[size 1]I put this on the "Off Topic" board, but thought that I might get a few more reponses here....... [/size]
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[size 1]I'm sure there are a few out there that know their snowmobiles pretty well...... I'm coming to you for some help.
I bought an old sled for cheap to pull my fishing gear out on the ice. It needed a little TLC, so I have taken the carb off and cleaned it out really well, and I have put some new gas in it and replaced the plugs. It still runs a little shabby. It won't really rev up good. When I do rev it up too quickly, it back fires. I can rev it up slowly and it goes about 25-30 miles an hour. It will idle for about 5 minutes if I just let it run, but then it will shut off.
I need some help with the carb adjustments. There are 2 screws on the carb, but I'm not sure what they do and which one I should be adjusting. Any recommendations?
Here is a pic of the screws..... the one on the right has a spring on it.
Thanks for the help!
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I'm not a mechanic by any means, but have worked on old motorcylce carbs a lot. That screw with the spring will adjust the idle. Get the machine running and then turn it one way and listen for the engine to run lean or not. If it starts to die then turn it back the other way. Snowmobiles usually run pretty high on the rpms so don't be afraid to turn it up a bit.
As far as the other screw, i'm not sure. (Can't see a picture in your post) But there is a jet screw that when adjusted right should keep it from backfiring. If you are running the machine at different elevations then it is use to, you might need to change the jet entirely to allow the engine to run rich enough.
Like I said i'm not a mechanic, but maybe that can help you out.
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Here's the pic....
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I don't know much about 2 strokes or there carbs but on old car carbs (holley's and such) if you back fire you blow the power valve in the carb ( so that will have to be replaced otherwise you dumping raw fuel in). Now on 4 strokes normally you back fire when your out of time. If you can ajust the timeing I would see if that is the problem with increaseing your throttle. your timeing may need to be advanced. How old is it does it have points or electronic ignition? If it has points you may need to reset the gap on them also.
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I'll have to look at my paperwork on it for the year but I think it is a 1980 Arctic Cat Pantera with the Spirit engine. It has points. Any idea where I could find the gap setting for the points?
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I would get ahold of a artic cat dealer (service center) to see if they can give you the info. But it being a 1980's model I would be surpised if it has points. You may just need to see if the timeing needs to be set. Did you set the air gap on the plugs right also?
I know on my old outboard 2 stroke that makes a world of difference. I have points on my outboard but it is a 1967. In the 70's they did away with points on alot of things. Pop the distruptor and see if it has points or not, I bet you don't have points.
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Thanks for your help BassAckward!
I'm gonna check it out this weekend and see what I can find out. Gotta get it running a little better.
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I would agree with the timing issue, lots of things will make it run crappy, but not very many will make it backfire. Definitely check that first. If you have points, and the gap is set wrong, you will usually have a week or no spark, but the gap there being off will not make it backfire.
That other screw is probably your fuel/air mixture screw. It does just that. If the end of your plugs are sooty, your mixture is too rich, if it's whitish/grayish it's too lean. The smell of your exhaust will tell you a lot on that one.
You will have to play with the mixture and timing a bit because the symptons can be deceiving a bit and can mimick each other.
Bad timing can foul up your plugs too, same thing, either make them sooty or will build up a whitish/grayish stuff on them. Even if you fix your timing issue, you will have to deal with the plugs. Recommend that you keep a close eye on your plugs as you troubleshoot the timing stuff.
Let me know what happens, I've fought with a lot of small engines. I've fixed a bunch of them and beat the crap out of a few as well. They can be frustrating.
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I'm thinking that the carb in the picture is an old Mikuni. If so then the little screw on the left is the idle speed screw & the one with the spring on it is the idle mixture screw. To set that one, get the engine idling, then just turn it in (right) until the engine begins to slow down. Then turn it out (left) and count the turns until the engine gains speed and then begins to slow down. Now turn back in just a little less than halfway from where you first stopped and you should have a good idle.
The backfiring makes me wonder if the thing isn't running too lean. If that is the case you might be able to richen it sufficiently by raising the metering rod in the slide. You do that by unscrewing the nut affair that the throttle cable goes into. Once it's undone, you can lift the slide right out of the carb. There is a little screw down in top of the slide that holds a little bracket that kinda goes around the metering rod. Take it loose or out & in doing so note which groove on top of the metering rod the retaining bracket was in. There should be several grooves. To richen the fuel mixture you need to reset the retainer so that more of the rod is above the retainer. I'd try moving it a groove at a time until you get it to run right. If you plan on doing most of your riding at higher elevations like Strawberry, don't go too far with this if you're setting it down here in the valley or it's gonna want to run a little rich at the higher altitude.
I hope this helps. If not, try the local public library. If they don't have a book on that sled, I'm betting they can get one for you to look at.
Good luck
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Nica and Geezer,
Thanks for all the good information! That's GREAT stuff! I should probably go fishing this weekend, but I think I'll spend some time and get this thing going.
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Two more things for you.
1.) There is nothing that brute force and ignorance cannot solve.
2.) If all else fails.....get a bigger hammer.
Them right there are words to live by.
Uri
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2.) If all else fails.....get a bigger hammer.
Them right there are words to live by.
Uri [/reply]
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I'll be sure to bust out the sledge hammer
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