So...a clean burning engine will produce a tan (think cardboard) color on the plug. You want that color where the quad will be producing the most load on the engine...so you have your youth find a long run...zip along at the maximum throttle position you are allowing, then cut the engine at that throttle position (don't slow down then kill it...kill it while still moving along). Have some tools with you so you can pull the plug & "read" it. If lighter than cardboard you're lean if darker then rich. Now...because this may be at 1/2 throttle moving the needle may alone do the trick. Moving the clip up one slot will lower the needle leaning out the mixture...opposite if you move the clip down the needle. However, when the little tyke has access to full throttle this procedure should be done again and it's the main jet that will need to be replaced (when that time comes)...not as precise as a pipe sniffer, but it'll get you close enough...

 

You're the man! Thanks for the info. I'll have to do that check next time we fire the beast up. I will post a picture here when I have done the test.

 

So I did the spark plug test today. At first the kids drove for aprox fifteen minutes at various speed and rpm. Then I jacked the up the rear wheels and put the pedal to the metal until it ran clean, kept it there and killed it. This is what the sparkplug looked like.

 

So...a plug chop needs to happen with the motor under load...as in with the driver driving it at full (on your case part) throttle, then kill the engine. To get the best reading that is...


Obviously you are running VERY rich. I'd move the clip on the needle 1 space up (dropping the needle further into the slide) and re-test. If you're not running the iridium plugs I'd highly suggest the extra cost as they are almost foul proof.


If you plan on giving the tyke full throttle right away get yourself a 90 main jet...factory is 92.5 (I believe). Of course, with a smaller main, you may need to go back and richen the needle as you now have less fuel being drawn through the main jet...maybe...


Getting carb jetting right can be a tedious process...but once close the machine will be much more responsive.


Word of caution...I always lean towards the richer side of jetting...too lean and you'll hasten the demise of piston/rings...

 

I was gonna also suggest just putting in the 90 main jet. No need to move the needle jet on these little bikes. If your using the oil injection system they have it running rich anyway. I've deleted oil injector on all 4 of mine, so I can control the oil amount ratio. Have you inspected the air filter, those are often overlooked. With the throttle limited it takes a little longer to clear out than one with wide open throttle. I have 2@full throttle , 2 @1/3 throttle and they take a little longer to run like the ones @ full throttle.

 

I was thinking of removing oilinjector also. I don't trust that **** so I go with 1% mix in the fuel as well. Have you physically removed the pump or just drained the tank? I had an idea of just leading the oil back to the oil tank and pump it around instead of removing the pump.

 

2 of them removed pump and drained tank. Other 2, I drained tank plugged tube leading to pump with fine thread bolt and Teflon tape screwed in, then got assorted automotive vacuum caps and capped the pump and carburetor oil port. This way you can easily put back to stock form when you decide to sale. Be sure and save the little tube that goes to the carb.

 

Ok. I was afraid the oilpump would be damaged if I left it running dry. But that's no problem? Just have to post a picture of today's winter driving.

 

You should remove the lil plastic bow tie that turns the pump. It's on the end of the crankshaft.
You need to do clutch maint anyway.

That looks fun! (pic)

 

Alright. I'll leave it for now since they pretty much drive every day. Picture taken in northern Sweden. Minus 2 degrees Celsius and perfect sun.