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Info needed on running lean / rich

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sunbear
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PostPosted: 14:54 - 13 Apr 2010    Post subject: Info needed on running lean / rich Reply with quote

Hey fellas,

This might sound thick, but it's something that I just can't grasp ...........

Can someone tell me the exact symptons of a bike running rich or lean ? And why it does this ?

Cheers Thumbs Up
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P.
Red Rocket



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PostPosted: 16:11 - 13 Apr 2010    Post subject: Reply with quote

my GS was running rich, basically dumping too much petrol into the cylinder.
Caused spark plugs to get ruined, wasted petrol and cost me more money Sad

running lean is too much air/not enough fuel. I think lean is more dangerous than running an engine rich.
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sunbear
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PostPosted: 16:17 - 13 Apr 2010    Post subject: Reply with quote

Ok Thumbs Up

But what are the actual physical symptons of each that you notice when riding ie.... popping on the overun, bogging down at certain revs....etc... ?
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Bikes had : BMW F650, suzuki tr50, gt125, SV400, GSXR600 SRAD. Honda CBR900RRP, CBR600FX, CBR1000F, VT600, Transalp 600, mtx125, nsr125r, CB500T, Yamaha fy50, tzr125, tdr125, XV535, Diversion 600, Fazer 600, TDM850 MK1 & MK2, Majesty 400, XV 1100. Cagiva mito evolution, Aprilia rs125, Piaggio x9 125. DNA 125 . Suzuki Bandit 600, GZ125 Marauder, RF600 , RF900RS2, Kawasaki ZZR400, ZX6R Ninja, ZZR600 . Ducati 750 Sport . Triumph Tiger 955i. CURRENT : 2004 Kawasaki Z750 and LOVIN IT !
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Red Rocket



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PostPosted: 16:27 - 13 Apr 2010    Post subject: Reply with quote

sunbear wrote:
Ok Thumbs Up

But what are the actual physical symptons of each that you notice when riding ie.... popping on the overun, bogging down at certain revs....etc... ?


The GS bogged down about the mid range of the revs..
its the only rich running bike ive owned.

I think having after market cans.. possibly making the mixture lean causing the lovely pop on de-celeration
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cb1rocket
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PostPosted: 16:59 - 13 Apr 2010    Post subject: Reply with quote

The best way to tell is to check the spark plug!

Fairly wet, smells of petrol = Rich

Tan Brown = About right

Insulator showing strong signs of wear/burnt ash deposits = Lean!

Looking at the temp gauge helps to give an idea.



Best way to be the safe side is too keep the bike stock, ie stock carb and settings , stock exhaust etc
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Howling Terror
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PostPosted: 17:17 - 13 Apr 2010    Post subject: Reply with quote

Quote:
Can someone tell me the exact symptons of a bike running rich or lean ? And why it does this ?
..Err no.
We need a proper petrolhead to answer this.
I'll do some filling-in the meantime.

The mixture can alter in many ways. Maybe the air filter is defective. If its blocked, you'd get a rich mixture. If its teared or leaking then you'd get a lean mixture. Both of which will mean a loss of performance.
Black sooty plug ..rich
white or burnt plug..lean
[plugs also tell other stories, so just cos its white doesn't always mean its too lean]

Worn jets in carb.

Mixture screws have wandered from correct settings.

Pat
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Odie
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PostPosted: 20:07 - 13 Apr 2010    Post subject: Reply with quote

Follow steps in order....First, dial in:

1. Top end (full throttle / 7.5k to redline - Best Main Jet be selected before starting step 2!
Select Best Main Jet
To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the highest top speed / pulls hardest at high rpm.
If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.
If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.


2. Midrange (full throttle /5k-7k)
Select best needle clip position
To get the best power at full throttle / 5k-7k rpm, after you have already selected the best main jet,
If the engine pulls better on a full throttle roll-on starting at <3k, when cool but soft when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets that produce the best power at high rpm. You will deal with the low-end / cruise next.


3. Low end (full throttle / 2k-3k)
Float height (AKA fuel level & how to..)
To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
Example: change float height from 15mm to 14mm to richen up that area.
REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, also check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs.


4. Idle and low rpm cruise
Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs use a special "D" shaped driver, usually supplied in the carb recal kit.
Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation.
Pilot fuel mixture screw settings, float level AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm
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sunbear
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PostPosted: 07:39 - 14 Apr 2010    Post subject: Reply with quote

Thanks for the replies fellas Thumbs Up
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Bikes had : BMW F650, suzuki tr50, gt125, SV400, GSXR600 SRAD. Honda CBR900RRP, CBR600FX, CBR1000F, VT600, Transalp 600, mtx125, nsr125r, CB500T, Yamaha fy50, tzr125, tdr125, XV535, Diversion 600, Fazer 600, TDM850 MK1 & MK2, Majesty 400, XV 1100. Cagiva mito evolution, Aprilia rs125, Piaggio x9 125. DNA 125 . Suzuki Bandit 600, GZ125 Marauder, RF600 , RF900RS2, Kawasaki ZZR400, ZX6R Ninja, ZZR600 . Ducati 750 Sport . Triumph Tiger 955i. CURRENT : 2004 Kawasaki Z750 and LOVIN IT !
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temeluchus
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PostPosted: 11:10 - 14 Apr 2010    Post subject: Reply with quote

This assumes you are running carburettor(s)


1) Running rich

symptoms:
-Starts easily in the cold withoput using choke/enricher
-runs well cold but runs more poorly when warm
-hesitation/stumbling at part and/or full throttle
-sooty spark plug
-if very rich, a petrolly smell from the exhaust
-flames etc shooting out of the exhaust
-high fuel consumption
-Running VERY rich will cause the motor to shut down and feels very much like running out of fuel. Thats counterintuitive but there you go.


You may have some or all of the symptoms depending on how and why you are running rich.

Things to check if you are running rich:
-Leaking float valve/needle
-incorrect mainjet
-incorrect pilot jet
-incorrectly set idle mixture screw
-incorrect adjustment of the needle
-worn needle/emuslion tube
-leaking gaskets
-faulty float
-incorrect float height
-blocked air filter


2) Running Lean

Symptoms:
-Hard to start from cold
-Stalling at idle
-engine stumbles or hesitates when the throttle is opened quickly. This is similar to rich running but does feel different.
-engine surges (ie picks up and slows down) on a steady throttle
-You may get popping from the exhaust, similar to an exhaust air leak
-if the mixture is VERY lean the engine can shut off when the throttle is opened.
-engine runs better when warm
-spark plug has a very light white appearance.

Things to look for:
-incorrect mainjet
-incorrect pilot jet
-incorrect adjustment of the needle
-incorrectly set idle mixture screw
-incorrect float height
-Air filter assembly leaking at a joint and/or incorrectly fitted
-air filter absent
-exhaust leaking
-blocked fuel tap, lines, filter or faulty filler cap breather
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