Jetting Qs



244 replies to this topic
  • neWRiver

Posted November 08, 2001 - 01:04 PM


Taffy, I am addressing this to you only because you feel compelled to confront me directly in your deliberations about who's right and who's wrong and who's smart and who's ignorant.

Let me clarify, I am ignorant. I am new to jetting dirt bikes and am not schooled or even very experienced. That is why I am here. If and when I do reach a "point of satisfaction" you will likely not hear much from me on this topic because I will be out riding. Or maybe I will be posting questions about suspensions or exhaust systems or some such thing that I am wishing to improve upon or learn about. And maybe, if someone were to ask me, I might be able to say that a gent by the name of "Taffy" had a thing or two to teach me about jetting when I had been in the need of such information.

You are smart! (there, do you feel better?) You obviously spend a lot of time and energy doing your research and testing. But, from what I've read, you are still as much a work in progress as I am. Have you reached a point of satisfaction such that your pursuit of jetting changes has reached an end? I'm just trying to get my bike rideable and performing up to it's designed capabilities. Where are you trying to get to? If you want to be considered some sort of "jetting god" then I wish you well on your journey, but this subject is just not important enough for me to establish some form of worship just in order to get helpful advice.

In this apparent battle of who's right and who's wrong, you are winning. You are the only one really keeping score. As for me, my jetting still needs looked after, but I don't have time for 20 hours of homework (you know, family, work, riding, etc.), so thanks anyway.

And I really don't appreciate your addressing my observations and questions as if they should be measured against some standard which you hold up for everyone to follow. Respect works both ways. You don't have to slap someone down in order to be right or to feel smart.

[ November 08, 2001: Message edited by: neWRiver ]

  • Taffy

Posted November 08, 2001 - 01:51 PM


i took exception to your comments of 23/10. after JD and i had had a dig at each other you jumped in. that was the slap down. your comments seemed churlish and unnecassary.

later on you brought the ACV chat on the thread and recommended directly that riders go back to #100PAJ even though several of my threads in the last few days have basically said "lads get on with it!!!".

i took 30 minutes the other morning to answer your post as analytically as i could. yes it was done with a pat on the proverbial head. JD does that to me every day!!!

so quite the hard time stuff and next time look at the context you've put your threads in....

so lets forget it.

i inadvertantly put my first test up on here and kept everything here since so that it's of easy reference for everyones benifit. the original subject matter is irrelevant as can be seen by 90% of threads on this site. hardly ever does the last post reflect anything to do with the first post.

this thread would have died but for a sustained period of tech chat between JD and i that eventually spawned lots of Q's. Q's that could have started on their own, indeed the posts were from some people's own thread but played out here. i don't have a problem with that and i doubt if funktree is apoplectic about his thread changing subject. after all his Q was answered AND it is his name at the head of a 150+ thread.

a point to be proud of i suggest!

Taffy

  • neWRiver

Posted November 08, 2001 - 02:30 PM


Originally posted by Taffy:
i took exception to your comments of 23/10.


Well, that is the thing isn't it. You don't approve of me stepping up to comment. You find it rude that I was voicing disagreement with you.

And you're going to continue to preach to me about when and in what context I should feel that it is appropriate to post?

As far as recommendations, I have made none. I merely asked a fellow poster if he had tried a thing in order to hear HIS feedback. It really wasn't on my mind that you may have already spoken to that issue.

Okay, fine. Let's forget it. But, honestly, you say that the original question has been answered. I will concede that it may have been and that I missed it. Help me please. What is the answer???? Is it a lean conditon? Is it an anomaly of the CDI programming? Is it nothing worth thinking about at all? Pretend that I haven't read every little thing that has ever been posted and that I have a sincere desire to know the answer without wishing to offend you.

  • Stefe9999

Posted November 08, 2001 - 05:12 PM


Taffy,
Regarding "proverbial slaps on the head", ever noticed, I don't take them at you. Don't feel the need too. You requested "tell us what's wrong" and part of my response was:

"The knowledge gained on this thread will benefit you when you go to your stroker pipe if you have any trouble with rough running"

You replied:
"you must stop saying that i'll learn from your experience (etc) when i go to an open pipe. i'll bet you a pound to a pinch of salt that i'll have it done in one day. and who is actually teaching me"

Nowhere did I say that I or anyone else is teaching you anything. You chose to see my comment degrading or something. It is not! I am certain you'll know exactly what to do if your bike runs funny with the open pipe. And, I'm sure you'll share it with us.

But, you *have* learned from the group on this subject, in a lot of cases you've learned what doesn't work, but that is something! Everyone that has read this entire thread better have learned something. I totally believe you that you'll have your open pipe jetting it done in one day, don't have any reason to think otherwise.

I rarely get to ride, so I like to try to enhance my knowledge on jetting once in a while by gathering opinions, sharing experiences and and trying recommended things when I get time.


