Post-jetting result

[mnnthbx]

I was having a plug eating problem with my new 200. I just rejetted to a 158 main and a 45 pilot. (one jet smaller each circuit). The bike starts and idles well. It has slightly crisper mid and top end, but is more sluggish off idle. I have to hit the band before it will pull 2nd now. I played with the air screw a bit. Stock, it was set at 3/4 out. As I neared 2 full out, the idle speed increased a bit. (which to me says, it must be closer to correct) Anyway, in highly sophisticated lawn whellie popping tests and general off idle blippery, I could never fell any real change with any air screw adjustment.
I have a good fundamental understanding of carb tuning, (albiet, PWC) but I'm a bit baffled here. Where should I start to search for my off idle, puddle popping, power?
The bike is stock, w/ air box drilled. All other aspected of it are in like new, perfect working order.................thanks.

 

[23jayhawk]

Well, if you can back out the airscrew to around 2 or 2 1/2 turns, and you still don't get a lean bog off-idle, that could indicate that your pilot is still plenty rich. If it were not, then you would be able to create a lean condition as you go past the optimum A/S setting. Perhaps try a smaller pilot until you CAN determine a change with the airscrew.

Everyone has their own methods. I usually start out cold in the morning with my A/S close to 1 turn out, even though I know I'll end up around 1 3/4 to 2 turns out. Then after warm up, I just keep backing it out a 1/4 or so until I get a little bogging, go back in a smidge and ride. By then I'm warmed up enough to hit the trail. :cool:

Others will have different methods to offer, I'm sure.

-- Ken 

  

 

[TVRider]

What is a lean bog like? If the bike bogs a little off idle (CC has mentioned at walking speed in 2nd gear a snap of the throttle should give immediate response) does that always mean too lean? My bike defintely doesn't have that snap off idle. Could it also mean too rich? Just tryin to understand! I was going to try to play with it some tonight.

 

[mnnthbx]

Hawk, I fully understand your logic of "pilot may still be too rich", but since it felt good on bottom before I reduced my pilot, it's hard to think it would help to go smaller again??????? I'm by no means disaggreeing with you point, my situation just has me baffled. Thanks for the help.

 

[mnnthbx]

One other thing.....I moved the needle clip up to the second grove from the top, as as thats what I saw recomended on CD's site, and was told it would help with the fouling issue. Could clip placement move the powerband up some?

 

[23jayhawk]

Lean bog - best metaphor I can come up with is it feels like there is a rubber band wrapped around the crankshaft. If you just roll the throttle on hard from closed or almost closed, you find yourself leaning over the bars in anticipation of the response that isn't there. Then the rubber band unwinds and away you go. That's probably a poor image, but it's what it feels like to me. It's like a vacuum waiting to be filled.

mnnthbx - reading your original post again, I think I see what you're saying. You had better throttle response before dropping your jetting across the board. My point was that if you are approaching a good setting as you back out the A/S, but can't quite get there, then that is usually a sign you need to move to the next pilot. You're comment on increasing idle speed might indicate that you're getting close. The final test of the A/S is really how it feels. That's why I don't do the increasing idle thing. I also find it hard to discern the boundary of a rich condition. Lean seems easier to feel, which is why I take it to the lean side then fatten it up a bit.

How does your plug look after some wide open running? What about your exhaust plume? Kinda heavy and blue, or just a faint haze? If you're still off on the main, that can have some effect on the mid, probably less on the bottom.

Just a personal note on clip settings. When I was still running the stock needle, I couldn't go to the second clip until temps were above 90F, or I would get a huge lean flat spot about 1/4 throttle. So sometimes the suggested starting points on CDaves page are just that - a starting point. Another thing - it's been my experience that the needle setting can sometimes have quite an impact on the off-idle feel. As far as the powerband, I don't think jetting can move that around.

Hopefully some of the jetting gurus will jump in here and offer some profound observations.:confused:

 

[Jim Crenca]

IMO,
The main jet should be set by WFO plug chop method before any serious jetting can occur. I prefer 4th or 5th gear under a slight uphill grade.
Get a nice tan color at WFO and go from there.

CC, Fred, BRUSH, CD - Is this your current thinking as well?

 

[svmtbman]

I was having the same problem on my '03 200. I thought I was getting a lean bog when I dropped the pilot to a 45 but it turns out it was still a little rich. I just dropped the pilot to a 42 and it seems to be right. I can now get a change by turning the air screw like I should, and when I got it dialed in at about 1 turn out the bike runs awesome. I tried a 155 main but I think the 158 is a little better. I'm basically running a stock bike except for the airbox lid removed. I'd say spend the $4.00 on a 42 pilot and give it a shot. Also, my bike runs alot better with the clip in the #3 slot on the stock needle, I tried #2 and it fels a little flat.

 

[mnnthbx]

Thanks very much. This thread is helping me a lot. I went back to the #3 clip position, and it seems to help a bit. I will try to go smaller with the pilot once again if you guys think thats not overly lean. ( I doubt it is, as my RPMs increase as I near 2 turns out on the air screw). My bike smokes mildly when I let it idle from a cold start. When it's warm enough to take gas, it leaves some decent blue smoke clouds, then nearly stops smoking when it is fully hot. Does this sound about right? This is running 32:1 Kawi brand race oil. I am switching to BelRay senthetic when this tank is used up. I assume it will burn a bit cleaner? Again, thanks for the help.

