2006 Summit 800 or 2007 Summit 800r

they are both great sleds its most likely that a a 07 with have had the
crank update done since its 7 years old but make sure it has been done
and it should be pretty darn reliable ( for a snowmobile :face-icon-small-dis)
good luck

My brother in law had an 06 and it was a nice sled. I had an 07 and after I had the lower end updated it was very reliable and had a lot more power and just flat out performed the 06 in every aspect. The brother in law actually sold his 06 and bought my 07 last year! If you can prove the 07 has the updated lower end I would buy an 07 in a heart beat over an 06.

I had a 06 800HO summit adrenaline 151" for two seasons which was my first mountain sled. It was wrecked this spring on a buried obstacle. It was a great running sled but it did have some trenching issues. I parted it out and put the money into a 07 800r summit adrenaline 151 I bought this spring with a bad crank pto crank seal. I had a rebuild on the motor with crank update done along with the clutches rebuild, I also went from a 21t to a 19t bottom gear. I have only had one 10 mile break in ride in about 2' of snow but there is a very noticeable performance increase. I cant tell for sure if I will still have the same trenching issues but I think it will be better. The 07 adrenaline also has a 2-1/4 paddle where as the 06 only had a 2" paddle. My 2 cents for what its worth is to go for the 07.

My 06X has a 2.25 lug (which measures closer to 2.3) as did all the 06 X's