wanaride

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Jul 18, 2003
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I've worked on the jetting of my new 200 for about two months and I'm still confused as what I should expect for "proper" throttle response. (I have used the search function on this site, read CDave's carb tuning tutorial, and am NOT running stock jetting; Main=155, pilot=42, needle 2nd clip from top, AS=1TO, airbox snorkel removed, 32:1 H1R, stock pipe & silencer)

Let's say the bike is completely warmed up. I'm lugging around the yard easily in second gear (flat riding area) with no real engine loading other than my girth...and then I twist the throttle open.

If the jetting is properly dialed in, will there be any hesitation or "bog" at all, or will the engine start screaming up in rpm?

Thanks for helping me out!
 

CaptainObvious

Formally known as RV6Junkie
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Jan 8, 2000
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The bike should "jump" when the throttle is wacked open. If it falls on its face you're too lean on the pilot, a/s or, less likely, the needle. If you get a bike baaaaawaaaaaaa you are too rich on those same circuits.
 

canyncarvr

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Oct 14, 1999
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Maybe a defiinition of 'instantaneous'?

There is a 'hesitation' you could reasonably expect that keeps a small motor that has traction from hitting 6kRPM. More likely the back end with break loose, which will make that 'hesitation' considerably less.

How about this? Consider you have your stereo running at a fairly high volume, but the speaker switch is 'off'. Turn the speaker switch 'on' (well to a postion that selects an installed set of speakers?).

How fast do you hear noise (or blow up your stereo ;) )?

Not 'instantaneous' I guess, meaning not exactly at the same time you hit the switch....but close enough to it that there isn't a whole lot of realtive argument to the contrary.

Depends on speed, too. From .5mph, a flick to 1/2 throttle in second/third gear isn't likely to be too amazing.

From your description of the situation, I'd expect the bike to be pretty much happening now when you wick-it open.
 

wanaride

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Jul 18, 2003
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Nope on the wheelie. When I'm charging hard and shift into third on level ground, the front wheel will come up, but when I'm lugging around the yard in second gear (maybe 5-10mph) and open the throttle quickly, no wheel loft.

When I have some speed (on an open trail) and I open the throttle, the response is pretty quick, but there is definitely some hesitation when lugging around the yard. Maybe it is a loading thing instead of a jetting thing...
 

canyncarvr

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Oct 14, 1999
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There is quite a difference between the two (plug loading and carburetion).

If your plug is loading up (due to whatever reason....wrong plug, bad plug, weak ignition, bad fuel, too much fuel, etc) the bike will misfire when you crack the throttle. 'Misfire' in this case meaning it won't fire. Surprisingly, this state of affairs seems to be often confused with over-rich carburetion.

Not exactly.

Maybe the plug loaded up in the first place due to too much fuel, but the burbling, misfiring mess you get as a result is due to ignition failure. The bike in that case is 4-stroking...firing every other time like a 4-stroke does, not every time ('time' being a TDC ..top-dead-center..event).

IF you are experiencing plug loading due to excessive fuel it is more likely a needle problem than it is a pilot circuit problem. Well, unless your pilot circuit is way off.

All of the carb circuits work together and thus overlap quite a bit. A too-far off main can effect the idle circuit and thus off-idle throttle response. Trying to resolve such a jetting situation by turning the air screw is a waste of time.

If your bike is jetted fairly correctly, there will be no plug loading problems from carburetion. Out of the box, the kdx will indeed have loading tbls in most situations.

.....which is why rejetting is such a large benefit.

You might try a different plug. A BR8EG is a good choice. Any new plug...even a standard fat electrode/nickel ES plug will run better for a little while.

See if that clears up the hesitation you are experiencing.

You should have none, nada, zero, zip hesitation in the situation you describe.
 
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skipro3

Mod Ban
Dec 14, 2002
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My experiance when I have the carb set right:
At a slow crawl in 2nd gear, almost stalled and bike wobbly, no clutch; I wick the throttle and the front wheel instantly leaves the ground without using any body language to help it up. I notice this because it looks cool to do a wheelie up to maybe 25mph with the front wheel not turning at all. I do this on pavement becuause then I don't get rear wheel spin.
The most important adjustment in my opinion for this test is the A/S. I will play with the airscrew at 1/8 turn at a time and can definately tell a difference in performance with just that little amout of adjustment. This setting is very sensitive to atmospheric conditions and I find that I might need to touch it up as the day heats up or the elevation changes. I keep a small screwdriver tucked into my boot for a quick 1/8 to 1/4 turn during the day. Once you get it set right, you will know what to look for and what direction to make your adjustment. Keep working with it and don't give up until you understand what affects your performance.
 

canyncarvr

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Oct 14, 1999
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Preach on brother!!

