Vintage Dirt Bike Q & A

Read first: my overflow leaks fuel if i leave the petcock on after shutting the bike off. I forgot to shut the petcock off and noticed it leaking. It didnt leak with the floats set uncorrectly at 23mm. I adjusted the float height to the factory setting of 19mm and noticed it. I am positive that it didnt leak at the height of 23mm cause I was working on the bike with the petcock on and fuel in the carb.

I recently bought a 1980 cr250r for 100$ and it would start then it would die. I changed out the gas that was in it for some new 40¦1 mixture and cleaned the carb. I set the float height to 19mm, it was at 23mm. I also checked needle clip height which is second down from the top. Air screw is 1.5 turns out.

The bike now idles and revs fine, tons of power! First gear screams from 0 throttle until 1/4 and no power past that. Bogs down. The k&n pod filter that was on it is pretty nasty which could starve the engine, but the power is crazy under 1/4 throttle. It has the stock keihin carb along with the stock needles and slide. The float needle doesnt have a viton rubber tip on mine, is it supposed to? Also, if I pull the spark plug at idle its wet with fuel.

So should I buy a new float needle or just make sure the petcock is off? Or is it the reason for the throttle issue and wet plug? I have to mention though that I had only rode it once and that was with theair screw almost completely screwed out. I didnt know the fuel was bad in it when I bought it since the guy said it was fine. But the bike would start and die. It would only start with theair screw way out. So after cleaning the tank and carb then adjusting the float, it idled great!!! And I took it for a test drive without screwing the air screw in and then out 1.5 turns.

So could the throttle issue be the float needle leaking, the air screw turned almost out, or the k&n filter being a bit nasty? Sorry for the long post. It was late when I test drove it and then remembered about the air screw. I then adjusted the air screw 1.5 turns out and it idled fine, if I screwed it all the way in though the motor wanted to die. I am going to take it for a new test drive with the air screw adjusted and will post what happens!

Update!!
So i just ran the bike through the neighborhood and the bike now has great power, though now it is hesitating a bit when I get on the throttle. This is the first time starting it and running it with the air screw adjusted 1.5 turns .out. the idle immediately was sky high since the last time it was run. I lowered the idle but maybe I did too much because------My problem before was there was tons of power when opening the throttle and no power past 1/4 with wet spark plug. This was because the air screw was turned out almost all the way. Now there isnt as much power from take off, there is lots of power- but not like yesterday.

So i know that the dirty air cleaner wasnt the root cause of the upper powerband problems. Now, i hope all that is needed is an adjustment of the air screw and or idle. If no on can help me figure it out then I will do more research. I do know there is a youtube video of a 1980 cr250r idling. I dont know what mods he has though.