I installed a dynojet carb kit and 4-1 header. Bike runs good but is a little lean down low. The kit says to run the adjustment screw at three turns out. Is this a fuel or air screw. Do I turn it in our out to make it richer off the bottom?
- this is the brass adjustment screw on the top front of the stock carb.
thanks.
Air fuel mix.More turns out = richer mixture.
Confused. On dirt bike 4 strokes have "fuel" screws so out is richer. 2 strokes have air screws so out is leaner. Confused by the "air fuel" title. You know for sure it is richer as you turn it out?
thanks
As you turn it out it lets more fuel through.I have a dinojet kit in my 85 with a kerker 4-1-2 pipe.I was super rich with there settings.3 1/2 turns was to much for my bike and I had to drop my needles as well.I think I at 1 1/2 turns now and needles all the way down.
The mixture screw is beyond both the air intake and the fuel intake of the idle circuit. Therefore it controls the amount of an air/fuel mixture that is allowed into the intake tract. It is neither an air nor fuel screw, it is a mixture screw. This is not a dirt bike.
Start at 2-1/2 turns out and do the blip the throttle test.
If you don't know what that is, then do some reading in the files section.
DavidR.
Quote from: SlowOldGuy on November 06, 2010, 12:50:47 AM
The mixture screw is beyond both the air intake and the fuel intake of the idle circuit. Therefore it controls the amount of an air/fuel mixture that is allowed into the intake tract. It is neither an air nor fuel screw, it is a mixture screw. This is not a dirt bike.
Start at 2-1/2 turns out and do the blip the throttle test.
If you don't know what that is, then do some reading in the files section.
DavidR.
I know it is not a dirtbike... Duh but thanks for that. I have jetted and tuned MANY bikes and am quit good at it thanks. It was a simple question. thanks Scotsman for a good answer. And actually I believe it is a FUEL screw NOT a mixer SCREW. There is no MIXTURE at that point it is fuel and the changes the air fuel mixture after you add or subtract more fuel which this is controlling. Some bikes have air screws some have fuel, this appears to be fuel. Mine needs to be richer as it has a slight ping and hesitation off the bottom. I have found blip tests not under load do little but will indicate lean spots in the pilot jet or needle position. Mine does fine when blipped not under load but is for sure running lean in roll on situations. Want to play with the screw first then the needles if need be.
Anyone know the working range for this fuel screw? Dynojet has you start with three turns out with pod filters and exhaust like I have. Used there settings / slide springs for this setup and other than the slight lean off the bottom runs great.
HA! told you Dave.
It is indeed a mixture screw (or fuel/air, Yamaha refers to it as a pilot screw set) It controls an air bleed connected to the pilot circuit. This bleed controls the amount of fuel the pilot circuit is able to deliver at closed throttle and partial throttle. Turning the screw out opens the circuit allows a larger amount of air to flow creating a lower pressure and lifting more fuel. (Correct me if I am wrong Dr Raforth) In a CV carb both the pilot and main circuits have air jets located in the carb throat. In the case of the pilot circuit this is fine tuned by the mixture screw. Changing the size of the air jet alters the amount of air available for fine tuning. In many cases a larger air jet will help cure a lean part throttle condition.
Adjustment range of the mixture screw is usually 1-4 turns out from seat.
Quote from: Ride on November 06, 2010, 10:07:26 AM
Quote from: SlowOldGuy on November 06, 2010, 12:50:47 AM
The mixture screw is beyond both the air intake and the fuel intake of the idle circuit. Therefore it controls the amount of an air/fuel mixture that is allowed into the intake tract. It is neither an air nor fuel screw, it is a mixture screw. This is not a dirt bike.
Start at 2-1/2 turns out and do the blip the throttle test.
If you don't know what that is, then do some reading in the files section.
DavidR.
I know it is not a dirtbike... Duh but thanks for that. I have jetted and tuned MANY bikes and am quit good at it thanks. It was a simple question. thanks Scotsman for a good answer. And actually I believe it is a FUEL screw NOT a mixer SCREW. There is no MIXTURE at that point it is fuel and the changes the air fuel mixture after you add or subtract more fuel which this is controlling. Some bikes have air screws some have fuel, this appears to be fuel.
(popcorn)
It's a fuel screw. What it actually controls and how it works matters not so much, but by giving it a simple name where it fundamentally makes sense makes communication clearer. Out is more fuel and richer, and v/v. Calling it a slow pilot mixture idle controlling adjusting screw is being pedantic.
