Kazuma 150: starts right up & idles good, dies at 1/4 throttle.

[JDbuggyman]

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!

[metalstudman1]

I'll answer a couple!!!#4. I use experimentation,temp does play a small factor,elevation plays a big factor #5. yes, that's my best successful method #6.see response for number 10. #7. it's to drain the bowl. #8. it just dangles #9. yes #10. Look under 150cc GY6 and under tech-Sticky: SLGK-160 Buggy Info - GY6 Manuals And Wiring Diagrams -should be some help

[wasjustlooking]

If your plug is burning white, it's running way too lean. It's being starved for fuel and can't run on air alone. A larger main jet is a must. At your elevation with stock engine, a 114 might work. Here is a guide to help with jetting.
http://www.4strokes.com/tech/howtojet.asp

[JDbuggyman]

Guys, Thanks for the great info. Studman, I'm gonna check out those manuals and diagrams as soon as I'm done with this.
Justlooking...Great info on 'how to jet', but after reading that I have a couple questions. The writer talks about "checking and adjusting the float level" and also the "slide".

*How do I check and adjust the float level?
*Should this be done with the carb off the machine or when its up and running?
*Is the "slide" the black cylinder shaped diaphram in the middle of the carb with the needle sticking out of it?

I did not check or adjust the float level when I inspected my carb and looks like it could be one source of problems. Two of my local shops did not have the main jets in stock, so I'm still on the hunt for them. In the mean time, I'd like to rule out all other causes. Thanks again for the info and advice guys!

[wasjustlooking]

You will need to do a google search for your brand and type of carb to get the correct measurement for the float level. It should also give instructions for adjustment.

[BuggyMaster]

After cleaning what seems to be about a million carbs, I can tell you that it is very rare that the float level is a culprit. Generally speaking, I have only had to mess with the float when someone else prior to me felt like they needed to mess with the float. Then I had to go back and correct it. Usually when there is a float problem one of two things happens:

1.) The float closes off the fuel supply too early and it will run out of fuel on a wide open throttle run (starve).

2.) The float doesn't close it off soon enough which results in fuel pissing out of the overflow tube. Usually when it is coming out the over flow tube it is more likely the needs and seat are bad and it is unable to close off the fuel supply. I have had to deal with this a few times.

Point being, I wouldn't worry about the float just yet. When you do mess with it, it is done with the carb off of the machine and upside down. I do inspect each one to make sure the needs is not stuck. I will gently raise and lower the float and physically watch the operation of the needle to make sure that it does in fact move easily.

Your problem is most certainly going to be in that main jet if in fact the passages are clean.

The factory one that had in there is very lean but this is what these guys are being required to do now a days to get through emissions testing in order to sell to the U.S.A.

All 150cc carbs are not created equal and in fact the vary widely from manufacturer to manufacturer. As an example, in an American Sportworks machine, right off the bat I put them at about a 128 or so main jet, up from a factory 114, and they like it there in stock form. On the other hand, on a Baja Motorsports machine, it came with a 108 and I bumped it to a 112 and it would flat out fall on it's face due to over jetting. It has to do with how the individual manufacturers deal with the fuel passages (best I can tell).

That said, in your case, you have to find out how sensitive it is to jetting. The proper way to do it is all trial and error and you inspect a brand new spark plug after a wide open run. (you may find you go through many plugs until you find the sweet spot...a plug cleaner is a good investment). I actually used a wide band controller on our Helix to find the optimal jet size at one time and somewhere (on this site) I have a picture of a perfect plug.

So, in your case, I would first try a 105 (or 108) and see how it does then read the plug. If it runs on that but the plug is still white, bump to a 114 and see what it does. You have to find what's too much and then start backing off from there. Tom at SYC powersports should have the jets you need. Click the banner above and contact him.

Going with an open element is a very effective, yet cheap, easy power gain and will in fact require a re-jet again. How big you go depends on how sensitive the machine is to your initial jetting experiments.

If you mod the exhaust, you will need to jet again. CDI may or may not require a rejet depending on how extreme you get. Same plug across the board as far as I am concered.

The screw on the bottom of the bowl is used to drain the float bowl for servicing.

There are two tubes on the carb that go to nowhere. One is the vent for the fuel bowl and the other is an overflow tube. What you described appears normal.

There is another tube that (in your case) goes to the intake manifold. This provides the vacuum that is needed to raise the slide during operation.

There are manuals in the tech section.

Originally Posted by JDbuggyman

Guys, Thanks for the great info. Studman, I'm gonna check out those manuals and diagrams as soon as I'm done with this.
Justlooking...Great info on 'how to jet', but after reading that I have a couple questions. The writer talks about "checking and adjusting the float level" and also the "slide".

*How do I check and adjust the float level?
*Should this be done with the carb off the machine or when its up and running?
*Is the "slide" the black cylinder shaped diaphram in the middle of the carb with the needle sticking out of it?

I did not check or adjust the float level when I inspected my carb and looks like it could be one source of problems. Two of my local shops did not have the main jets in stock, so I'm still on the hunt for them. In the mean time, I'd like to rule out all other causes. Thanks again for the info and advice guys!

