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Old 01-12-2013, 05:57 PM   #1 (permalink)
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91 Mach 1 617cc bog issue

ok got a 1991 Mach 1 617cc with 32xx miles.

I am having a problem keeping it running. If i prime it, i can keep it running, but it bogs almost like its firing on one cylinder, but if i pump about 3 primes into it while its running, it will come out of it for about 5 seconds and rev up perfect then it goes back down to bogging which makes me think this is a fuel issue.

I took off the carbs and cleaned them and i unscrewed the top throttle line on both carbs, the nuts may have moved a little so i dont know if that can do anything, and also i accidently hit the star looking screw on one carb, but i twisted it back to the position i thought it was.

Also it looks like the right side carb isnt getting fuel flow into the large gas line. i sucked up the gas through the line and hooked it up, but then the line runs out of gas and doesnt flow....

but like i said if i prime it alot while its running it will come out of the bog and run great....i had it professionally serviced about 300 miles ago and compression was 165psi in one and 167psi in the other.

any help would be great
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Old 01-13-2013, 06:14 AM   #2 (permalink)
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Clean the carbs again. There is a tutorial in the how-to's section of this forum. If you have to keep priming it, the pilot jets are plugged.
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Old 01-13-2013, 08:57 AM   #3 (permalink)
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cleaned them again, and i did the small wire in the jet ports that it said to do because i didnt do that before. put it all back together, and same problem, one carb is not getting fuel, i can see the large line run out of fuel until i prime it then it will fill up, but if i dont prime it it uses the gas thats in the line and doesnt pump anymore through....i can see that each large line that goes to each carb have a small square shaped piece that the lines come out....not sure what they are but maybe that is the culprit?

runnin out of ideas....going to get a compression tester and try that, but what makes me think against that is the fact if i prime it alot it runs beautiful until that line runs out of fuel then goes back to bogging...and like i said 300 miles ago it was 165/167 psi in the the cylinders and i have not been hard on it that 300 miles.


also just to give a bit more info, and i dont know if this has any relevence but i took off chain case cover cleaned inside and filled up with new amsoil chaincase oil. so thats fresh.
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Old 01-13-2013, 09:09 AM   #4 (permalink)
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Sounds an awful lot like the needle and seat valve is stuck closed on one carb. When you had it apart did you try spraying some carb cleaner down the inlet where the fuel line connects and see if it's flowing through? It should flow if you let the float lever hang down and stop if you push the lever up.
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Old 01-13-2013, 11:13 AM   #5 (permalink)
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yes i sprayed in all the ports and all had clean stream, but i just took them apart again, i think i had one of the floats upside down....not sure cuz it fell out quick but i think it may have been, and the large fuel line that goes to the little box, i can suck fuel up through it, but now blow fuel in, that how it should be?

i read one of the how toos and it said something about this....gotta look it up again
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Old 01-13-2013, 02:38 PM   #6 (permalink)
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Start it and remove each line going to each carb one at a time. While it's running fuel should shoot out of each line. If it still doesn't come out of the one line then the line or pump has an issue. Make sure the carbs are right first.
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Old 01-13-2013, 03:08 PM   #7 (permalink)
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ok i pulled carbs back off and gave a very good clean, much more than i did before. i looked online, readjusted all the screws and the throttle screws on top, started on first pull and didnt bog or stall at all and i didnt touch the prime or throttle once started, but now it runs great, but the idle is to high, which one is that? the star screw or the very small flathead screw?

The star screws are adjusted to two turns out, and the small flathead screws are about 1 1/4 turns out which is what they were set at.

after running it around the house to get it moving, i stopped held my brake (which hasnt worked since ive had it, i found the brake adjuster and thats all it needed) and when i let go of the break the sled popped right up and did a wheelie the length of my backyard....ive never been able to do a wheelie more than 10 feet with it unless i was going uphill....sled runs better then it ever has since ive owned it, but like i said the idle is very high
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Old 01-14-2013, 06:22 AM   #8 (permalink)
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The big star is the idle. Adjust BOTH carbs equally until it idles around 1800RPM. Glad it's running! I have 2 Machs- love them both!
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Old 01-14-2013, 04:20 PM   #9 (permalink)
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i adjusted the star screws both to 1 1/2 turns...made idle good, but when i hit the throttle to rev it up a little the idle wont come back down....my tachometer hasnt worked since i bought it, so i dont know how high its idling but its enough to where i tap the throttle and it will move, but when i shut it down and start it again, idle is down normal until i hit throttle...

