Jetting



19 replies to this topic
  • jim-in-so-ore

Posted February 01, 2003 - 11:32 AM

#1

I just got back from my local Yamaha shop to get jets for "UTVOLS" jetting specs and lo & behold, no starter jet. I had to order that. They said it should be here Wednesday or so. I decided to only do this once so I am waiting till then to do the main and pilots jets. It never was my idea of fun to tear apart the carb even if it's only the float bowl. OH well , I'll do this later in the week.
Jim

  • ThumperWR450F

Posted February 01, 2003 - 11:43 AM

#2

jim i only changed my main (160) and pilot (48)and the bike starts and idles fine and RUNS GREAT !!it took me 5 mins to take the float bowl off change the jets and start her up !! with the stock jetting it wouldn't idle and all she did was pop and sputter. what a diference a little adjustments make. on another note i have no clutch problems and the electric start works fine !! knock on wood !!

  • allinson

Posted February 01, 2003 - 06:01 PM

#3

My 2 cents worth. I think folks are making a big deal out of the starter jet. I have rejetted XRs, KLXs, WRs and YZs, and never once touched a starter jet. :)

  • Superbike

Posted February 01, 2003 - 06:18 PM

#4

I can understand lean jetting, but this thing was so lean it would have overheated if I would have ran it much longer! I just can't believe they would send them out running like that. Imagine when someone who is clueless to jetting buys one. You can not even ride it like that. Will not Idle with out choke. ---Mike

  • xr600r

Posted February 01, 2003 - 06:42 PM

#5

thank god for thumpertalk

  • Taffy

Posted February 04, 2003 - 12:13 PM

#6

i think i started off this SJ thing. i did it coz i like the bike to run sweetly while i put my helmut and gloves on. it should be your idea as well.

if the rest of your jetting is done you must ask yourself how long did it need choke?

when did it eight stroke?

for instance my bike used to eigth stroke before it was warmed up!

this resulted in
start
chug
choke in
stall
choke out and start
eight stroke
choke in
stall
choke out and start

getting the picture?

they shouldn't eight stroke you know ge-dung, ge-dung, ge-dung fizzzz (death warble)

Taffy

  • john450f

Posted February 04, 2003 - 12:48 PM

#7

Excellent article on 4-stroke jetting in MXA this month. Good info on how to determine richer/leaner @ which jet to check @ how. By the way anybody use plug color as a guideline or even tried to get it out. Almost have mine out as soon as I get thru this last frame member with hack saw.

  • Hick

Posted February 04, 2003 - 01:12 PM

#8

I with Allinson and Taffy (sort of).

My YZF wouldn't even attempt to start with the stock choke jet, and would not run with it on. It made cold (for here, anyway) starts a bit of a hit-or-miss proposition, and I had to run the idle really high to get the thing to warm up.

I finally got tired of that this fall, so I just guessed blindly at a choke jet, I think I went two sizes smaller, and my choke actually worked after that.

If your bike starts w/ the choke in cold weather you probably don't need to fool with it.

My two cents.

  • Hick

Posted February 04, 2003 - 01:13 PM

#9

I saw that MXA article, I have no comment other that IMO plug reading is not a very good way to jet your bike.

  • Hick

Posted February 04, 2003 - 01:14 PM

#10

I just can't believe they would send them out running like that.



Doesn't it come w/ a restricted exhaust, throttle stop, and air box lid?

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  • neWRiver

Posted February 04, 2003 - 01:40 PM

#11

Well heck, I never messed with my choke jet either. But, come to think of it I CAN NEVER USE MY CHOKE!

I do live in a warm climate, so cold to me is not very cold and I always considered that this was the reason I never needed the choke. In the colder months, though, cold starting is kind of little dance. Couple squirts with the throttle, tries to start, won't idle. Pull choke, kick not even close (never works, I don't know why I still bother to try). Couple more squirts try again. Pull the hot start and decomp and clear the excess squirts. Kick some more. Turn up the idle. Kick some more. Finally catches and if I nurse the throttle it'll smooth out and idle (with idle still adjusted high). When the idle rpms take off after a few minutes, turn the idle back down.

