running lean

[tony120]

thanks to this site i have tuned my 85-140 pretty close to what I think is almost perfect.but when i run it for a few min at 5000rpm then slow down and pull it into neutral, the idle will be around 1100-1200.then it will calm down after about a min,and idle back at 900.my fuel lines are all tight the bulb is always hard.I thought that i read here that if your running at WOT and push the primer in and it stumbles right away its LEAN? I dont remember.I've had jc4's-QL78YC's didnt make a difference.they both looked pretty clean.87 octane.how do I know if its running lean for sure?

 

[ob]

Re: running lean

Check the condition of the sparkplugs after a run.This is your best indicator of rich or lean cylinder condition.If you are running full out and bump the primer and engine stumbles ,it is an indication that things are good as they are.The bumping of the primer is flooding the cylinders.<br />if ,on the other hand ,bumping of the primer button at full out ,caused the engine to pick up,it would indeed be an indication of fuel starvation.

 

[R.Johnson]

Re: running lean

If your yanking the throttle back from WOT to idle, the cylinders are simply burning of residual fuel till they clean them self's off. This is normal in a 2 cycle. Simply don't run it like that.

 

[tony120]

Re: running lean

yee haa. thanks ob. i may rebuild my old 89-120 myself,thanks to here. now if I could only figure out why someone, before I owned this engine,has drilled out the holes in the throttle plates bigger

 

[tony120]

Re: running lean

no R.johnson I'm not doing that, Im slowing down slowly...then just creeping before pulling it into neut. then it will go and idle at 1100,then idle to 900

 

[R.Johnson]

Re: running lean

I don't have a clue on the drilled out throttle plates.

 

[Dhadley]

Re: running lean

What you are describing is typical of a looper if its running on the lean side in the mid and/or high speed range. The drilled throttle plates would tend to lean it out also. This could be why your builder backed off the timimng so far. The damage indicated a lean condition so he reduced the timing. <br /><br />To check the jetting at any given throttle setting, engage the primer. If it stumbles immideately its rich. If it picks up for a split second before it stumbles its lean. If it does nothing different for a split second then blubbers, its dead center. At that point we go slightly richer. Creates a "buffer" of rich. Running right on the edge of lean you stand a chance of damage from outside influences like weather, slightly old or hot fuel, etc.<br /><br />With modified carbs (drilled plates) the stock jetting doesnt count. You will need to do your own. I would suggest to jet it at the low timing setting and then work the timimng up slowly while rechecking the jetting each time you change the timing. <br /><br />I would stick with the cooler plugs too.

 

[tony120]

Re: running lean

thanks Dhadley,it stumbles as soon as I engage the primer.I want to put the right throttle plates back in,so I can put my idle timeing back to 3-5degrees.theres an outboard place near me that says i have to bring in my old one to match it up.i dont mind doing that.my idle jet didnt have any #'s on it. mid was #40 high i havent checked.the guy that rebuilt it did say he richened up the idle jets.it doesnt cough or sneeze when idleing cold. thanks for the info...keep ya posted

 

[Dhadley]

Re: running lean

Ok, you mention idle timing. In your other post you were talking about WOT timing. Two completely different issues.<br /><br />Then you said the throttle plates were drilled out. You say a local mechanic wants you to bring in the original ones to match them up. Were they drilled out or changed out?

 

[tony120]

Re: running lean

definately drilled out!!sorry for the confusion.

 

[ob]

Re: running lean

Are we now talking about the 85' 140 hp or the 89' 120 mentioned later?

 

[tony120]

Re: running lean

85-140

 

[ob]

Re: running lean

10/4.