Newb Question

[mtbikemike]

I just bought a yamaha yz85 for my girlfriend. We took the bike up camping at 5000+ ft. I think I mixed the fuel too rich ... 40:1. After about 20 minutes of hill climbing the engine started blowing smoke and puttered out. Didn't have my tools with me and decided not to pull the plug or mess with the jetting until now.

So what's the next step? Pull the plug and check if it's spoiled? Drain the tank and re-mix? Take it to a shop? :(

TIA!!

 

[Chili]

Likely just fouled the plug, throw in a new one and ride until it dies again, or dial in the jetting.

 

[CHR!S]

if you took the bike to higer elevation, chances are its running rich because the air is thinner. 40:1 sounds right for an 85, though.

 

[GODsRebel]

lean it out with a lower ratio (32:1) if you dont have a variety of jets to work with.....i had to go down cause its been so humid and hot down here in south florida

 

[mtbikemike]

thnx for the help. Anyone know the best way to drain a YZ85 fuel tank?

 

[IndyMX]

thnx for the help. Anyone know the best way to drain a YZ85 fuel tank?

Simple... remove the fuel line from the petcock, put a length of 1/4" hose on the petcock that will reach into the container you are draining into. Insert hose into container. Open petcock. Go have a beer while the tank drains.

 

[j32]

40:1 is leaner than 32:1
40 is less oil per gallon it should have been ok
check the plug
im guessing that you mixed it wrong ,because you think that 40 is rich- ok
mix new fuel ,and change the plug
simple mistake,but too lean will ruin your motor
you need a tan color on the plug,after a few minuts of riding check it

 

[yz250-effer]

40:1 is leaner than 32:1
40 is less oil per gallon it should have been ok

That is leaner on the fuel mixture, but not the jetting. 40 to 1 results in more fuel/air compared to 32 to 1. (40 to 1 results in more fuel to air). Rich or lean should be more of a jetting issue, not a fuel mixture. You should always run between 32 and 40 to 1 for mixture, and it won't change the jetting significantly between the two. You shouldn't try to change you jetting with a fuel mixture adjustment.

What altitude was the bike run at before you bought it? If it was run around 1-2 thousand, I would have recommended lowering the needle at least one clip position.

Low revs from a beginner rider can also make a bike run more in the lower revs, resulting in easier fowling.

A manual usually gives recommendations for appx. jetting for altitudes and temp. Good baseline. This is one of the pains of 2 strokes over 4 strokes. ;) If not enough info in the manual, do a search for 2 stroke jetting tips, and you will find some good info for sure, regardless of the 2 str. you are trying to jet.

 

[j32]

if it is drooling oil that means its not burning it--- crappy oil,or too much
too much oil fouls plugs oil not burning fouls plugs
low revs or high revs throttle response should be the same with prpper jetting ,but first use a good oil and mix it right,and it will stop the need to (clean it out)
you jet rich-bigger -the plug will be wet and foul