You have provided the brunt of the knowledge on this subject, that is appreciated. Like NewRiver, I don't know much about jetting either, but how else do we learn?

Lets try to keep this an enjoyable forum in which to discuss the one pastime we all have in common.

  • gavin500

Posted November 10, 2001 - 10:47 PM


I took my carby off yesterday and gave it a compressed air/carby cleaner blow out. Just to make sure nothing was mucking up my testing.

In my manual it states(in the spec's part) there are two PAJ?? One is size 75 and the other 90.
I couldn't see this other PAJ it was talking about when I had the carby off and my PAJ is 75, while the MAJ is 200. Thus stock.
Where is this second PAJ at size 90?

  • Taffy

Posted November 12, 2001 - 01:37 AM


gavin

it's just a guess but maybe they're on about the "octopuss". this has jets in it. there was an air jet on the end of a tube that came out of the inlet stub.

Taffy

  • LarryCO

Posted November 12, 2001 - 10:01 PM


Taffy/JD,
Rode yesterday on my EJQ3 needle with a 160 main (results to come tomorrow hopefully), but wanted to quickly ask about the difference between a D series and E series needles. Having my friend's bike there to compare to with a D needle, my bike was definitely more torque-ey on the low end...but seemed to lack that same midrange power (1/4 - 3/4 throttle). Would you say that is a factor of the needle...or just a jetting problem?

Larry

  • Taffy

Posted November 12, 2001 - 10:48 PM


this is probably one that many other riders could respond to better than i. i can barely remember the day i went to YZ timing.

i did the needle first then the YZ timing so that with the exception of some testing i did in february/march (reported in "snap....) i haven't done the 'D' series justice. some riders report a slight lose of torque when going to YZ timing.

by the way when i did my own cam timing i 'rocked' the exhaust cam forward 1/3 of a tooth.

the secret of the 'D' series is that the bike is very snappy at low revs from tickover etc. the bigger the taper of a needle, the nearer you're putting the taper start and the point in the needle that is right together.

that's why the taper start is stuck 9-10mm down the ET with the 'E' series. it'll be worse with the 'F' series still. whereas the 'D' series would only be stuck down the ET by say 6mm (i'm guestimating here ok).

your bike shouldn't lose anything in midrange once it is set up properly.

Taffy

  • Taffy

Posted November 12, 2001 - 11:05 AM


this is probably one that many other riders could respond to better than i. i can barely remember the day i went to YZ timing.

i did the needle first then the YZ timing so that with the exception of some testing i did in february/march (reported in "snap....) i haven't done the 'D' series justice. some riders report a slight lose of torque when going to YZ timing.

by the way when i did my own cam timing i 'rocked' the exhaust cam forward 1/3 of a tooth.

the secret of the 'D' series is that the bike is very snappy at low revs from tickover etc. the bigger the taper of a needle, the nearer you're putting the taper start and the point in the needle that is right together.

that's why the taper start is stuck 9-10mm down the ET with the 'E' series. it'll be worse with the 'F' series still. whereas the 'D' series would only be stuck down the ET by say 6mm (i'm guestimating here ok).

your bike shouldn't lose anything in midrange once it is set up properly.

Taffy

  • LarryCO

Posted November 12, 2001 - 12:12 PM


Taffy (and all),
Something I forgot to mention in my little D vs. E study...

Jim's bike (my friend) has the D needle (DRR#3, 155 main, 200 MAJ) AND has the YZ timing mod. My bike has WR timing with the use of EJQ#3, 160 main, 200 MAJ. Both are uncorked and otherwise fairly similar.

Given that info, would you still say that my midrange loss in power from moving to the E needle is a jetting issue on my part? Or can some of the difference be attributed to his YZ timing and/or the difference in D & E needles?

Larry

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  • Taffy

Posted November 12, 2001 - 02:31 PM


larry

this is a struggle to quantify. are you saying that you've lost power? that shouldn't have happened. the change to YZ timing is worth more than the 'E' needle that you have.

the midrange of your mates bike will be boosted by the YZ timing. put the two together though and you should get your nose back infront again.

Taffy

  • Stefe9999

Posted November 12, 2001 - 03:01 PM


Larry,
Any trouble with rough running or constant rpms?

  • LarryCO

Posted November 13, 2001 - 05:00 AM


Taffy,
Thanks amigo. That's pretty much what I thought. We're sort of comparing apples and oranges here due to his YZ timing and my WR timing. And regarding your comment about "my nose out in front"...that will only occur after about 40 miles of tight singletrack...when my friend and his mostly-out-of-shape ass gets tired! He's a much better rider than I... :)

Stefe,
After 13 hours of work yesterday, I havent even started to think about pulling my thoughts together on my ride. I'll hopefully get a chance to do it tonight and post everything in painstaking detail. Probably will start a CO/high altitude jetting thread, as this one's freekin' huge! I can tell you that it wasnt running rough in the midrange, but I think it IS rich (as halfway thru the ride, I twisted the throttle 1/2 open to launch off of one of those cool "mounds" on that Dakan Rd. trail and it totally bogged...almost like the plug was about to foul...turned the PScrew in from 1.5 to 1 and that resolved the problem artificially for the rest of the ride).