 

[mnnthbx]

Still working...... Here is what happened my last ride.

I started the bike. (cold motor) Very little smoke. If I blipped the throttle, I could produce a fair amount of smoke while the rev were up and falling.

I pulled away (mildly warm motor). Rode easy. Motor was very rough when nearing power band, and did not want to get into the band. Possibly not warm enough.

Decently well warmed motor. Bike bogged. Started smoking like a fire bomb. Backfired one good time. I had to fight to keep it running for 60 seconds. (this is while setting still) Kept trying to rev it, to "clean it out". Would rev fine in nuetral. Try to pull away and it would just want to choke and die.

Finally got it to pull away. Got through the power band one good time 3 min. after start-up), and it ran fine for the following 30 min. Very little smoke while at idle, little blue cloud when grabbing a hand full.

Honestly, I'm getting very discouraged. Happened to run accross a local "guru" that I have'nt seen in years. I'm gonna leave it with him on Monday. For the time being, he gave me some Motul 800. Said I should drain the tank, and fill back up at 40:1. (as to not mix the synthetic and Kawi oil).

 

[muggy]

Hello mnnthbx,

I'm no jetting expert, but i live in oak ridge and just rejetted to a 155 main and a 45 pilot, clip is in the 2nd position from the top. I have a 2001 kdx200 that i just bought used, and it was completely stock with no mods. (original tires even).

I've had good results with these settings and can't tell much difference on the position of my air screw.I suspect i may be slightly rich on the bottom, but i have very good throttle response. A WOT plug chop revealed a very lite tan on the upper part of the center white piece of the plug, with a darker ring down in the plug covered by the threads, so i'm playing with being a little lean on top, i think.

I suspect you are still pretty rich from idle to 1/2 throttle, after reading all the posts.

This is with the stock airbox, haven't drilled it yet. Stock pipe. Used a 32:1 mix with honda pre-mix. (its cheap)

If you want to work on jetting and compare notes, i'm up at windrock most w/e's until i get this new scoot ironed out. Heh, i guess i'll be up there most w/e's anyway. I run class C vet in hare scrambles and am always looking for other like minded idiots to ride with...i mean riders. :>)

 

[TVRider]

mnnthbx,

As far as oil goes everyone has there own preference. I talked to Fredette when I got my new '03 200 and he said Golden Spectro at 52:1 will keep the Kips valves very clean.

As far as jetting, I agree with Jim Crenca. You need to get the main jet right first. Go to: http://www.dirtrider.net/forums3/showthread.php?s=&threadid=60392&perpage=20&display=&pagenumber=1 and read this entire thread. It describes the only reliable way to check your main jet. Once you have that right then start playing with everything else. I am still messing with my bottom end, but after doing a WOT plug chop I found that the main jet my buddy was running in his similarly modified 200 was too rich. When I dropped the main jet down another size it really made a big difference. Rich Rorich says in the thread above something to the effect that spot on jetting will make all the difference in the world in performance. I know your concerned about the bottom end but thought this would help. It has helped me.

Good Luck,

Tom :thumb:

 

[wibby]

Back to the analogy... Would a lean bog be similar to water in the gas? or is it not that severe?

And I assume a rich bog would be similar to running with the choke on??

I'm just trying to get a feel on this stuff.

I wish it would stop raining so I could go up in the mountains and do a WOT chop! :worship:

 

[mnnthbx]

OK, here's my latest semi-knowledgable theory. I dropped a jet size each circuit, moved the clip to the #2 position, and the bike seemed to have no power off idle. Put the clip back in the 3rd position, and it seemed to help, but it still fouls plugs badly. (my original problem). So.................

#1 While warming up, it smokes very little idling, and quiet a bit (even smoke rings) when I give it a quick rev. and...

#2 When I feel the plug starting to foul, it won't take gas, and doesn't produce enough power to pull away, BUT it will still idle fairly well, THAT...

it is probably still too rich on the high speed jet. (currently a 158) It developes a lean bog (I think) when I set the air screw two turns out, so I guess the pilot is close. (air screw set around 3/4 out)

I'm still leaving it with my "guru" Monday, but I'm gonna ket him in on these thoughts. (though he probably does'nt need me in the way) I'm guessing the good set up will be in the neighborhood of:

45 Pilot
155 Main
Clip in 3rd notch
Air screw @ 3/4 out

Does all my ignorant gibberish sound like it may ring true? For anyone wondering why I don't follow all the standard plug check methods, I don't have a good place to run a good chop, and if I did I would probably kill myself trying. One last thing. When I pull a fouled plug, it has quiet a bit of material on it. (crusty carbon, not aluminum) When I finally get this thing jetted right will it burn itself clean or do I have a big crusty mess inside my mill? Thanks.

 

[kevinkdx]

to answer wibby question about what a lean bog feels like, I had that problem before due to a seal leak. Anyway, you will be going along and then all of a sudden your bike will just like go boooooooooouuuuuuuuuu and may even stop like mine did. Now i had a severe case where i melted the plug and the piston as for what a slight lean bog is like i dunno.

 

[canyncarvr]

TVRider posted some crucial info that I don't see being acknowledged.

The main is set first!.

That not having taken place, all the descriptive 'doing this here', 'doing that there', changing clips, air screw adjustment etc is a waste of time.