Can I get a AMEN!


This has been harped on considerably.....cuz it's important.

The air screw is indeed a significant (putting it mildly) piece of the puzzle. It's likely more of an issue on a modified carb (as from rb-designs).

I do it a bit differently, though: ;)
  • I carry my screwdriver in my crossbar pad
  • I've found 1/16 turn to make huge differences

Certainly it is something that I change often during a single ride depending on elevation, temps and the type of response I'm after. It takes just a bit of a tweak to the air screw to reduce front wheel pop-up in nastier stuff, or put it back in if I want to be picking the front end up on a regular basis.

It is indeed a fine tuning device. Take that either way you want.

Oh..keep in mind that an air screw adjustment will likely NOT be fully evident immediately. Don't adjust it, blip the throttle once in 2nd gear over a 10' distance, decide you need to adjust it some more. Run it for 30 seconds or so to get the carb settled on your new setting before you change it again.

Once you know how it responds, you can dial it in as easily as setting your microwave to an exact 'seconds' setting to perfectly reheat that warm, very warm, cool or plain cold cuppa.
 
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CaptainObvious

Formally known as RV6Junkie
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AMEN Brothers, Amen.

CC, good idea on the cross bar pad. I knew it was there for a reason.
 

skipro3

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Dec 14, 2002
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For some reason I don't like using the crossbar pad......Oh yea, Kawadougie keeps reaching over and taking it for his own use when I'm not looking! At least in my boot, he has to ask, and if he is riding too fast for me, I won't loan it to him!
 

canyncarvr

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Oct 14, 1999
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One of the good reasons to keep it in the pad is that you get to buy a new screwdriver a few times a year.....after it's fallen out....again.

But I keep a spare in my fender bag!
 

wanaride

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Jul 18, 2003
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First, many thanks to everyone who takes the time to help out newbies like me! :worship:

I must not be "there" with the jetting. I tried learning wheelies this weekend and there was NO WAY I could loft the wheel in 2nd gear while my butt was on the seat. When I stood up AND compressed/released the front suspension AND jerked up on the handlebars AND rolled the throttle, YES, the front wheel would loft in that situation. Of course, now my arms and back are sore...

I WISH I could get the performance skipro3 is talking about. Is 200lbs too fat for this kind of performance??? :laugh:

Main = 155, Pilot = 42, Needle = stock and in 2nd clip from top, Air screw = 1 turn out, airbox snorkle removed...I guess the jetting needs more work.
 

skipro3

Mod Ban
Dec 14, 2002
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Keep playing with it wanaride. Sounds like you could go leaner in all the circuits, but start with the WOT and get the main right. Work from there. Do a search on jetting if dare, there is a ton of info here at DRN on the subject. Buy lots of plugs and a fresh hacksaw blade and a couple of jets. Use only fresh gas and oil mix, or better yet, use a race gas. The race gas won't give you any performance enhancement, but it will provide a fuel that will not change your jetting charactoristices between tank fulls. I use VP C-12 becuase it was recommended and it works for me. The fact that you want to improve performance and are willing to research it, tells me that you will succeed. BTW I am 180 butt neked so 200 is not too fat by any means. You will however, start looking to improve your suspension once you got the jetting right.
 

G. Gearloose

Pigment of ur imagination
Jul 24, 2000
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Actually, you have a wheelie advantage...

Ever ride a kx65for kicks? (perhaps not) Not much for power but you just can't keep the front end down...

So your 'higher CG' should help, not hinder. Perhaps train with some 12 oz curls? go for the burn...

Or go back to a 45 pilot and try dropping the needle lower..
 

wanaride

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Jul 18, 2003
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Man, this really sucks...

I went to a 152 main this weekend (with 42 pilot, needle in 2nd clip, airbox snorkel removed) and tried the AS from 0.5 to 2.5 turns out. No noticeable performance change amongst the AS adjustments. I'm running Maxima K2 32:1 now and I noticed spooge from my silencer for the first time this weekend...after tons of carb jetting changes!!!

Nothing like being at the bottom of an uphill section, wicking the throttle in 2nd gear and hearing "boo-wah" before the revs build up.

And I have NO chance of lifting the front wheel when I crack open the throttle while crawling along in 2nd gear, just "boo-wah" and then acceleration.

Is the "boo-wah" indicative of a rich or lean condition???

The local mechanic thinks 152 is already too lean for the main, but based on what I've read here and what I'm seeing in the bike, I guess I need to go leaner still.

I think I'm close but I'm tired of throwing time at the carburetor...any additional tips would be appreciated.
 

