Temperatures

[mack]

Anyone know what the normal idle temp range is at the first header bend. This wouldn't change with a 4-1 would it?

[motoman]

Anyone know what the normal idle temp range is at the first header bend. This wouldn't change with a 4-1 would it?

Hot................BTW, why the concern and why would it matter? Curious mind needs to know.

[natemoen]

Hot enough to make water sizzle and evaporate instantly.

[mack]

Temps

Well.... After almost three decades in the army I don't hear so well so tuning by ear is not an option. I'm old now and my eyes aren't what they used to be. I have a color tune but have no idea what the real cobalt blue should look like. I googled it and had about fifty choices. I used to just set the idle turns out about 1 1/2 turns on the SF and 3 turns on the LH, but these are 35 year old carbs and the orifices and internal components wear down (according to mikuni)Then of course, if you've ever had to remove a broken mixture screw, the orifice is damaged. Maybe not so much with the 80/81 carbs but the needle seat in the early carbs is tapered to match the needle, during the removal process this tight taper is altered.
I've been finding my plugs don't look as good as they used to after tuning runs.
So what I've been doing, with good success is setting the screws to factory spec, doing a quick sync, then taking an IR thermometer and checking the temps at the header. If one is out of whack to the rest I'll make an adjustment to the idle screw (richer or leaner depending) so that all four cylinders have the same temps (+/-) five degrees. Then do a fine sync after. And recheck the temps.
It actually speeds the process up but I have no bench mark on what the temp should really be. After the final sync mine are at 135-140 degrees F. And the plugs look good. Just being anal i guess, but initially before leaving the factory, this is how Yamaha tuned them( or a variant of it)

[TADracer]

There is no normal

Too many things would affect the temperature at the first header bend like stock pipes (double wall) vs. after market (single wall), idle mixture, idle speed, spark plug heat range, if the headers are coated inside and out with ceramic, timing, compression and a host of other things.

I think if you are using a measurement like that for tuning then the most important thing is if they are all even. Then, the better place to measure cylinder temps are at the base of the spark plug because that is a true reflection of cylinder temps.

[mack]

True enough

The SF is all stock. Recommended NGK plugs all gapped the same. It's running like scalded dog.
The LH is all stock with ceramic coated pipes.Same NGK plugs gapped the same.
These are as close to factory as you can get.

[skids]

Anyone know what the normal idle temp range is at the first header bend. This wouldn't change with a 4-1 would it?

It is enough to "flash fry" your forearm when fooling around near those! (Don't ask )

[Yahman]

It is enough to "flash fry" your forearm when fooling around near those! (Don't ask )

Or quickly burn a hole in the arm of a good jacket!

Ride safe,
Larry

[cajun31]

mack

I like the concept of the IR thermometer. What kind is it, cost, availability? Sounds to me like an easier way to approach setting the carbs.

[mack]

mine is

a TIF 7610. Real cheapo , less than 13 bucks at a Canadian tire clearance bin, but I didn't care at the time what the accuracy was, only that it could compare cyclinders to each other.

[cajun31]

thanks

definitely something I will be adding to my toolbox.