Pilot Jet Screw ? & stuff 03WR450F 160MJ, 48PJ
Posted February 18, 2003 - 04:19 PM
I'm still waiting on my YZ throttle stop screw. The manual refers this as the screw that sets the Idle "Turn the throttle shaft assembly left while holding down the lever 1 5 and fit the throttle stop screw tip d to the stopper e of the throttle shaft assembly pulley." page 4-16. Is that correct? It don't sound right to me. Where is the throttle stop located?
When my PAJ #100 gets in this week I will also put it in. I know I'm changing too many things at the same time, but don't have enough time before first race? Does this look like I'm going in the right direction? Hopefully I will be able to ride Friday! and see what I've done! I'm basically trying to get rid of the off idle bog.
Posted February 18, 2003 - 07:15 PM
Good Luck, Jeff
Posted February 19, 2003 - 06:37 AM
Posted February 20, 2003 - 02:10 PM
what do ya mean yer in a hurry? you could be running to shoot your own foot off! slow down! test the changes, get a feel for it. who on earth told you to put a 100PAJ in it?
crazy! stick with the 75PAJ it's better and get a 40PJ. oh! and don't take even my word for it. test it first and back to back.
Posted February 20, 2003 - 04:59 PM
Posted February 20, 2003 - 05:50 PM
Maybe you guys should just save yourself some time and skip right to what works?
Posted February 20, 2003 - 06:07 PM
Posted February 20, 2003 - 09:41 PM
I got that from your post in the " Jetting Qs " (http://www.thumperta...er=&postmarker=).
Your last chart read:
" my chart therefore reads;
Is this not a good place to start on this bike?
How do you time the squirt? It looks to me like it just squirts as you turn the throttle and the adjustment just controls the amount of gas coming out.
Posted February 20, 2003 - 09:45 PM
Posted February 21, 2003 - 02:23 PM
waht pairing i feel you should use is another. anyway let's chillout coz you certainly don't deserve our wrath individually.
just to cut things short and real simple.
the PJ/PAJ ratio is only about 20% of idle. it's there for 20 mph in 4th gear and snapping the throttle.
a needle that reads well over 'M' for sea level and 'P' for altitude to keep the 'fat' in the hole and run it lean will need lots of help from the pilot circuit to 'juice it up'. thus the high numbers you inevitably employ.
i'm guestimating here but a typical scenario at sea level is 'P' needle (as in EKP) and 42/45 PJ.
on mine it would be a thinner 'M' needle and 35PJ and a nice middle one would be EMN and 38/40 PJ.
now the difference at tickover is diddly-squeek but when you roll that throttle in fourth at 20mph we are now on the pilot circuit.
now we can have a rich mixture or a leaner but correct mixture. it's up to you. so always pick your PC jets in the ratio i suggest but go lean and take the richer needle straight.
having ridden no higher than 1,000ft in my life i can only take hicks word for it but some of the 10,000ft boys are on a **Q needle and nice 35 or 38 PJ's.
the squirt should be as short as is humanly possible, BTW 1 second is the minimum before the system refuses to function properly.
Posted February 21, 2003 - 03:49 PM
Yesterday I changed the stock needle (OBDUT-4) from 4 to 5th from top. I changed the squirt 1/2 turn shorter from stock (Seems to be right at 1 second), and set the Jet screw 1-1/2 turns out (stock was 2). It ran good but had the off idle bog (2nd gear about 10mph) and backfired while in neutral while goosing it.
Today, Replaced the stock needle with 5TA-14916-JN-00 (#NDJN) (YZ-450F 2003). Left all else alone. Backfire in neutral gone, OFF IDLE BOG GONE I have always ran the 160 MJ, 48 PJ, 70 PAJ and am at 800 ft. very humid.
If it quits raining I'm track ready now. Need to test at greater speeds and conditions. While writing this I remembered I had to turn that ignition off. Ha, I didn't mean to offend anyone, I guess I didn't understand those were ratios, sorry! Can you explain the ratios?
48/110-125 ?48PJ =110-125 is this a % of something?
Taffy, I read all your posts in the jetting Q's with open eyes, you took great pains, I just did't understand everything.
Posted February 21, 2003 - 11:37 PM
so you see you're closer than you think!
the 48PJ/100-125 PAJ implies that the amount of air and fuel is so high as to barely be worth recording the difference.
now you've got a thinner needle in you can afford to go to lower PC ratios so start work now!
you'll be good for a PAS and a ratio of 40PJ and 75 (or 70 PAJ!)PAS.
Posted February 22, 2003 - 08:29 PM
Posted February 23, 2003 - 10:22 AM
48PJ/100-125. I am pretty sure the 48PJ stands for 48 pilot jet but I dont know what the rest of it refers to.
What is PC and PC ratios
What is a PAS
Does 75(or70 PAJ!)PAS refer to what the manual refers to as a starter Jet
Can the blip of throttle low end bog be cured with a accelerator pump screw adjustment and pilot jet adjustment or is the BK mod and all that just about required to cure the bog.
Posted February 23, 2003 - 12:04 PM
The "PC" is the pilot circuit. Folks usually refer to the carb having 3 different "circuits"...a low speed pilot circuit, a midrange (controlled predominantly by the needle taper and clip position), and the top end (controlled predominantly by the main jet).
What he was referring to by the 100-125 was the pilot AIR jet. There are a few combinations of pilot jets/pilot air jets that seem to work well...and he's stating that the 48PJ works well with a pilot air jet in the range of 100 - 125.
The PAS is an adjustable pilot air jet (known as the pilot air screw). It can be purchased at Sudco for about $15 and can be adjusted to provide you with a pilot air jet range of somewhere around 50 up through 125 based on the number of turns out from fully seated that the pilot air screw is set to. Good purchase for you to make, since you'll never need to buy another pilot air jet.
The starter jet is a completely separate jet used to squirt additional fuel into the carb throat during startup...not used for anything else. Some folks have changed the starter jet from the stock one and have noticed some improvements in "start-ability".
To cure your low end bog, you should both jet your bike correctly AND do the accelerator pump mod...or atleast verify that it's currently squirting fuel for about 0.5 secs. Most bikes "off the shelf" have been known to have upwards of 3 secs squirt duration...way too much fuel than what is required...and thus, folks do the mod to eliminate the hesitation from being way too rich for those few seconds.
Finally, some camps go with the larger PJ/PAJ ratios for tractor like torque. Others go with the smaller PJ's/PAJ ratios for a "snappier" throttle response. As long as your PC ratio and needle diameter are close to being matched, you're bike will run well off the line.
Hope this helps...
Posted February 23, 2003 - 01:25 PM
jim i don't follow you're individual needs therefore you're talking dutch to me. run the FIGURES by me.
Posted February 23, 2003 - 02:44 PM