400exc

[deagle]

General question here. I have a 2002 400exc, Big Gun pipe, power now with clean filters and clear breather hoses. I have noticed a few times when after about an hour of tight riding, it "sometimes" wants to run a bit rough and cut out when you first crack the throttle. If you turn it up through the rpm's, it runs fine, just not right off throttle. Sometimes it comes, sometimes it goes. I thought maybe the motor was getting hot but even if I hit a somewhat open area and let the motor get some air, it still may be doing it. My guess is that the valves are a bit tight and it only happens in certain riding conditions. Normally, you can smash the gas off idle and it throws you off and never misses a beat. I have probably put 500 miles on the bike and have never had the valves adjusted which is why I think this may be the problem but any suggestions would be appreciated.
Thanks

 

[Blackie Dave]

adjust your valves! while you got it apart..., take a look at your plug. see if you might need to lean out the pilot(?)(gas screw under the out-bell on your carb). while you got the plug out..., replace it.

good luck!

 

[jsned]

Adjust the valves soon. I noticed mine started doing the same thing about 2 tanks of gas after the first valve adj. I got nervous and readjusted them right away. It didnt do anything and then I remembered I bought the last can of gas at a different gas station than I had ever done before. I drained the gas and went back to the Amoco Ultimate like before and it cleared up right away. I now mix about 3 gallons of Amoco prem. with 2 gallons of 100 octane race gas and I noticed a big improvement. If I didnt notice a improvement I wouldnt keep doing it because it is expensive.