Proper throttle response???

[canyncarvr]

Try this: Set the air screw to highest idle. Do it on a thoroughly warmed up bike. Turn the AS out (slowly..say one 'tick' in 10-15 seconds) one slot width at a time (say 1/16 turn) until the bike reaches highest idle. From that point, turn the AS in a tad under 1/4 turn.

Oh...and take note of how far out that 'highest idle' setting is.

Say again how you service your air filter.

I'm myopic here I realize.....but this '..couldn't tell a difference..' part regarding AS settings is a problem that must be resolved.

Is your fuel 'old'?

If you happen to have a gallon of berryman's around....take your carb apart and give it a good soak, blow out every passage with clean/dry air.

Again, IF there is no difference in throttle response with any setting of your AS you're either far off jet-wise or something is plugged.

What's your elevation? RH? How does the bike response change with a 45 pilot? Does your plug load up (bike 4-strokes) after a fairly long idle time (long downhill)?

And if that's not enough for 'ya.....what is the difference when the bike is good'n hot with a BR7ES (or BR8EG) in it?

There is an answer. Hope you keep after it.

***edit*****
Gearloose's post got 'inbetween' (I didn't see it). Didn't mean to repeat what he said...but he said good! ;)

btw..'RH' is 'relative humidity'

 

[Houndog]

Originally posted by G. Gearloose
I suggest a 42 pilot is too skinny for a stock needle at your altitude and mix ratio.

At sea level 20C I run a 155 main and a 40 pilot, any richer on the pilot and it loads up. 95 200, air box mod, clean air filter, rev pipe, stock needle, 40:1 Yamalube 2R and a BR8ES plug. I experimented with the jetting in small steps (set main 1st), it now runs great but I admit I was a bit squeamish about running too lean at first.

 

[G. Gearloose]

Thanks,CC
Wanna,
I just recently identified a partially-clogged pilot on my bike. it also made the AS less effective; but could still stall the bike with AS closed. It doesn't take much debri or scale.
food for thought.
Houndog I can't suppose why a 40 works with your stock needle, it sound AY-typical, but if your happy, thats all that counts, right?

 

[Houndog]

Gearloose, I tried the 48(stock), 45, 42 and 40 until I got it to run 'clean' and combined with the 155 main I still get some spooge but no blue smoke to speak of. It wheelies in 4th and will carry the front wheel over dips in 5th, but a 158/42 seems to work almost as well with the exception of the loading.

I'm relatively new to bikes and jetting, and I realize that all bikes are different, but what would you expect my base jetting to be? 160/48 was too rich, but that's what it had until this spring when I started playing with it (bought bike last fall).

 

[G. Gearloose]

Oh, my thinking was you're using a pilot that others use with smaller diameter needles, so I thought it odd. Combining your large diameter needle with small pilot means not much gas off idle. But hey, my experience is with a #6 slide so whats that meen?
I'm sure its powerful. Is it still optimal off idle? Was there a comprimise off idle to cure overall spooge and 'loading up'? Perhaps you're a canidate for a C taper needle. just curious...

 

[canyncarvr]

re: 'what would you expect my base jetting to be..'

I would expect it to be what resulted in: 'it sound AY-typical, but if your happy, thats all that counts, right?'

A clean bottom-end is a great thing, 'eh? ;) Please consider a needle change...something in a 'C' or 'D' that will give you a smaller straight diameter (more rich, yes) but combined with a later taper start. 4-stroking due to plug loading becomes a thing of the past. And if you like 'hit', a 'C' needle will knock your socks off!

****edit******
Mom!!! He's doin' it agin!!!

Dang...submit a post to see gear snuck in and said the same thing already...agin.

I'm not just repeating what he said, really! On my PC, I said it all by myself!! ;)

 

[G. Gearloose]

Originally posted by canyncarvr
****edit******
Mom!!! He's doin' it agin!!!

Dang...

:)
thats just too funny!..
I'm hearing echos of "Don't make me stop this car!"

 

[Houndog]

Right off idle there is a spot that could be better. I have a CEL and a CEK, and I like a 'hit'. I tried both and found the CEK to be richer down low, and not having a 38 pilot I put the needle back in the jet box. I am missing a 150 jet, that may have helped also. With it getting cooler I might try the CEL again and order the couple of jets I am missing (never had).

Great feedback, thanks guys :)

 

[canyncarvr]

Again.....you might try the 'D' taper....

Was just looking at a chart that lists the keihin 35mm pwk as 'stock' with a 6mm cutaway throttle valve. Note that the kawi 'H' kdx comes with a 5mm slide.

The 6mm will help off idle response, too. Especially with the 'K' diameter.

I'm using a 7mm at the moment with a DEK.

These things (kdxs) can run so good with a proper carb tune....it never ceases to amaze me.