Huh, change the choke jet so I can use the choke? Duh, maybe I'll try that. :)

Thanks. :D

  • xr600r

Posted February 04, 2003 - 02:20 PM

#12

speaking of cutting thru the last frame member with a hack saw...... why did yamaha bury the plug like its a bear hibernating ??????? i thought my XR was a little out of the way....but this is crazy. :)

  • xr600r

Posted February 04, 2003 - 02:23 PM

#13

sorry....that was suppose to be a re-ply to john 450f

  • Superbike

Posted February 04, 2003 - 02:44 PM

#14

XR600, the yamahas have always been like that. ----Mike

  • xr600r

Posted February 04, 2003 - 03:10 PM

#15

i knew that mike....a good friend of mine has a 98'wr.
:)

  • Taffy

Posted February 06, 2003 - 03:56 AM

#16

manufacturers and carb designers try and set a bike up so that the correct extra % of fuel is added by the choke to a reasonably correct mixture.

but if everyone runs rich at low revs they have to find another way to start the bike. a twist, three twists, two kick throughs whilst on the kill button getting the wife to piss in the tank etc etc.

but if you get the low end jetting right then it's simple-you need choke. i went through what you're saying when i bought the bike.

THEN when i had done the jetting, i needed choke.

that's why in "jetting Qs" i did the choke jet and the APJ last. 26 months ago i left the bike in the shed for three months and said phuq it because i had fowled a plug so i've been there.

Taffy

  • neWRiver

Posted February 06, 2003 - 07:17 AM

#17

Yeah, I agree Taffy. The choke can only work together with proper low end jetting. I am probably still a tad over juiced with a __P needle and a 40 PJ, but it seems fairly close. The choke jet seems way off, though.

You're right, though. I'm going to get my needle straight and pilot jetting dialed in a little better before I test any choke jet changes.

Right now I am at 170 MJ, ELP #3, 40 PJ, 65 PAS, about 1 turn on the FS. This has been hit and miss as the winter oxygenated blends here seem to very a great deal in quality and consistency. I've switched to VP MS103 in order to get more consistent (and cleaner) fueling. That jetting seems to be a little fat across the board with this fuel, so I'm gonna be tweaking it a bit at a time.

What do you think about some of the more recent suggestions to go leaner on the needle straight? I ride mostly in the range of about 2,000 to 6,000 ft with temps in the 80F range right now. Some have expressed good results from going to ELQ and juicing the pilot up a bit, what do you think?

Thanks. :)

  • Taffy

Posted February 06, 2003 - 01:45 PM

#18

well JD (james) did always like the P needle and it was good i trust. so what was his altitude?

i think the big problem is the fight to get people to keep going forward to leaner jetting instead of falling back "into the pocket"-an american term i believe- where it's easy to overjuice and be happy.

the needle straight has to be right on it's own. it can't really be lean or it would be a horror.

remember that at sea level the 'P' needle had a hidious flat spot on mine.

so i guess that if it has no "five yard flat spot" then the Q will be a good needle.

on opening the throttle the APJ and PJ start to take over and although i don't think the APJ has anything to do with it, a lot of riders are running high PJ to PAJ ratio.

so much so that i'm pretty sure that the shear richness of the PC is well over the top and is the reason that the needle can go back to a lean 'Q'.

if you look at jetting Qs (which i'm not but let's try my memory out) the PC is the 20% 'top-up' on the needle's straight diameter.

for me though the balance is wrong-richer needle, lean pilot is better for a snappy reaction (like a trials bike) as opposed to perhaps the drag strip overfueling some look for, when going from zero.

at the end of the day though as we have all said; if it works, it works!

Taffy

  • neWRiver

Posted February 06, 2003 - 03:09 PM

#19

Okay, I think I may be close at ELP #3, and the PJ might need a drop. But the main has my attention as my most noticeable lacking on the last run was in the 3/4 - WOT. Just not wanting to rev out sharply and even running a little flat. Gonna try 168 and 165 and see what that does to crispen it up. Then, I think I may like the 38 PJ. I will sort the needle clip at the last, but I have a feeling it may clean up on it's own with the changes at both ends.

Then again, I'm just guessing and I won't know until I try each little bit. Perhaps I'm just hoping 'cause for as tiny as it is, that little clip should be a heck of a lot easier to adjust. :)

In the meantime, I'll order a couple smaller SJs. :D

  • Taffy

Posted February 06, 2003 - 10:49 PM

#20

i'm pretty sure it'll take that lower jet but if it doesn't, keep the same MJ that you have now and try the 160 MAJ and i think it'll fly.

but the test conditions need toi be spot on for a true back to back test.

so no rough old tracks and try and find a bit of highway somewhere.

Taffy




 
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