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Sherco 2.9 2002 leaking clean oil from carburetor

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Hello,

anybody had this problem? my Sherco 2.9 is constantly clogging spark plugs. I believe fuel/air mixture is ok. however it  smokes like we are putting double the 2T oil in fuel.  it takes 1-2hrs and the spark plug goes all black and fails to work. bike doesn`t really have sharp response. i was planning to check the left side crankshaft seal, until i found that from one of the hoses of the carburetor (top one) leaks pure oil. I am really wondering how this is happening. it creates like 20-30ml of oil on the ground for 48 hrs. is there any chance that oil in the transmission enters the carburetor?

thank you in advance!

sherco leak 2.jpg

sherco leak.jpg

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 The only way it could enter the carb is if the engine vent was connected to it. Take more pictures.

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My guess would be a carb float issue as that looks to be an overflow. All it could leak is fuel, but when it evaporates it will leave oil behind so it could be mistaken for an oil leak.

This would also cause over fueling which would cause smoke and foul the plug. 

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As far as I know gearbox oil has a significant smell when burned and should easily be detected. Totty79 seems to have a good theory.

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That is a vent for the float bowl not a overflow. If that hose is run low on the bike it will actually suck water up the tube if you ride in water. That hose should be routed high on bike.Over flows come out below ventura so if the float needle fails the fuel does not flood into carb.Also check your reed valves as if they are worn and not closing all the way you may be getting blow back into carb.Ussaully when reeds are bad bikes are hard to start and acts like it is flooding out.

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Carb flooding,check the float and float needle valve shuts off  the fuel.Is the fuel consumption really high?

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hello guys,

thank you for the feedback. I was finally able to disassemble the bike today. last time we rode the bike it died totally. it was leaking oil from the crankcase vent under the cylinder. here are the answer to your questions:

- valve float closes 100%. valve is moving smoothly. however i am not sure how to measure the closing level, as there is no option to keep the fuel inside the bowl as the bottom screw is draining the fuel when being unscrewed? 

- exhaust has the awful smell of oil ( gearbox oil)

- bike was very difficult to start

- i removed the reed valves. nothing is broken or cracked. i don`t know how to check them properly, so i sucked with my mouth and it seems they are ok, but i plan to install new ones

- it was very interesting that the crankcase was full with about 150 ml of fuel. i guess the last 2-3 minutes of riding the engine wasn`t able to burn most of the fuel, or it was overfilled by a faulty carburetor.

my main concern is the crankcase seal. what i did is that i disassembled the clutch and found out the crankcase seal was a bit sideways, very loose and also i believe it was installed the opposite wrong way. could anybody confirm how it should be. and in case someone can send me a service manual would be great! :)

i disassembled completely the carburetor and everything seems ok  here are the size of the jets:

main jet - 70

jet in the lower bowl screw - 124

pilot jet - 33

choke jet - 60.

could anybody confirm the original jet sizes.

what i also noticed is that the choke wasn`t closing 100% when disengaged. i was blowing with my mouth through the choke jet (choke closed) and air was able to pass by the small rubber seal. is that normal, should it close 100% or  not?

thank you guys in advance , your help is highly appreciated.

cheers

Ves

 

 

IMG_8515.JPG

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I just got back from jet skiing for a week. Nobody has a reply? The early SHercos would spin the mains in the case. I would do a complete tear down.

 The fix is ti peen the bearing location on the cases to get it to hold.

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