Maybe you can try with other radiator cap? For me they are first to check on the list. Also, with some good synthetic oil my bike run at lower temp. Unfortunately, my long term choice, Elf 4 xt tech 10/50, has been discontinued and replaced with 4 tech and bike is running now a little bit on higher temp.

Hugo. Some advice from an old XT fan, DONT WORRY!!! The XT is a fairly bulletproof engine and gearbox and Yamaha must have made zillions of this engine cos it is fitted to the Raptor Quad (in 700 form since 2006 ish) as well as the MT03 and the XT family. You need to take a notepad and pen and write down anything you do to your bike cos you always need to know how to go back IF the mod was not a good one.
Your bike sounds like it is running a bit warm. But before you try anything else I would give the bike a total service and fit a decent air filter and remove the stupid snorkel, she needs to breathe better. Use a top oil like Castrol or whatever and usually a 10/40 is best. THEN when she is tip top you can start to try some CO settings. Have fun!!!

Thx for the advice, I have installed a DNA racing filter and airbox cover with extra (filtered) vents. Unfortunatly haven t been able to test yet since I have replace the throtle cables and one of them is malfunctioning. I try fix this ASAP, also verry curious for the extra grunt with the extra vents!

hot running
 

Sounds very much like your engine is running too weak, try putting the snorkel back on and the standard air filter back in too confirm this is the cause. if you let the engine breath a lot more freely you must richen the fuel mixture.

I haven t removed the snorkel. I just installed the filter, up until now it was a stock filter... Could not test the dna filter yet.
But I was thunkingin the same direction. My engine is allready running hot, addind more air might make it run weaker, no? We will see as soon as I can sort out the problems wut OTR...

I briefly teated the new filter and. Wow!
I notice having more range in 1 gear, more power in the lower revs.
Quick respons on the throtle
Smoother ride

The only downside, less engine braking. But since I have slower respons on closing the throtle and seem to run hihger revs stationairy, I think I have to adjust the stationairy screw. Rather than having to play with mixeture settings, or not?

I haven t test it enough to see if runs hotter or not... sure runs faster now!

Anyway, so far thanks all for helping out!

wwith the new air filteryou ll have to find the new best CO value.

to find it more easily :
1- let the stationnary as it is.
2- increase de CO value by 5
--> if the stationnarie increase, then repeat
--> if it decrease, lower the CO value (by 2 for exemple)

--> you just have to find the right spot when changing de CO value, the stationary is at its peak.

For the filter, it is a very good thing ! i agree with less engine braking, but the gain is significant on other perf so...

Snawbool,

I am sorry but I do not understand. Your descriptuon seems to be looking foor even higher revs at stationary. I wish to decrease my revs...
Could you give me some more explanation for your methid please?

Thank you

Edit
Oh I think I grt it! First find peak on co value than drop revs to normal with stationairy screw?

Hi all,

Months later K still struggling with this over heating problem, putting the bike to work here in fench alps, I manage to get the coolent warning light the light up and the cooling fzn tondo a lotbof overtime. Still in the direction of a lean mixture, how do I get to richen the mixture???

Thank you

Hugo

add kev mod, O2 eliminator or booster plug.
and find more suitable CO setting, then set your idle screw to 1500-1600 rpm.
is your radiator not clogged with dirt?
is the impellor not loose from the waterpump axle, might not be spinning round with the axle but just loose on the axle?