At about 3200 miles my 2008 S40 started intermittently not accelerating past what felt like 1/2 throttle. I would twist the throttle to about the 1/2 way point with normal acceleration, but "flat" after that. Took it to the dealer when it was acting up who had no idea, they cleaned the carb and contacted Suzuki. Suzuki told them it was probably the petcock which was changed out under warranty. It was better, not gone but better acting up much less often. At about 11k miles it acted up for about a day and a half on a road trip. Then went away again.

Now, just shy of 14k miles it is back again. When it acts up I have tried the petcock in every position with no change, checked all the vacuum hoses for leaks and kinks. I run premium (helps minimize the back fire issue) from a national chain when ever possible usually from the same station near my home.

It feels to me like an air valve is sticking, any ideas are appreciated. 2008 Suzuki S40, no mods except for K&N air filter.

So, I'd bet it's the slide...

At'd be my first guess

Thanks for the ideas! I put in some Sea Foam to see if it will help with what ever is sticking for a possible easy fix. If not then I'll dig into it.

I'll also checked to make sure the battery is full and will hook up a voltmeter the next time it occurs. I ride year round and have managed to never go more than 2 weeks without getting out so a charge has been maintained.

Thanks again for being part of a great site!