How much fuel wash is too much ?

[Langbolt]

I thought I'd pull the head off my 330R and inspect the bore & O-rings.....this is what I saw.....nice and clean....the bore is fine with no scorring or markings. I did notice a bit of a small burn mark on the outer edge of the Inner O-ring.....so I replaced it with a new one (Outer was fine....but I changed it too!) I was amazed at how much fuel wash I had.....only that little bit of carbon on the top of the piston.....the dome was clean as a whistle!

I'm guessing I'm still a bit rich on the jetting (185 Main, DGH 3rd clip, 60 Pilot)....but better to be on the safe side.

[rsss396]

yes that is a very safe piston wash, not allot of heat is building up on that dome. If you ride in the cold and hot weather and do not like to change jets then if its running good you are probably wear you want to be.

You may need to flat plate the cylinder and head to provide a better mechanical seal but its pretty normal to get a little carbon on them when they are closer to the bore. My ligers orings are so far away from the bore they almost never have any marks on them.

[Jerry Hall]

A piston crown that looks like yours is running cool.  A piston crown that looks like the one you have pictured is because the time at full throttle is very brief and or the jetting is on the real safe side.  If you are running it at full throttle for more than 10 to 15 seconds at a time there is probably a little more power to be had by leaning the main jet a little.

The marks on the o-ring are usually on the inside of the o-ring closest to the bore not on the outside of the o-ring.  Let the o-ring relax and see if the marks are still on the outside.  If the marks are on the outside the groove may have not been machined to specification and the o-ring is being pinched.  If this is the case the groove should be machined to spec.

[Langbolt]

Thanks Dave, & Yes Jerry...you are correct....I rolled the O-ring so the nick was on the Inside of the O-ring. I'm always afraid of running too HOT or lean and squeaking it! The coolant temperature max's out at 178 degrees F.....so i'm safe there too! And that's on the hot days in the summer. Full throttle is brief....If I was running wide open for a long time....I would continue with this jetting. My friends mock me for using the Oil that i do.....just goes to show it works fine for me....it's Yama-Lube 2R (semi-synthetic)

[GO OVRIT]

How many hours do you think are on that?

[Jerry Hall]

Thanks Dave, & Yes Jerry...you are correct....I rolled the O-ring so the nick was on the Inside of the O-ring. I'm always afraid of running too HOT or lean and squeaking it! The coolant temperature max's out at 178 degrees F.....so i'm safe there too! And that's on the hot days in the summer. Full throttle is brief....If I was running wide open for a long time....I would continue with this jetting. My friends mock me for using the Oil that i do.....just goes to show it works fine for me....it's Yama-Lube 2R (semi-synthetic)

Your piston would look about the same even if the water temps were 250 deg. F.  The water temps do not affect the piston crown temperatures very much especially when the engine is not being run very long at wide open throttle.  The piston crown temperature is a function of combustion temperature, pipe restriction and the length of time the engine is held at or near full throttle.  

Yamalube is good oil and so is all of the oils that are sold as oem oils.  Most of these oils are outboard motor 2 stroke oils.  Outboard oils usually run real clean.

[Brett]

Man my jetting must be really fat since I'm running a 195 main in my 310 and I think I have a 60 or 65 pilot jet in mine. I should take off my head too and see what's happening in there. Then again my time at full throttle is almost non existent haha

-Brett-