Alltoys:

Like when someone adds a K&N filter on the trail then goes for a long pull down a gravel road without changing the jets LOL


When you got your 2" measurement, you are saying that applies to ALL 4 stroke quads? I believe you got that from the Digitron instruction for probe location. The 1200 degrees you are talking about , how did you arrive at those numbers?

Let me understand this.

When we install digitrons on our sleds, they say the same thing except 7" from exhaust ports but here is what we do.

Run the unit for 1/2, 3/4 and full throttle run for 1/2 to 1 mile each. Kill the engine while holding the throttle open at which ever run you are checking for ( 1/2, 3/4 or WOT). Check you plugs AND your piston wash. Dial your jetting, needles till your have the nice coffee with cream plug colour AND a nice area the size of your ( average size person here [img]i/expressions/face-icon-small-wink.gif[/img] ) thumbnail on the piston head at the exhuast ports. ( remember 2 stroke)

Once this has been achieved THEN we turn on the digitron and record the temp readings. THIS is the temp you will allways jet for no matter what temp and/or elevation or mod addition or what ever, you will always be spot on if you are running the reference temp. .Basically we are verifiing our jetting by the color and wash and using the digi reading as a reference for when the variables change

We do this because some probes are different than others. My 800 runs SWEET at 1350- 1375 and is a DOG at 1200 where my buddies runs Sweet at 1150 and would melt at 1300 As a result we run quick probes that respond 3x faster than stock Digitrons so you know quicker if you will be melting or not.

Can we do this " work backwards" to get a reference on the quad?. CAN you check for wash on a 4 stroke??.

What I am thinking is to get the color, patterens motor response ect ( like when you told me I was a tad lean cause when you let off the throttle, the motor reved a bit before it slowed down). Once you have the bike dialled in the take a 1200 degree stick and test where it slowly melts.and record the length It may not be 2" on every bike.

1: what are your thoughs on this

2: Are we riding this Saturday??? ( I am not going to the Outdoor NHL game afterall)

 

Wow,
Technical responses from engine gurus that is great. I say 1200* as this is a good place to begin for a basic stock engine if you have high compression pistons, titanium valves and so on you will be able to run higher temperatures but then you better be running better fuel as well. There is a total misguiding going on the forum when it comes to jetting. People are always asking how to jet there machine and what should I be using for my application well who nows it is still up to individual how they want to have their machine perform. For instance if I am going to race my quad then I will jet differently most likely run it on the lean side but you must understand to run it lean without aftermarket parts you run the risk of melt down. I don't care who you are a sustained run of 1500* will result in destruction simple mechanics tells me that metal melts at a temperature.

Plug color and piston wash is a basic step in determining the sweet spot as it were. How far do you want to take this I would not put my basic motor through a 1500* run because I know what will happen. How did I come up with this 1200* optimum temperature? Well how did you come up with 1500* trial and error I would think. I have ruined a few engines on my up the ladder so 1200* is a good step to start from. @ 2 inches from the head is where digatron says to run their sensors I have basically done the same with other units as well so it seems a good place to start. I am not an engine guru I have learned from good ole trial and error and what works I stick with. I can get on a machine take it for a run and tell what is needed to make it go faster and run better. This comes from experience, this experience has taught me that 1200* is optimal for a base stock 4 stroke the rest can be determined through dynos, plug color, and piston wash.

n2xlr8n, XC800,
I applaud you both you have valid concerns and excellent ways to find the right jet size to use. Temperature is only a tool it is a result of all other things that form a conclusion. From this conclusion you can use it in conjunction with other modds as you do them to reach the all important SWEET SPOT.Now go forth and jet your machine!!!!!!!!!!!

 

I believe that 1200 is in the right neighbourhood for both 2 and 4 stroke. What I believe is inportant is that the exact real true temp at

say 2" could very well be 1200. The important thing to remeber is all probes and all Digitrons or any EGT for that matter will have a slightly different reading at the 2 " point. Hence the true determinig through plug color piston wash THEN use the Digi to track any variables. Truth to the matter is my 800 probably was running a true 1200 to 1250 but the reading was hi on my paticular issue of Digitron.