I have been troubleshooting my 99 Scrambler 400 this week. I went riding over the weekend and suddenly lost bottom end power. When the throttle is pegged from stop the bike starts to roll slowly but hesitates. It will not pull up the front end anymore. Once it builds some revs the bike takes off like it always has. I have checked the airflow, fuel line, carburetor and reeds. I have also checked the clutch. All of these seem to check out ok. The bike is ported, shaved head, k&n filter, ram valve, ritter midrange pipe and silencer, and the carb is bored to 35.5mm. The clutch has an orange primary spring and a violet secondary with a 44-36 degree helix. Does anyone have any idea what the problem might be. Could it be the electrical system? I run NGK BR8ES and the plug checks fine and the bike has never fouled a plug. Please help.

 

What exactly did you check on the carb?

 

I pulled the carb off and checked all of the jets, I tampered with the air screw and idle speed. I removed and cleaned the pilot jety and main jet, although both were clean. I also checked to make sure the slide was seating properly. I am running a 320 main and have the stock needle in the carb set to the second lowest ring on the needle. What I didn't do is remove the air screw completely to see if there was something gunked up inside of it. However, I don't even now if this is possible. I ran into these problems at Flat River. We will have to go riding down there when we both get our bikes fixed.

 

Great, Ritter has my jug and is re-working the porting. I should be riding by the end of the month, I hope!!!

Have you called him, or a dealer for help? Drain your tank and make sure the vents inside it are'nt clogged, then trace the entire line to the carb.

What does your plug look like? Your needle may be "clean" but, that does'nt mean you have the right one in. Also clean you filter, or buy a new one to be sure.

 

I'm no Polaris mechanic, but after many years of ridin' 2-strokes hard, I know they can sometimes get in the mood not to rev. I don't know the terrain you rode last leading up to this or the weather, humidity or temperature. All I know to tell you is if it's sputtering, you could have some tank sweat, line or carb problems. If it's bogin' down or moanin' you definately have carb problems. Or, sometimes if mods are new, they run ok for a while and all whaked out after some hours. If you don't have fouled plugs I wouldn't think it would be the electrical. I'D CHECK THE TANK, LINES, AND GET NEW FILTER JUST IN CASE. IF THAT ISN'T THE PROB, HUNT DOWN THE ONE WHO DID YOUR WORK.