[Arioch]

Have you fixed your buggy yet?

I have a Kazuma 150 buggy that i bought a week and a half ago for daughter making the honor roll. I got it home and we spent the day riding it around despite it being cold and raining. Did this another day after work. I even put a garbage can full of dry wall in it and ran it out to the end of the drive way on garbage day. Second weekend I got it out made a lap around the yard and wide open it just bogged out. Of course at the furthest point from the garage in the flooded part of the yard. Yes I'm just that lucky. I thought maybe it just wasn't warmed up yet. So I let it warm up and could not get it going. I pushed that thing through the flooded yard back to the garage. Runs great, starts up like nothings wrong. I put it on a jack so I could see if tires off the ground with no load would actually spin and no. If you idle up slowly it just dies. If you floor it you can actually get the wheels to spin but then bogs out. I took off the carb and it looks pristine inside. I cleaned it out and put it all back. Still same thing. I am not sure I did it right tho as I have never done carb before. I'm going to attempt the jetting described in one of those links but first I would like to know if there is a how to video on carb cleaning someone would recommend that would give me an idea if I'm doing it right.

[TeamBreakem]

Just go to youtube and search for gy6 carb cleaning. There are a few videos. I always use a guitar string (the thinnest one) to make sure all holes are free of debris/gunk. Gas has a really good way of making the inside of a carb look very clean and new, but little tiny anythings can mess with your jets. I am thinking you will have success after watching those videos and cleaning your carb again. Blowing everything out (with compressed air) very well after cleaning really makes a difference when cleaning a carb that already appears to be clean.

[Arioch]

I did youtube it and was very successful. I discovered that you could actually hold the jets up to a light source and see the debris in the holes. I got it clean and running. I also bought a high flow fuel filter and placed it in the gas line between tank and carb to help prevent this. I took the 95 jet out and replaced it with a 98 jet. That made major improvement in performance. I didn't think it would but it literally spins tires with the 98 and can't with the 95.

Not to mention, it sounds a lot better too.

[sherry]

[QUOTE=Arioch;13467]I did youtube it and was very successful. I discovered that you could actually hold the jets up to a light source and see the debris in the holes. I got it clean and running. I also bought a high flow fuel filter and placed it in the gas line between tank and carb to help prevent this. I took the 95 jet out and replaced it with a 98 jet. That made major improvement in performance. I didn't think it would but it literally spins tires with the 98 and can't with the 95.

Not to mention, it sounds a lot better too.[/QUOTE
I just want to make sure you are talking about a 150cc kazuma falcon, Is that correct? Thanks

[Arioch]

Yes I am sherry. Now the kids managed to throw the battery out and run it over ripping the wires out and cracking the battery and one of the motor mounts is failing. they were not really made to last.

[sherry]

Originally Posted by Arioch

Yes I am sherry. Now the kids managed to throw the battery out and run it over ripping the wires out and cracking the battery and one of the motor mounts is failing. they were not really made to last.

thanks for quick reply. your talking about the atv right?

[Arioch]

its a mini-buggy. red, 2 seater big enough for adults with a flimsy roll bar only good for pushing tree branches out of the way. why whats up?

[sherry]

Originally Posted by Arioch

its a mini-buggy. red, 2 seater big enough for adults with a flimsy roll bar only good for pushing tree branches out of the way. why whats up?

Mine is a 150cc Kazuma falcon atv. Same size 95 jet on carb, so I'm thinking switching it out to a 98 will work just the same.

[Arioch]

ya it should go great. might want to try a little bigger as i didnt. the jet was ony $5. if u do go bigger let me know how it goes. as it is right now with 180 pound adult on the street it does 36 miles an hour. a little scary with my 9 year old daughter behind the wheel.

edit: the falcon has the same exact engine and carb on it. i believe the only difference i found is the falcon has a fuelfilter and the motor mounts are different for obvious reasons

[sherry]

Originally Posted by Arioch

ya it should go great. might want to try a little bigger as i didnt. the jet was ony $5. if u do go bigger let me know how it goes. as it is right now with 180 pound adult on the street it does 36 miles an hour. a little scary with my 9 year old daughter behind the wheel.

edit: the falcon has the same exact engine and carb on it. i believe the only difference i found is the falcon has a fuelfilter and the motor mounts are different for obvious reasons

Great! thanks so much!

[sherry]

Originally Posted by Arioch

ya it should go great. might want to try a little bigger as i didnt. the jet was ony $5. if u do go bigger let me know how it goes. as it is right now with 180 pound adult on the street it does 36 miles an hour. a little scary with my 9 year old daughter behind the wheel.

edit: the falcon has the same exact engine and carb on it. i believe the only difference i found is the falcon has a fuelfilter and the motor mounts are different for obvious reasons

Hey, Where did you find the 98 size jet???

[Arioch]

Sorry for the really long time with no reply. I mean REALLY long time.

Your average cycle/atv shop won't have it but should be able to refer you to someone who will. I checked a couple a shops and ended up at Road track and trail. It is best if you simply take the carb and a flat head with you and say hay I need this jet just a little bigger.