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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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  • 6 months later...
 
  • 3 months later...

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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  • 2 weeks later...
 
 

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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  • 1 year later...

The 320 developed a bad habit of cutting out while stationary. You heard it running rougher and rougher at tick over, and with a big yelp would quit on me. Could live with that, if it would start the first kick after that, but it didn't. It would take 5 min of frantic starting, walking of frustrated, come back 15 min later, and having it running without trouble. 

Messed with the carb settings, but I was unable to get it behaving the way I wanted, and never got solid feedback from the motor on the air screw. (3/4 out). 

Not sure where to start, I stumbled on the Maikuni PWK carbs.

US $34.00 | Motorcycle Racing parts Carburetor pwk 21 24 26 28 30 32 34 mm PWK Carb With Power Jet Fit Scooter ATV Dirt Bike cub

https://a.aliexpress.com/_BTh7YK

Price was good, it looked the bizz, never mind the reviews, just order and see. I choose a slightly bigger one this time, 26mm. (the OKO was 24)

It's a quality item, different to the OKO in many ways. The gas slide was a perfect fit on this one, as opposed to the OKO, which had quite some play all around. 

Fitting it was a half an hour job, but could not get it to run using slightly larger jets. 

Tried 6 other configs, until there where signs of life. Settled for the Maikuni on a 35 pilot jet (38 on the OKO), and a whopping 115 main jet. (85 on the OKO). 

It likes a first kick with choke. Choke off, one kick, running very stable on low tick over. Generally speaking this carb seems to suit the bike very well. Instant grunt, easy starting, also when warm. 

We will see if the cutout problem has been solved with this mod. 

The CSP Air screw is 1 1/2 turns out, and bike responds well to changes.

Jobs left to do: there's 1 cm (1/2") of rear wheel suspension play at the bottom, probably because of linkage bearing play. Have a set new ones laying around. 

Might top it off with a new TRP shock. 

Edited by proper
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  • 3 months later...

Hola volviendo a Sherco 320 cc.Que opinais de que esta moto chorree aceite por un tubo grueso que tiene en la tapa de balancines? cuando digo chorro es bastante cantidad.Incluso me ha llegado a manchar la camiseta.El caso es que no estaba caliente.

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  • 4 weeks later...
On 1/1/2021 at 4:30 PM, proper said:

The 320 developed a bad habit of cutting out while stationary. You heard it running rougher and rougher at tick over, and with a big yelp would quit on me. Could live with that, if it would start the first kick after that, but it didn't. It would take 5 min of frantic starting, walking of frustrated, come back 15 min later, and having it running without trouble. 

Messed with the carb settings, but I was unable to get it behaving the way I wanted, and never got solid feedback from the motor on the air screw. (3/4 out). 

Not sure where to start, I stumbled on the Maikuni PWK carbs.

US $34.00 | Motorcycle Racing parts Carburetor pwk 21 24 26 28 30 32 34 mm PWK Carb With Power Jet Fit Scooter ATV Dirt Bike cub

https://a.aliexpress.com/_BTh7YK

Price was good, it looked the bizz, never mind the reviews, just order and see. I choose a slightly bigger one this time, 26mm. (the OKO was 24)

It's a quality item, different to the OKO in many ways. The gas slide was a perfect fit on this one, as opposed to the OKO, which had quite some play all around. 

Fitting it was a half an hour job, but could not get it to run using slightly larger jets. 

Tried 6 other configs, until there where signs of life. Settled for the Maikuni on a 35 pilot jet (38 on the OKO), and a whopping 115 main jet. (85 on the OKO). 

It likes a first kick with choke. Choke off, one kick, running very stable on low tick over. Generally speaking this carb seems to suit the bike very well. Instant grunt, easy starting, also when warm. 

We will see if the cutout problem has been solved with this mod. 

The CSP Air screw is 1 1/2 turns out, and bike responds well to changes.

Jobs left to do: there's 1 cm (1/2") of rear wheel suspension play at the bottom, probably because of linkage bearing play. Have a set new ones laying around. 

Might top it off with a new TRP shock. 

I am sorting out my 2008 320 4T here near Roosendaal - and was considering the OKO 24mm (38 PJ, 85 MJ) vs the Maikuni 26mm (35 PJ, 115 MJ).

Any further recommendations or updates on replacing the stock Keihin PWK 28mm (50 PJ, 122MJ, JJH Needle 3rd clip)? Local Sherco supplier is Peter M @ PMTrials and Splatshop.

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Nope. I'm still running the Maikuni on those jets. 

Experienced one instance where the bike refused to start. Didn't feel like pressing on, had others things to do on the club, so I left it. 

Started it next week without trouble. Guess we all have an off day sometimes.  
 

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