Danny Stein

Member
Nov 12, 2002
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Just Rejetted my 2002 KDX 200 after routine maintenance oil change, clean air filter and re-oiled, and new plug, also repacked the wheel bearings, and just basicallly re-torqued everything. I have never jetted a bike before this. So sunday I spent the day putting the bike back together and jetting for a big trip to Rausch Creek this upcoming weekend. Well lets get to the point removed the snorkel and rejetted to say the least it wakes up the motor is a serious understatement. The bike almost feels like a new motor or top endit just feels awesome. If your bike does not stand up when you wack the throttle wide all the way up into fourth gear please do yourself a favor and rejet. I was so suprised to see how much power I found just by rejetting. I knew the bike was always running rich; I quess for break-in only kawasaki jets rich for that reason or so I thought I read somewhere? I'm almost afraid to go ahead and order a new pipe and silencer untill I harness all the power I found locked up in the jetting process. Please rejet if your front wheel isn't lofting off the ground through the gear box. Just wanted to say thanks to all the info on the website. Helped out like no other
 

canyncarvr

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Oct 14, 1999
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wanna-
I'm nonplussed on what's going on with your bike.

A 'fall flat' response is usually a too lean situation.

Maybe it's a matter of definition? Exaggeration for effect, but if you're in 4th gear @ 2mph and give the throttle a quick flick, you aren't going anywhere. There isn't enough mass in a 200, and it's not going to get kicked hard enough to have any sort of 'response' in that situation.

You can tune to 'best response' in 2nd gear and the bike will respond from a slow roll with a quick flick. But, if slow roll means barely moving, there just ain't enough gear to get any kind of 'loop-it' response.

The 'no noticeable change' in AS adjustments is a problem. There certainly should be between .5/2.5 turns. IF that is indeed so, something is plugged up.

Does the idle speed change within that turn range? Turning the AS all the way in on a warmed up idling bike kill it pretty quick. Is that so with your bike?
 

twocycle

Member
Feb 21, 2002
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The 2nd gear idle test works quite well for testing your jetting overall.

I headed out the other day to try this test. I adjusted my air screw to the best of my ability. It was running quite crisp. I slowed the bike to a crawl in 2nd gear and then proceeded to wick it. It was darn near instantaneous. The bike went vertical and beyond, no hope for recovering with the brake. It tossed me in dirt and as I sat there in disbelief, I felt both pretty proud of the bike and pretty embarrassed at my current situation. I now have hinged rear fender. I guess I really didn't think it could stand up that quickly. Thanks to everyones posts I think my bike runs pretty well now.
 

Danny Stein

Member
Nov 12, 2002
53
0
Yup sure running the Stock Pipe. Got a fresh top end not to long ago once, jetted properly the bike will not want to stay on the ground if I flip through the gear box, through my Flat Field that I test my bike on adjacent to my house. If your new to jetting rip the snorkel right off the lid and ride just feel the power gain from that , then imagine more pull once it's jetted properly
 

canyncarvr

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Oct 14, 1999
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So where does this leave wannaride?

What are the answers to:

The 'no noticeable change' in AS adjustments is a problem. There certainly should be between .5/2.5 turns. IF that is indeed so, something is plugged up.

Does the idle speed change within that turn range? Turning the AS all the way in on a warmed up idling bike kill it pretty quick. Is that so with your bike?
 

wanaride

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Jul 18, 2003
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CC, thanks much for sticking with me through this... :worship:

Yes, when I turn in the AS fully CW until it stops, the bike dies very quickly. Beyond that, I really couldn't tell a difference in throttle response/performance from 0.5-2.5 turns CCW on the AS. I was trail riding in 2nd/3rd gear during the AS adjustments too. I stopped on the trail, made an adjustment, rode for a while, repeated several times, and couldn't tell a difference. I DID notice spooge coming out of my silencer though, and I never noticed that while running H1R...

I presume your "fall flat" comments refer to the "boo-wah" I notice when I rip open the throttle while slowly moving in 2nd gear?

To reiterate, when I am moving very slowly in 2nd gear on level ground and I rip the throttle wide open, I get a "boo-wah" for about a half-second and then the engine begins to quickly rev, but absolutely NO front wheel loft.

Stock pipe and silencer, Main=152, pilot=42, AS variable, needle=2nd clip from top, airbox snorkel removed, 32:1 Maxima K2 with 93 octane fuel, BR8ES plug.

Thanks for putting up with my posts... :thumb:
 

G. Gearloose

Pigment of ur imagination
Jul 24, 2000
709
0
I suggest a 42 pilot is too skinny for a stock needle at your altitude and mix ratio.

Also drill a few more holes in the airbox cover. Without them, the higher rpms can still run rich, skewing your main and needle selection, thus leaning lower rpm operation beyond acceptable.
 
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