I did a basic carb gasket kit on my KA 100. It was running great, with only about 4 hours on it, this was only done since everyone recommends doing it. (I should have just left well enough alone). Popoff was 10, holding about 7-8. I also marked the jet positions, cleaned it out, did not remove anything but the gaskets, and high and low jets, then and replaced everything EXACTLY as it was following the power republic YouTube video.
The kart fired right up after the rebuild but ran like garbage on the track with very poor pull, and would not rev over 13000, it had high end cut outs, big time, so I messed with the high speed needle, then low end cut out. Messed with the low speed and finally got it running ok but it will only run with the low speed 90* richer now (15 minutes from where it was). Kart runs strong here and I put down my fasted time of the day, but why would the low speed be THAT far off? I pulled everything apart and put it back again to check for anything off, but it was all normal. I thought this carb only required 2-3 minutes adjustment either way—max. Now it is 75 minutes out, when it was at 59 before the rebuild.
Also the popoff is now 12, holding about 9 now. Why would this change with a gasket kit? Is this the reason for my issue on the low speed? I literally did not touch or remove the needle and seat. I thought this was only adjusted with spring pressure or bending the little tab (which I didn’t touch).
Thoughts? Should the low speed ever be this rich? Or is something wrong?
If its not the needles…..I know you said you followed the video, but you may want to take it apart and check it all again. I have screwed up the order of the gasket and flapper and the gasket and diaphragm too. The clue is it doesn’t run right.
Thanks for the replies— it’s not the needle mixup, I pulled them out one at a time and put them back in before doing the other one so I couldn’t mix them up. The gaskets are also in the correct order, triple checked. I was hoping this is what it was.
Could the popoff moving higher (for some strange reason) cause my low-speed to need to be so rich now? It runs great now, strong as ever. I just don’t understand why my low-speed needs to be 15 minutes richer all of a sudden. Both were set very close to 60 minutes before.
Now high speed is at 62 and low speed is at 75 minutes to run clean through the whole range, max out rpm, an max EGT at 1250 ( heavy duty sensor). If I put the low speed back at 60 minutes (where it was) it has no power and won’t rev out. It feels like a rental cart.
Pop off shouldn’t change if you didn’t remove the fulcrum and spring. Pop off is just a measure of how much pressure is needed to overwhelm the spring and allow it to open the fuel delivery needle. If you are checking the pop off with a dry carb and then again with fuel in it, I suppose that could reult in a change.
I generally don’t touch the low speed needle much but the high I would say it is not unusual to adjust 15 min in or out. Have you tried the low at 60 and open the High?
I acidently installed the reed cage on my ka100 upside down one time and it ran really funny. Maybe check that. Also if you had the carb off double check to make sure that it seated back on all the way, sometimes it can get wedged a bit and there will be a gap between the carb and reed cage.
The stack could be right but the pumper and diaphram gasket could still be installed upside down and cause running issues. Make sure they are not inverted despite being in the right order.
otherwise take the low jet out and blow a bunch of brake clean and compressed air through it to make sure there’s not something stuck somewhere in the passage, 75 minutes is far too much for any senior KA carb i’ve ever come across.
The popoff shouldn’t change from just gasket changes in the carb but as noted above the testing values are only as good as the procedure. There needs to be fuel around the needle when testing so if the intitial tests were dry vs. wet the results could be off. Increase in popoff would make the low end leaner but I doubt it’s the cause of what you’re seeing here.
Follow up - finally figured this out - pulled both needles all the way out and reinstalled “again” (they were in the correct locations) but for some reason taking them fully out then putting them back for the fourth time fixed the issue. There must have been something slightly off with that little o-ring in there or something because the low speed tuning went back to normal range settings of (60 min instead of 75) and performance/lap time/even peak RPM increased very noticeably.
Glad you figured it out! Just for future reference, another gotcha I’ve seen is someone double stacking the o-rings. Pulled the needle and the old o-ring was still in there. So running it home to zero before backing them out was off.
