My buddy just bought a used 2000 400ex. We rode it for a few days, and everything felt great. He decided to take it to a friend of ours (a registered honda mechanic) to get it checked over and have a new sprocket put on. He switched the front sprocket from a 15 tooth to a 14 tooth hoping for more low end power. Anyway, he got it back, and says it feels faster now, but it doesn't pull the front end up like it used to. Before it would yank the front end up really fast in first and second, to the point that you had to be careful not to go over backwards. Now it will do it with more effort in first, and barely at all in second. The only other things done to the quad while it was checked over was it was given a new spark plug, the chain was tightened, and a K & N airfilter was installed. Can anybody explain to me why it doesn't have the power to lift the front like before? Thanks in advance.

 

Maybe it is lean now from the K&N. I put one on mine and lost alot of torque. Check the jetting now. I that isn't the problem, maybe the sprocket change wasn't as stated

 

Sure you got that right?? 15 to a 14?? When I went down a tooth in front, I could hardly keep the front end on the ground. It was great fun, but on the trail, I was always getting in trouble from doing wheelies.

The bike is jetted LEAN at the factory (to make emissions specs). You didn't mention a rejet, because without a rejet after the K&N, it should now be REAL LEAN (dangerous for your engine!).

 

Thanks for the input guys. I am sure about the sprocket, at least sure that it is now a 14 tooth. I counted it myself, and my buddy counted the one before that as well, and said it was definitely 15 tooth. I hadn't thought about the jetting. We'll have to look into that. Any other suggestions? Thanks again.

 

Same dang thing happened to my Warrior...went from a 13 tooth to a 12 tooth and it was HARDER to wheelie!! Don't ask me why because I am still not sure! Just go back to the 15.