Scooterotica

jonashford wrote:regarding this 4 inches away from the piston measurement. What exactly does the mean??? straight line? when the piston is tdc or bdc?????

any one know for sure? Also does it matter how far in the probe is?

If I spend the extra for a koso id like to get it right, if I havent already!

Most people set their gauge at around 5 inches from the piston. This is because if you set it too close it will read very high i guess.
It should be measured like this......take exhaust off just stick your finger up your exhaust port and see if you can feel the skirt of the piston (do this when engine is cold! ). If you cant feel the skirt turn the engine until you can (take your finger out while turning the engine! Ouch!). Measure from that skirt to the end of your exhaust stub. Lets say that equals 1.5 inches.....then measure another 3.5 inches down the exhaust taking into account that some of your pipe is going to sit in the stub (like a JL for example).
When measuring the pipe, the measurement should follow the angle of any bends.

How far the probe goes in can effect readings. There is no garaunteed method here but i would say anywhere between 10mm actually sitting inside the pipe to half the diameter of the pipe.

The main thing is that you know what your bike is reading when its running correctly so you can tell if its gone unusually low or high, as both these can spell potential doom!
EGT's can vary greatly between different set ups.

Timing can effect EGT's greatly as well! Lets say your running 16 degrees and then you advance to 19 degrees.......surprisingly, it is likely that your EGT temp will go down and your cylinder head temp will go up!
There are many variables, so get to know what your bikes normal EGT reading is.

Cheers for all the info guys Im gonna take my probe apart see if its a fault that can be fixed

jonashford wrote:Cheers for all the info guys Im gonna take my probe apart see if its a fault that can be fixed

Please lit us know what you find. Mine just died, no eratic behaviour but then if it is a broken wire then that would explain it either way.

I cut through the probe with a hacksaw. Obviously not all the way thru! The two wires in side were still intact, but the braided wire that travels down the tube of the probe was burnt. Basically at about 10 - 20 mm before the end of the probe body sits the 2 wires joined together, then about 10 - 20 mm again is the braided outer cable that travels all the way to the gauge. I reckon that with this particular style of probe, it should not be inserted all the way in to the downpipe. Mine was quite a way into the downpipe. maybe this is the problem and only about a half to a inch should be inserted. I might ring mcgills and get another probe, but im not sure if I can be bothered again!!!

jonashford wrote:only about a half to a inch should be inserted. I might ring mcgills and get another probe, but im not sure if I can be bothered again!!!

Cheers John, my new probe arrived from Mcgill, my old probe was inserted to the mid point of the pipe so I will take your advice and not insert it quite so far. I'll let you know if there is any noticable difference in temps recorded.

Coaster. did u get your replacement probe???

jonashford wrote:Coaster. did u get your replacement probe???

I did and I fitted it with the probe inserted just short of half way. A couple of blasts at full throttle only got the temp up to around 500 degrees even when I held it at 7.500 rpm in third. But the CHT was climbing over 200 degrees and I knew it was likely to nip up at 210 so backed off. It LOOKS like not inserting the probe far enough is causing the gauge to under read a fair bit, when it nipped up last time it was reading 680 ish degrees (CHT 210) which would be about right. I think I might insert it all the way (ooer missus) until I'm happy and then pull it back again and just use it as a yerd stick. The wires on the new one are insulated in a kind of rubber rather than the textiole insulation on the original so may be from a different supplier?