Low End Bog

[srhill]

Hello from the Land of Dixie.
I have just bought my first KDX (1997 220R). I took it out for the first time and loved everything about it except it didn't have much pep on the bottom end. In first gear I have to get the rev's up to get her going, for the rest of the gears it seems like I have to get past 1/4 throttle before I get much response, once it catches up its a rocket.
Here is my current setup. FMF Fatty pipe, Power CoreII silencer, air box top removed, sprockets 14 & 50 tooth, #5 throttle valve, R1173L needle 2nd. clip from top, #42 pilot, #152 main, the air screw was 2 1/2 turns out, BR8ES plug kind of wet but good color, and 32:1 mix (Castrol TTS). I checked my float with a set of calipers it appears to be right. I took my reeds out, I think they are stock (1 solid clear plastic piece on each side?).
Can somebody help me get it going better on the bottom end?
Would a set of Boysen 607 Power Reeds help?
32:1 seems like a lot of oil. Could I cut it back to 40:1? Thanks

 

[canyncarvr]

1. Would a set of Boysen 607 Power Reeds help.

They will improve throttle response, but won't fix an existing problem (well, unless the problem is bad reeds ;) )

 

[canyncarvr]

1. Would a set of Boysen 607 Power Reeds help?

They will improve throttle response, but won't fix an existing problem (well, unless the problem is bad reeds ;) )

2. Could I cut it back to 40:1?

Yes. Unlikely you would ever run your bike hard enough to 'need' 32:1. Keep in mind that changing TO 40:1 is a change to the rich side from 32:1. That is going to make a jetting issue worse.

...which is likely the problem.

Check:

http:/justkdx.dirtrider.net

1997 to 2001 KDX220
With a performance pipe/expansion chamber, air box mods , the factory or after-market silencer and the stock 33mm carburetor run a 42 pilot, the stock R1173L jet needle in the second from the top clip position, a 145/148 main jet and fine tune the pilot circuit using the air screw.

the jetset you're running is closer to a 200 setup.

All circuits pretty much effect all other circuits. A too fat main will easily mess up the pilot/AS circuit. Chances are you're WAY rich on the main.

I say 'chances are' cuz each bike/rider is different. Only YOU can do it up right.

Still...jetsets on particular bikes are USUALLY close.

The only way (well, excepting fancy A/F ratio devices plugged into your exhaust) to check the main is a WOT plug chop test on a new plug.

After that is set, set your pilot/AS on throttle response, or 'seat-of-your-pants' results.

The kdx can and should snap immediately on an off-idle to 1/2 throttle quick-wick. With a 220, you should have trouble keeping the front end on the ground doing that!

Why a 14T CSS? With a 50? You're kinda going opposite directions on the two sprockets. That's not helping bottom end response issues.

If this is a 'new to you' bike, there are other possibilites...like no compression in the motor. Don't fret the big stuff 'til you fix the small stuff. (imo)

BTW...13 on the front is OEM (13/47). Again...why 14/50? That's higher than stock (47/13=3.61 vs: 50/14=3.57). That's not generally the direction riders wanna go.

 

[srhill]

I thought this would be a good time to replace them since I had them out. Does the jetting look close? I seen in the tech tips, with similar mod's, the main should be 145 to 148.

 

[srhill]

sorry I cut in before you were through. Thanks for the tips. It is new to me and I don't know why 14/50 sprocket combo.

 

[canyncarvr]

AHA!!! Thought that might be so.

Then by all means change the front sprocket!!!

As long as your chain isn't worn out, you should be able to put a 13T back on.

You'll be happy with the effect I'll bet'cha. If not, you can change it back..and the sprocket will only run you $12-15 or so.

Put the sprocket on in addition to getting the jetting right, and you'll be surprised the first time your 220 tries to dump you on your keester!! :)

Oh...the stock reed or not question.....

You're looking at fiberglass reeds. Those are stock. That's what boyesen power reeds are, too.

What MAY tell if they are stock or not is whether the oem reed limiters are still in place. On both sides of the cage oem limiters are big, rather heavy metal items that limit the reed movement to somewheres around 45º or so.

If you're looking at a properly installed set of aftermarket reeds, those pieces will be gone. In their place will be a couple (one each side) of narrow (3/16") metal strips.