 

[DougRoost]

Learned from someone who really knows 2 stroke jetting that the best way to do this is to start from bottom and work your way up. AS should be at 2 turns out +/- half turn, else rejet pilot accordingly. Next is the needle, which is the most important since it controls the bulk of the range. I agree that trying a D taper is probably a good idea if you want more hit. Finally is the main jet, which is dependent on the needle's taper.

In fact, I recently heard a case of a guy who rode a CR500 for some time. They got into it later and discovered there was no main jet! But since the guy was mortal, he never rode it wide open, so never found that problem!

One other suggestion. I used to run Bel-Ray H1R since that's what came with my bike (bought it used). It was okay but seemed to smoke more than other guy's 2 strokes, so I switched to Amsoil 2000. The bike ran so much crisper I couldn't believe it. In fact, I had to rejet for the different premix oil, which I wouldn't have guessed since both are full synthetics and mixed at 40:1 in my KTM 300.

 

[canyncarvr]

Sorry, but that is 100% and otherwise irrevocably, completely, absolutely, undeniably wrong!

Hope that wasn't too tact-less. ;) At least I didn't say anything like, 'consider the color,' or somesuch....

Jetting is done from the top down. The main is set first. That is because the main can effect the slow circuit, but the slow circuit has zip.nada to do with the main.

The needle can effect the slow circuit too. Try it sometime. Put in some whack-job needle (maybe an AEJ) and see what happens to the pilot/slow circuit.

Don't make me stop this car!!

Cheers!

 

[DougRoost]

Well, I guess canyncarvr told me! But let me bring Keihin to my aid since they seem to agree with my friend and advice above.

Check out: http://www.keihin-us.com/tune.htm. Click the first link and it tells you the order to go about jetting, starting with step 1 of checking for correct float height, then step 2 setting idle speed, then step 3 setting 1/4 to half throttle. Then click the link at bottom (or use your back button) and go to the next link down. That will show you step 4 is the needle, then finally step 5 is the main jet. I.e. - working up from the bottom.

Note the pic to get back to your point ("the main can effect the slow circuit, but the slow circuit has zip.nada to do with the main"). Technically you're correct as the pic shows. But note the main has no effect below 1/4 throttle and it's negligible until 1/2. But the needle does have an effect even at WOT, though most people usually ignore it to simplify things (as the pic shows not a good idea).

Anyway, our friend is having problems in the idle to ~1/2 range and this means he must tune the pilot and needle circuits. And since the needle is so important and does effect the main, I suggest following Keihin's suggestions, which means doing the main once everything else is sorted out.

 

[Rich Rohrich]

Originally posted by canyncarvr
Sorry, but that is 100% and otherwise irrevocably, completely, absolutely, undeniably wrong!

WRONGO CC, Doug is absolutely right. :confused:

All the REAL tuners do it from the pilot up and work the circuit overlaps in that direction, then once it's close you go back and recheck.

What size butt-hat should we send your way?

 

[KDXRyder200]

Well i'm only 15 and i have a 1989 KDX200 that has a FMF Fatty Pipe and a FMF PowerCore Silencer that has been jetted for maximum performance in the area i ride and when i'm going up this dirt road in about 3rd gear not in the powerband but in Mid-rpm i can get the front end up into a wheelie with just pulling up on the handle bars slightly and gunning it without slippping the clutch....what do u have to say about that?

 

[d rockwell]

Ron had suggested this needle to me when I described the type of trial riding I do in the Jemez Mtns. N.M. I've been riding 3 times since and I'm amazed how powerful off idle 1st & 2nd gear become; I believe more off idle torque then BEL,CEL, or CEK. The bike seems to jump over roots & rocks with ease and pulls way down low in the switch backs. I did take a little getting use to because the bike reacts so quickly off idle. My '96 200KDX is running a shaved head, 607 reeds, K-35 pipe, RB Carb, air box mod, 150 main, 38 pilot, DEK at #4. It's a little lean snapping the throttle open but rolling it on is very powerful. Are you finding the same kind of results? & Has anyone tried a DDK needle? Jason at Sudco said he uses a DDK in his 250KX Dave

 

[bigred455]

I definetly agree with canyncarvr JET MAIN FIRST AND GO DOWN FROM THEIR. Example went over to avgas stock jetting 165 MAIN.
PILOT 52
NEEDLE NAFH 2ND POS.
POWER JET I believe 50.
Bike 03 kx250 when I switched over to avgas she was running lazy and dull down low and mid power was very dull also, Full throttle she was breaking up and missing.I worked down to a 160 main the motor woke up everywhere of course up top ,but also way down low and mid, the motor came alive. I tried the needle in the 3rd clip just to see if I could get it to run rich(make sure I wasn't to lean in the 2nd pos) It did, the motor was missing down low to half. So I went to 2nd pos again to get a feel for it then moved to 1st and then 1.5 pos. I had no noticeable improvement going leaner on the needle pos I put it back to stock running strong. The pilot moved up to a 55 got lazy went down to a 50 felt real good went back to 52 stock felt just as good as the 50. I also changed my porting recently, pretty aggressive, the motor was blubbering and lazy all over I mean all over. Too make it short I jetted the same way as above ended up with a 150 main yes a 150 main, motor woke up EVERYWHERE!!! each step I took with the main. needle and pos is stock I did go down 1 on the pilot. What I am saying is if you are rich all over and full throttle is also rich, start with the main it does wonders.canyncarvr is 100% correct with my findings. :thumb:

 

[canyncarvr]

So...

