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'09 Sherco 320 4T Rebuild Blog

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Started really easy, first kick. Little throttle, no bog or lag. Adjusted air screw and idle. As the engine warmed, the bike started running poorer. The fan works. Spat a few drops of cooling fluid from the overpressure valve in the cap, but that seems normal to me on the first shakedown. Teeny weeny oil leakage from the valve side cover. Forgot if I used threadlock on the cam chain sprocket bolts, so will check those too while I'm at it. 

Had a few hot starts. Procedure seems to be:

Close fuel tap. 

Kick one time with half throttle. 

Kick one time closed throttle

Next kick starts the bike. 

This worked every time. 

Air temperature is raised to 15°C this weekend. 

Will keep the needle position, but go back to 42 on the pilot jet. 

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Found out I'm running a 102 main jet instead of 105. 

Changed a lot:

42 pilot jet (back from 45)

Replaced choke mechanism (from an OKO repair kit, had better seals against air leakage) 

Decreased choke jet bore (difficult to explain, but I crammed an O-ring cutoff inside the choke jet that's in the bowl, then created a small hole with a jet reamer. Highly experimental. Not recommended. 

Mounted OKO slide instead of the Keihin slide. (Fits snug, the Keihin slide has much more play, possibly letting through air during starting, when high vacuum is needed) 

Removed fuel filter (to prevent air in fuel hose) 

Set float height (it was a bit off) 

Replaced needle (had a nice shiny one in the OKO repair kit) 

Replaced and rerouted fuel line (previous hose developed a slight kink)


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Getting there! 

It started cold on choke this morning! 

When warm, choke off, no bog, no lag, instant power from idle. 

Better still, it hot started first kick... 

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Still had noise from the valve area. Managed to bugger up the valve cover seal while reassembling the camshaft side bearing cover. (You need to lift the valve cover to do this)
So, I bit the bullet, and started to disassemble the bike. There's a lot to remove to be able to get the valve cover off. 

While mounting the camshaft side bearing cover, I run my finger through the needle bearing hole, and felt a very loose bearing with a very rough bearing surface. You could actually hear it rattle while turning the bearing. The surface feels like constant dimples, it's like your childhood bike with a playing card through the spokes.

I ordered a new bearing, luckily it's not a press fit, and the old one pops out with ease. 
I'm very worried that this means new valve clearance adjustment, but at least another source of noise is eliminated.

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Got the new needle bearings in. The camshaft was raised by this, meaning I had to shave of about 0.05mm from the shims. Did this to great effect with a wetstone lubed with WD40. 

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You've made a terrific job of this.Youve even got it to start when hot,which most didn't,well done

  • Thanks 1

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Thanks! More luck than skill, I'm afraid, but it's always a gamble how modifications will work out. 

Got it running again today, after 8 months of just being pretty in the workshop. I hated this little job, and I learned not to start those jobs, if you're not mentally prepared and ready for it. 

Nothing more frustrating than to strip a bike you just assembled afters years of building it, and spending a fortune on it. 

In the mean time I just rode the old 290 spare bike we have. Luxury, and it's a nice vicious thing to ride and crash on. 

In the end, all it took were just 2 half days, to disassemble, repair, and assemble the bike. No more clunking noises from the valve/camchain area. It started third kick cold after I refreshed the fuel in the carb bowl. It runs a very solid dab-dab-dab, no choke required. 

Plan is to ride trial together with my youngest son (8) on his OSET tomorrow.

#Good times

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