Just installed a K&N air cleaner and upgraded chain on my sons jm125.Afetr about 10 min of riding i went to put the chain guard back on over the sproket and noticed that the engine was smoking hot? Is this normal.Never checked before.Just happened to touch the side and wow its Hot.Is this ok.Could the chain being to tight have anything to do with it?Want to go ride for about 5 hours tommorrw?

 

installing the k&n increases the airflow, and without increaseing the fuel you create a lean fuel mixture which cause the engine to run lean which makes it run hotter, you need to do a plug check then start rejetting the carb, do not ride the atv without rejetting, you will burn up the engine

 

What should the plug look like.The machine runs great.Shouldnt it run funny if its not jetted right?How do i no what jets to use?

 

engines always run better in a lean condition but that doesn't mean it's good for them, the plug should be tan in color, black means rich mixture, white means a lean condition, you need to start with a new plug, then make a high speed run and at full thottle turn off the ignition, stop, let it cool a little, pull the plug and see what it looks like,

 

Did the same upgarade to my daughter's JM125 and same results. Rejet is a must! I'm alos playing with the gearing -- dropped to a 14T on the front and testing. Would like to have a different sprocket for the back but haven't found an appropriate fit.

"3rd" gear seems to really bring the quad down almost like an overdrive gear. 4 gears = R-N-1-2 or R-N-1-2-3?

 

Can you explain in detail what i have to buy and do?What jets and from who?How do you install them?Im no mechanic but i can wrench with direction.Were do the jets go?

 

Just to be sure you have to do a plug check. What you need to do is get the quad warm. Find a socket and wrench to fit the plug. Find a long straight road that you can run wide open for a bit. Once you are wide open for a bit turn the key off and coast to a stop. Pull the plug and see what color the center of the plug. When I mean center its the white porcelan that holds te electrode in the center of the plug. White is lean, tan or brown is good and black is rich. If its anywhere near tan to brown you dont need to rejet. The factory filters flow very well but they dont filter very well. I have not had to rejet any of my quads with K&N filters. Most likely you will be fine. These motors are air cooled and they do run hot. Do the plug check and maybe even post a pic if you are not sure.

 

I will try this tonight,thanks again.How hot does your machine run?After 20 minutes of hard riding i would say you cant hold your hand on the side of the casing.my son was riding my hond yesterday also for about the same amount of time and just for the heck of it i checked the side of the honda which is a 4 stroke and it was very hot,couldnt keep my hand against it either.Maybe this is how hot they run.Just never checked before.

 

Ok warmed it up and drove for about a quarter mile wot.Pulled the plug and the insulator is white.Now what?

 

time to rejet, if you're not skilled enought to remove the jets and replace them then reinstall stock airfilter