Jetting issues on 1971 Suzuki F50 scooter - Reed valve questions

[tbrock]

I've been struggling to get my 1971 F50 running correctly. This has the same engine as the MT50 and other 50cc Suzuki models, so the carb feeds into the crank via a reed valve.

I originally thought there were electrical issues due to some mouse activity in the frame but have narrowed it down to carburation issues.

The problem shows up that 1/2 to full throttle falls flat and dies out, anything below that runs fine. I assume it was a plugged main or other blockages but no matter what I did to clean up the carb I couldn't get it to improve. I replaced the main and pilot just in case someone "fixed" it in the past. I was concerned about the float level but replaced the valve and triple checked the height was set at 23mm.

By chance I did leave the sidecover that covers that carb off once and it seemed to fix the issues. Made me change my thought of a lean condition to an overly rich. The jetting was stock and I have gone down from a 102.5 to a 97.5 and it is slightly improved but has me questioning what would cause this.

These 50cc engines do have reed valves, at this point I am beginning to think this is the last thing I have not checked. From what it sounds like a bad/open reed valve could let rich air/fuel mix back into the intake and mess with the mixture. What makes this painful is that the reed valve is inside the case and can only be accessed by splitting the case open. Would like to get some 2nd opinions before dropping and splitting the engine, or is it time to break down and buy a borescope?

Any opinions would be appreciated.

thanks,
todd

[Alan H]

No experience with reeds except the theory side, but this isn't something I've seen discussed (yet).
Whistle see if anyone can contribute.