98 ec250 carb and jetting

[OKFiremanMark]

I fouled the plug in my 98 250 the other day and so I started looking into all the jetting threads here on the site. Not much here on that old of bike. Today I replaced the plug and the bike runs great, but I thought I should check what the current jetting is. I pulled the carb and this is what I found. It is a kehin pwk and it has S54A3 LG stamped just above the bowl. Main jet 165, pilot jet 35, needle n1ec in the fourth clip from the bottom, slide #7. Air screw is about 2 1/2 turns out. This is a smaller main and pilot than any one else is running. When I got the bike, I checked the plug and it was definitely darker than paper bag brown, but not too bad. So my question is... Is this a different carb than is on the 2003-5 models where everyone is running a 172-180 main and a 38+ pilot? Altitude here is around 1500 feet. The bike runs great but there is a slight hesitation just off idle. The plug was definitely wet fouled. It ran great earlier that day, I got home and hand washed it. About an hour later I fired it up, (2nd kick) and made it a couple blocks down my street and it bogged down and died. I was keeping the revs down so I would not bother the neighbors. Any advise would be helpful.

 

[Rick]

I'm sure we have the same crab 38mm PWK AS1. My 200 uses the same model.
178mj
40 p or 35 p
Slide#7
needle LTR
Air screw 1.75 out
S54A3 MJ

I would check your reed pedals and cage gaskets. Look for cracked,, chipped or reeds not sealing tight against the cage.

Float height

Pull the plug and kick it over to ensure your getting a nice dark blue spark jumping across the electrode. Verify spark plug gap.

Dose the crab leak gas from over flow drain tube while on a stand or on the side stand? If so adjust float height. If it still leaks remove the floats and check for gas inside the floats. Check float needle valve and o ring for wear. The rubber tip can be worn down allowing fuel to continue flowing when the floats should be closed.

Check your transmission oil....is it low? Your jetting seems really lean....does the bike smoke? If so what color? Could be pulling transmission oil into the combustion

Hope this helps.

 

[OKFiremanMark]

Thanks Rick. The bike was leaking out the overflow while on the side stand when I got it, but I adjusted that a month ago and have ridden it several times with no problems.

I have not checked the reeds yet, but I will put that on my list.

I changed the transmission fluid about a month ago as well, and it does not appear that it is any lower now than when I changed it.

I am currently running yamalube 2r at 36:1. It is the only thing readily available in my town. I was not sure what the previous owner used or at what ratio. The bike smokes when you start it, but not excessively. Once it warms up, it does not smoke as much. I have almost zero spooge. Like I said, it really runs well, the only complaint is that it does hesitate a little just off idle. It pulls hard all the way from there. I am going to play with the air screw and see it I can make an improvement there. It idles perfectly and will for at least a minute. I have not tried to let it go any longer than that. It also settles in to its idle very quickly.

The lean jetting is what prompted me to post. It sounds like my jetting should be closer to yours and most everyone else. What bothers me is that the plug looks a little too dark (rich). Am I putting too much stock in the condition of the plug?

 

[Neil E.]

Do a compression check just to be sure the rings are good. If the compression is low, the jetting might have been leaned out to compensate for worn rings.

 

[OKFiremanMark]

I think the top end is pretty new, but it wouldn't hurt to check. What would be a good compression range?

 

[Neil E.]

150 on the low end, 200 on the high end. Most are in the 180 to 190 range.