bad jetting and not running well - Snowmobile Forum: Your #1 Snowmobile Forum

jagfixer · 02-26-2007, 05:51 PM

ok so i swapt my fan cooled motor with a free air motor on a 1980 arctic cat jag(the motors are exactly the same) and the new motor is running bad the spark plugs are white so im guessing that the jetting is way off. could it be the seals bottom end are crap, could it be that my oil to gas mixing is bad, or isit just the jets. im going to tinker with it but any idea's of what might be the problem would be helpful oh and it's back firing alot could that be a bad coil or just gas being pushed out the muffler and firing in the muffler. it also vibrates alot but it's pretty old so. i just need to make it run without it blowing up or melting down.

G.T · 02-26-2007, 05:55 PM

white plugs indicate a lean mixture. Do you have any history on the motor do you know the owner etc? Has the jetting been altered in any way? Are you running the correct airbox? Silly question but are the carbs clean with plenty of fresh gas?

**RJ Gleason** · 02-27-2007, 02:28 AM

The free air actually needs to be jetted "fatter" than the fan cooled. If you are using the same carb from the original engine, you will need to change the jet at least 2 sizes larger. The gas/oil mix should be at least 40:1.

jagfixer · 02-27-2007, 05:57 PM

well i dont know the history and i have no air box at all. but really it's such a crappy motor that i just need it to keep from running too lean. i'm actually changing the secondary drive shaft it's so worn out so i cant run it quite yet. but i can understand that i need to jet it leaner.

so how do you jett an engine fatter or could it just be a crank seal gone bad that's letting all the oxyen in?

G.T · 02-27-2007, 06:23 PM

richer not leaner!

jagfixer · 02-27-2007, 07:00 PM

my mistake that's what i meant. so what do you you think about the seals? could that be the issue.

G.T · 02-28-2007, 08:26 AM

You have so many other issues, no airbox etc If you are running lean and you want to just be able to ride the sled if you have no supply of main jets try slightly making the main jets larger, normally i would not suggest this at all but it would be a quick fix/botch. Is the sled running lean on full or mid throttle? Have you tryed raising the needle's?

jagfixer · 02-28-2007, 05:17 PM

it's running lean im guessing full throttle. i was thinking of raising the needle or the main jets. keep this in mind this is not a high performance sled at all.

ok so when i put it back together i'll try that and if not the needle.
all i need is just for it too be really rich til the plugs are light brown.

my personal opinion on fixing sleds is that the older ones are easier because al you need to do it for it to have spark gas and oxygen the newer one's have all the electical lots of other stuff for you to fix but they are way better when in good condition.