[rtillery02]

since search program is down, I'll fresh'n up an old topic. 2002 iron barrel, alloy cyl. upgrade runs great. jetted up carb. to 130 main. Been runnin nice n cool, took it to work yesterday, 45 deg F outside, did great till bout 40 mph, quick heat jump, pulled over when it reached 280, just pullin over @ idle the temp started fallin quickly, let it run till it reached 230 deg, took off, two miles later had to do it again. Runs great all the time w/no odd noises, the 280 temp didn't effect the idle or change tappet noise, without the temp guage I'd have nev'r known there was an issue. Any thoughts from anyone that I may be overlooking as to why I've got this issue? It's cold here & I'm still runnin 20/50 multi visc. in the engine.

[ace.cafe]

When it's cold, the mixture goes leaner due to denser air. You may need re-jetting.
Be aware that the bigger main jet only affects full throttle position. At some partial throttle positions you may be lean, and these partial throttle mixtures are controlled by other jets and the needle.

[crock]

What are you measuring, the oil temperature? Where is the thermocouple or temp sensor located?

[rtillery02]

Crock, the temp indicator is just a "trail tech" assembly with the ring sensor under the spark plug with a digital readout. The rest of the engine is "cool as a cucumber", even @ 280 deg. the cylinder was touchable, even the intake side of the head was bearable to the touch. I think I'll try to step up my pilot/idle jet some & see what gives, it still pulls much better with the choke ON, so this'll be the 4th jet upgrade since the beginning.

[rtillery02]

ACE, the last main jet installed had .130 stamped on it & was considerably larger than the one removed, BIG acceleration improvement, but still room for more I think since with the choke ON, it PULLS better still (don't idle too well) but uses all I can give it, so far. I've never flooded or seen a rich fuel situation on this machine yet. Since it's a stock machine, what would your "ballpark guess" of a "hefty" pilot jet be, to pair with this .130 main jet that's installed now?

[Arizoni]

I think this is a case of "Too Much Information".

The temperature sensor is picking up the heat the spark plug is conducting away from its center electrode.

The engine is still quite cool and when you stopped, the cylinder head pulled the high heat out of the spark plug (even with the engine idling).

As we know, that spark plug center electrode gets hot enough to burn off any carbon deposit that tries to form on it.  In other words it, and its steel base gets hotter than hell.
That heat is normally conducted into the cylinder head.
In this case, it's conducted into the temperature sensor before it can get to the cool cylinder head.

If the cylinder head or the fins on the cylinder get up to 280-300 degrees F it would burn the crap out of your fingers if you touched it.  Even at that temperature it wouldn't be really overheating (although it would be getting close).

Just ride the motorcycle normally like you've always done.
Check the sensor temperature guage and learn where its normally at and be happy.

If you really want to find out what reading is indicating a dangerous temperature, wait until a really hot day.  Then find a deserted road and ride for a mile at WOT.  Then check the temperature.  Even that temperature probably  isn't dangerous but it does give you a good idea of what the "MAX" should be.

[ace.cafe]

ACE, the last main jet installed had .130 stamped on it & was considerably larger than the one removed, BIG acceleration improvement, but still room for more I think since with the choke ON, it PULLS better still (don't idle too well) but uses all I can give it, so far. I've never flooded or seen a rich fuel situation on this machine yet. Since it's a stock machine, what would your "ballpark guess" of a "hefty" pilot jet be, to pair with this .130 main jet that's installed now?

27.5 pilot.
Rarely would any larger pilot be needed, even at sea level.
The needle jet is the most used jet in normal use.
P2 usually is sufficient at sea level.

[cafeman]

I'd agree with Arizoni, too much info from the wrong spot. I'd think at the back of the barrel up near the head or something, away from airflow to get a better read on heat there. At the plug is about as useful as taking a reading at the exhaust pipe. I know when I pull a plug on anything after its been running its insanely hot. Better to get a general idea what the piston is seeing??

[rtillery02]

Yep, maybe so. The whole idea behind the temp gauge install was to keep the head temps away from the 300 deg. exhaust seat install range, since that's where the initial problem occurred (didn't wanna drop another seat) But, if 280deg. is too soon to cool it, & @ 320 the damage is likely already done...there's probably not much point in havin a temp gauge installed at all. If on a cold day it jumps right up to 280, I doubt an East Texas summer day is gonna cool it down any. I may just park it & ride the C5 but there's just something about that 4spd rt. shift that really inspires me...we'll see. Thanks All, R.Tillery

[ace.cafe]

FWIW, we just point an IR thermometer at the head in the central area, and read temp that way, when we are unsure of what it is.
Normally the head won't run over 300 unless the tune is off, or it is a very hot day and it has been running for a while.