I've been struggling to get this thing running decent, the clutch is completely rebuilt, we really took our time with the fuel system, tank was spotless, new lines, pump, carb cleaned with new pilot and main, needle/seat..... and still it wouldn't run right. Set everything at factory specs, fresh set of plugs and it would run decent for about 10 minutes then bog and be barely rideable. We tried a different set of floats, different needle/seat, set the float level, then tried lower it a bit for more pressure. Still same problem.
So today I ran out of ideas and threw a hail Mary pass out there just to see what would happen. Had a pair of 34 mm carbs off an older Polaris 440 that were destined for my Scorp project. Took one apart, cleaned it up, installed a 30 pilot and 180 main, needle in the middle, air screw 1 turn out, squeezed the factory airbox on it. Got it running and took it for a careful little spin listening for popping or hesitating...nothing, it ran great. Got more aggressive to the point of running it full throttle and really working the engine hard through deep snow. Checked the plugs and they are light tan, almost a golden color but dry.
Am I paranoid or should I try and get them a touch darker into the cardboard brown stage? Thinking of screwing in the air jet maybe 1/4 turn, pick up the needle one notch and see how it runs. Oh and the only real "mod" to the engine is the stock exhaust has been modified a little with some of the inner baffle pipe removed (mostly by rust). Appreciate the help. I love this machine and would hate to blow it up after it ran so great today.
Think I'm going to fry my Snowfire?
Think I'm going to fry my Snowfire?
Last edited by AJ Sparko on Sun Dec 21, 2008 2:21 am, edited 1 time in total.
Think I'm going to fry my Snowfire?
I would probably up the main 1-2 sizes, possibly raise the needle one notch, to be safe. How was the weather today, compared to a usual riding day?
Take this with a grain of salt, but this is what I have gathered from playing in almost every form of motor sports:
On a 2cycle you will want to see the plugs a little darker then you would on a 4cycle in a similar application. In a race application you will want them pretty light colored, and in a everyday rider you'd want them on the dark(safe) side.
To be safe an aircooled engine should be a little richer than a liquid cooled engine.
On 2 strokes Ive tuned on my dyno, I shoot for just a little darker than a good suntan brown, and thats probably what I would look for. Its a good compromise between safety, and power.
Take this with a grain of salt, but this is what I have gathered from playing in almost every form of motor sports:
On a 2cycle you will want to see the plugs a little darker then you would on a 4cycle in a similar application. In a race application you will want them pretty light colored, and in a everyday rider you'd want them on the dark(safe) side.
To be safe an aircooled engine should be a little richer than a liquid cooled engine.
On 2 strokes Ive tuned on my dyno, I shoot for just a little darker than a good suntan brown, and thats probably what I would look for. Its a good compromise between safety, and power.
Think I'm going to fry my Snowfire?
Today was pretty typical, 20's, I never go out when it's in the single digits since my daughter is on her sled. I've gotta order some other stuff so I'll add a 185 and 190 main to that, probably a 195 to boot since it's never a bad idea to have extras for other sleds.
Think I'm going to fry my Snowfire?
Never even thought of that, the expense of one is probably why. That's just not in the budget at the moment (Christmas), and yeah I know it's cheaper than a complete rebuild but more than likely I'll be doing that in the summer anyways. 
So running a 180 now and getting a tan color, going pig rich would be a 200 jet or what would you recommend? Don't worry, I appreciate the suggestions but understand fully that I hole a piston it's no one's fault but my own. I'm just excited it finally actually runs good.
So running a 180 now and getting a tan color, going pig rich would be a 200 jet or what would you recommend? Don't worry, I appreciate the suggestions but understand fully that I hole a piston it's no one's fault but my own. I'm just excited it finally actually runs good.
Think I'm going to fry my Snowfire?
Try a 185 or a 190, see where that puts you. An egt is nice but it isn't the end all. You can't really tune by it, rather you use it to make sure your not too hot. Every engine its different, and egt will depend on lots of variables. Ignition timing, fuel quality (octane, and amount of alcohol), compression, port timing, altitude. You can't really say "tune it so the egt says xxxx degrees". Rather tune it so it runs good, then use the plugs, and egt to check that its a safe tune.
Rich is very right about starting rich and work your way lean. I'd say your very close to perfect, so no sense richening it way up, give it just a little bit more fuel for saftey.
Rich is very right about starting rich and work your way lean. I'd say your very close to perfect, so no sense richening it way up, give it just a little bit more fuel for saftey.