I raced my friend several times on pavement when I first got my 650 and had him by maybe 4-5 lengths to 55 mph. Now it's down to 1 length max. Neither of us has changed anything. I have a similar slow down of my 650 when I race my 400ex on pavement now too. Could mine have slowed down? If so, how. Possible belt problems? Thanks.

 

The first thing I would check would be the air filter and choke cable. I noticed on mine that the air filter gets dirty pretty quick. Also check the choke cable to make sure that the choke is fully disengaged when running.

 

When you say you raced when you first got it, did you follow the break in procedure or were you running it full throttle be for 10 hours. If you did not break it in properly you have found the result. If you did do a proper break in clean the air filter and adjust the valves.
Good Luck
Wayne B

 

I own a 450 foreman now and it did the same thing,until I adjusted the throttle cable back to specs.It took out the slack from stretching and allowd the carb to open all the way up again.

 

I just got mine back from the dealer after complaining that it was losing power. They balanced my carbs and now it seems to have more power than it ever did[img]i/expressions/face-icon-small-happy.gif[/img]

 

Thanks for the responses. What exactly is carb balancing, and how is it done?
Thanks.

 

My understanding is that they use a special tool which measures the exact amount of vaccuum being drawn by each carb. Im not sure what they actually adjust on the carbs when balancing but the goal is to get the vaccuum reading exactly the same.
FYI, this not only brought back my lost ponies but she also idles smoother as well.

 

They use mercury balance tubes. It is easy to do if you buy the mercury tubes. I have a set somewhere for my old '75 Kawasaki Z1 900. If you can get you hands on some mercury they are easy to make. If you are in the Wash DC area I have a bunch of mercury.
Wayne B.