Flamethrower!!!!


12 replies to this topic
  • dunecj2a

Posted January 19, 2005 - 06:31 PM

#1

OK now I am on part II from my post earlier this week :cry: I am new to 4 strokes and believe that I am an idiot when it comes to carb adjustmments. :cry: I have an 04 450 that is still running like crap from closed throttle to about 1/4. I got some advice earlier this week and have not tried everything yet. I cleaned out the carb ports, jets, and chambers.
Now the fuel screw does make a difference when I adjust it but I still have that bad bog right off the bottom. I have the complete FMF Titanium 4 system. 42 pilot jet, 165 main, 3d clip on the needle.
The bike is now spitting out flames and the idle is really sporadic. Its revving real high then it just drops. It bogs when you gas it and then shoots flames and idles really rough. I jetted the way FMF told me. What do you guys think :cry: The flames look cool, but I hate the way it runs :cry:

  • jimmyg

Posted January 19, 2005 - 06:44 PM

#2

is it bogging when on the stand or when riding?

  • Chills

Posted January 19, 2005 - 07:06 PM

#3

How far out did you screw the Fuel Mix out? Once you get to a certain point, you have to change the pilot. DSP recommends after 3 1/2, but I think if you have to go to 3 and still get the hesitation, you need to bump your pilot, and screw the fiel mix back in.

I my recomendation would be drop the clip on the need down to #4, put the fuel mix screw back to where it was, and try again. If you are still getting bad hesitation, and after trying to adjust the fuel Mix screw 1/4 at a time, bump the pilot jet up, and start over again...

  • dunecj2a

Posted January 19, 2005 - 07:51 PM

#4

is it bogging when on the stand or when riding?

On the stand, I havent had a chance to ride it yet.

  • dunecj2a

Posted January 19, 2005 - 07:55 PM

#5

How far out did you screw the Fuel Mix out? Once you get to a certain point, you have to change the pilot. DSP recommends after 3 1/2, but I think if you have to go to 3 and still get the hesitation, you need to bump your pilot, and screw the fiel mix back in.

I my recomendation would be drop the clip on the need down to #4, put the fuel mix screw back to where it was, and try again. If you are still getting bad hesitation, and after trying to adjust the fuel Mix screw 1/4 at a time, bump the pilot jet up, and start over again...

What up Chills. Yeah I'm gonna fool with it at the track tomorrow night. Whats up with the flames :cry:

  • Jetsprint2

Posted January 19, 2005 - 08:10 PM

#6

OK now I am on part II from my post earlier this week :cry: I am new to 4 strokes and believe that I am an idiot when it comes to carb adjustmments. :cry: I have an 04 450 that is still running like crap from closed throttle to about 1/4. I got some advice earlier this week and have not tried everything yet. I cleaned out the carb ports, jets, and chambers.
Now the fuel screw does make a difference when I adjust it but I still have that bad bog right off the bottom. I have the complete FMF Titanium 4 system. 42 pilot jet, 165 main, 3d clip on the needle.
The bike is now spitting out flames and the idle is really sporadic. Its revving real high then it just drops. It bogs when you gas it and then shoots flames and idles really rough. I jetted the way FMF told me. What do you guys think :cry: The flames look cool, but I hate the way it runs :cry:

To me it sounds like you are too rich and it needs leaned out. The flames comming out the pipe is the result of raw fuel being burned in the exhaust and not in the combustion chamber like normal. The bogging is from being too rich as well. Try leaning it out in small steps until desired setup is reached. For whatever reason the FMF settings are not what your bike likes in your location. Make sure you make a change, if you are way to rich it is possible to create more compression (with the extra volume of raw fuel) in the combustion chamber and blowing a head gasket or doing even more damage.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • dunecj2a

Posted January 19, 2005 - 08:18 PM

#7

To me it sounds like you are too rich and it needs leaned out. The flames comming out the pipe is the result of raw fuel being burned in the exhaust and not in the combustion chamber like normal. The bogging is from being too rich as well. Try leaning it out in small steps until desired setup is reached. For whatever reason the FMF settings are not what your bike likes in your location. Make sure you make a change, if you are way to rich it is possible to create more compression (with the extra volume of raw fuel) in the combustion chamber and blowing a head gasket or doing even more damage.

What about the sporadic idle :cry: Should I drop the pilot down to the next smaller size and leave the main alone?

