How to adjust Carb properly for running lean?


5 replies to this topic
  • underground-mpyre

Posted December 14, 2015 - 08:23 AM

#1

Weather is changing here and need some advice to adjust my Carb to not run lean. I had to run my choke for longer than usual yesterday and need advice to properly adjust it for proper mixture.

 

Oh, aftermarket fuel screw is in the works too.



  • Krannie McKranface

Posted December 14, 2015 - 12:44 PM

#2

Do you mean the bike would not idle off the choke, until you left it on the choke for a longer period of time?

 

That is normal, and should not be  tuned out.

 

If it's colder, it takes minutes longer for the motor (actually, the carb body) to get warmed up.

 

You only change the choke (power jet) value when it will not start with the choke unless you first pump the the throttle 5+ times...then you go up one size on the power jet.

 

All the fuel screw does is fine tune the pilot circuit. Nothing more.

 

If you have to turn your fuel screw out past 2 turns to reach a higher idle, then you need a larger pilot jet.

 

None of the info you have stated has any evidence of a lean condition.



  • underground-mpyre

Posted December 14, 2015 - 01:11 PM

#3

I ran it a good 10-15 minutes through the woods yesterday on choke. The moment I pushed in the choke before that it would die. It idled on choke for 5 minutes before I took off for the trail. So thinking the fuel screw needs some adjustment, but not sure how to properly adjust for right mixture.



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  • Krannie McKranface

Posted December 14, 2015 - 06:42 PM

#4

I ran it a good 10-15 minutes through the woods yesterday on choke. The moment I pushed in the choke before that it would die. It idled on choke for 5 minutes before I took off for the trail. So thinking the fuel screw needs some adjustment, but not sure how to properly adjust for right mixture.

 

You have a lean condition, thats why you need the choke.

There is no reason to change jetting if it once ran well with the jetting you have now.

You need to service the carb, especially the fuel screw, hot start plunger, and pilot jet and passage above the jet, all for corrosion or debris.



  • WRF-Rowdy

Posted December 15, 2015 - 12:53 AM

#5

With my trusty WR450F '2003 I'd swap in a richer pilot jet for winter (48).

On the 45 the bike would not idle cleanly when commuting to work (~18mins).

With the 48 pilot + one radiator blocked by cardboard at least she'd start more readily and be all warmed up have way to work.

Mind you, the spark plug became rather dark when running the 48.

 

Lazy me ended up leaving the 48 pilot in all year and adjusting the mixture towards lean.

Perfect e-start, maybe a little richer than necessary aorung 1/8 th throttle during summer, but ok.

 

Please be gentle, I might have gotten the numbers worng, maybe it was 42 vs. 45, I don't recall correctly, bike is sold.



  • underground-mpyre

Posted December 17, 2015 - 12:18 PM

#6

Can I just turn the fuel screw in a counter clockwise motion to enrichen  the bike from lean.






 
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