Loss of power, torque. Sputters at full throttle
 

I was riding the other day and suddenly my GZ250 just lost power and torque. Now it sputters at full throttle in every gear. I can't get over 45 mph. I changed the oil and filter and it's still the same. I also added Berrymans b-12, but it hasn't changed. Please help. :)

Re: Loss of power, torque. Sputters at full throttle
 

Change spark plug

Re: Loss of power, torque. Sputters at full throttle
 

How does it respond with less than full throttle? Does 1/2 throttle respond better, for example?

Re: Loss of power, torque. Sputters at full throttle
 

Hey Jonathan, there is no sputtering at half throttle, but the torque/power isn't there. Raul, I changed the spark plug and it hasn't changed anything.

Re: Loss of power, torque. Sputters at full throttle
 

Not being able to get over 45 would indicate to me that you have an air leak somewhere, and a big one. Does the bike idle alright? Does it also buck like a bull with a yellow-jacket on it's haunches?

Take some WD-40 or some ether or something similar and give a little spritz to all areas of the carb where a seal or connection exists. If your idle changes at all while you do this, then you need to fix whatever is causing the leak.

Re: Loss of power, torque. Sputters at full throttle
 

I sprayed all the boots and around the carb and did not notice an idle change.

Re: Loss of power, torque. Sputters at full throttle
 

do you check the air filter
my do that when i mod the filter before i change the main jet to 140

Re: Loss of power, torque. Sputters at full throttle
 

When it sputters, try full choke. If there is no improvement then the problem is likely ignition or a plugged air intake. If there is even the slightest improvement then it is likely carburetion.

Re: Loss of power, torque. Sputters at full throttle
 

Raul, I checked the air filter and box. They both seemed fine. I am mechanically inclined when it comes to jets. JohnC I don't have a choke on my bike, I have never noticed one before and I don't see one. Where would it be? I bought my gz250 used over a year ago and never had any problem with it.

Re: Loss of power, torque. Sputters at full throttle
 

These things have a factory choke... Left handlebar control.

Can we see your setup?

Check the "S" tube that runs from the crankcase to the bottom of the air box.