..then once it's close you go back and recheck.

..

Yeah. That works. If you want to do it twice, that's fine! ;) In the end, you're doing it my way, 'eh?

If you mark your throttle to indicate circuits, you can just jet the circuit you want, too.

Butt, if you're sending one, make it a 7 5/8''! I have a big butt...I mean...head. Butthead?

CCM
724 s. central
#104
medford or 97504

As far as: 'But note the main has no effect below 1/4 throttle and it's negligible until 1/2.'

That's fine (maybe) with a jetting sequence that's close in the first place. If it's not (close, that is) a poorly (wrong) selected main will screw up the works..and you won't get it right until you 'recheck' it (do it all over again..which in effect is exactly what I'm saying excepting the waste of time doing it in the wrong direction in the first place!)

BTW..how long do I look at the 'page not found' from <http://www.keihin-us.com/tune.htm> before it takes me somewhere? ;) Yes, I understand that link is faulty, and I understand why, too. Amazing, huh?

In any case, I defer to the experts (want a definition of that?) regarding: 'WRONGO CC, Doug is absolutely right.'

I:

• Apologize for the error of my ways :worship:
• Will continue to follow a 'top-down' sequence
• Will continue to say 'poh-tay-toe'...
• ...while you say 'poh-tah-toe'

As sage once said, 'this is suppost to be fun!'

And so it is!

.....I never wanted to be a REAL tuner anyway..... :(

On another note..re: d rock and a 'DEK'

Yep. That's what I'm running.

BTW...regarding the slight hesitation off idle? Try this. After your bike is well warmed up (hot!) try readjusting your air screw to a further out position than you'd think reasonable. Start with an additional 1/2 turn out, then proceed in 1/16 out increments until you get to the point that the hesitation is gone, 3rd gear pulls harder from a 2->3 shift at midrange rpm than it ever has and the throttle response is more linear than you thought possible.

You'll find that setup to be useless on a choke cold start. Turn the AS back in 3/4 or so to start..readjust later for the above based on temps and conditions.

My bike is prolly different from everyone else's in this regard. But give it a shot and drop me a line if you find it works as well for you as it does for me.

Cheers!

 

[Rich Rohrich]

Originally posted by canyncarvr
If you mark your throttle to indicate circuits, you can just jet the circuit you want, too.

Too much overlap for that to work for anything other than the mainjet. :confused:


FWIW. Once I run through the sequence from the pilot up, I try to zero the main by reading the plug, and don't usually find it necessary to run back through the sequence.

Clearly you can start anywhere and eventually get it working if you are persistent enough. My point was, guys who make a living this way seem to agree on the pilot up approach.

As long as you can make it run how you get there doesn't really matter I guess. You just might want to be careful when making BLANKET statements about there being only ONE TRUE ABSOLUTELY CORRECT WAY , especially when your way goes against the accepted practice. :confused: ;)

 

[canyncarvr]

re: 'You just might want to be careful..'

'Tis true.

Thus the abject and profound apology..with worshipping graphy and everything!

Well.....kinda...;)

Where's that hat?

***edit***

I just ran some setups thru jd's spreadsheet. An 'off' main selection, say comparing a 148 (reasonable) to a too rich (162) shows up clear down to just off idle.

Meanwhile an 'off' pilot, say comparing a 38 (reasonable) to a too rich (48) shows up only below 3/8s.

Why bother messing with a pilot when the main is 'in the way'?

I have an email addy for jd. I'll get right on letting him know he's not 'real'. ;)

Really folks.....all in good humor. I believe the facts to be: Your way works. My way works. I prefer mine (because it works better ;)...but anyway). I am certainly, absolutely and otherwise completely in every way NOT saying everyone (or anyone) else is absolutely without merit.

 

[Rich Rohrich]

Asking the best way to sort your Jetting is like asking what's the best oil/fuel/ratio/bike ... well you get the point :)

 

[canyncarvr]

'what's the best oil/fuel/ratio/'

Yeah. I know the answer to that, too! ;)

 

[Rich Rohrich]

Originally posted by canyncarvr
'what's the best oil/fuel/ratio/'

Yeah. I know the answer to that, too! ;)

I never doubted it for a second. :confused:

 

[tedkxkdx]

And don't forget that ones mans rich jet at altitude is another mans spot-on at sea level and right temps.