How to tell if your bike is running lean or rich by sound!

[crxtasy169]

Ok guys I hear a lot of this on this forum how do I tell if I'm running rich or lean, so I will let you in on a "Bike Technicians" old secret for tuning by ear.
I've been a bike tech now for 4 years and this was a technique I had to drag out of my favorite instructor at MMI.

Blip test:
1. Start by warming the bike up to normal operating temperature.
2. Blip the throttle up several thousand RPM's or up to redline if you so desire.

As it comes back down to idle one of three things will happen and these are the three results:

1. Upon return to idle it hangs. Where ever it hangs in the RPM's it is running lean. Even a slight hang just before returning to idle means it is running lean at idle.(Must return directly to idle without popping,lag, or hanging).
2. Upon return to idle it goes slightly past and below idle then returns back up to idle speed momentarily. This is a rich run condition.
3. It returns directly to idle w/o any lag, hesitation, or going below idle you have a perfect a/f mixture and run condition.


This system has been around for years and it is proven. It will work for carbed bikes or fuel injected bikes. Once you have your result make your adjustments and repeat process until you get result #3. Happy tuning.

 

[Supermanrider]

Nice to know

 

[konarider94]

the bike can hang like you describe in #1 from an idle that it set a little high. this doesnt sound very legit to me. the only real way to tell if you running lean or rich is to use a lambda sensor.

 

[crxtasy169]

This of course is assuming your idle is set correctly! A hang is when it waits momentarily before returning to your idle!!! Not returning to a poorly set idle. And yes the works I have been using this system for several years now and it has made me one of the best tuners around! Take it for what it's worth to you, if you don't beleive me that's fine but i do this for a living!

 

[xxspudxx]

Good info.

 

[ztied]

Thanks for the info.

 

[Miami78]

What happens if one cylinder is running lean and the other is rich?

 

[aptbldr]

Neat tip/trick [up]

What happens if one cylinder is running lean and the other is rich?

Or, vice versa? [smirk]

 

[crxtasy169]

Well you would know from looking at the plugs!
But as for the blip test No offense to anyone but you have to use some common sense in conjunction with this test! Read your plugs, set your idle if needed, make all other adjustments needed to keep it in good tune,such as service, and maitanence.
If you have a completely erratic idle, completely different colored plugs, mechanical, or electrical issues, then you need to deal with those first.
This test is for fine tuning not diagnosis for major problems. This will help eleviate off idle stumbles and flat spots.

 

[Miami78]

Sorry, wasn't trying to be an ass or anything...I had the ebr ecm installed, bike was idling like hell, plugs were showing one rich/one lean (just a bit), installed a hotter plug in the front to compensate, wasn't sure if there would have been a way to diagnose that from the idle. Got really tiring pulling the plugs so often, finally sent the race ecm back and put the stock back in.

 

[crxtasy169]

No worries man I hear a lot of buells have similar problems and i would say the only way to fix it would be to dyno it, pull the plugs and have a pro plug reader check the plugs and adjust accordingly. Along tiring and exspensive way but the only way I would know to do it without hving it hooked to a gas analyzer on each individual cylinder.
Changing the plug is what I would have done as well for time being let me know how it runs and works out for you!