Post by meniscus on Nov 16, 2020 8:20:10 GMT -5
So, the previous 72bkk we put on the Icebear Maddog suffered from blowby about 600 miles after install. I'm guessing the cylinder wasn't really round and the rings were not able to seat properly. Luckily, there was no major damage and the magnetic drain plugs caught all of the metal pieces from the rings.
Issue: A new 72bkk was installed and we now have 100 or so miles on the motor. It seems like even after letting the scooter warm up for several minutes (3-4 minutes), the engine tries to flood after full throttle. It doesn't happen all of the time and it doesn't matter if you are easy on the throttle even after warm-up.
Symptoms: After 2 or so minutes worth of warm-up, you can hear the idle drop (I'm assuming the auto/electric choke is disengaging). After running the bike for about a mile and a half, it sometime makes a wheezing sound for a second or two, the power drops off, and the engine stalls. Immediately after, the starter can't turn over the engine unless you use the kick starter twice. Then it will start back up. The engine turns over like normal.
If the bike is allowed to warm-up for 5 or 6 minutes, it doesn't seem to happen as often and this doesn't happen every time. After the bike is really warm, you can do whatever you want and there's absolutely no issues no matter what you do. If you turn the bike off and run it again in 5-10 mins., we can't replicate the issue.
Setup: 72cc BBK, Extra long case, 20mm carb (but measures 19mm), 28 idle jet, 88 main jet, stock cam, 6 gram rollers, and yes, the carb is completely clean (all passages). After running for 10 mins, top speed with a 255 lbs rider is 40mph (verified by GPS) on flat ground. Valves are set at .004 for both sides. Yes, the piston is installed correctly with the intake on the top side. Battery is new and has good voltage. Stator is new and has good output. Pickup sensor was measured and has the minimum gap recommended. Coil is good. CDI is good. Running an Iridium plug.
Any ideas on what may be going on or how we might remedy this situation? I'm assuming this is a flooding situation, but I don't know. When we do a plug chop, the plug looks right and the motor response is completely smooth all the time, regardless of throttle input. Unfortunately, we haven't had the tools to do a plug chop when the engine dies/stalls.