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'09 Sherco 320 4T Rebuild Blog


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I tried a 6.5mm drill bit first,  since the original shaft measures 6.4mm. Still too much play.  Then I tried a 6.6mm drill bit,  and this looks to be about perfect.  

First,  the holes in the rocker arm will be drilled to 6.6mm, then I'll grind a new shaft to the correct length from this cobalt drill,  then TIG weld it back in the rocker arm. 

IMG_20170321_215059272_zpsmzjsjnkx.jpg

IMG_20170321_214852179_zpswoayl9ay.jpg

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Hi there got the same problem,have just ordered New rocker . Let me know how you go with the welding looks very intricate, would it be difficult to make sure you avoid touching part of one of the roller ends , I am familiar with welding through work just not tig .very interested to hear how you go ,good luck regards steve

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@ralphy: Thanks Steve!

@Copemech: The part of the rocker where the shaft/wheel is, has very thin walls. It's also made from very hard/brittle material. The cobalt had great trouble drilling the hole up 0,1mm.  

I'll guess pressing the new shaft could work if one hole is identical to the shaft size, and the other hole a bit tighter. Then I'll not risk cracking/bending the first rocker side wall. Also, if the shaft and the rocker are both from very hard material, pressing with 0,1mm hole size difference might not work. 

I'll see how I get along. 

Yesterday in the shop I wondered how to cut the cobalt drill bit, without going through 5 angle grinder cutting discs. For over 10 years I have a reinforced fibreglass cutting disc on my trusty wireless Dremel that has seen some pretty impressive abuse without obvious sign of wearing out. It cut the drill bit like butter....

(https://www.dremel.com/en_US/products/-/show-product/tools/426-1-1-4-fiberglass-reinforced-cut-off-wheels-5-pack)

  

 

 

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  • 2 weeks later...

As much as I would like to say good progress has been made, the reality is I'm two steps back.

I've handed over the exhaust rocker to my TIG welder, giving specific instructions about using minimum amps, and earthing the piece in such way, the current would not flow through the needle bearing. You can imagine my disappointment after I got the rocker back with a seized bearing with obvious signs of current passing through the roller. 

I have thought about grinding the shaft out again, to see what can be saved, but now the most sensible thing to to is just order a new rocker. What a bummer after all this work.  

Up next was the exhaust. Cranked up the air pressure to 4 bar, and it turned out to be leaking at at least a dozen spots. Most notably, all weldings of that additional damper box where cracked. I considered drilling out all the leaks, welding them up, and try getting the dents out, but it's just no good. Most sensible thing to do is just order a new exhaust. 

I needed a bunch of gaskets anyway, so Splatshop received another big order from me. They still have the best price on the parts I need, and their webshop is by far the best on the net for Sherco parts.  

Turned my attention to the swingarm. Looking at it, it just begs to be polished. Some local shop carried an angle grinder with adjustable speed. Just the thing I needed. After some fiddling, I got the hang of it:

- Grind the surface with 120 grit flap disc on low rpm (maybe around 4000 - 5000). Even deep scratches can be removed easily.

- Polish the surface with a combined grinding / polish flap disc. (http://www.cibo.be/en/products/gamma/flap-discs/rcd-conical?l=en)
This disc is magic. Without any effort, the rough surface is polished to a dull shine. It's quite durable too. All kinds of small scratches can also be removed.

- Treat the surface by hand with a pad of red Scotch Brite using Belgom Alu polish (http://www.thepolishingshop.co.uk/acatalog/Belgom.html). The whole surface turns black from the alu polish. 

- Using a big Polishing Mop in the hand drill a mirror shine appears within minutes. No polishing paste is used, just the Belgom applied earlier.

I'll post some pics of your royal shineyness soon. 

Also tidied up the bash plate, but unfortunately the angle grinder speed control broke down.Need a visit to the shop to claim warranty.

Greetings,

Vincent

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Hi there sorry to hear about your attempt to fix your exhaust rocker it did look a difficult  and tricky job , it's not a good design and is expensive for what it is , including mine i'v heard of 3 or 4 exhaust rocker faults with this bike ( it's not like the bike is popular or common ) . anyway I have just received new rocker ( 163 Australian dollars ) will attempt reassemble soon as , just hoping shims will be ok I have kept old shims so have choice of 3 sets if not will order new . Good luck with yours 

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Thanks! The forces on that rocker roller are huge. Still, the inlet valve rocker seems fine. It has to be oil or temperature related. Anyway, I'm waiting for my valve shims to arrive by post. In the meantime the new red anonized footrests have been greased and mounted on the frame. I used a single copper washer to get rid of the axial play. 

Next up was the usual mayhem called rear suspension link system bearings. Just when you think you've had all of the rusty seized needle bearings cleaned, oiled, cleaned, oiled, loosened up the bearing, cleaned, oiled, cleaned and greased, and patched up all the shafts and bolts, another bearing seems to appear out of nowhere... But this has to the one job where you'll notice the biggest improvement while riding. (But a sorted front fork goes a long way too)

The rear shock spring has been sand blasted, zinc coated and spray painted white. I used Motip Wheel spray, which should give a nice glossy petrol and scratch resistant finish.

Mounted the new side stand on the swingarm. Greased all the moving bits, and some copper slip to the base. Took a while before I figured out how to mount that massive side stand spring. Luckily I had a spring puller tool, otherwise it would have been near impossible to get it done. 

Also, a new rubber chain guide plate, tyre guard and S3 chain tensioner are mounted.

Need some fresh new nuts and bolts before the rear can be assembled.

Pics will follow soon!

 

 

 

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Another set back. The frame was standing on a hydraulic bike lift on the highest level. Yesterday I placed the rear wheel next to the lift, as I was planning to do some work on it. Imagine my horror as I entered the shop today, finding my frame on the verge of tipping over, and fully touching and grinding the work bench. It seems like the rear wheel touched the bike lift foot pedal, slowly but surely lowering the lift. At some point, the lift platform touched the rear wheel, preventing it to go lower on that side, tipping the frame towards the bench. It's really unbelievable this happened.

Was it coincidence I ordered a fresh can of black metallic 2 days ago, and got it delivered today?

The damage, of course, is right in eyesight. It will be difficult to repair this in a such a way you can never tell it ever happened. 

Repeat: I like bike projects, I like bike projects, I like bike projects. That's much better.

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I took the OKO wannabe carb apart to check for the things described here:

http://www.miniriders.com/carby-and-tuning/26815-keihin-pwk-copy-carb-mods.html

It turns out my carb is actually quite good:

- It has the big  hex drain screw in the fuel bow. That's good.

- Has the required 8 holes in the main jet holder. I did find one hole that wasn't neatly finished. Drilled it out with a 0,8mm drill bit, sorted.

- The big float valve is there.  All good.

- It has the 2 holes at the side of the float valve boss. 

-  The D slide is indeed a low quality item. The chrome finish is lacking quality . But the slide from the 28mm Keihin is identical in size and fits my OKO without any problem. In fact, the whole assembly of D-slide, needle, spring, cable and cover fits on the Chinese OKO. Problem solved.

The needle from the Keihin is thicker. Mental note to self: replace needle in case of problems.

So far so good.

 

 

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  • 2 weeks later...
 

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