Runs rich and then becomes lean

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Sep 26, 2018
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I'm running a DIO reed kit with a Runtong 16mm carb (dellorto SHA knockoff). Stock muffler chopped off at the weld. Moderately windowed piston and light exhaust port raising (2-3mm). Timing advanced half of keyway (approx 20 degrees)
Runs rich but leans out as time goes by. Confuses me like crazy. I ran a 77 jet and its (expectedly) rich. I went down to 67 ish (soldered 70 micro drilled out) and it 4 strokes sometimes. It then leans out and it 4 strokes less then eventually the engine loses power and dies.

Give it a minute with it off and all my power is back.

I noticed signs of detonation on the spark plug but the plug is ashy brown. No blistering. The piston is the same color brown and no signs of detonation (pitting, melting) on it.

I personally think the spark plug ground electrode is getting so hot it's causing preignition. I'll try retarding timing back closer to stock. But anyone else have any idea what it could be??
 
I guess you would see oil around one of the bearings underneath the magneto cover or side gear cover.
 
Shoot, I've noticed black/grey goo getting everywhere. I thought it was just me using too much oil in the premix. I'm headed to get an Allen key because I'm 8 miles from home and forgot mine at home.
 
Yeah that might be it. I’d do replace them make sure to order a complete gasket kit.
 
I’ve had myn for like 2 years and it has like 50 miles. Hopefully it lasts 200 going at this rate.
 
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