blip test...Rich or lean ??

[1outlaw]

I have read that if you blip the throttle and it goes below idle then back up to idle that it is lean but i have also read that means it's rich. I'm just wondering if someone can clear this up for me. I just bought an 84 fj1100 it has a supertrapp 4 into 1 and a uni filter. all the jets are original i think...main 112.5 pilot 37.5 air  160 and the needle is a 5fz62 set at the third clip. Everytime I check the plugs they are are pretty white with a few black spots on them. I'm also wondering what the recommended jetting would be for this setup.

Thanks
Paul

[andyb]

http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html

[imikie]

if u blip it and it hangs up and then drops back its running lean.if it drops below idle and recovers its rich.if u run #40 pilots,#160 air and #115-117 mains with 4 into 1 should go well.

[1outlaw]

Thanks for the info, I did read the factory pro page but also read a post on here that said the opposite.

[Ganboy70]

Hey Paul, I think this is what you may have read before...that is correct:

blip throttle and rev the engine..... if the engine speed hangs and slowly returns to idle then its too rich- turn mixture screws IN

blip throttle.......if engine speed drops quickly to below idle set point then recovers you are too lean... turn mixture screws OUT

[gripit_N_ripit]

I would go by link andy provided.He knows his shit.....

[Pat Conlon]

I would go by link andy provided.He knows his shit.....

+1 Yes he does... He really helped me.

[SlowOldGuy]

Doesn't really matter which way is lean or rich.  If you don't like the results of the blip test, then try turning them one way.  If it gets worse, take the mixture screws the other way.  If it gets better, keep going until it gets worse then backup.

Very simple.

I'm not so sure the FJ mixture screws behave in a "normal" fashion.  When you adjust them, you're adjusting the amount of a fuel/air mixture allowed into the intake.  You're not simply adding more fuel or air.  Logic would tell you more is richer and less is leaner and that may be the case.  The key is to make some change and see if it gets better or worse.  That's the only way to know for sure.

DavidR.

[andyb]

^ Best answer ever.  No two motors are the same, nor the conditions they're being run in, nor the way the rider interprets how they run!

The idle mix screws allow some adjustment, but I feel that they're adding, say, 50:50 fuel:air; they do make things richer, but their real purpose is for balancing and smoothing things.  Changing the pilot jets themselves is where the big adjustments are made (ime and imo).

[Kopfjaeger]

   nice link Andy.

[1outlaw]

Thanks again, I ordered some new jets 115 main and 40 pilots and i'll go from there.

Paul

[Ganboy70]

Great link Andy, I clearly thought the opposite.