How lean is too lean? - Wrist Twisters
 
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post #1 of 25 Old 09-13-2014, 06:31 AM Thread Starter
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How lean is too lean?

I came across a good deal on a PC3 even though my pipes are stock. I did a -5 across the board except for 80 and 100% full throttle and above 8K.
It immediately ran better so I slowly worked my way up to -10 and I have a KOSO to monitor the emgine temps, so far no difference.


It still smells rich, can I keep going?

edit- for a 919 btw

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post #2 of 25 Old 09-13-2014, 11:53 AM
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i wouldnt.... but im dumb as shit so i play it conservative.

can i get a copy of that map to check out?

i know when i ran some of the more aggressive maps out there my temps would rise a lot quicker in stop and go traffic.

i wouldnt use the rich smell or the temp gauge to be 100% certain you're not running to lean, things can happen and then you're blowing motors

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post #3 of 25 Old 09-13-2014, 12:29 PM
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Excessive lean can cause a fuel smell in the same way rich can, for a different reason: as the A/F ratio goes further into the lean range the combustion efficiency decreases to the point of causing incomplete burning of the fuel in the cylinder, resulting in excess fuel being expelled out the exhaust. For this reason a fuel smell is not an even approximate indicator of the A/F ratio. And, of course, too lean can cause a whole bunch of unpleasantries such as burned valves, holed pistons, and detonation induced deterioration of the ring lands, all of which requires a top end teardown to diagnose and cure.

As many tuners say: "Play with rich, but sneak up on lean carefully!"

The only way to really get an accurate fuel map for your bike and location is to get it run up on a dynamometer while monitoring A/F ratio, exhaust temp, throttle position, and whatever else the operator is set up for. Otherwise you are shooting in a pitch black dark and can do considerable damage in the process.

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post #4 of 25 Old 09-13-2014, 01:14 PM Thread Starter
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Hmmm crap. Should I have a look at a spark plug?

The map is simple,

-10 everywhere except 80 and 100 throttle and above 8K. Zeros everywhere else.

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post #5 of 25 Old 09-13-2014, 02:32 PM
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Quote:
Originally Posted by Auron View Post
Hmmm crap. Should I have a look at a spark plug?

The map is simple,

-10 everywhere except 80 and 100 throttle and above 8K. Zeros everywhere else.
That assumes the 919 is equally rich everywhere, but it isn't. Look at using one of the maps from the drop box if you don't plan to get it dyno tuned.

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post #6 of 25 Old 09-13-2014, 03:50 PM Thread Starter
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I guess I'm equating it to the carbed bike it grew up as. Changing a main jet was the same idea. Or is that not comparable?

Thanks for the help btw

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post #7 of 25 Old 09-13-2014, 06:51 PM
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Quote:
Originally Posted by Auron View Post
I guess I'm equating it to the carbed bike it grew up as. Changing a main jet was the same idea. Or is that not comparable?

Thanks for the help btw
I'm a carb guy that transitioned.
Mains are mains and but a wee portion of the overall fuel delivery curve that a tuneable carb will deliver.
Let's see now .....what all do we have to play with and get in concert with one another ?
Float level height
Air screw setting
Pilot Jet
Emulsion tube
Air feed diameter to emulsion tube
Slide cutaway
Needle
Needle Height
Main jet
Then there's airbox effect ..........................

So, a -10 across the board for all but 80 -100 % would be like a main jet, while ignoring everything else.
Nowadays so much is masked by ignitions that work so well, that one can get away with tinkering level stuff that years ago would have left the engine stumbling and stuttering or worse.

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post #8 of 25 Old 09-13-2014, 06:52 PM
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Quote:
Originally Posted by robtharalson View Post
Excessive lean can cause a fuel smell in the same way rich can, for a different reason: as the A/F ratio goes further into the lean range the combustion efficiency decreases to the point of causing incomplete burning of the fuel in the cylinder, resulting in excess fuel being expelled out the exhaust. For this reason a fuel smell is not an even approximate indicator of the A/F ratio. And, of course, too lean can cause a whole bunch of unpleasantries such as burned valves, holed pistons, and detonation induced deterioration of the ring lands, all of which requires a top end teardown to diagnose and cure.

As many tuners say: "Play with rich, but sneak up on lean carefully!"

The only way to really get an accurate fuel map for your bike and location is to get it run up on a dynamometer while monitoring A/F ratio, exhaust temp, throttle position, and whatever else the operator is set up for. Otherwise you are shooting in a pitch black dark and can do considerable damage in the process.

Rob
Amen on all points.

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post #9 of 25 Old 09-13-2014, 07:06 PM
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Quote:
Originally Posted by robtharalson View Post
Excessive lean can cause a fuel smell in the same way rich can, for a different reason: as the A/F ratio goes further into the lean range the combustion efficiency decreases to the point of causing incomplete burning of the fuel in the cylinder, resulting in excess fuel being expelled out the exhaust. For this reason a fuel smell is not an even approximate indicator of the A/F ratio. And, of course, too lean can cause a whole bunch of unpleasantries such as burned valves, holed pistons, and detonation induced deterioration of the ring lands, all of which requires a top end teardown to diagnose and cure.
Rob
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post #10 of 25 Old 09-14-2014, 06:39 AM Thread Starter
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So it seems to run better than before with zero changes in throttle sensitivity. Everytime I went from -5 to -6 to -7 to -8 to -9 and finally to -10 I rode it for at least 50 miles the engine got smoother and smoother. If -10 is equal to one main jet and the 919 is rich from the factory I'm going to stick with it.

