KDX220 won't idle when warm

[lemmy]

I have a 2003 KDX220 with the 35mm 200 carb. I have a new spark plug (BR8ES), 44:1 new 93 octane gas (Motul 8002T), CEK needle with clip in #3, 35mm pilot, 155 main, 1.75 turn air screw, woods pipe, newly packed powercore2 silencer, RAD valve (reeds in great shape) and float is 17.5mm and clean air filter. I can start the bike easily when cold and immediately turn off the choke (might even start without it) and it idles fine. Even after riding for 5-10 minutes it idles fine. But after 30 minutes or so it won't idle or will idle just barely even with the idle screw all the way in and no matter what I do with the air screw. If I pull the choke out it is even worse (so I assume it isn't too rich). Any ideas to try?

I recently fixed the kips (it was stuck open due to previous own putting the "claw" on incorrectly) and now it opens when it should and closes (slowly). It doesn't seem to return to the fully closed position at idle but it is within 1 tooth on the gear under the slotted cover. I manually turn it all all the way closed and it doesn't make a difference.

 

[G. Gearloose]

Still bad, huh,
There is a chance the enrichment circuit (what you called a choke) is not shutting off completely when closed.

If its worse when the engine is hot, the extra fuel does fit the conditions you describe.


Sounds like everything is suspect now.

 

[jason33]

are you using the proper 50-50 coolant? if its hot it will do that ,all bikes will , they dont like to run too hot, and lose power when blowing steam

 

[lemmy]

I took the enrichment/choke plunger out and everything looked ok. Is there any way to make sure it is sealing off?

I run engine ice pre-mix so it should be as good or slightly better than regular coolant. I had no reason to believe the bike was running hot, but of course I can't be 100% sure.

 

[G. Gearloose]

Ok. No, I don't know a another way.
Regarding coolant, you purged the air in the head too?

How bout this..?.. remove the pipe and watch the piston. There is a hole under the rings that should face the intake. If you can see the hole, then the piston is 180 off.

 

[lemmy]

I did purge the air in the head. I also remember looking in at the piston and seeing the piston and don't remember seeing a hole.

I was thinking of soaking the entire carb (after taking parts that would be damamged) and see if that helps. I was also thinking of checking compression. Could that be a problem?

 

[Hoffies]

If you rev it up(crack throttle open)and close it quickly does she return to idle speed quickly or does it seem to hunt down slowly to idle speed? Does it take a while to die on idle (seem to hunt around slower and slower until no kickover?) or is it as if the idle is just too slow?

 

[lemmy]

Thats a good question. If it is cold or not THAT warm yet (5-10 minutes) it idles fine and returns to idle very quickly without dipping low. If it is hot and I give just enough throttle to keep it running and then I let off. It will keep getting slower and slower until it dies. Might make it 30 seconds. Sometimes (with the idle screw all the way in, not the air screw of course) it will get lower and then stabalize just on the edge of dieing, but not actually doing it.

Also, when it is running ok after 5-10 minutes and you do something that makes the idle go low (like screw in air screw too much), it almost dies (like it should) but when you quickly back it back out (even more than what you had it before you started messing with it) it won't recover unless you give it some throttle. Not sure if that is normal or not.

 

[sr5bidder]

how about a very worn out piston/ cylinder? have you thought of that?
Seems to me there is nothing wrong with the carb if it works fine when you start it up

gets hot everything is fully expanded and loses compression.

I have seen this alot esp. on old honda 50's and 70's people try to sell, I'll just let it sit there and idle while i talk to them if it slowly dies I say no thanks or tell them the piston is wore out I'll give you xxx less for it.

 

[lemmy]

I just got a compression gauge about two days ago. I am going to try to get it hot and try tonight. Should I let the motor get to full operating conditions first?

 

[_JOE_]

I just got a compression gauge about two days ago. I am going to try to get it hot and try tonight. Should I let the motor get to full operating conditions first?

Yes. Hold the throttle open as well. Kick it until the guage stops rising.

 

[glad2ride]

Is a 35 the typical pilot for a 35mm carb on the KDX220?

 

[_JOE_]

Have you tried leaning the air screw any further?

 

[sr5bidder]

Go ahead and try it cold then get it up to normal op. temp and try again, compare the results.

I had raced rc trucks for 6 years and have seen many wore out engines (piston/sleeves) people chase the "tune" around the carb and can never get it to run right when its warm.
I myself have done this and when I would buy the new piston and sleeve ($25) it would run great and was not so finicky about carb settings.

Also I've seen and experienced with two stroke motorcycles people tuning to the point where there motor will run great with lots of power by leaning out the jets while it doesn't lean seizure on them it does drasticly shorten the usefull life of the piston and cyinder.

For me I keep my settings fat as far as jets "spooge" is fine with me, its the lack of that would scare the hell out of me.

"spooge" or as I think of it is unburnt oil, oil that did not get to fulfill its dream of becoming blue smoke it is also oil that past through the crank bearings, wristpin and cylinder walls keeping everthing happy and reducing wear.

sorry for the long post I just get frusterated when everyone starts buzzing around the carb and jets and so on when there are so many other possibilties

 

[G. Gearloose]

Is a 35 the typical pilot for a 35mm carb on the KDX220?

with a CEL needle, yes.

 

[lemmy]

Ok, I started the bike and let it idle for about 5 minutes. Then I rode it back in forth in my neighborhood 6 times (about 0.1 mi each way) then let it idle another 5-10 minutes. I thought the problem was fixed (after the carb dip). But then out of the blue it started wanting to die. Then I screwed in the idle screw a bit (I didn't have it anywhere near all the way in) and it idled ok after that. I finally shut it off and immediately checked the compression. It was about 150+. I thought that was high, so I released the pressure and did it again and got the same results.

