Simple...kinda...AFR Questions

[EZRider76]

I have two very simple questions, it may even be a "really, are you really asking that" kind of questions. I have a feeling that they may be not quite so simple to answer.

Here goes. Thinking in terms of AFR...

1. If you have too much fuel, you'll flood the spark plug and foul it, right? Which will make it act boggy and act like it wants to cut out?

2. What if you aren't giving enough fuel? How little fuel will still allow combustion? Will too little fuel make it act boggy and like it wants to cut out?

 

[blasterdemon7]

It tends to act the same both ways. Fuel in liquid form will not burn. To much fuel will limit the vapor in the combustion proses giving a smaller and less powerful explosion. Much the same with lean. It produces less vapor resulting in weaker combustion.

 

[mjgnslngr]

I have two very simple questions, it may even be a "really, are you really asking that" kind of questions. I have a feeling that they may be not quite so simple to answer.

Here goes. Thinking in terms of AFR...

1. If you have too much fuel, you'll flood the spark plug and foul it, right? Which will make it act boggy and act like it wants to cut out?

2. What if you aren't giving enough fuel? How little fuel will still allow combustion? Will too little fuel make it act boggy and like it wants to cut out?

or, is the ignition only burning Some of the fuel due to weak spark??? thus creating a rich condition??? sounds familiar, thats why i ask...

 

[EZRider76]

It tends to act the same both ways. Fuel in liquid form will not burn. To much fuel will limit the vapor in the combustion proses giving a smaller and less powerful explosion. Much the same with lean. It produces less vapor resulting in weaker combustion.

So, if I pull a plug and it is wet, it is just flooded. If I pull a plug and it is covered in black soot then it is fouled. And if I pull a plug that just was cutting out and it appears dry, then I'm too lean for good combustion.

or, is the ignition only burning Some of the fuel due to weak spark??? thus creating a rich condition??? sounds familiar, thats why i ask...

Hmmm, back to that electricity thing again. Spark is spark though, if you have enough spark to burn some of the fuel vapors, seems to me that would combust the remaining fuel vapors. Maybe there is an intermittent signal and not combusting every rotation.

Although, up to that 3/4 range I'm running strong, just can't get that WOT. So I don't think spark is my problem. I'm just trying to determine my lean vs. rich scenario, whether I'm flooding or starving the spark.

 

[Blaaster]

I have two very simple questions, it may even be a "really, are you really asking that" kind of questions. I have a feeling that they may be not quite so simple to answer.

Here goes. Thinking in terms of AFR...

1. If you have too much fuel, you'll flood the spark plug and foul it, right? Which will make it act boggy and act like it wants to cut out?

2. What if you aren't giving enough fuel? How little fuel will still allow combustion? Will too little fuel make it act boggy and like it wants to cut out?

Too much fuel will not make it boggy, it will make it babble (four stroke) and not gain any more revs.

Too little fuel will make it boggy (Blaaaagh) and make it want to die out.

The difference between bog and babble has a marked difference.

 

[blasterdemon7]

Seems I'm always wrong so maybe I should stop giving advice.

 

[EZRider76]

Too much fuel will not make it boggy, it will make it babble (four stroke) and not gain any more revs.

Too little fuel will make it boggy (Blaaaagh) and make it want to die out.

The difference between bog and babble has a marked difference.

That is the second time I've seen you babble and blaaaagh, but I don't get it. I'm technically tone deaf, and I have a Outlander that runs awesome, but I don't know the babble sound you are speaking of. Does anyone maybe have a video?

Seems I'm always wrong so maybe I should stop giving advice.

BD7, don't be like that. I think your response earlier has merit, even though Blaaaster has wisdom. I wouldn't have asked the question had I known. At least you are offering advice....who knows, maybe some day you will get one right. 8-| Seriously though, I think you are right...I will say from experience you can dowse a fire with liquid fuel....tricky, but possible.

 

[Larry's Shee]

I don't see where BD7 is wrong. It's a bog either way, the trick is to determine which it is Lean will be flat and rich sputters from the plug trying to get drowned out.

 

[Blaaster]

A babble from a too rich mixture, is like how the motor runs when it is first started when you leave the choke on too long. The motor only seems to fire every fourth stroke but will stay running but not gain any more speed.

A bog from a too lean mixture, the motor will lack power and the engine note will change to a sound like Blaagh, and the revs may die away.

Some people also refer to a bog as a flat spot, where there is not enough fuel to keep the fire alight.

 

[Blaaster]

It tends to act the same both ways. Fuel in liquid form will not burn. To much fuel will limit the vapor in the combustion proses giving a smaller and less powerful explosion. Much the same with lean. It produces less vapor resulting in weaker combustion.

Correct in both cases, the problem lies in terminology, different people call it different things.I:I

 

[EZRider76]

A babble from a too rich mixture, is like how the motor runs when it is first started when you leave the choke on too long. The motor only seems to fire every fourth stroke but will stay running but not gain any more speed.