Of course, I've heard of aftermarket reeds still WITH the oem stops....

In any case, replacement of reeds once a year is a good idea if you ride regularly at all.

One thing for sure....if looking at the reeds there is ANY gap to the reed block, they are sprung and should be replaced. Stick your finner inside, manually open the reed, see that it seats rather firmly back into place.

Oh..the double/partial post above was my doing. No 'cutting in' on your part. I 'prematurely exclamated'.....or something.......

Cheers!

 

[kx200]

sounds like a stuck power valve, my 97 220 thinks it's part four-stroke

 

[srhill]

Thanks Canyan Carver, you have put my mind at ease. I am ordering jets, reeds and 13T sprocket this morning, along with a few other goodies. Don't sweat the "premature exclamation", it happens to the best of us every now and then.

 

[canyncarvr]

So much for the 'mind at ease' part.....

Certainly wouldn't hurt to check the KIPS. Take the pipe off, remove the slotted cover on the LH side of the engine, manually activate the KIPS by rotating the nut under said cover whilst looking up into the exhaust port.

Make sure the main valve raises on activation. Also that the subport drums both rotate in sync and are correctly positioned relative to each other.

If that's all well...you can certainly rest easy(er?)

Post your results???

Good luck!

 

[srhill]

Checked my power valve last night, everything looked good. :thumb:

Still waiting on the "little brown truck" to visit my house. When I get my reeds, jets and new sprocket installed and everything tuned I will post my results. Thanks again guys. :)

 

[canyncarvr]

Does the clutch hook-up ok? Slippage would certainly make for a boggy bottom-end...and life as a clutch can be tough(er) with a high drive ratio.

Go Brown!

Did you get 607s?

It would be fun to see your smile after you get it sorted out. You're going to have a blast!

YeeHAw!!

 

[srhill]

Clutch seems to engage fine, it's the dis-engagement part I am having problems with. When motor not running, in gear and cluch dis-engaged the bike is hard to push. I was going to change oil and see if that would loosen things up. Is this wishful thinking? Or do I have major problems? Any ideas on what I could check or clean to free it up.
I hope I havn't bought a Heap. The bike visually is in excellent condition, and really runs strong. It never occured to me to try and push the bike with it in gear. Live and learn. I am enjoying working on it anyway. My 12 yr old is starting to take an intrest in working on things and I'm proud of that. He helped check the power valve last night and when he looked in the exhaust port and seen the piston he said "cool".

Yeah, I bought 607's.

 

[canyncarvr]

Oh oh....you can't push the bike easily when it's not running and in gear?

oh my!!


YOU have a NORMAL kawi!!

Actually, I can only vouch from my own experience. My bike has always been hard to push when it's in gear. I'm owner #1. Well, guess technically my WIFE is owner #1, cuz SHE bought it for me.

I'm just a user;)

re: It never occured to me to try and push the bike with it in gear.

Forget you ever tried it, and never do it again! ;)

Still a good idea to change the oil. Who knows when that happened last.

BTW...kawis make a whole lot less noise if you overfill it some. Use 100ml or so of the quart to help flush out the last of the junk, plug it back up and dump the balance (say 850ml or so) in.

The 'flush' is my method. Some riders just dump the quart in.

Either way (although mine is much better!), clutch noise goes down quite a bit.

NONE of which meant to imply I have ANY idea whether your clutch is toast or not!

It's ALways somethin', 'eh?

Now then.....where's that brown truck!!??

 

[23jayhawk]

As far as the clutch not totally disengaging & hard to push - same here, since the day I brought it home new.

Gets a bit better when its hot, though. Not to worry. :cool:

 

[KdxChode]

It's just a KDX thing. My bike won't move when in gear but my brothers Suzuki rolls like it's in nuetral when ya pull the clutch in.

 

[srhill]

Thanks CC and J-Hawk and Chode. Mine pushes a little easier after it's warmed up. It's good to know there is a place like this to go to for answers.

I'm stuck at work this weekend, wished I was riding.

Oh well, my Kawi is tore down anyway and it just wouldn't be the same having to ride my XR250. Man I have got to get that ting sold.

