Starting Yamaha YZ-490:

Hi I recently acquired a 1987 Yamaha YZ-490 which I am finding very
difficult to start. You need to put boots on just to kick her over
since the sheer compression really hurts your feet. At any rate I have
been turning the fuel on at the tank, closing the choke (down on the
lever?) the Yamaha manual is vague, saying kick it until it sputters,
minding that I crank the kick lever until the piston is near the top.
I think that the choke should be off in the down position, the carb is
a Mikuni slide type. Any help here is appreciated.

Bush

 

Your motorbike doesn't have a real choke. There's no plate that closes
to make the carburetor suck air harder than normal in order to pull
fuel out of the float bowl.

Unstead, when you raise the lever all the way up, you are pulling a
valve open. There's a bypass passage that goes around the slide. Air
goes through the passage when the little valve is open. The air sucks
fuel right out of the float bowl.

This mechanism is called a "starting enrichener". If your pilot air
screw
on the side of the carb is set right, and the starter jet and pilot jet
in the float bowl is clean, the engine should start, or at least act
like it wants to start without you turning the throttle at all.

You might have to twist the throttle a little after two or three kicks,
but not on the first kick. An open throttle defeats the starting
enrichener. It can't suck gasoline if it is not the main source of air
flow through the carb...

In order to help the starting enrichener do its job, you need to turn
the idle speed screw all the way out, so it isn't opening the throttle
slide at all.

This maximizes the vacuum at the starting enrichener so it can suck gas
out of the float bowl.

 

Ed can you tell me how to position the choke?

Thanks,

Bush

 

Oky doke, I'll try it tomorrow and let you know, Thank you for helping
me.

Bush