Author Topic: 39mm PWK - Issue with Idle Screw??  (Read 2694 times)

PilotNut

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39mm PWK - Issue with Idle Screw??
« on: December 19, 2003, 01:39:30 PM »
I was speaking with the good 'ol boys over at ATV Racing about carb jetting when installing a 39mm PWK on a pilot. It was mentioned to me that one of the things that I needed to watch for when doing this conversion had to do with the spring on the idle screw - it may need to be altered (cut in half is what he said) in ORDER to get the Pilot to idle. Apparently the factory installed idle screw spring that comes on the carb will actually "bottom out" before you will be able to get the machine to idle.

I have never seen this specific potential issue mentioned before in any carb swapping posts/pages. If this is true, I can only speculate that some of the "I can't seem to get my machine to idle properly" posts may have been caused by an idle spring that was just too long?? I could see how something as simple as this could drive a person crazy when trying to troubleshoot why his machine would not hold idle after installing a new carb.

Has anyone experienced this??

PNut :?

dhjunkie

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39mm PWK - Issue with Idle Screw??
« Reply #1 on: December 19, 2003, 01:52:26 PM »
Not to be a jerk, but that sounds like a band-aid fix for a more serious problem. First, you shouldn't have to screw in the idle screw that far to begin with. Idle speed can be controled via the correct slide cut and pilot/idle jet combination. This is why there are many different cut aways on carb slides, every engine and rider have different settings. Second, it sounds like they didn't want to take the time to do a proper carb conversion (which is very time consuming and requires a lot of documentation) to help out the general public. Carbs are simple but they can become a nightmare, I suggest you study what part of the carb has a replacable jet, tube,needle,slide etc and see what and where it functions. Then see if there are alternate parts available (leaner/richer).
 It may end up being that there isn't a slide available with the proper cut away (bigger) and you may need to machine the existing slide a bit. If you go this route, carefully measure the slide in stock form and gradually cut away material. measure this amount and document it. This will come in handy when the slide wears out and needs to be replaced.

LiveWire

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Re: 39mm PWK - Issue with Idle Screw??
« Reply #2 on: August 22, 2011, 01:21:40 PM »
Although this is an old post, I thought it was good to point out the correct answer.

Change the 60 slow jet that comes in a 39PWK to a 45 and you will be able to adjust the idle just fine.