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post #11 of 25 Old 09-14-2014, 06:55 AM
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Did you try the map for stock 919's? That is what I have and it is great. It is in the community dropbox

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post #12 of 25 Old 09-14-2014, 06:57 AM
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Quote:
Originally Posted by Auron View Post
So it seems to run better than before with zero changes in throttle sensitivity. Everytime I went from -5 to -6 to -7 to -8 to -9 and finally to -10 I rode it for at least 50 miles the engine got smoother and smoother. If -10 is equal to one main jet and the 919 is rich from the factory I'm going to stick with it.

Lemme see that map! What rpm did you start the modifications?

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post #13 of 25 Old 09-14-2014, 08:37 AM Thread Starter
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Quote:
Originally Posted by SGKukov View Post
Lemme see that map! What rpm did you start the modifications?
I don't know how to post it

I started with the stock 919 map found on this site. For everything below 8K and less that 80% and 100% throttle I put in a -10%. Less stink and better mileage.

Keep in mind I live in denver. My 919 runs like a 599 up here

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post #14 of 25 Old 09-14-2014, 09:19 AM
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yeah that just sounds like a bad idea.... get it dyno mapped or use one of the known good maps.

but just leaning out across the board like that is a bad BAD idea.

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post #15 of 25 Old 09-14-2014, 09:30 AM Thread Starter
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^ How is it different than changing the main jet in a 900RR engine?

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post #16 of 25 Old 09-14-2014, 09:32 AM
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Quote:
Originally Posted by nd4spdbh View Post
yeah that just sounds like a bad idea.... get it dyno mapped or use one of the known good maps.

but just leaning out across the board like that is a bad BAD idea.
+1000.

It's not that the 919 runs rich straight across the board. The issue is that the fueling is all over the place across the rpm/throttle range.

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post #17 of 25 Old 09-14-2014, 10:46 AM Thread Starter
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-999

OK, fine. I'll load the original 919 map.

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post #18 of 25 Old 09-14-2014, 02:31 PM
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Quote:
Originally Posted by boogunoogun View Post
Did you try the map for stock 919's? That is what I have and it is great. It is in the community dropbox
I'm not sure common sense is available anymore, and your comment contains significant amounts of it.

Consider yourself one of the few, which wad once one of the many.


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post #19 of 25 Old 09-14-2014, 02:56 PM
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Quote:
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^ How is it different than changing the main jet in a 900RR engine?
because the main jet in a carb truly effects only a small range of throttle (like 80-100% throttle). You have other factors like the needle shape, needle clip position, slow jet, fuel mixture screw etc etc etc, that change the fueling over different ranges of throttle.


Just blatantly going and leaning out a HUGE portion of the throttle range over a whim is not the same.

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post #20 of 25 Old 09-14-2014, 03:26 PM Thread Starter
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Got it. Thanks.

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post #21 of 25 Old 09-14-2014, 03:28 PM Thread Starter
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I'm not sure common sense is available anymore, and your comment contains significant amounts of it.

Consider yourself one of the few, which wad once one of the many.

Now come on... I tried the stock map and the bike still stunk so I tried to go a little leaner.

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post #22 of 25 Old 09-14-2014, 05:05 PM
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the bike is always going to stink.

Running with 87 octane will help as it provides more complete combustion.

But the fact that the stock exhaust / slip ons expel exhaust into the low pressure area behind the back of the rider is the reason why you stink.

If you want to get rid of the stink a 900rr header + low mount exhaust.

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post #23 of 25 Old 09-15-2014, 05:00 AM
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Now come on... I tried the stock map and the bike still stunk so I tried to go a little leaner.
For the fix, "Click Here"

Anyway, I'd probably of done the same thing, post it on the forum, LDH and others would rip me a new one for being such an idiot, I'd get all offended and rip right back into them. LDH would end by telling me I sound like a little kid and ultimately, the cycle would repeat.

If you don't know who LDH is, he has forgot more than we'll ever know. He knows anything and everything about anything and everything there is to know anything and everything about in regards to motorcycles. He rides on water and lives the life he dreams about, complete with trophy wives and balls made of inconel. Still, he's OK, and I understated the actual magnitude of his greatness.

Have to admit, you'll light years ahead of me in regards to a proper response, and for that, I applaud you.

We're both idiots, and we're in good company.

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post #24 of 25 Old 09-15-2014, 07:53 AM Thread Starter
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Not sure who he is, only come here when I have a question but thank you. Might have saved me some engine damage. The plug looks a little dry and gray, not white but enough for me to load the stock map. I like it quiet so I'll put up with it, still a great bike.

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post #25 of 25 Old 09-15-2014, 08:14 AM
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Auron, just head over to our Dropbox folder: https://www.dropbox.com/sh/ra9j3gn4c...L4JuwuBKa?dl=0

Tons of maps in there - all should be safe for the 919. Most were actually created on a dyno.

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