DS650 - Running Lean
 

Let me preface this by saying that this is my 3rd DS650 and I would consider myself mechanically inclined.

I however can not get this atv to run richer. DS650, ProCom CDI, ProCircuit Exhaust, K&N air filter. Good battery

Mikuni BSR42 carb, I have jets from 160-200. I’ve put in a larger pilot, raised the needle to the richest setting (bottom rung with a spacer).

It hiccups slightly at the highest rpm’s. I’ve removed the gas cap to make sure it wasn’t gasping for air. I’ve removed airbox lid, reinstalled, put sock over filter, removed airbox tubes, reinstalled. I’ve sprayed carb cleaner all over hoses/boots while it runs and the idle never changed so it doesn’t seem to have any leaks. I drilled a couple of extra holes in the slide which seemed to help.

I thought it might be a hiccup relating to spark. Changed coils which made it worse. Oddly enough it would only run off of one coil (either coil, either plug). As soon as you hooked both coils up to both plugs, it would die ( would love to understand this). Put both factor coils back on, back to running normal.

Valves were slightly tight? Had local machine shop grind them and they are all within tolerance now.


it runs 95% perfect. If you drove it up to 80% throttle you wouldn’t realize there is an issue.

could a trigger (pickup assembly) act like this? The reason I ask is the hiccup is so fast almost like it misses a spark or two.

im ready to try literally anything! Wish I could hook it up to a computer or something.

I normally do only one change at a time to where I’m not chasing my tail on this.

In the end, the plug tips are always white and I’ve went through a TON of plugs!