  • Indy_WR450

Posted January 19, 2005 - 08:36 PM

#8

170 main, clip #4 from the top, 50 pilot jet, #40 leak jet! :cry: The bogging is a lean issue! Flames is a lean issue! :cry: Due to the FMF pipe change. :cry:

  • Jetsprint2

Posted January 20, 2005 - 08:56 AM

#9

170 main, clip #4 from the top, 50 pilot jet, #40 leak jet! :cry: The bogging is a lean issue! Flames is a lean issue! :cry: Due to the FMF pipe change. :cry:


How do you figure, if it were lean there would be no extra fuel to burn in the pipe to create flames, (Flames = the burning of raw fuel that has not been used in the combustion chamber, the raw fuel reaches proper temp in the pipe and presto, Flames out of the pipe). The bogging is associated with being rich. If it were lean there would be a popping sound, beyond the point of being crisp. The tempermental idle is the case of being to rich as well, the engine loads up on fuel and then boggs, burns the fuel off and continues changing the idle RPMS drastically and speratically. Of course this is just IMO though, but I would be willing to bet this is the case. :cry:

  • Jetsprint2

Posted January 20, 2005 - 09:01 AM

#10

What about the sporadic idle :cry: Should I drop the pilot down to the next smaller size and leave the main alone?

If it were me in your situation I would go back to the stock settings and go from there. It will give you more of a baseline than the FMF settings. The sporadic idle is a rich symptom as well, The engine loads up on excess fuel and burns it off, when it loads up the idle is low unsmooth and when it burns it off the idle increases RPMs and the process starts all over again. Go ahead and pull the spark plug and inspect it to see how rich it is. If it is as rich as I think it is than the plug will be very black.

  • Chills

Posted January 20, 2005 - 12:56 PM

#11

There is a simular post going on about the same thing...Here it is:

http://www.thumperta...ead.php?t=98996

Also, in that list of posts, one of the best explanations I have read about was posted in this thread...

Guys, the best explanation of decel poping I have ever heard was written in the knowledge base in ATM. Here it is. :cry:

Subject: Re: DECEL POPPING?

After spending the day on the dyno Saturday, my 450 popped and shot flames out 4 inches after 11,000 rpm runs. The O2 sensor indicated we were a tad rich on the pilot and needle. I attributed it to unburned gases in the exhaust igniting on decelleration and jetting wont help that. Most times a lean condition WILL be indicated by popping, but not always.



--------------------------------------------------------------------------------


This is exactly correct! If you think about the mechanics of what is going on upon decel, it makes perfect sense:
You start out with an engine that is turning high RPM with a carb that is open, flowing freely. Next, you close that slide. This has the effect of creating a tremendous vaccuum in the intake manifold (CHOKE!). This vaccuum does curious things:
1. It pulls air and fuel from wherever it can--including the idle and low speed jetting in the carb.
2. To counteract the vaccuum, air will take the path of least resistance--including sucking exhaust gases back into the combustion chamber during valve overlap (the brief period of time that the exhaust and intake valves are open at the same time.

So what does this mean? Well, now you have a disproportionate rich mixture heading for the cylinder AND what little oxygen is drawn in is further diluted by gases that are coming back into the chamber from the exhaust valve. The result is poor, incomplete combustion! Depending on the temperature of the exhaust pipe and gases, reignition is possible once this mixture is introduced into a more oxygen rich environment. This produces the "pop."

Why does a lean running engine have a tendency to excessively pop? The exhaust gas temperature of a lean engine is substantially higher than one that is running on the rich side ( an EGT probe will show this). Therefore, the high EGT serves to heat the pipe more and the gases themselves become a much better source of re-ignition. By richening things up, you are cooling down the exhaust temp and therefore reducing potential re-ignition sources.

Any 4 stroke engine--even those that are flawlessly tuned will pop on decel. It is harmless, but can be annoying--granted. However, I would never alter the jetting of an otherwise performing motorcycle to get rid of it. Go by the seat of your pants and the color of your spark plug rather than the popping as an indication of the jetting of your scoot! :cry:

-----------------------------------------------------------

So, based on this explanation I believe the problem could be either an air leak on the intake causing a lean condition or a plug that is not firing hot enough. Both are pretty easy to find. :cry:



  • jimmyg

Posted January 20, 2005 - 08:52 PM

#12

they will almost always bog on the stand if you stab the throttle quick. you have to ride it & see how it acts. if your at low rpms you should roll the throttle not stab it you will get more traction no bog & actually be faster.

  • Dovii

Posted January 20, 2005 - 09:51 PM

#13

OK now I am on part II from my post earlier this week :cry: I am new to 4 strokes and believe that I am an idiot when it comes to carb adjustmments. :cry: I have an 04 450 that is still running like crap from closed throttle to about 1/4. I got some advice earlier this week and have not tried everything yet. I cleaned out the carb ports, jets, and chambers.
Now the fuel screw does make a difference when I adjust it but I still have that bad bog right off the bottom. I have the complete FMF Titanium 4 system. 42 pilot jet, 165 main, 3d clip on the needle.
The bike is now spitting out flames and the idle is really sporadic. Its revving real high then it just drops. It bogs when you gas it and then shoots flames and idles really rough. I jetted the way FMF told me. What do you guys think :cry: The flames look cool, but I hate the way it runs :cry:


You put the slide plate in upside down. Many have made this mistake. The symptoms are identicle to yours.





Related Content

Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.