 

[owenlo]

I would check your pilot circuit. If your air screw is out 2.5 turns, and the recommended range is .5 to 1.5 turns. Maybe just an air screw adjustment would fix the problem. The more turns out you are the leaner the circuit. Too lean would also cause a lean bog. Plus with it being within the first 1/4 throttle is even more evidence of the pilot circuit being considered a possible culprit. Just my .02 cents


Obie#8 ;)

 

[KDXTrreme]

What owenlo said!! Turn your airscrew in all the way.. try 1/2 turn out, 1 turn, 1 1/2 turns, etc.. until you find the right spot.. I've lost the spring that holds my air screw from turning.. when i ride, it turns intels out.. I can tell it's gone too far when I get that low end bog.

 

[uoof1]

All the suggestions are good, but in addition, what is the condition of your piston/cylinder? Your bike is a 97, how many hours are on these parts? Low end suffers first as you get out of spec. Kevin

 

[srhill]

Well guys the Brown truck made a visit Monday. I installed a 148 main (prev. 152), new 607 power reeds, and 13T sprocket (13/50). The air screw does have an effect when prev it did not (motor reve's up at about 1.5 turns out). I warmed the motor up and it is still bogging, done a WOT test and the plug looked VERY clean, there may have been just a hint of color at the base of the plug.
Kevin, the bike is new to me so I don't know. I think checking the compression is going to be my next move. The bike seems strong though, if I really get on it, it will bring the front wheel up in third gear easy.
If the compression is down that will cause it to run lean want it?
How would low compression cause the motor to bog?
This is all new to me, I havn't had a 2-stroke since I was a kid so I'm learning as I'm going. Thanks for everybody's input so far. If you have any more I need it. Over and out

 

[canyncarvr]

I don't read that you ADJUSTED that air screw for best throttle response. Saying, 'motor reve's up at about 1.5 turns out' makes me wonder where you left it.

Again, set it to best throttle response. The AS having an effect now where it did NOT before tells you you are going in the right direction.

Low compression won't cause it to run lean, just bad (no !spit!, hence bog). I wouldn't spend a whole lot of time worrying about that just yet. Other things you say indicate the top-end can't be that bad.

Do some more tweaking.

 

[srhill]

CC, I left the AS about 1.25 out. I didn't get to tweak on it much, I ran out of daylight. These were just some preliminary results. I guess It was to much to hope for that I could change the MAIN and all would be well. :(

Rog O on the more tweaking.

 

[Canadian Dave]

Srhill the stock KDX220 uses a 33mm carb (the size of the hole/bore) and the KDX200 uses a 35mm carb hence the difference in jetting. If you have a set of calipers or even a metric ruler measure the bore of your carb on the exit side and ensure that it hasn't either been bored to 35-36mm from the stock 33m or perhaps replaced with the carb off a KDX200 which has a 35mm bore. If this is the case you certainly wont want to uses jetting recommendations for a KDX220 with a stock carb but rather you'll want to go back to the specs quoted for KDX200s. This is a very common mod so you'll want to double check. Once you know what size carb you have for sure it will be easier/possible for others to help you work through your lean bog etc.

David

 

[Tom Ludolff]

My '03 KDX220R came with a stock #42 pilot & 145 main. From idle to 1/2 throttle or more I was getting a bog / hesitation. Once I got it revving it was OK. Turning the air screw in from 1 turn out stock to 1/2 turn out helped but didn't completely fix it. I went to a #45 pilot and #148 main and it fixed it. Apparently the idle was too lean and it took a split second for it to richen up once I hit the throttle. The richer main gave it lots more power at full throttle. Hope this helps.

 

[Canadian Dave]

Tom you'll want to watch your jetting now at lower throttle settings. If the bike is billowing smoke with lots of spoog exiting the silencer tip and the plug is loading up at lower throttle settings you might try reinstalling the stock pilot and move the jet needle's clip down one position. If this makes the lean bog disappear but the jetting is too rich at lower throttle settings try dropping the pilot down one more size or see if you can tune it out by turning out the air screw. If the lean bog reappears move the jet needle's clip down on the shaft one more position. Though my KDX220 has been modified and yours my not be I've generally found the stock pilot is too rich already and the bog you're describing can often be tuned out and throttle response improved by leaning the pilot and moving the jet needle to a richer position. No two KDXs will the same but you might want to give it a try and see how your KDX responds.

David