A bog from a too lean mixture, the motor will lack power and the engine note will change to a sound like Blaagh, and the revs may die away.

Some people also refer to a bog as a flat spot, where there is not enough fuel to keep the fire alight.

Ok, making more sense now. I would have to say I'm getting a babble, it runs along great, but once I push it to WOT, it starts to spit and sputter (or babble) like it isn't firing and then it will just cut if I pin it....let off back to 3/4 throttle and it will pick up just like nothing happened. :-/ The thing that scares me though, is I am on my leanest setting on the needle and am running a #250 on the main, with a 32.5 pilot (now). I have a pipe and exhaust listed in my sig, and I read that FMF recommends a #270....I don't know.

 

[Larry's Shee]

Then try pulling choke when you get to the blubber, if it gets worse you're rich, better then you are lean.

Misnomer disclaimer: it is actually an enrichening circut

 

[Rich]

Then try pulling choke when you get to the blubber, if it gets worse you're rich, better then you are lean.

Misnomer disclaimer: it is actually an enrichening circut

Good call larry this was what I was going to recomend.Pulling the choke will make it richer.Sounds to me its on the rich side.I dont think I ran that rich of a main and I also run fmf fatty.

 

[Blaaster]

it runs along great, but once I push it to WOT, it starts to spit and sputter (or babble) like it isn't firing and then it will just cut if I pin it....let off back to 3/4 throttle and it will pick up just like nothing happened. :-/ .

To me, this description is way too lean on both the needle and the main.

I feel that #250 is going to do damage.

#270 is what FMFtells you.

FMF I believe is more a low/mid pipe and could like a richer needle setting.

For whats it's worth try dumping the #270 back in there and running the needle richer on the second to bottom clip.

The above settings are for the airbox lid on a stock air filter.

 

[Rich]

The needle setting does sound lean.Let me pull my bowl off my old carb and see what jet size it is.I believe 270 is way to rich.But let me double check.

On my stock 26mm running factory jet size pilot with fmf fatty and boyesen power reeds.230 main.I may have changed the throttle valve cut away and running a jjh or jj (banshee) needle in second from bottom slot.But keep in mind the cap on my carb was striped and had to be liquid cemented and held down tight with bailing wire.Its been a while to remember exact.But any case hope this gives you a little info on how much larger a 270 is.Im guessing a 240 and factory needle in middle or 2nd slot on rich side.Given you are running a 28 mikuni imo only on the blaster main should be in the 240-255 range with a richer needle(You did not mension what needle you have).But like larry says best way to test it is to pull the choke when it starts to act up Ive read people running up to a 330 but Idk about that.Maybe if your winters are in the teens Idk.....................And in this case I would recomend a plug chop to be sure if your in fear of running lean

May I ask what does AFR mean.

 

[Blaaster]

On my stock 26mm running factory jet size pilot with fmf fatty and boyesen power reeds.230 main.


May I ask what does AFR mean.

AFR is air to fuel ratio!

Air–fuel ratio (AFR)

The air–fuel ratio is the most common reference term used for mixtures in internal combustion engines.

It is the ratio between the mass of air and the mass of fuel in the fuel–air mix at any given moment.

For pure octane the stoichiometric mixture is approximately 14.7:1, or λ of 1.00 exactly.

In naturally aspirated engines powered by octane, maximum power is frequently reached at AFRs ranging from 12.5 to 13.3:1 or λ of 0.850 to 0.901.
......................................................................................................

FMF recommends a #270.

#230 main with an FMF Fatty, sugguests to me, that it is way too lean, even with a sunken float you wont get enough fuel to fire the fatty, unless you are running a toilet roll as an air filter.

 

[Blaaster]

Below are a few examples I found on what other FMFowners are running.

Hope this may be of some use.

.................................................................................

1) What type of aftermarket exhaust do you have? FMF

2) What type of airfilter do you have? K@N outerwears

3) cfm airbo
4) What is your elevation? 3500ft

5) What size pilot jets are you using? stock

6) What size main jets are you using? 290 main

7) What is your Bore Size? stock

8) Do you have a port job? no

9) What kind of carb? stock

10) What size is your carb? stock

..................................................................................................

1) What type of aftermarket exhaust do you have? fmf fattey w/ pc2

2) What type of airfilter do you have? k&n w/ outerwears

3) stock airbox with lid removed. replaced by outerwears

4) What is your elevation? 500'

5) What size pilot jets are you using? 32.5 stock

6) What size main jets are you using? 300

7) What is your Bore Size? stock

8) Do you have a port job? no

9) What kind of carb? mikuni stock

10) What size is your carb? 28mm stock

11) Where is your needle located? Center Clip (stock location)

12) What is your airscrew setting? 2 turns out

13) Premixing at 32:1

14) 89 octane
...............................................................................................

