My kids got a gently used Kazuma (Coyote) 150 for Christmas from their aunt and uncle. The previous owner had no owners or service manuals at all.
It has a stock 150cc gy6 engine with an air box and stock exhaust. It starts right up and idles great, but when i slowly throttle it up it dies when i get to about 1/4 throttle or as soon as its under load.
1. I reset the air/fuel set screw to 1.5 full turns out, then moved it out in quarter increments(road testing) to about 2 3/4 turns out where it ran better, but not good. Turning it out past that didn't help.
2. I removed the spark plug. The ground electrode was white and the center electrode was clean to slightly white. I cleaned it and reinstalled. Unsure of correct gap?
3. I removed fuel line from carb and opened petcock (non-vacuum operated). Gas flows freely from the line.
4. I removed the carb from the machine and disassembled. It was clean as a whistle inside. 35 pilot jet was clean and clear. 95 main jet was clean and clear also. It really looked like brand new inside. The only thing I noticed and question is the black cylinder shaped diaphram inside the middle of the carb (with the needle coming out of it) was extended downward about 3/4 of the way (when looking thru the intake). I'm guessing this is the venturi and that black cylinder rises (opens) with vacuum as the throttle is depressed (thus allowing more gas and air thru the carb??? I didn't check or remove the choke at all.
5. I removed, inspected, dielectric greased, then reconnected the electrical connections to the CDI. All looked OK.
From reading prior posts, it sounds like my only problem is that my main jet is too small and should be replaced with a larger one. Which, should give me smooth throttle response throughout the powerband.?
Questions:
1. Without any modifications, a 108 main jet should give me smooth throttle response throughout the rpm range and fix my problem. Is that correct? what will a 105, a 110, or even a 112 do?
2. If I install an open element air filter only with stock CDI and stock exhaust, it sounds like a 125 main jet would be best? Advice or Opinions?
3. What if I upgrade the air filter, and add a hi-po CDI, with the stock exhaust, which jet should work best? Do I need to upgrade spark plug also?
4. How do I determine the best jet size? Is outdoor temperature a factor? or elevation (I'm 1200ft above)?
5 Should I be 'experimenting' with a small range of jets? trying a few to see which works best for my specific machine under my specific circumstances?
6. Proper spark plug for this machine and its gap?
7. What is the screw for on the very bottom of the float bowl? should it be turned in tight and shut off or open slightly?
8. Should the rubber tube extending from the bottom of float bowl be connected to anything? or just dangle?
9. Should the black vacuum hose coming from the carb be connected directly to the nipple on intake manifold? Mine is.
10. Is there a comprehensive service manual out there that covers all aspects of the 150cc GY6 engine? or even a couple that cover it all? Where can I find it? Is the Clymer Manual for Honda 125 the correct service manual?
Thanks much fellow buggy lovers!!
I'd just like to get this thing running good before spring, so the kids can enjoy it when the weather gets better. I know I've given alot of info. and asked a lot of questions, so I greatly appreciate any knowledge and experience you may be able to share that will help me get this thing running SMOOTHLY without dying on me. I'm very impressed with this site so far, and I'd really like to be able to contribute something back to it at some point. Thanks in advance for your advice!