According to the factory, I suppose we could argue that they're emmissions adjusters that are then sealed :)
(popcorn)
Gee, I guess you can re-write all the information in the files section since you're such an expert. If you post an OPINION, you're going to be called on it if it's incorrect.
A FUEL screw controls the amount of FUEL allowed into the circuit. An AIR screw controls the amount of AIR allowed into the circuit. On the FJ carb, it's a MIXTURE screw. At that point in the circuit, it is controlling the amount of an air/fuel MIXTURE allowed into the intake. That A/F MIXTURE is a function of the size of the idle jet and the air pilot jet.
Take a look at the schematic of the FJ carbs. I can probably draw it with my eyes closed.
But you can believe what you want. I've tuned MANY FJs and am quite good at it. And how exactly would you go about performing a "blip the throttle test" "under load?" I have "found" that this test is very good at getting idle mixtures spot on for the FJ. But you just go on "believing" what you want to.
DavidR.
Quote from: the fan on November 06, 2010, 10:35:32 AM
HA! told you Dave.
Yeah. Man, I hate being wrong for all these years. Nevermind everyone! Ignore whatever advice I've given you over the years. It was all BS. Sorry about that.
Quote
It is indeed a mixture screw (or fuel/air, Yamaha refers to it as a pilot screw set) It controls an air bleed connected to the pilot circuit. This bleed controls the amount of fuel the pilot circuit is able to deliver at closed throttle and partial throttle. Turning the screw out opens the circuit allows a larger amount of air to flow creating a lower pressure and lifting more fuel. (Correct me if I am wrong Dr Raforth)
Just a few small corrections, Bill.
The mixture screw is not an air bleed. It's just an adjustable orifice controlling the amount of the idle circuit A/F mixture allowed into the intake. In a CV carb, the "amount" of air has no affect on the mixture, it's the velocity of the air that matters.
Quote
In a CV carb both the pilot and main circuits have air jets located in the carb throat. In the case of the pilot circuit this is fine tuned by the mixture screw. Changing the size of the air jet alters the amount of air available for fine tuning. In many cases a larger air jet will help cure a lean part throttle condition.
True, there are air bleeds for the idle and main circuit. But, if you're lean, a smaller air pilot jet will richen the circuit.
Did you install the 144 air pilot jets that came with the DJ kit? That is supposed to help the lean spot caused by a 4:1 exhaust.
In the olden days, the V&H pipe was known for a bad lean surge. I think the recommended cure was exhaust restrictors.
If it's not a bad stumble, you should be able to get there with idle circuit tuning. A 140 idle jet is another option.
DavidR.
Thanks for the info. Sorry i pissed people off. Seemed like i was being talked down to like i knew nothing because i come from a dirt bike back ground. CV carbs are somewhat new to me. There is no stumble, bike runs good, idles perfect. There is a slight hesitation and I can hear pinging under load right off the bottom some times. I am running the 144. Pipe is a Kerker header with a muffler i graphed on.
(http://motosportz.smugmug.com/Motorcycles/101210-FJ1200-ride/IMG5376/1058942097_YDPV2-L.jpg)
Nah, you were being talked down to because you come across as a dumb fuck who won't listen to blokes who've given you exactly the right advice.
Now harden the fuck up, this is FJ.
You listen to what these blokes tell you and you cannot go wrong.
Dr Ratfart in particular, why do you reckon he is known as the carb Doctor?
Quote from: Klavdy on November 07, 2010, 04:30:35 PM
Nah, you were being talked down to because you come across as a dumb fuck who won't listen to blokes who've given you exactly the right advice.
Now harden the fuck up, this is FJ.
You listen to what these blokes tell you and you cannot go wrong.
Dr Ratfart in particular, why do you reckon he is known as the carb Doctor?
New here, do not know anyone or who knows what.
"Now harden the fuck up, this is FJ"
Does that mean I need to be a dick and call people dumb fuck... OK I'll try.
Course it does, no punches pulled here.
'Bout the only things that get a bit of attention would be:
Hatred
Nudity (the occasional hint gets overlooked)
Bigotry.
Apart from that, yeah, you'll get really good advice here and maybe make some lifelong friends.
We cuss and swear, pull pranks and stir the pot, but there is no more a supportive group than this one.
Cheers and welcome.
