help! 22-cent mod renders motor non-running!?!?!? ('99 klr)
Posted: Mon Apr 07, 2014 11:56 pm
Engine had been running fine for years and several thousand miles (13,XXX miles on odometer). I'd had some off-idle stumble so I'd exposed the mixture screw and opened it up. It worked best at 1-1/4 (1300 RPM IDLE; I ride at sea level), which helped but didn't entirely fix the stumble.
A few months ago I developed a new problem: freeway cruising above 5000 rpm, motor would start to miss. First just occasionally, then increasingly, missing more and more cycles at a time, until it felt like a bucking bronco. Though the problem never began under 5000, once it started, slowing down to under 5000 didn't fix it. I'd limp home, go out the next day and again it ran fine until I cruised over 5000, then the problem started again.
I discovered this in fifth on the freeway, then tested in fourth and third and got the same problem: missing started just over 5000 rpm. (My countershaft sprocket is 14 teeth; 5000 is 65 mph actual.)
I thought I'd check the main jet. It looked fine, even under the magnifying glass, but I soaked it with a denture-cleaning fizzy on general principle. My amateur eye didn't turn up any problems with the carb,but I didn't go over it thoroughly.
But while I was doing this, I also did the following;
-Installed a new spark plug, NGK DPR8EIX-9 (Irideum), .034" gap;
-Installed the Big Cee gravity feed petcock kit;
-Installed a new length of 1/4" fuel line;
-Drilled the forward hole in the bottom of the slide to 7/64";
-Installed a #4 SS washer, .032" thick, under the head of the jet needle;
-Installed a new float bowl gasket, with Copper Coat in the groove of the bowl and grease on top of the gasket;
-Installed a CV Performance EZ-Just mixture screw, with new O-ring, washer, and spring. Started with it two turns out.
Result: motor stumbles and dies if I try to rev it from idle. If I start at idle and very slowly open the throttle, it'll get to 2000-2400, then die. Once I was able to rev it up, and it stumbled like crazy (puh-POP, puh-POP, pub-POP), then died.
It did this at every mixture screw position from one turn out to four. I switched back to the OEM mixture screw: no help. (I re-installed the thumb screw). I checked that I'd re-installed the slide frontwards (drilled-out hole toward front): I had. Then I removed the washer from the needle: no help!
The carb is back just the way it was before I starting messing with it, except for the hole in the slide. I can't believe anything I did (intentionally) caused this. But I can't find anything I broke or put back in wrong, or didn't put back in at all. Can anybody tell me what to check next?
Any suggestions appreciated. And the weather's just getting good here, too!
-James