Photos of piston and valve with stock crank vent system.
#31
08-21-2018, 02:14 PM
Seasoned HDF Member
Yes. Venting to an alternative source permanently eliminates additional carbon buildup, as long as good-quality fuel is used and the rings and valve seals are doing their job. You can get what remains out of there by using a good fuel cleaner (I prefer BG 44K).
You are correct, but always run the risk of carbon chunks getting caught between the valves and seats. Stopping it at the source is always a better solution.
You are correct, but always run the risk of carbon chunks getting caught between the valves and seats. Stopping it at the source is always a better solution.
#32
08-21-2018, 02:36 PM
Road Master
The carbon build-up on pistons must be accounted for by the designers. I've seen carbon build-up on every working piston I've ever seen, even when I was a kid, long before EPA started forcing the manufacturers to vent the cases back into the engines. Sure, it'd be nice to have shiny clean piston crowns, but I doubt it matters at all in the actual running of the motor.
Oil is going to find its way into the combustion chambers from other sources as well. Piston rings will let some past, and valve guide seals will also let some through. Gasoline also leaves deposits behind. That's why I think that the designers account for this, and probably even use it to advantage in some ways.
Most likely, if we just leave these motors alone and don't think or worry about deposits on the pistons and valves, the motors will run just fine for over 100k. But one of the major advantages of this type of motor is that heads are relatively easy to remove and have them cleaned up, if need or want be. I pulled the heads off my Yamaha Road Star at 40k miles, just to clean them up. There was plenty of deposits in there. I cleaned them using a chemical cleaner for this purpose. I removed the valves and cleaned them up. Replaced the valve guide seals, which were showing some signs of cracking around the edges. Replaced piston rings. Put it back together and it ran exactly the same as it had before the take-apart. It was an exercise in just 'cause. It was fun, but completely unnecessary.
Oil is going to find its way into the combustion chambers from other sources as well. Piston rings will let some past, and valve guide seals will also let some through. Gasoline also leaves deposits behind. That's why I think that the designers account for this, and probably even use it to advantage in some ways.
Most likely, if we just leave these motors alone and don't think or worry about deposits on the pistons and valves, the motors will run just fine for over 100k. But one of the major advantages of this type of motor is that heads are relatively easy to remove and have them cleaned up, if need or want be. I pulled the heads off my Yamaha Road Star at 40k miles, just to clean them up. There was plenty of deposits in there. I cleaned them using a chemical cleaner for this purpose. I removed the valves and cleaned them up. Replaced the valve guide seals, which were showing some signs of cracking around the edges. Replaced piston rings. Put it back together and it ran exactly the same as it had before the take-apart. It was an exercise in just 'cause. It was fun, but completely unnecessary.
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