ported machine

M

maxco

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Sep 30, 2009
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56
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coloraDO
I have a question for the group. I recently purchased a mm2000 with a port job on it. I dont really have a baseline for how a snowmobile should run. My machine runs well. it seems ok in the mid range, and low end. when I get to about 6500 rpm you better hold on. It seems to just want to fly. I really gets up and runs. I would like to know if this is typical. If it is or if it isn't is there a way to make the machine smoother in transition. If you are going on the trail and not looking, you can hit that rpm and be in for a suprise. I have been working on dialing in the jetting, but I want to know what I am up against. Do I keep working on the midrange for better response, or just realize that a ported machine will behave like this. Any thoughts or ideas are apreciated. I will be riding this weekend :2strokes:
 

Our stock SX's seem to be about the same way, I just think its all in the motor and where it maybe switches over in the carbs?!? I'm not sure why it does that but I've noticed it too.
 
My thought is the powerband runs high in these sleds. Most of your power is 7,000 - 8,900 (peak rpm) rpm's in these sleds.



You are probably right on!





Mike
 
My 2005 Mtn Viper does the same thing, so just hang on and enjoy the ride! ;)!
 
i would disagree as to it being the nature of the machine. by comparison, stock 03 viper mtn, stock 00 mm and 01 mm with bender pipes, all three are strong from bottom to top. no "power surges". the piped 01 pulls harder, obviously, but it seems equal throughout the ranges. i have ridden bikes and sleds with poor porting that only hit at a certain range and then its as you describe. look into the clutching and carbueration, or its a pipe or port thing.
 
so keep workign on jetting, and clutching to get smoother response, but it may actually be a bad port job?
 
i have ridden bad port jobs, i have done bad port jobs, and i have paid others to do bad port jobs for me. your issues sound like some things i have dealt with in the past. but, its hard to diagnose with a keyboard. based on the previous posts, mine included, your situation sounds like a tuning issue, bad porting, or the nature of the pipes. i remember in the mid seventies simply adding a pipe to a mx bike and totally changing the ridable qualities. same applies to sleds. bad pipes makes bad power attitudes. i have no experience with hauck pipes. i have purchased misc parts from them in the past and picked their brains for knowledge in race applications. just for fun, if you have the resources available, try throwing a stock single pipe on the sled and see what happens. you failed to mention the clutch engagement rpm as well as the existing clutch set up. this info may be helpful.
 
clutching

The engagement is 4000. It has a lightning roller clutch, on a hartman helix. I do not know how to tell the degree on the helix. The machine has a green artic cat spring, and I do not know its rating, it came with the machine when I bought it. thanks for responding to my questions everyone
 
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