Thumper pumper tuning question

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May 24, 2001
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#1
Finally got my 35mm fcr bolted onto my KLX300 and am having a minor idle problem. Every 4th or 5th time I blip the throttle, the idle sticks up a tiny bit. Not real high, just higher than the last time. A little blip and its gone. When it is a bit higher, it doesn't drop back down until I blip it. My understanding is that if it is lean, it would eventually drop back down.

I've richened up the pilot fuel screw and pilot air screw to recommended specs by both Stroker and Sudco. If I go any richer, it stalls, so I don't think it is lean. Also sprayed carb cleaner all over the thing to check for air leaks, and no response from that.

So my hunch is that the slide just hangs up a tiny bit once in awhile. The cable has play so that isn't the deal.

Any ideas on eliminating this, or is it just normal tolerance and learn to live with it. My CVK didn't idle completely consistently either, so maybe I'm just too focused on it.

Thanks,

Mark
 

penguin

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#2
there might be some wear on the slide causing it to stick, or some dirt. when I first got my FCR, it was pretty dirty inside. Pull the top off the carb and take a look, it might just need a good cleaning. I was about to answer your question in the KLX group but I browsed over here and saw your post

Tom
 
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#3
Thanks Tom,

Guess I'll pull it off once more and give it a good bath. Should've done that before even putting it on, but wasn't comfortable taking it apart right away. Oh well. It is so much easier to put on with that klx250 manifold that I'm no longer dreading the thought of maintenance on it. Interesting that the 250 manifold has the exact same intake port size as the 300. It matches the 35mm intake spigot exactly. They put on a bigger carb, but didn't change the port size on the head.

Got some jetting specs from Spodekill, and they call for one richer on the pilot and needle clip. These were per Stroker with just the exhaust, so that may also be the issue. Time to start building up that jet collection.....

Mark
 

DougRoost

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#4
Mark, just keep in mind Spodekill had his FCR on a 365. He ran a Mikuni 33 on his 250, before he went to the 365, and a 36 on his son's 300 (Penguin's old bike). Penguin's FCR is on his 300 with Stroker pipe.:cool:
 
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#5
Dougroost,

To the best of Spodekills memory, the spec's from Stroker were for stock motor with just the exhaust. The specs are only slightly different from what I have (bigger pilot by one size), so this might be why I'm having the idle hitch. Bought a 48 pilot tonight, and of course, they gave me the wrong one. I even questioned them on it, and he insisted it was the right jet for the 35mm fcr. Unfortunately, didn't have the original with me, so my mistake for believing him.

Maybe tomorrow.....

Mark
 

penguin

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#6
Spodekill got that carb from Sudco. It came in a Sudco box with the Sudco receipt. The carb had been into before I got it, and it had a 45 pilot, which I changed to a 48. It helped the starting some. But when you change the slow fuel jet, you have to start changing the fuel screw and main air jet, needle clip, settings as well. it is a never ending battle. Try 1 change at a time and test if you try to change too many things at once, you will have it screwed up in no time, trust me on that one to.