65 miles at Rampart = 10000 whoops to go over = 1 very tired and sore body!

Late

  • gavin500

Posted November 16, 2001 - 08:43 PM


Guys, installed the pilot air screw today.
Config -
Elavation - 700Metres(Aus, NSW)
170MJ
200MAJ
42PJ
PAS 1/2 turn(65)
DRQ needle Pos#3
PS 1turn

From 1/4 throttle on the bike is a beast! But I have proven that in earlier testing. Reason for wanting this setup.

New problem - since introducing the PAS, I get engine bog from nil to 1/4throttle.

Get the revs up a little, blip it, no worries very responsive. Blip it from dead idle and the engine will bog, blip it twice at this rate and the engine cuts out. To me this is saying I have a rich pilot setup.

Twisted the PAS to 5/8turn which should be 75. It has improved the bogging. There is still a hint of it there and it now only bogs it left to idle for 30secs+. This new problem doesn't affected anything else. Turning the PS seems to have no affect.

Hmmm... So I will try next putting the old PAJ back in to prove that the PAS has caused the new bog at nil to 1/4 throttle. If this is successfull I will try the PAS at 3/4turn 'just to see' what happens. Then I will replace the 42PJ with a 45PJ. I don't really want to do this cause in my pass testing I have shown that the bike is only happy with the 45PJ when a 165MJ is in place(not 170MJ). The reason for prefering the 170MJ is that the bike takes longer to rev out in top gears and seems to have more power that way than reving out faster at the top with a 165MJ.

Any advice?

  • YAMAKAZE

Posted November 19, 2001 - 04:45 AM


YO TAFFY,

Thanks....Completed the Jetting you and JD gave me this weekend. Lots of snap, Lots of power. It was very strange at first though...at home altitude of 780ft bike ran great...had to back off the airscrew from two turns to 1 1/4 because it was blowing black smoke in the driveway. Once I got to the ride site, Alt 1090 ft, it started acting up and was popping pretty bad. (Glad I brought my race trailer.) First put the AB lid back on (Man it was dusty) that help a little and I didn't feel any loss of power....Then on the trail I had to adjust the AS to 1 3/4 , but the popping stopped and it's like riding a new bike. Several times I was surprised when I cracked the throttle in 3rd gear coming out of a corner and the front wheel went skyward with my 220 lb butt on the tank. I know I probably need to tune a little more to get the lid back off the box....I'm just elated at the major difference I see right now.

Thanks....

Bonzai :)

  • The_Missile

Posted November 19, 2001 - 06:04 AM


Hi Yamakaze,

when you refer to the PAS in your comments I think you really mean the Pilot Screw or the Fuel Screw, right ? The PAS (Pilot Air Screw) is a an infinately adjustable replacement for the Pilot Air Jet or Slow Air Jet.

My 2 cents....I recently did some jetting changes and the backyard tests revealed different results than a real ride....just like yours seemed to. I think my problem was that the bike was not up to operating temps when I was "back yarding". I will definately only make test runs now when I am out riding as I mislead / misdiagnosed myself with my backyard runs.

I THINK :D your popping is/was a sign of leanness...so undoing your fuel screw richened the mixture thus removing/reducing the popping.

One thing I am struggling :D :) with in my own testing is identifying a rich / lean condition throughout the throttle range (off idle as that is straightforward if you read the BURNS article).

Can anyone confirm that, generally :
Rich condition : little or very slow throttle response, or a 'bogging' 'dying' kind of feeling. Blackened spark plug...

Lean Condition : Popping on deceleration.
But what about on acceleration ??... 'surging' rough/erratic running ?

One thing that really helped me to (try) to understand this jetting thing is to read the Patrick Burns article and create a flow chart/trouble shooting guide from it.....I'm still working on mine, when I get satisfied with it maybe I'll post it for comment, however going through that process really helped me to understand what I was reading as I found that the "cause/effect/solution" through the article is a little confusing for the "beginner".

Good luck with your tuning and glad to see you are back on the bike.

  • LarryCO

Posted November 19, 2001 - 06:59 AM


Heh Missle...

I too am in the same boat as you regarding diagnosing a rich/lean condition at the various throttle ranges. I also await the jetting guru's responses. The only change I would make with what you've writting given my little experience is regarding a lean condition...I wouldnt think it would be "rough/surging"...I would associate that situation with a mildly rich condition. I would think that slightly lean would be fairly smooth, yet not as explosive in acceleration.

