Need help. Where to start

[Wypipo]

Thanks for all your help. Yes it feels good to be getting close. That black screw thats higher up on the carb...fuel screw? Any reason to ever adjust this? Not many things I have read or watched mention adjusting this screw but it seems like some people do?

 

[Davehuge]

The black plastic screw with a spring on it?



That's the idle speed adjustment screw. Basically if you screw it in it lifts the throttle slide (as if you were twisting the throttle) and the idle speeds up, screw it out it lowers the slide and idle speed slows.

There's no Fuel Screw on the PWK carb.

 

[Wypipo]

So this will come in to play then when I?m trying to base my pilot size off of idle speed?

 

[Davehuge]

So this will come in to play then when I?m trying to base my pilot size off of idle speed?

Not sure what you mean?

But from what you said previously, it sounds like you've got the correct size Pilot Jet. Once you have the correct size Pilot Jet and the Air Screw set THEN you can adjust the Idle Adjustment Screw to speed up or slow down the idle speed to suit.

 

[Davehuge]

By the way...where in the world are you?

 

[Wypipo]

Ok I see. I was misunderstanding it. So it does not have any effect on the fuel/air mixture.
I am in USA

 

[Davehuge]

Ok I see. I was misunderstanding it. So it does not have any effect on the fuel/air mixture.

That's correct, no effect on mixture.

Well done, sounds like you've learnt a lot about your carb in a short time. Good luck with your racing!

 

[RudolfHucker]

On the setting float height debate, I have always found this to be a nightmare and fundamental to setting the baseline for all the rest of jetting set-up. I'm surprised that Keihin don't have an info sheet for this.

This is the only video that I have found so far that seems to give a straightforward and no-nonsense approach that is sufficiently idiot proof for me to follow. It also seems to concur with the basic set-up info in the KTM engine workshop manuals.

Ignore the 1st section and start at 3:08 for float height setting. 4:30 onward details vent hose rerouting if that is of interest. Nothing particularly new here but valid advice.

See what you think:

https://www.youtube.com/watch?v=96949V9hdVc

 

[Davehuge]

Looks a good video, I think it's important to make sure the tang on the float just touches the spring loaded pin on the float valve, but doesn't depress it when it's at the correct height.

However, I don't agree it's a good idea to loop the carb overflow pipe 'up and over' as he's got it...if you look at it, the fuel level would have to be pretty high before it would run out of the overflow. Effectively, it's increased the overflow height, there's a chance it would flow into the reed block/crankcases before it could flow out of the overflow pipe.

 

[Jat]

Float height

I use an old drain plug with a clear hose connected through a hole drilled into its base, hold the hose up by the side of the carb turn on fuel and you can see the fuel level.the downward angle of the carb on these bikes makes finding the sweet spot hard.