What is the actual measured pop-off pressure on each Carb? Those A/M Mikuni SBNs normally come with 115gr Springs. HSI could have forgotten to swap or installed wrong Spring?
You could insert a Jet (try a #60) in the Return Line to raise the Fuel Pressure going into the Carbs so that the Needle...
Group K did have a rough maintenance schedule relative to Piston Speeds:
4000+ fpm – Completely unpredictable life span of crankshaft components
3700 fpm – Crank life can predictably be 20-35 hours
3500 fpm – Crank life can predictably be a full season of use
3300 fpm – Crank life is...
1993 YAMAHA 1100 BLASTER 1 in Excellent Running Condition
93 Yamaha Blaster 1 with Kawasaki 1100 93 Octane Pump Gas Limited Engine. Billet Aluminum Cylinder Head by Cool Head ($350). Compression 125 psi even on all three Cylinders.
Triple Aftermarket Mikuni SBN Racing 44mm Carburetors ($600)...
Probably because the Carburetor Throttle Plates and Shaft Bushings are worn allowing more Air to pass at Idle and Low Throttle, thus requiring more Fuel...
If the Pre-Mix had the right amount of Oil, then either Water washed away the Oil lubricating/coating the Pistons or the Carbs settings were lean or there's an Air Leak somewhere.
Once the Rings seized or stuck flush inside the Ring Groove, the Cylinder lost compression, because the Rings...
Looks like Water intrusion or Lack of Oil on bofth Pistons. The blow-by came later after the Rings seized.
Have new ProX Pistons for the rebuild at just $100 each : https://www.x-h2o.com/threads/prox-pistons-for-yamaha-700-1100-100-ea-plus-shipping.208134/#post-2134537
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