Hey all...I am in need of some help here. A freind of mine brought over an 85 or 6 atc 250r. It seems to run fine for a while then acts like some one pulled the choke. Anyway, I pulled the carb to clean it and do a visual and stuff. The carb is stock and has a 165 main in it. That seemed to be very big to me for a 250. But then i don't know either. Can anyone tell me if that is the correct main for pump gas.
T.I.A.

 

I had a pipe, K&N filter and no air box lid on mine and only ran a 158 main. That seemed perfect for my
250R. it did alright with a 160 main. But I wouldn't have gone any higher than that. what mods does
the bike have? Doesit atleast have a pipe? I think a 165 main is high for just a stock bike with a pipe.

 

250R4LIFE, Thanks for the input so fast. The bike is totally stock except K&N / no lid. The pipe is even stock. I thought the main was fat. But I don't know what a stock r is suposed to be. I'll pick up some new mains tomorrow and see what happens. Thanks for confirming what I was thinking.

 

Thats way to biug of jet for that bike (those mods) Mine has a 152 in it and is a raped ape (see sig.) I would defintly change that. Dont forget to do your plug chops.

 

I think mine had a 155 main it it when it was stock. I think...[img]i/expressions/face-icon-small-confused.gif[/img]

 

The 85 ATC came with a 142 main stock and jets from 138 to 148 for changing as needed, lean it out and do plug chops. It will run much better.

 

Sound like you are fouling the plug, way to fat on the main.
Probably needs about a 148 to 152, Make sure you dont drop the main too many sizes all a once because you dont want to get too lean! Drop a couple of sizes at a time untill the problem stops, and look at the plug as you go to make sure. Cardboard brown to chocalate brown should be the coloration of th porclain part of the plug.

 

plug check is the only safe way to tell, wide open 3rd or 4th gear runs for that, then pull the kill switch and clutch. make sure motor is good and warmed up. about 10 mins worth of riding time before each plug check. also, i have seen coils go bad and do the same thing, run great till they get hot and then nothing.