Post by urbanmadness on Jan 23, 2014 1:25:34 GMT -5
So my little 250 hasn't had a good idle and just hasn't been performing well. I already know I'll be replacing the carb soon, as the ACV on it leaks vacuum so it's disconnected and the line is plugged for now. The ACV keeps them from poppin' when the throttle is closed.
When I do the carb, I'll also do the intake manifold.
So anyway, I figured, that since I'll have to ride it for a couple of months before I can spend more money on it, I decided I'd pull the carb and see what I could do to make the bike run as well as I could with what I had.
I started by pulling the float bowl and took a look at the main jet in the bike. It was a #107. This is way, way too small. A 107 is lean, even for a 150 and this is a 250. I took a look at my collection of junk and stuff, and found I had a #109 and a #115 jet, so it was off to the Helix forums to see if I could find what these guys were using as a base line.
From what I read, the Helix runs a bit lean from the factory as well with a #110 jet. Many of the Helix guys put in #115's on there stock bikes with good results so, I put the #115 in, set the a/f screw to 2 1/4 turns out (also per the Helix guys), pull the diaphragm and set the pin on notch down from the top (leaner) put it back together and fired her up.
Much much, can't believe how much better. The bike really came alive and the stupid flat spot off of idle is completely gone. The only thing is setting the idle speed is a bit ugly. This is probably because of the ACV and I wouldn't be surprised if the intake manifold was leaking a little.
What I finally did was let it warm up, set the idle speed. The only problem is when it's cold, it idles way too fast. So the strategy, until I can replace the carb and intake manifold is to let it warm up on the center stand for about 2 minutes before riding it. From there, it's butter.
Oh a tip for would be CF250 tuners.... the 250 uses the same jets as a 150 so, if your scooter shop/distributor doesn't have 250 parts, you can ask for jets for a 150.
I figured I'd post this as it's a good baseline for the other CF250 style engines that are in many scooters. If you change exhaust or intake, you will need to adjust your jetting accordingly.