Hello everyone
Ive been riding a 2011 s40 for a few months now and I lurk here. Got it with 17k its now around 19k.
I'm in Florida..I'm 25 but this isn't my first Rodeo Ive been tearing chit apart and building/tinkering with mechanical things since I was a little kid.
Before this I built some racing scooters lol. High compression ceramic piston titanium valves bla bla.. So I have a thing for thumpers I love the sound.
This bike was very neglected it looks much older since it has been left in the elements its entire life until I rescued it haha.
Ive already rebuild the carburetor, jetted it and added a K&N filter.
Drilled out this carcass of an exhaust..
The carb float was leaking depending on the temperature outside and engine temp.. it would seal once warmed up and eventually stopped sealing filling up the airbox with gas and coming out of the overflow float bowl hoses. I think some got into my oil and might be a factor in this "slapping sound"
New NGK sparkplug
Amsoil with zink additive (if it works in a ceramic coated airsol 11.4:1 high compression 91cc 1.5mm stroker living at 13k rpm why not the s40) lol
Valves are in spec and cams look brand new.
Chain tensioner is getting close to flying out it had about 5mm left. Just ripped that thing out and I'm sending it to Verslagen
So this slapping sound was present since I purchased the bike.
At idle the bike sounds fine..once you give it a little throttle it makes a "slap"ing sound. I thought it was the piston. My buddy's 80cc made a similar sound and it was his piston rings they were completely worn out from mileage and it burned oil. So I assumed when I got it that it would need some work.
It progressively got worse but never present at idle. Only when your on the throttle. When you start rolling it would only happen at some rpm's.. kind of random. After my last long trip it was BAD and did it at any speed but not at idle. I used a stethoscope to listen and it sounds like its coming from around the counterbalance area.
SOOO
Ive torn the entire thing apart engine's out and on my workbench. I'm getting a flywheel puller to see what the heck is going on.
Hope to share the experience and ill have pictures once I'm allowed to post some LOL