Gone to taffy jetting-still have a midrange bog!



41 replies to this topic
  • michaeltrundle

Posted August 22, 2002 - 09:02 PM

#1

hey all
I've just gone to the smaller "taffy" style of jetting as its known and cant seem to get rid of a bog when snapping open the throttle from almost closed.
I am running as follows:
38 pj, 60pas
158 mj, 162 maj
obeln pos 3
1-1.5 turns out on fuel screw
(rest is in signature.)
throttle response is nice and crisp down low and the snap wheelies in 1st or 2nd are good but if I cruise along in 3rd-4th gear at low revs and crack it wide open I get a bog for a split second then she lunges and goes like the clappers. Turning the fuel screw 1/2 a turn either way doesn,t seem to make much difference at all.
I suspect my needle may be a bit too rich.
How does the ELN compare to the EMM or EMN with regards to clip position, taper etc
Can someone recommend a better pos to try than 3 or should I buy another needle and be done with it or even change my main jet.
Is my 158 main jet going to be on the rich or lean side of things with a 162 maj
(no 160's in stock)
If any of you jetting gurus can point me in the right direction or spot anything I may need to change, it would be much appreciated.
I have trouble spotting a 'lean' or 'rich' bog on a fourstroke as compared to the ol' kdx.
thanks in advance.
mick

  • MN_Kevin

Posted August 22, 2002 - 10:31 PM

#2

Is this from a CLOSED throttle position?

If so, I might try reducing your AP squirt to 0.2 - 0.3 seconds. It is an easy enough external adjustment. Have you checked the AP squirt TIMING so the fuel DOES NOT hit the slide?

  • racemile

Posted August 23, 2002 - 05:31 AM

#3

Trundle,

When you wind it up and back off the throttle, does it pop a lot softly? If yes you may be to lean move clip to pos 4, or does it pop once or twice (backfire) then you may be to rich go up one position on the needle. If you cant adjust it out one way or another. Go with a smaller MJ if you are still to rich at the top position. If you are still to lean on the bottom position of the needle then go one size larger on the MJ and start again.

This has always worked for me.
Mark or Taffy may have a better suggestion though. If they do, ignore me and listen to them.

Race

Race

  • racemile

Posted August 23, 2002 - 05:33 AM

#4

Trundle,

My bike has exhibited a bog on occasion, but, after its warmed up and ready to thunder (about 10 to 15 minutes of riding) The bog goes away

Race

  • Hick

Posted August 23, 2002 - 07:12 AM

#5

I agree with Racemile, it sounds to me (good description BTW) like you are lean on the clip position.

As for the questions about the other needles...

EMN would be a half clip leaner than ELN, so if you wanted to split hairs you could go to EMN 4, that would be a half clip richer than ELN 3.

EMM is half clip leaner and one size richer on the straight diameter, which governs mixture just off the pilot before you "come onto the taper."

Hope this helps.

  • Hick

Posted August 23, 2002 - 07:14 AM

#6

Originally posted by michaeltrundle:
...she lunges and goes like the clappers.

And some folks think I talk funny.

  • YAMAKAZE

Posted August 23, 2002 - 10:02 AM

#7

Down Under Dude....

The only way that you are going to eliminate the hesitation off idle is to shorten the duration of the AC Pump squirt either with a P-38 (Works Great on my YZ) or with a RC Wheel Brake Colar on the Pump Rod as I did with my WR.

Bonzai :)

  • Taffy

Posted August 24, 2002 - 03:24 AM

#8

don't have all your details like

elevation
wr timing
pipe

but i'd say that you should set your jetting without the APJ for a while. it really is a case of a stitch in time saves nine.

i think that as long as you have an open pipe the problem is that you should drop the needle. if that doesn't work lean off the PC one more with the 35PJ/45PAS combo.

let us know.

Taffy

  • YAMAKAZE

Posted August 24, 2002 - 06:21 AM

#9

Damn Taffster....I was begining to wonder if you were still amoung the living!

Good to hear from ya...