Quote from: Klavdy on November 08, 2010, 12:08:59 AM
Course it does, no punches pulled here.
'Bout the only things that get a bit of attention would be:
pull pranks and stir the pot
Did you hear the one about the pinecone in the tankbag?
Thanks good stuff. I am a smart ass dick but try not to be. :diablo:
For reference I own and operate a off road motorcycle accessory company. We manufacture lots of parts for off road bike. Engineer and CAD operator by trade. Been working in the motorcycle industry for many years and riding since birth. Have always owned street bike but my main love is off road as there are no rules and WAY less death.
Sorry to snap back at the original and good info.
Carry on fuckfaces. :mocking:
Quote from: Ride on November 07, 2010, 02:22:24 PM
Thanks for the info. Sorry i pissed people off. Seemed like i was being talked down to like i knew nothing because i come from a dirt bike back ground.
You couldn't have been more wrong... many on this board own/ride dirt bikes.
Take a look around here, and you'll find there is even a dirt bike section here.
The ECSR has featured a dirt bike ride for the last couple of years, as well.
Quote from: Ride on November 08, 2010, 09:00:12 AM
For reference I own and operate a off road motorcycle accessory company. We manufacture lots of parts for off road bike. Engineer and CAD operator by trade. Been working in the motorcycle industry for many years and riding since birth. Have always owned street bike but my main love is off road as there are no rules and WAY less death.
You may want to post up in the vendor section, too... :good:
Randy T
Indy
Quote from: Klavdy on November 08, 2010, 12:08:59 AM
Bigotry.
But it's okay if it's "friendly" and constant, no matter how offensive it actually is to people.
Quote from: Ride on November 07, 2010, 02:22:24 PM
Thanks for the info. Sorry i pissed people off. Seemed like i was being talked down to like i knew nothing because i come from a dirt bike back ground. CV carbs are somewhat new to me. There is no stumble, bike runs good, idles perfect. There is a slight hesitation and I can hear pinging under load right off the bottom some times. I am running the 144. Pipe is a Kerker header with a muffler i graphed on.
(http://motosportz.smugmug.com/Motorcycles/101210-FJ1200-ride/IMG5376/1058942097_YDPV2-L.jpg)
Thats a fine lookin FJ ya gots there. I be liken the looks of that pipe. :good2: What is it? And sounds like you got it almost dialed.
And yup, these guys know there chit.... :biggrin:
Cheers...Jake
I used to resell Barrett mufflers from Australia. I have several left and this one fit perfect on the Kerker header I scored off Ebay for $55.
http://www.barrettexhausts.com.au/html/our_pipes.htm (http://www.barrettexhausts.com.au/html/our_pipes.htm)
Quote from: andyb on November 08, 2010, 09:40:34 AM
Quote from: Klavdy on November 08, 2010, 12:08:59 AM
Bigotry.
But it's okay if it's "friendly" and constant, no matter how offensive it actually is to people.
It's not "BIGOTRY" if it is aimed at Bloody Seppos.
Quote from: Ride on November 08, 2010, 09:00:12 AM
Have always owned a street bike but my main love is off road
+1 (popcorn)
Quote from: Ride on November 08, 2010, 09:00:12 AM
Have always owned street bike but my main love is off road as there are no rules and WAY less death.
Same here.... started riding in the dirt at age 10 1/2. 41 years of dirt riding and racing, mostly desert stuff.
Welcome aboard!
(popcorn) :flag_of_truce:
Quote from: simi_ed on November 08, 2010, 12:45:22 AM
Did you hear the one about the pinecone in the tankbag?
Oh, yes, the Pine Cones secreted in my luggage, ha ha.
What a jolly jape.
I'm happy to say that Australian Customs did not discover what would have been viewed as an extremely serious and expensive breach of quarantine regulations.
Penalties for breaching Australia's quarantine laws include fines of up to $60 000 and imprisonment.
Quarantine breaches are considered far more serious than,say, a bag of dope.
That's because Australia is one of the very few countries that is free of many biological hazards,you know, fruit cankers, rabies etc.
Quote from: Klavdy on May 27, 2011, 01:42:19 AM
Quote from: simi_ed on November 08, 2010, 12:45:22 AM
Did you hear the one about the pinecone in the tankbag?
... fines of up to $60 000 ...
Can I cheat you out of it, rather than owe it to you?
Talk to my financial adviser, DerbyBrit, he's the Go-To man for those matters.