both carbs are matched on all the screws, but i read that they should be slightly different (read it last week sometime, dont really remember) is there any truth to this?



and i love my mach as well, great little sled especially since i only paid $400 for it and it had 2700 miles on it when i bought it...i wanted an older skidoo because my father had an old formula (89 i think) mx 477, and i loved that sled, i drove it until the suspension crumbled underneath it. Last year first thing i did when i bought my sled was put new suspension brackets in so i wont have to worry about that.....i do plan to upgrade this summer, but ill keep my mach as an ice fishing sled until she dies.
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Old 01-15-2013, 06:18 AM   #10 (permalink)
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If you adjust the small screws 1/4 turn in or out at a time, it may come down sooner.
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Old 01-16-2013, 05:20 AM   #11 (permalink)
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got another problem....

i went and looked at her and i have one carb that is covered in frost, but its not from condensation, its gas thats all over the carb. its only on one carb. yes i did leave the gas on, but i have left the gas on overnight for the past week, and for some reason now its covered in gas. no leaks from any of the gas lines.

and this was the carb that was getting no fuel a couple days ago...now its getting to much?


i have pulled this carb off im letting it dry then im going to have to clean it because the gas residue/slush is all through the carb...









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Old 01-16-2013, 06:10 AM   #12 (permalink)
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Replace the inlet needle and seat in that carb.
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Old 01-18-2013, 08:27 AM   #13 (permalink)
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ok, so everythings good now except one issue.

When i first start the sled it has a very high idle, idles as high as it takes to get clutch to engage because if i tap the throttle, it moves, BUT, when its warmed up idle goes normal. Now i adjusted the idle screws many many times, and cant get it to run normal on cold start.

and yesterday i rode it around a bit, parked it for about 2 hours, and when i started it, normal idle.....now last night it was -2* and this morning she starts with the very high idle, but comes down once warm.

I dont dare do a cold start again for im afraid of cold seize....thanks



and on a different note, got to say thanks to this site because i got all the carb info here, and have never touched a carb on a sled before. ive taken the carbs right down to pieces and was able to put them all back together. and i have to say now my sled runs 100x better since ive had it. has alot more throttle response and pick up.....so i have to say thank you.
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Old 01-18-2013, 04:10 PM   #14 (permalink)
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You're welcome! High idle usually meas lean condition. Are the carb boots OK? No cracks? If you adjust the smaller screws does it make a difference?
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Old 01-18-2013, 05:41 PM   #15 (permalink)
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Make sure you put the air box on. It won't run correctly without it.
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Old 01-18-2013, 05:46 PM   #16 (permalink)
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carb boots are mint, i do thorough checks on those regularly...like every 1500 miles, unless its been sitting then i check them when im near ready to start it....my old arctic cat jag blew up because of bad carb boots so ive learned my lesson...

yes i did adjust the small one as well....they are both set exacally the same...BUT after some more in depth reading, ive been doing it backwards....i thought you turn idle screws in to lower the idle so thats what ive been doing....tomorrow when i have some light i will back off on them hopefully to fix my issue because im ready to take her on the lakes this weekend.

Also ive driven it about 2 miles id say around the house, havent checked condition of my plugs yet, and i put new plugs in when i cleaned the carbs...so ill report the color tomorrow as well.

and i started it again this afternoon, and it was out of gas, put some in, and now idle stays up, didnt come down after warmed up....


On a side note....i reupholstered my seat today...never done it before, didnt have a heat gun, but it came out decent since i got the leather fabric for $6.59 and i had to cut some off, so for 7 bucks to reupholster my seat i dont think is to bad.....has ripples at the back where pouch starts but hey like i said 7 bucks to do it.....looks good to me and thats all that matters....ill post a pic tomorrow.
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Old 01-19-2013, 12:43 PM   #17 (permalink)
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................wow................well i rode it around last night was running great...parked it and shut off the gas......just got home from work and now under the sled the snow is all soaked with gas.....every bit came out of my tank.....and like i said i shut gas off.......havent looked at it yet but im not happy.
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Old 01-20-2013, 07:39 AM   #18 (permalink)
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Needle and seats on the carb. Again.
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Old 01-20-2013, 03:27 PM   #19 (permalink)
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really? i just had them replaced.....looks like its going right back there tomorrow....


and i did find something, i have a line that comes out of the gas tank near where you fill it up under the plastic that goes into the motor bay....long line and goes to nothing.....but everything is hooked up....theres no spare "ports" for it to go in....
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Old 01-21-2013, 06:16 AM   #20 (permalink)
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That's the overflow for the tank.
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