Bonzai :)

  • Taffy

Posted August 24, 2002 - 07:28 AM

#10

hello yama

yeh i wondered if you all missed "old peculiar!".

i've had my second hard drive melt in 18 months and someone said that fujitsu aren't admitting to a dodgy job lot...

anyway done now, and back up and running. i'm just so useless with 'puters i hate it, always at someone elses mercy.

i'll tell you all that i've had such a rotten time with the husey importer/dealer that i might get rid of it. great bike to ride and very little wrong with it.

last sunday, coz mine wasn't running right, i came about 10th of 110 on a gas-gas 300. what a superb bike. i was actually about 3rd but i was on mx tyres and we get a 20% reduction so tenth it was. 3rd fastest lap though and i'm in love (again!). that makes it a ktm 520/gas-gas 300 plus plus that i want.

anyway not really the thing to say here-but i had to.

Taffy

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

Posted August 24, 2002 - 08:29 AM

#11

I here You Dude....

I myself have been admiring the new Gas Gas 400...I haven't had the opportunity to ride one yet but my dealer has been playing with one for about 3 weeks and cannot shut up about it. I'm going riding with him in a couple of weeks so I'll get my chance then.

Reguardless, no one can fault you for speaking the truth....

Glad to see your back online...Fujitsu has always pleaded ignorance when it comes to hardware issues. Thats why I only use Western Digital now...Atleast they make good on things when they go bad.

Sorry to hear that your magic pumpkin is giving you fits.....I'm sure you've got a handle on it though...

Be Safe....

Bonzai :)

  • michaeltrundle

Posted August 25, 2002 - 01:07 PM

#12

Ok guys,
Thanks for all the ideas on what to try to fix this little hiccup.
I went for as good ride in the bush on the weekend and paid a lot of attention to whats going with the jetting etc. Down really low its great, nice and crisp but as soon as I wind it on out of a corner the midrange bang is just gone. I dont have anywhere near the midrange or top end I used to. I used to be able to pull monos from 80-100kmh on the road in 4th or 5th no problem at all but since I have changed to the smaller air jets and fuel jets I have no chance of doing this.
It will barely wheelie at all once I,m up to 3rd gear or higher.
The only misbehaving I got the whole time was a bit of weird missing or 8 stoking while cruising at a constant throttle at about 80 kmh. I wound the fuel screw 1/2 a turn out to 1.75 - 2 turns and it went away.
Hope this info can help you guys help me.
thanks

good to see taffy is back again.

  • YAMAKAZE

Posted August 25, 2002 - 01:26 PM

#13

Your doing a pretty good job of answering your own question. Remember the rule's of jetting... if you must go 2 turns or better on the pilot to stabilize the you need to go up one size on the pilot. There are way too many factors to say that a particular set of jets will work perfectly for you seeing that climate, altitude and temps all play a role in manual jetting.

Stabilize the pilot circuit FIRST, then work on the main. You probably will not have to go up as much as you think to get everything stabil again. But if you change more than one thing at a time you will be chasing the carb all over the place.

I know several folks that Taffy's leaner settings work great for....I tried but my bikes like things a little fatter...It means that when the temps drop below 50 I go to my winter jetting, but it works for me, and I like to tear my carbs apart atleast one a year anyway.

OH Yeah...Almost forgot.... You want that thing to peel the hair off your butt when you smack the throttle....Get an OBEKN needle and set it on the 3rd clip from the top....That'll turn it back into a wheelie machine for sure....Not to mention massive mid range.

Bonzai :)

[ August 25, 2002, 04:28 PM: Message edited by: YAMAKAZE ]

  • Hick

Posted August 25, 2002 - 05:19 PM

#14

The misbehaving at constant throttle sounds like the Pilot Air circuit. Try a bit larger, like 75.

Still sounds like you're lean on the clip. Did you lift the needle one spot yet???

  • michaeltrundle

Posted August 25, 2002 - 07:45 PM

#15

OK OK OK
First things first, The only hint I have of being lean or rich was the small patch of weird missing or 8 stroking that happened at a constant throttle. Richening it up with the fuel screw by 1/2 turn while I was riding along seemed to fix this so I think I will try to richen up the pilot a little bit to get the fuel screw back to around 1 turn. From there I will chase the midrange /top end power problem.
I dont have any more clues such as backfiring or popping on decel (or under power)to work with unfortunately.
This part confuses me a little bit though- taffy says to go down on pilot jet and pilot AIR jet, hick reckons I should go up on the pilot AIR jet and yamakaze says to try a bigger pilot jet.
I regularly read all your guys advice and posts but I dont often see everyone saying to try something different, AAAARRRHHHHHH!!!!
Can one of you please clarify, are you all saying the same thing in a different way or am I missing something.
Can I richen my pilot circuit by adjusting the pas to a smaller size or do I have to go to a bigger pj/paj combination to achieve this?

