anyone running a similar set up @ 4000 ft. (2003 KDX 220 R)

[vargar]

The cold Canadian winter finally released it's grasp, and the snow turned mud was finally drying up ( and I thought ..great I'll finally be able to try all the recent mods I'd been reading about in these threads ) and we were hit with a unprecidented amount of rain in June ( 11 inches)
Sadly now it's July and with all my wrenching long since done I can't even get to the unloading area. This winter I sent my carb and cylinder head off to RB Designs to be modified (sweet workmanship) and replaced the OEM pison with a Wiesco on my 2003 KDX 220. In an effort to maximize seat time when all this mud drys up I was wondering if anyone was running a similar set up at my elevation already had theirs dialed in ( I got out once this year, but really only broke in the new piston and rings) it seemed to run rich and there was lots of spooge coming from the silencer, and the additional mods didn't really rock my world. 2003 KDX 220 Boyesen Rad valve,FMF gnarly woods pipe,FMF power core 2 silencer,after market Twin Air silencer,air box cover removed ,FRP torque ring ,RB Designs card and head mod,stock gearing, pump gas mixed with Amsoil Dominator at 32 to 1 running at an elevation of 4000feet. the current set up back from RB Designs was CEK-3 #40 pilot jet, 152 main jet. mixture screw @ 7/8 turn. If any of you are running a similar set up and be willing to share your knowledge I'd like to use this time to source any recommended parts ,.......hoping to spend my time roosting instead of plug choppin'.........oh Happy Independance Day..Thanks !

 

[razrbakcrzy]

I think the Dominator should be running at 50:1? This could be the cause of the spooge. Remember the settings given to you by RB will be suggestion, with all the changes you will most certainly be doing some carb jetting and plug chopping.

 

[John Harris]

What size carb did you wind up with? Is it still the stock 220 size or the 35mm size on the 200? Maybe RB only does one size? If this is a 35 carb there are jetting charts on Canadian Dave's site. I would suspect that the altitude was not compensated by the RB group. Just guessing that you can use one size smaller on primary and main, say 40 and 150. If you do not plan to do plug chops, try the smaller pilot first and see how it works. Engines usually do not sieze at low speed! Every engine is different! Cheers John

 

[fundgh]

I have similar mods on my 01 220 with exception to the head. I called Ron and he said that at 4k I would not have to adjust the jetting. Only when I went up to 8-9K did I change. I went one size smaller on the pilot jet and 1slot lower with the clip (per Ron's recommendation). It seemed to ride the same at 8-9K with those adjustments, as it does at 3-5K without the changes. I am pretty sure my carb is jetted the same as yours. I have never noticed anything wrong with it, but I am new to tuning so I might be missing something. Good luck!

 

[Woodsquest]

Hi Vargar,
We are very close to the same mods. Here is what I have on my 220:
RB modded Air Stryker Carb (a 35mm carb bored to 36mm)
RB modded head
VForce 3 reeds
NoToil Air Filter
Air Box lid removed
Wiseco Piston and rings
K-35 FMF Gnarly Torque Woods Pipe
TurbineCore2 Spark Arrester/ Silencer
Fredette torque ring. (now removed, get rid of yours too)
Fly Wheel weight
Running 50-50 premium and VP C-12 Race Gas mixed at 40:1 with Maxima Super M


Now for jetting:
#38 pilot
CEK 3rd clip from the top
140 main
Also, the air screw is between 3/4 turn and 1 full turn out depending on elevation and air temp. I adjust it a few times during a day's ride.

I just changed from a 145 main due to the warmer weather. I have noted more spooge in the last couple of weeks. The 140 was tested on my property at 1800 feet and 85 degrees air temp and ran fine. It was then run at 4000 feet up to 6000 feet from an air temp about 55 to 72 degrees as the day warmed up. It ran great. Spooge is now gone like it was with the 145 during winter.

I recommend you drop to a 145 main and do a WOT plug chop the CORRECT way. (Don't know the correct way? I think it is in the link to Canadian Dave's site). Then if things look good there, leave it. If it still looks rich, then bump down to the 140 main. I don't recommend moving the main to 140 right off the bat. The C-12 tends to go a long ways and allows my bike to be jetted leaner than usuall. When I was running straight C-12, I was down 2 more sizes on the main from 145 at the leanest point without coming close to being too lean. (based on the mixture ring on my plug after several WOT plug chops.)

Get ready for some excitement because once you have that carb dialed in, including the air screw, That bike is going to amaze you. It will easily pull the front end up in 2nd gear from a crawl, no clutch, just wick the throttle from shut to 1/4. Instant lift. Awesome for logs, or anything else you need to clear.

I don't know what gearing you are running, but right now I dropped the front sprocket by one tooth: 12 and left the rear stock. I hardly need first gear now. 2nd is much more range and user friendly for anything but picking up after a crash on a steep hill, or gettng out of a ditch; things like that.

If you have ANY questions on any of this, just let me know. I would be happy to help you get this sorted out. Ron Black is an awesome guy and once you get the carb dialed in, let him know where you ended up. He can use the info for more enhancements to his products.

 

[Woodsquest]

I called Ron and he said that at 4k I would not have to adjust the jetting.

The main reason behind that recommendation from Ron I would guess is because at the lower elevation the air temperature is warmer than at the higher elevation.
So, 75 degree air temp at, say, 1500 feet of elevation will have about the same amout of oxygen as, say, 60 degree air at about 4,000 feet elevation. Not much need to rejet.

As air warms, the molacules move quicker and the air thins out. As you go higher in elevation, the air thins out as well. Start a ride on a cold mountain in the morning and the jetting may seem great. Same day but now hotter as the sun warms the air and soon you are running a tad rich.

Make sense? I only responded because you said you were new to jetting. I thought I might be able to help you understand part of what's happening.

Keep in mind: making jetting changes over several days while trying to dial in the correct set-up is better than spending a whole day at it if the air temperature or the elevation is changing during the jetting sesson. I usually do one change at a time with conditions as close as I can duplicate each time. This usually means I'm making a change at the staging area I ride just before taking off in the morning. I warm up the bike, make sure it is performing as it did the last time I rode, make my adjustment, then ride that combination all day long. It's slow, but it is less frustrating than trying to get it all done at once. Trust me.

 

[Rhodester]

It is certainly jetted 'safe' with that jetting, but I'd be inclined to experiment with a 150 main jet or even a 148 if it's real hot out. I'd lose the torque ring. It doesn't do a thing for you (in practical terms). It just limits your top end revs 200 to 300 RPMs. If I recollect, RB carbs are all bored to 36mm. If you want a little snappier bottom end try a DEK/3.