Anytime you change exaust pipes on a snowmobile engine you MUST re-jet the carbs. If you dont do this, you WILL melt down the engine. This happens because the exaust scavenges out of the cylinder much better and inturn allows for more air/fuel mix to enter the cylinder. With most of the exaust gasses gone out of the cylinder due to the exaust pipes you will get need more fuel to keep the combustion process cooler.
As for the clutching, its not necessary, but it is highly reccommended. A clutch kit will help put all that added horse power to the gound more efficiently.
This kind of thing is kinda hard for me to explain without the use of some diagrams or pictures. It would also be much easier to explain in person. If you have more questions i can try to explain, or im sure someone can put this into words much better.
Polaris is my way out - Other people just use a door.
The pipes usually add most of their power in the upper midrange and up. Low end snap or throttle response can actually decrease. I have to disagree with ToU because its been my experience that you must always change the clutching when increasing power by adding aftermarket pipes. You will definately have to rejet and sometimes not only the mains. If you are looking for snap in the trails, consider some UFOs. They are hard to set up but made a huge difference in my 680.
If you pipe that machine, you should definently get a clutch kit. That machine really wakes up with the triple pipes, so the stock clutching would not utilize the power gained. You also might need to re-gear it, b/c those pipes should add about 10mph to the peak speed. 144 studs will help put the power to the ground too. If you do this work, you will have an awesome cross country and lake racer machine, that will probably beat the new 600 twins on top end.
Did you pipe your Ultra?? Something about that machine has always interested me, maybe the killer graphics or the sound. That thing sounds like a jet fighter when you meet one on the trails. I am considering getting one and making a lake rocket, it should be awesome with triple pipes, like about 150hp??
the pipes should have came with instrutions for jets and needle settings. I had a 95 with slp pipes heads, thundershift wieghts and the clutch kit it came with and geared down the top to a 20 tooth. in 98 when the 6and700 twins came out I could smoke the 700 in the short run, like up to 700feet. at the 1000 foot it was a tie and on top end they were a little faster but the xtra 12 takes away top end and i am also 6'4" 240lbs that slowes me down a little also. them other guys are right it will be an awsome trail machine with good clutching and suspension set up.
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