The odd thing is that if I screw in the air screw (from 2 to bout 1.5) and it starts to run rough, and I screw it back out to 2. It takes several minutes of revving it to get it to where it will idle again at 2 turns.

So the carb is surely clean. Compression isn't a probelm. Jetting is at least ballpark. And the reeds look good (but it is the crappy RAD valve). I can't think of anything else. The bike is running fairly good though.

 

[lemmy]

Also, it seems to be smoking more than it has in the past.

 

[dansavage]

I've been following both of your posts and everyone's responses pretty closely. It seems as though you've done a fair amount of work to fine tune your bike, which is good.

While I am no mechanical expert, one thing that I do know is to start with the simple stuff and move towards the more complex. As an example, we once had a bass boat that had a 'running' problem, the engine would run short on fuel after 20-30 minutes of use and an engine alarm would sound, followed by an infamous 'stall'. Many mechanics attemted to fix it, with no avail, the problem couldn't be found. As it turns out, there was 'trash' in the fuel tank obstructing the flow of gasoline into the carbs. The tank was removed, cleaned, problem resolved.

If you haven't already done this, pull the tank, fuel valve, and screens to be absolutely sure nothing within the system is obstructing the flow of gasoline into the carb.

Good luck!

 

[lemmy]

Thats a good idea. I was actually going to do that tonight because I had cleaned the carb a few days ago, went on one ride and then saw some junk in the float bowl of the carb. But I ended up putting an inline filter in the line that goes from the tank and the carb. So I can see the fuel coming in and it is not obstructed at all. But I still think I will take the tank and petcock out to make sure it is clean.

 

[dansavage]

Tell me about the CEK jet needle, I have a 35mm carb, 42 pilot, 155 main, and R1174 needle in mine. I did plug chops last weekend to ensure the needle positioning is on and the main is right. It is fast, no doubt, but I think it is human nature to want 'more'...

Follow up and let me know about your tank.

 

[sr5bidder]

ok so try looking for an air leak around the intake reed gasket
something expands when its hot and leaks air.
think about it cold the throtle snaps shut the engine rpm responds by lowering quickly. ...throttle slide cuts the air.
hot it does the same thing ...so is there air getting in someplace becouse expansion?

or does anyone turn thier fuel off and let the engine empty the carb when done riding for the day??? notice when the bowl is just about empty how the rpm rises considerably just before the engine cuts out???
think about what is actually happing

BTW 150 is fine the book says 95-151 usable range
(factory kaw)

 

[lemmy]

Tell me about the CEK jet needle, I have a 35mm carb, 42 pilot, 155 main, and R1174 needle in mine. I did plug chops last weekend to ensure the needle positioning is on and the main is right. It is fast, no doubt, but I think it is human nature to want 'more'...

Follow up and let me know about your tank.

I got the idea to try the CEL, CEK, or BEL needle from Gearloose and this thread here
http://kdxrider.net/media/CC.doc

it is a long thread about people trying different jetting on their KDXs. I was confused at first becuase I knew the stock needle worked ok and it is a B taper. But the more I thought about it and using JDs spreadsheet to look at relative jetting
http://home.att.net/~wbarrow/jd/JD_Jetting_2002_VS.zip
I was convinced and gave it a try. The 1174L is a taper of B, diameter of Q and L1 of between F and G (no direct translation for the L on the oem needle). So If I say the stock needle is a BFQ and I use a pilot of 42 and I compare that to a CEL with pilot of 35 you see with the spreadsheet that with the exception of just off idle and between 1/8 and 1/4, the CEL setup is just a bit richer. The L diameter is smaller (richer) so this is why I use a leaner pilot.

 

[lemmy]

I started the bike up today and it was about 70 degrees. It wasn't idling that great even when cold. I had to screw in the idle screw all the way. I let it sit for about an hour and put in a new spark plug and it is idling better now and I am able to back out the idle scew some because it idles too high now. But the thing that I am confused about is the bike is smoking quite a bit now. I ride down the street (0.1 mile) and turn around and I am riding through a cloud of smoke. It never did that before and all I have really done since it wasn't smoking that much is fix the kips, put new o-rings where the exhaust joins the head, dip the carb, and replace the CEK with the CEL needle. After letting it idle for 5-10 minutes spooge is starting to run down the end of the pipe. Is this much smoke normal? Is lots of smoke a sign of too much oil in the fuel? I have been running 44:1 Motul 800 2T and the gas is only about 1 week old 93 pure gas with no ethanol.

 

[lemmy]

I decided to go back to where I started except a bit leaner because I was trying to fix a problem which turned out to be the KIPs being screwed up. I went to 42 pilot, R1173L needle clip is one from top, and a 152 main. I started it up and it was idling much higher (but it is about 15 degrees cooler now) and it seemed to be smoking much less. This doesn't make sense to me though becuase if I compare 35/CEL/#3clip/155 to 42/1173L/#2clip/152 using JDs spreadsheet, it shows the setup I have now to be leaner everywhere except much richer 0-1/16 throttle.

 

[G. Gearloose]

Lemmy i wish we still had the expertise we had here 4-5 years ago, we could set you right.

Yes, typically with the stock needle set, if you set the needle for good midrange, there is a pesky lean spot transitioning off the pilot. That is why the trend for more-taper, smaller diam needle have worked very well for most.