How do I know if I am running lean ?

[MarkHPCA]

Is there an easy way to know if you are running lean (apart from piston meltdown ) I understand that a lean running motor will appear to be running well, maybe too well.

 

[Dhadley]

Re: How do I know if I am running lean ?

What motor are we talkng about? The V4 looper, right? Are you talking about lean in general or trying to isolate a certian cylinder?

 

[MarkHPCA]

Re: How do I know if I am running lean ?

I did a carb rebuild over the winter and also added a foot throttle. I havn't got it in the water yet but on the mufs the idle is a lot lower than it was last fall. Typicaly I would get about 1200 RPM on the muffs but in the water it was OK at 650 in gear. Now it runs about 500 on the muffs and stalls if you don't give a little throttle. I have just done the link & sync and was going to set the WOT timming this weekend. If I understand right the idle is set by adjusting the idle timming right? My only concern is if the carbs are not running right I don't want to melt stuff...

 

[Dhadley]

Re: How do I know if I am running lean ?

It may be that the carbs were ever so slightly advanced before. Now the sync & link is correct. If the motor was lean at an idle it'd be running funny and / or running faster slightly. <br /><br />With the airbox cover off -- and NEVER NEVER run it under a load with the cover off, NEVER -- at idle stick a tooth pick in the idle jet (lower of the 2 air bleeds). If that cylinder starts to bog right away its OK. If it should pick up slightly then bog its lean.

 

[MarkHPCA]

Re: How do I know if I am running lean ?

Does it matter what the idle timming is in degrees or just do I just set it for the correct RPM?

 

[MarkHPCA]

Re: How do I know if I am running lean ?

Just curious an not that I would do it but why not run with airbox removed?

 

[Dhadley]

Re: How do I know if I am running lean ?

We dont worry about what the timing is at idle as long as it idles good. A lot depends on how low the motor sits in the water (backpressure). <br /><br />On a looper if you remove the airbox cover the carbs lean out about 12 - 15 numbers. Makes for a nasty looking piston(s). And doesnt run any better. Those carbs are designed for the air to come from in back of them and "around the corner" so to speak.

 

[MarkHPCA]

Re: How do I know if I am running lean ?

I will get it in the water this weekend and hopefully get everything setup OK. I intend to use a 'cut down' old prop and have the boat backed into the water but still on the trailer to adjust the WOT timming. I will let you know how it turns out.<br /><br />Thanks for you help Dhadley, as always good advice.

 

[Dhadley]

Re: How do I know if I am running lean ?

Good plan. Keep us posted!

 

[papa_Lazerous]

Re: How do I know if I am running lean ?

a simple way to tell if you are lean is look at the plugs the colour they burn at gives allot away.