leg.
12. Re-mount the fork leg into the yokes and tighten gently.
13. Tighten the cap properly and put the blue air cap back in
14. Do the other fork leg now.
15. Once they are all back in place, use a torque wrench to get the bolts to the right tension.

Dust Seal and the Fork Seal

Done! Time to remount the wheels and go play in the mud and rocks again!