Has anyone encountered engine vibration on their Sportsman 335 at slow speeds ? It seems as if the engine requires alot of RPM to go 5-10 mph.

99' SP500 & SP335

 

I would check your engine mounts

 

I have a 335. This seems to be normal mine does the same thing. I have been told you can change the clutch springs and get a faster engagement resulting in lower rpms during slow speed riding but you may loose top end speed. I suggest you use low gear when riding at the speeds you listed.