1) What type of aftermarket exhaust do you have? FMF Fatty/ Shorty Powercore 2

2) What type of airfilter do you have? Uni Dual Stage

3) what air box?) no lid/ stock air box

4) What is your elevation? 3000 feet above sea level

5) What size pilot jets are you using? stock

6) What size main jets are you using? 290 (probably smaller in summer

7) What is your Bore Size? stock

8) Do you have a port job? no

9) What kind of carb? stock 26mm

....................................................................................................

1) What type of aftermarket exhaust do you have? FMF Fatty/Powercore 2

2) What type of airfilter do you have? stock ,waiting for Uni Dual Stage

3) what air box?) no lid/ stock air box

4) What is your elevation? 401meters don't know how much this is in feet
(i do have two feet myself do these count? )

5) What size pilot jets are you using? 30 might go back to stock

6) What size main jets are you using? 290

7) What is your Bore Size? stock

8) Do you have a port job? no

9) What kind of carb? stock 26mm

10) What kind of reeds ? Boyesen dual stage

11) oil injection or pre-mix ? Oil injection

....................................................................................................

1) What type of aftermarket exhaust do you have?

fmf gold series fatty with powercore 2 silencer

2) What type of airfilter do you have?UNI

3) Are you a)running a stock airbox with lid stock airbox with NO lid c) Stock airbox with vents d) no airbox at all......Running Outerwear airbox lid cover

4) What is your elevation? babout 725 ft

5) What size pilot jets are you using? stock

6) What size main jets are you using?.........280

7) What is your Bore Size?..........stock

8) Do you have a port job?..........stock

9) What kind of carb?...........stock

10) What size is your carb? ...............stock

 

[Rich]

AFR is air to fuel ratio!

Air–fuel ratio (AFR)
Aw I see.I always refer it to air fuel mixture.I get it now.

FMF recommends a #270.

#230 main with an FMF Fatty, sugguests to me, that it is way too lean, even with a sunken float you wont get enough fuel to fire the fatty, unless you are running a toilet roll as an air filter.[/QUOTE

Nope ran on the rich side.Ive had the quad running for 12 years and this is the size jet I ran untill just rescently after purchasing a new carb.Ran uni with open box and a hotter plug for overly rich setting ngk br7es.And yes the float was pretty sunken it always stuck but yes this is the size jet that came with it and the pipe.Also bored with wiseco guessing 1.8mm over just a guess but in that range.Timing advance boyesen power reeds.Just basic upgrades.And it ran great with the carb but the needle was richer jjj or jjh BANSHEE and maybe more taper on the throttle valvecut away(mid range)But it ripped but did not like the way the throttle jumped in and out of power band all the time.It was slug or go.With stock needle maybe different main jet Idk.Got me thinking though curiouse to see the out come.

 

[Blaaster]

AFR is air to fuel ratio!

Air–fuel ratio (AFR)
Aw I see.I always refer it to air fuel mixture.I get it now.

FMF recommends a #270.

#230 main with an FMF Fatty, sugguests to me, that it is way too lean, even with a sunken float you wont get enough fuel to fire the fatty, unless you are running a toilet roll as an air filter.[/QUOTE

Nope ran on the rich side.Ive had the quad running for 12 years and this is the size jet I ran untill just rescently after purchasing a new carb.Ran uni with open box and a hotter plug for overly rich setting ngk br7es.And yes the float was pretty sunken it always stuck but yes this is the size jet that came with it and the pipe.Also bored with wiseco guessing 1.8mm over just a guess but in that range.Timing advance boyesen power reeds.Just basic upgrades.And it ran great with the carb but the needle was richer jjj or jjh banshee and maybe more taper on the throttle valvecut away(mid range)But it ripped but did not like the way the throttle jumped in and out of power band all the time.It was slug or go.

This is why you got away with a #230, incorrect fuel level, flooding all the time.

To lean a main, combined with a flooded bowl, may have caused it to run like crap.

 

[Rich]

This is why you got away with a #230, incorrect fuel level, flooding all the time.

To lean a main, combined with a flooded bowl, may have caused it to run like crap.

It did not stick all the time had it on there for years and it ran fine.Just ran different needle which is why it was slug or go.I admit it was time for a new carb but even when the carb was in perfect working order this was were it was jetted.Running a banshee needle may have been shorter Idk as I have not compared stock and jj needle of banshee.I just looked up fmf main jet remendation and its

Jetting Results
Main Jet
260
Pilot Jet
32.5
Needle
STOCK
Needle Position
3RD
Power Jet
N/A
Air Screw
1.5
Fuel Screw
N/A
Comments
Remove airbox lid snorkel

But now look at this.This is the banshee jetting specs.
Jetting Results
Main Jet
260
Pilot Jet
30
Needle
STOCK
Needle Position
3RD
Power Jet
N/A
Air Screw
1.5
Fuel Screw
N/A
Comments
Remove airbox lid snorkel
They seem to close to be accurate imo.But all in all it recomends 260.