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Discussion Starter #1 (Edited)
95 MX 470...just had the carbs cleaned, new plugs, new belt.
starts like a charm, idles well,right around 1600-1700rpm, some odd times idle will drop at 1000, light tap on throttle then she's ok.

second, it sputters, or bogs at any RPM lower that 5000, as soon as i go below the 5k mark starts doing it, even at 4800, as soon as it's above 5k she's fine !?!?!..now when i'm below 5k and the doggyness starts, snap the throttle all the power is there. have noticed my PTO side plug is a bit wet, color of both plugs are good so wouldn't think i have an air leak. any ideas on where to start looking at??
 

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Sounds like carb trouble to me, especially if you're running two carbs. I know you said you just had them cleaned but even the smallest little piece of gunk inside a jet will cause endless head scratching (your's not the engine's). Or it could just be out of tune, for what it's worth it sounds like your needle jet clip is in the right position :p
 

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Discussion Starter #5
carbs were cleaned on sat. here's what i'm thinking....mechanic said he had to adjust mag side carb, i think it was a bit lean, maybe the previous owner took both carb apart and mixed up the jets. why mag side could have been lean, and my PTO side plug is always a bit wet since i bought the sled 2 weeks ago, if that makes sense. i haven't worked on sleds much before.
 

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Have you tried reading your plugs? I mean other than just popping them out after a ride and looking at them. There's lots of info out there on how to read plugs properly, but basically the jist of it is to run the sled on a flat open area for about a mile at different throttle positions then hit the kill switch while still holding the throttle at the same spot. When the sled stops you immediately pull the plugs and look at colour (for you americans, yes we spell colour that way up here :p) and different deposits on the plug. This will tell you if you have a lean or rich condition and for which jets as different jets correspond to different throttle positions. Sorry if this is all redundant information but it's what I would do.
 

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Discussion Starter #7
you mean a mile or so on 1/4 throttle then kill it, half throttle and kill switch, and so on?? i haven't done this, but ill give it a shot. it's fine at half throttle and up, but below half throttle is where i see the problem. ill try out what you said, thanks for the tip, much appreciated !!
 

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Not all the info is in that reply I gave you, thats just the basics. Check around online for the whole process, theres lots to know about the colours on different parts of the plug and how they affect performance.
 

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Discussion Starter #10
plug color is ok but one, have one a bit darker and wetter than one wants to see, just wanted to rule out other issues than carbs. but looks like a carb issue. thanks all ! :)
 

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Remove the pilot jets (up the tube) and run a piece of stranded wire threw them, then clean them as well as the choke system.
 

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Discussion Starter #12
well finally got the chance to take it on a good run at higher speeds last night, mag side running lean. low speeds plug color is good. any ideas??
 

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I couldn't find the website I saw a while back but this one has lots of info on carb tuning; carb tuning

On there you will find that at WOT the main air jet and the needle taper are the only factors that will influence your air fuel ratio. So assuming your needle on the mag side isn't dammaged in any way I would say you have a clog in the bottom where the needle seats or in your main jet. A tiny spec of crap right inside the end of a jet will effectively reduce it's capability to provide fuel. Sorry if my terminology is off a bit but it's been a while since I tore down a carb. In the past I have found that a tip cleaner for an acetylene torch works well for cleaning out jets but just dont go crazy since you can actually widen the opening with too many passes.



That's what one looks like, they are uber cheap and you should be able to get it at Canadian Tire. Hope this helps, keep us updated.
 

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Discussion Starter #14
thanks for the reply ! first ill do another starter fluid test to make sure it's leak free, if ok on that aspect i guess ill bring it back at the shop that did the carb work last sat. !!
 
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