PDA

View Full Version : 85 250R ATC sputtering


adamsj13
10-14-2005, 10:03 AM
Hi all, Great site here

I have a 85 250r ATC and having some problems. After I start the bike a let it warm up and go for a ride, when I open the throttle, it starts to sputter. It starts just after I start in the powerband. Any ideas what may be causing this? It still hauls butt, just embarrassing when it sputters racing in the dunes. It happens on dunes pavement or dirt. Thanks all for you help
Yamahondaman
10-14-2005, 10:21 AM
Sounds like the main jet...gap the plug at .02..then try it
Yardbird
10-14-2005, 01:40 PM
Try checking your float level.
shawn3169
10-14-2005, 02:33 PM
try turning the choke on halfway or even all the way cause my friends yz80 has the same problem but its his jet and he turns the choke on to go riding
TeamGeek6
10-15-2005, 03:49 PM
too rich or weak ignition or both. if it wont handle more than a 0.020" plug gap, the ignition is weak. Should jump a bright white spark at night when arced to the spark plug tip. Stuff a piece of wire in the plug cap and use that to jump to the spark plug.

A properly operating stock ignition system will handle a spark plug gap of 0.045 - 0.050". Ive modified my stock ignition and it runs at 0.065" + gap.

Carb-, drain the fuel bowl and measure the volume, it should be somewhere around 40 - 45 cc. if its more than that, it may be flooding due to a bad float, float needle or bad needle seat. If the seat is bad, new carb time. $120.00

If not that, then jetting.
Racedude48
10-15-2005, 05:22 PM
Check the top jet. The main jet operates all the time and the needle is from like zero throttle to a little less than 3/4 throttle. The top jet is used mainly from 3/4 to full throttle.
OldSchoolin86
10-15-2005, 05:35 PM
Check the top jet. The main jet operates all the time and the needle is from like zero throttle to a little less than 3/4 throttle. The top jet is used mainly from 3/4 to full throttle.
I know of the mixture screw (idle-1/4), the needle (1/4-3/4) and the main (3/4-WOT). There is a pilot jet too sometimes (low end) but what is a top jet?
Racedude48
10-15-2005, 06:46 PM
Its sometimes called a power jet. its connected to the tube that connects to the bottom of the bowl. And its the same tube that you read ** float levels with.
RedRider_AK
10-15-2005, 07:31 PM
try turning the choke on halfway or even all the way cause my friends yz80 has the same problem but its his jet and he turns the choke on to go riding

Same exact thing here! It's really cold and the YZ 80 doesn't want to get into the powerband so I just pull out the choke and it's fine.