Kx65 top end breaking up

I have an 09 kx65 that started to pop once in awhile on top end. Then would do it by time son got to end of street. Replaced the piece on the stator (cheaper than whole stator) with part from Ricky stator. Ran great for two tanks of gas.....now starting to pop again on top end. I am no good at rebuilding a whole motor but replacing, soldering, ect. parts is no problem. I did notice some milkeness in the crank case so that is ordered. Would that cause this? The bike is in nice shape and well maintained.....I use auto tranny fluid in crank case changed every four or five rides, was using quicksilver but just switched to castor 927 and run 93 octane. Any help would be great.....just ordered bunch of stuff for Xmas for it or would consider going back to klx110. Son LOVES this bike but sits more than he rides it. Thanks in advance from a frustrated father.

What does the plug look like? have you tried lowering the needle? My experience is popping studdering and not cleaning out has always been to rich on top end. raise the needles E-clip one position see if that helps. Give as much detail history of what you have or that has been to the bike.

^^^What he said. Maybe even lean the main 1 or 2. When my daughter had her 65, I had to drop 3 main and one pilot. It was super-rich with factory jets.


Also, any spooge from the pipe?

Bike is bone stock. Not much sponge at all. Have only had bike a short time but was very well maintained. Ran great until recently. Wouldnt think needle setting would change. Plug looks fouled. I did just clean air filter. I don't think I went overboard on filter oil, much less and don't think it would be effective. We live in sandy area so I think it is important to have some oil on it. Could they be that sensitive? Keep in mind when applying filter oil I pour maybe half teaspoon into my gloved hands, rubb them together then massage the filter. Filter is not gobbled up....just tacky.

What piece on stator did you replace?  Have you checked your coils lead wire for any corrosion? Have you tied a new plug?

Needle position makes a big difference. FYI, factory jetting on the 65's are extremely rich. My bet is the plug fouled.

I believe the part is called source coil....it is the part with wire wound around it on the stator. Would changing 2cycle oils matter? Went from quicksilver to castor 927. Somebody suggested the needle clip, but this problem is new, as stated I just ran two tanks of gas through it fine. I am reluctant to lean it out for fear of too lean. Are the air filters super sensitive on the smaller two strokes. Also would a leaky water pump seal cause this breaking up on top end. I purchased the rebuild kit. Thank you everybody for the help it is much appreciated.

I think we ran a 180 main and needle in 2nd from top. Ran 93 octane mixed at 32 to 1 back then.

Aaaah the good ole' days.


Edited by JBFL

Awesome pic...is that your boy 719? Leg way out front...great teqnique. Actually got bike from a guy that his son was starting out racing up there at Dade city. I will check to see where my jetting and needle are. Gonna look into the jetting anyhow, got him an fmf sst and power core silencer with a set of v force 3 reeds for the 25 of dec. But need to get it right so he can ride with his buddies for now. Again really cool pic to see the kids having good clean fun. Thank you.

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