Does anyone have taffy's chart of pj sizes verses recommended pas settings?

Thank you all for showing an interest, I really like the way she runs with the smaller jets, seems more responsive, has less vibration and feels cleaner running but I want my torque and midrange bang to come back, The more I think about it the more I think I,m a touch lean everywhere.

thanks again for the help.
mick

  • Hick

Posted August 25, 2002 - 09:54 PM

#16

Sorry for the confusion, I think everybody is just trying to help, but it is really hard to give that kind of advice based on a written description of what the bike is doing.

The reason I mentioned the PAJ is because that particular circuit matters more at higher RPMs. I don’t know why, just that it does. It sounded to me, based on your post, that you had a high rpm/low throttle blubbery rich condition. Since you also thought that lower rpm/low throttle was good I thought, “Hmm. Pilot jet is okay, but air jet is off...” If you do end up w/ a 40 pilot then you will, IMO, surely need to be at least 75 on the PAJ.

The reason I thought you were lean on the clip position is you stated that throttle response right off of idle was good (so pilot jet sounds okay and fuel screw must be in the ball park), it was when you grabbed a handful, like when exiting a corner, that you had a problem, but that after a slight pause she “goes like the clappers.” Not sure what that means, but it sounds good, and reminds me of being lean on the clip position. Sort of an air-sucking cough for a bit until things get rolling. That is how I would describe being one clip lean on the needle.

Hope this helps?

And what the hell is “8 stroking?”

  • michaeltrundle

Posted August 25, 2002 - 11:51 PM

#17

thanks hick,
From what you just described its like you've already ridden my bike. Thanks a lot for clearing up my dodgy fault desription and I do thank everyone for trying to help all at once.
The symptoms my bike exhibits are almost exactly as you just descibed them, and I was suspecting I may have to make same changes similar to what you've recommended but wasn't sure if I was chasing myself in circles and thought I would ask the experts first.
8 stroking to me is when it sounds like it is is only firing every 8th stroke instead of every 4th.
No backfiring or spluttering really, just sounds like every second bang is missing.
hope this helps as well!

  • Taffy

Posted August 26, 2002 - 12:03 AM

#18

trundle

a burp and go can still be a rich condition. as i've often said these bikes run good when the jetting is spot on and when they're very rich but when they're slightly rich they cough.

if you were lean in the midrange it would cough splutter and be a real bitch to ride.

i'm fairly sure that dropping the needle once and if bvetter even twice may be the cure.

i think everything is higher than the pilot circuit (PC) so i would go back to testing the MJ and needle.

you still haven't said which pipe you run or the elevation.

i think you could actually come down quite a bit between the MJ and the needle. this will affect your PC if you move more than one clip so i would hangfire before i played here because you may have to alter all the cutlery at the table again!

as far as the ratio goes between the PJ/PAJ i came up with a 15 air to each jet kinda rule. this however was with the correct needle straight fitted etc and the needle taper start not at extremes.

35PJ/45 PAJ
38/60
40/75
42/90
45/100

that should cover it.

Taffy

  • michaeltrundle

Posted August 26, 2002 - 12:44 PM

#19

thanks taffy,
I will try your remedy first seeing as I dont need to buy any more jets. I will drop the needle down 1 clip pos tonight and see if it gets better or worse. Hopefully you're right about them running good rich or with the correct jetting but a bit crappy when they are just a tad rich. I guess I'll find out.
I am running a bills thunder series open pipe and ride mainly from sea level and up to about 3000feet. the daytime temperature here in cairns gets down to about 20-25 degrees celcius in winter(if you could call it winter)and up to about 30-35 degrees for most of the year (endless summer)
The humidity is usually pretty high, in summer about 80-95 % and winter about 50-60%.
Its right in the middle of winter at the moment.
Hope this helps a bit more.
mick

  • okieguy

Posted August 27, 2002 - 03:32 AM

#20

michaeltrundle

I am running 38 pj, 60 maj, eln#4, 155 mj, 160 maj. ap at about .5.

I had to go from clip 3 to 4 to get rid of the bog.

Forgot to say the running all the free mods plus WB E series silencer.

Guy




 
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