CHT Temp vs. Plug Chop

[fatcharlie]

Hi all,

Regarding my 86 Aero -

My new Leo Vince pipe is installed with an 88 Main. Only changes to the bike are the new pipe, the main jet and a lightened vario with 7.5g rollers.

Plug chop shows a nice and dark color (just a bit darker than cardboard).

When I run 3/4 to WOT for a couple miles, I will see my CHT temps move up into the 360 range after a minute or 2. The motor has the stock top end on it. Is there any concern with these temps? If I back off the throttle, I see it drop pretty quickly into the low 300s.

One factor: I recently opened up my oil lines, so I premixed 40:1 to be safe. While a pretty negligible amount, I do lose 2.5% of fuel through the jet to oil volume. This in theory would drop my effective jet size to an 86. (Wikispreedia jet reference shows the jet # is referenced to the hundredth of a mm - 88 Jet would equal .88 mm - assuming the size changes are linear, that tells me that (.88-(.88*.025))=.858) = 86 jet)

So my question is... Long WOT rips show 360, is this a concern? I expect to see a slight drop in CHT once the premix in the tank goes away.

Is CHT temp monitoring a viable alternative to doing plug chops? I understand that CHT is giving me a slow refresh rate (compared to say - a pyrometer) but making the assumption that my mixture isn't way out of range and heating the internals faster than the response time of the display, is it safe to refer to it for tuning?

[fatcharlie]

One factor: I recently opened up my oil lines, so I premixed 40:1 to be safe. While a pretty negligible amount, I do lose 2.5% of fuel through the jet to oil volume. This in theory would drop my effective jet size to an 86. (Wikispreedia jet reference shows the jet # is referenced to the hundredth of a mm - 88 Jet would equal .88 mm - assuming the size changes are linear, that tells me that (.88-(.88*.025))=.858) = 86 jet)

One thought about jet calculation during premixing... I'm making the assumption that the atomization rate of the oil and gasoline are the same. They probably are not due to the viscosity difference between the two liquids, but is this negated since its homogenous?

[Bear45-70]

360┬░ is fine. You are right gas and oil do not atomize the same, It is doubtful the oil atomizes at all but it is suppose to separate from the gas in the crankcase when pressurized.

[bakaracer]

360 at wot is a good temp but don't rely only on the cht for jetting. Do a plug chop also to confirm the jetting is matching the cht. At 360 that plug should be that dark coffee brown but not real dark. If its really light or off color white or dark gray its lean or you have a leak somewhere.