Ihave a 2002 XCSP 500 with SLP airbox mod and a boost bottle. i was wondering where I should mount an EGT probe. and also how far from the Y-pipe. I race shifter karts and i know that on our 125 its 6inchs from the jug and we should be runnin around 1275-1300 (safely) are sled any different?

Hello,
I have the exact sled also with the Slp airbox mox and boost bottle, along with many other modifications. I have a Koso Dual EGT gauge that I purchased towards the beginning of the season. I was asking many of the same questions. I purchased a book put out by Exhuast Gas Technologies off of ebay that has specific inormation put out by various companies including the big 4 and aftermarket companies. The problem that I have with the book is that some of the specifics are listed for snowmobiles from about 1990-2000.But, Polaris has two specifications without any specific years listed or anything like that and they are,
1.Multiple cylinder single pipe: 1.5" from where the engine and the pipe meet (where the exhaust gasket goes)
2.One pipe per cylinder: 5" from the piston skirt.
The temperatures that Polaris provided are:
Above 1200 degrees F = Detonation
1150-1200 degrees F = Normal
I purchased a Dual gauge and put one probe on each side basically as close to the Y-Pipe junction as I could get them. This was about 1.5" from the block for me. I was only going to purchase a single gauge because of money reasons but after talking the the Koso rep at Haydays I bought a dual. He said that when people buy the single gauges they put it after the Y-Junction. He said this is the incorrect way to it because he compared it to taking hot water and cold water and putting them together to get luke warm water and an inaccurate reading. He also said that if you buy a single gauge to do as listed above but on the magneto side of the engine because it runs hotter typically. (which after installing a dual gauge I found this to be the opposite on my sled). So I don't know what to tell you man, I have spent countless hours trying to figure this out on my own and I am telling you what I know to try and save you some time. I found that with this topic alot of people were hesitant to give their input due to soo many variables and not wanting to be responsible for major engine damage.Personally, I try to keep my EGT's between about 1050-1200. It gives me a little safety margin and a little range so I don't have to re-jet every single time I ride. I have established this using the good old piston wash method. I also know that aluminum melts at 1300 degrees F. Well good luck to you and I hope this helps.