Check out my post "High-Altitude Jetting - CO" I made last week. I tried to break down Patrick's article into distinct tests that one could perform to diagnose problems with jetting. I was hoping to get some feedback but no one's responded yet. Let me know what you think...any feedback would be helpful...

Larry

  • LarryCO

Posted November 19, 2001 - 07:01 AM


Heh Missle...

I too am in the same boat as you regarding diagnosing a rich/lean condition at the various throttle ranges. I also await the jetting guru's responses. The only change I would make with what you've writting given my little experience is regarding a lean condition...I wouldnt think it would be "rough/surging"...I would associate that situation with a mildly rich condition. I would think that slightly lean would be fairly smooth, yet not as explosive in acceleration.

Check out my post "High-Altitude Jetting - CO" I made last week. I tried to break down Patrick's article into distinct tests that one could perform to diagnose problems with jetting. I was hoping to get some feedback but no one's responded yet. Let me know what you think...any feedback would be helpful...

Larry

  • Taffy

Posted November 23, 2001 - 04:47 AM


did a stint of green laning just now. got chased off a farmers land again! thought i was there by right but it was when i threw my bike over the fence to get from the fotpath i'd used as a short-cut back to the RUPP and he caught me, that i think may have pissed him off a little.

the last time i did some tests was on 3/11 (or 11/3 to you) and there are dozens of posts in between now.

anyway if you recall the bike had come down from 165 to 160MJ and went like snot. i had also accidentally leaned off the needle and the PC.

started with;
155MJ, 160MAJ, EMM c3, 35PJ, 65PAJ, PS=2 turns.
gearing was 14 x 48 as i was too knackered to change the front sprog.

test 1
155>150MJ
EMMc3>c4
35>38PJ
PS 2>1.5 turns

yes i know it's a lot to do in one go but i know what's happening now don't i, so gimme a break willya all!

sharper top end
revved through the middle great
a dry, vibby bit at low revs which i knew was a lean condition due to dropping the MJ from 165 to 150 in recent times. the 38PJ cured this.

no coughs or glitches just excellent stuff.

also ever since i dropped the MJ from 160 to 155 she hasn't ticked over the same, only just able to spin over etc. it had been spot on so now it had to be lean, right?

it was when i went to the 38/35PJ that i had turned the idle "knob" out a whole turn. half of this was because the revs had suddenly picked up. with such low revs it acts as a barometer of how i'm doing.

tickover was back to it's old smooth self. luvely, super, fabulous!

rode it like this for a few miles and thought about a kind of 1/4 throttle gruffness i've always had. don't get me wrong, on WOT you can't spot it and i knew that whatever it was, it only wanted a tickle.

i've never pulled the PAJ (screw if you like) down first. i've nearly always let the PJ come down first. this means -and i've always been open about it- that the PAS has been "dragging it's heels". so i turned it in to 3/8 turn which is just a 55PAJ. this meant that at 20 mph in 3rd gear i didn't feel that little bit of "hunt"/vibration from the engine.

the bike was excellent, nearly faultless. thrashing it home with the suitable flee in my ear from the farmer i could hear the softest backfire at high revs and nothing lower so the needle could go up perhaps 1/2 a clip. also the revs to the red line proved a little slow a couple of times.

to test the "red line" though i would want my 15/48 back. initially it does appear that a 155MAJ may be needed.

hopefully before i move on i will try the 'F' needle but the pipe is probably out the question as i intend flogging it and i've never done anything except have the bikes picture taken with it!

i'm afraid there's no way the 'F' will be better. yep! i've stuck my neck out to say it!!

infact i hit upon this equation the other day; if you have a long needle that barely tapers in and you set the needle on the right clip position for it to have a taper that's right at a certain point- i'll call X. if you get a needle with a greater taper and set it so that at the right throttle opening that the needles width on the taper is the same, more of the straight has to sit down the ET (tube) causing the hesitancy?

so even if the 'F' needle is better still on top end, more of the straight has to be sat in the tube causing a greater lag when "snapping" the throttle.

i'll say more after you've all digested this lot. JD?

Taffy

[ November 23, 2001: Message edited by: Taffy ]

  • James_Dean

Posted November 23, 2001 - 05:59 PM


Taffy,

I would have come out and said it, but let you make the conclusion first. When recommending more taper, like the "F" needle, I look at the main jet to get a perspective first. Since your main jet has been getting smaller, the "FH-" or "FM-" doesn't make a sense. When bikes are running 170+ mains then the argument is good. (YZ250F = #170-#180) The low end will run exactly like you said, more straight diameter in the nozzle than desired. The resulting lag would a problem which could not be resolved. No point in going there.

James

[ November 23, 2001: Message edited by: James Dean ]




 
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