I have a well used Scrambler 400. It runs pretty well, but I have an issue with low RPM operation. It idles fine, but when you give it gas and the motor is at "low" rpm, you are barely gets you moving. When it will kicks into a "high" rpm, it will move just fine, albeit pretty quickly.

I thought the belt was slipping at low rpm, but engaging at higher speeds, so I replaced it. It was quite old, and a new belt seemed to help.

But when climbing a steep hill, sometimes it refuses to kick up to a higher RPM, and I am stuck. It won't go up a steep grade slowly, no crawling ability at all.

I am wondering if this is an issue with the fueling? Carb? Belt? What should I be looking at? Should a two-stroke Scrambler be able to grind up a hill slowly, or do you have to wind it out always? Why won't it kick up to high rpm sometimes?

 

It's most likely a clutch issue...specifically your secondary or driven clutch...you'd be best served to pull/maintain both clutches while in there...if the belt was neglected I'll guarantee the clutches were also neglected.


If I were to take a guess I'd say the buttons in the secondary are worn...but it could be something else (the buttons are a normal wear item and pretty cheap to replace for the DIY'er).


If you do service it yourself, just be careful as they are under considerable spring preload...

 

Thanks, I will look into that. The belt was probably 20 years old, the clutches couldn't be much better!

 

Sounds like it's possibly a combination of both the carb and rear clutch buttons. Scramblers and almost all the 400s were bad about vibration and carbs eating up needle and seats. When worn too much fuel can "load up" the engine and clear up at higher speeds. Something that a good carb kit can help with. Plus don't over look the brass float arm and aluminum pin for wear. If it's wobbly,may need to be replaced and a dealer item,doesn't come in carb kits.Here's the best kit around.Shindy ATV Carburetor Carb Repair Kit Polaris Scrambler 400 03 0406 | eBay As far as the clutch,most times the 3 rear ramp buttons wear down and can cause engagement problems or can actually slip if ground down. They look like this.3 1997 1998 1999 2000 Polaris Scrambler 400L 500 Secondary Clutch Buttons | eBay Here's the only video I've seen that shows the rear clutch and how to take it apart. The buttons are under the helix.

 

Decent video...very doable with second set of hands...vid obviously had recently/newer clutch...sometimes it goes smooth...sometime not so much


Have the right tools...will make this project pretty easy.


Buttons can be PITA to get out...tiny screw holds them in if I recall...can't miss them, they look like little deer turds under the ramped helix...

 

This is the old non ebs clutch from the beginning.This is the same way I rebuilt them.. Never had a pair of helping hands just good pair of snap ring pliers and c-clamps is all you need.The helix when you barely push it down will stay in the sheath when you start the prewinding. A big belly helps a little also at times.. Good video except you prewind the clutch 1/3 turn,not just 1/4 turn as this guy did. When you hear metal on metal when you turn the sheaths you can pretty well be assured the buttons are ground down along with the screw heads and sometimes the blamed helix needs to be replaced. I've had them driven in,rolled in,drug in,in every condition possible. From pretty good condition that the clutches were in repairable shape all the way to great for paper weight use condition. Some people just drove them until they dropped.

 

Good snap ring pliers are a must...little thing holds it all together...I now use a clutch holder to assist...need to work on that belly...