DirtRider . Net MX, SX, Arena Cross, Off-Road Community
Dirt Rider . Net Text Version Home
Dirt Bike Dirt Bike Dirt Bike Dirt Bike

This is the text version of DirtRider.Net
Click Here for the Full Version


Pages: 1

220 pilot problem

(Click here to view the original thread with full colors/images)

Posted by: grahams---------------------

Hi there. I have been struggling with the bottom end power on my 220. Currently I run a 142 main with a 40 pilot at 5000ft (FMF desert, no airbox lid). The top end is running perfectly and very strong, but I just can't seem to get the bottom end right which is a bit annoying in the tight stuff. The float bowl height seems OK.

Should I try a 38 pilot, or one righer? Also, how much effect to reeds have on the bottom end?


Posted by: kdennan---------------------

what are you running for reeds? Check your air screw. and go to www.kdxrider.net (apologies DRN) Those guys have some great info. The forum posting for jetting is very helpful. You will want to look at the airscrew and pilot relationship and go from there. Good luck!


Posted by: Green Hornet---------------------

Higher the altittude=LESS AIR=BIGGER PILOT/COLDER AIR=BIGGER PILOT
Go up to a 42, adjust the AS and go from there


Posted by: kdennan---------------------

Hey Green Hornet. Let's go ride sometime this summer. I want to check out new stuff and you are welcome to come up to Vt. and check it!


Posted by: Green Hornet---------------------

Quote:
Originally Posted by kdennan
Hey Green Hornet. Let's go ride sometime this summer. I want to check out new stuff and you are welcome to come up to Vt. and check it!

All Righty-My MAPLE SYRUP supply is getting low & I need some Green Label Jack, also


Posted by: ridejunky---------------------

Higher the altittude=LESS AIR=BIGGER PILOT/COLDER AIR=BIGGER PILOT
Go up to a 42, adjust the AS and go from there

This is confusing because colder air contains more oxygen by volume than warmer air and air at higher altitude is thinner


Posted by: Green Hornet---------------------

Correct Cold Air=more air, but higher up contains LESS AIR=Smaller Main,.
OK I confused myself. It make more sense noww


Posted by: Tom L---------------------

I richer jet needle setting (lower clip groove) or richer main jet will also help low end and not hurt your top end significantly.


Posted by: John Harris---------------------

At 5000 feet with stock 220 carb. I believe you need to be leaner on the pilot. Try a 38 and of course you will have to adjust the air screw. Cheers John


Posted by: oldturtle---------------------

Here is my drill. Warm up motor. Raise idle slightly. Play with air screw until you get a positive point of maximum RPM. If max idle occurs at less than 1/2 turn out you are slightly lean so try one size larger piot. If max idle occurs at over 2 turns out you are slightly rich so try one size smaller pilot. If you can not detect any air screw setting where max idle occurs then the pilot is significantly either too rich or too lean. Usually you are too lean with stock jets but you could be too rich. After getting correct pilot jet and you locate max idle, many riders will turn air screw in 1/4 turn to error on rich side. Last thing to do is set idle with throttle stop screw.


Posted by: TimberPig---------------------

Quote:
Originally Posted by Tom L
I richer jet needle setting (lower clip groove) or richer main jet will also help low end and not hurt your top end significantly.


I think you need to revisit the circuits of a bike carburetor. The pilot and airscrew control the low speed mix, then the needle jet and jet needle take over, then the main takes over at high RPM. By changing the jet needle clip, and main jet you will be changing the midrange to high, not the low end.


Posted by: TimberPig---------------------

Quote:
Originally Posted by Green Hornet
Correct Cold Air=more air, but higher up contains LESS AIR=Smaller Main,.
OK I confused myself. It make more sense noww


It might make more sense if you think in terms of air density, and oxygen content, instead of volume. At higher altitude, the atmospheric pressure is lower, thus the air is less dense, because there is less pressure keeping it tightly packed together. Lower air density, means less oxygen sucked into the engine for a given volume of air, and thus leaner jetting is needed.

Cold air acts the same as higher atmospheric pressure (lower elevation), in that cold air is more dense because at low temperature, the air contains less anergy and thus is more densely packed together. This causes cold air to also have a higher oxygen content, which requires richer jetting to maintain the correct air fuel mixture.


Posted by: KDX CRAZY---------------------

Timberpig

The way I understand the jetting is with the amount of throttle opening not engine speed as you stated .


Posted by: Green Hornet---------------------

Quote:
Originally Posted by TimberPig
It might make more sense if you think in terms of air density, and oxygen content, instead of volume. At higher altitude, the atmospheric pressure is lower, thus the air is less dense, because there is less pressure keeping it tightly packed together. Lower air density, means less oxygen sucked into the engine for a given volume of air, and thus leaner jetting is needed.

Cold air acts the same as higher atmospheric pressure (lower elevation), in that cold air is more dense because at low temperature, the air contains less anergy and thus is more densely packed together. This causes cold air to also have a higher oxygen content, which requires richer jetting to maintain the correct air fuel mixture.

Yeah thats what I ment.
I Think


Posted by: TimberPig---------------------

Quote:
Originally Posted by KDX CRAZY
Timberpig

The way I understand the jetting is with the amount of throttle opening not engine speed as you stated .


Throttle opening directly corresponds to engine speed.

Low end = 0 to 1/4 throttle - pilot and airscrew
Mid =1/4 to 3/4 throttle - jet needle, needle jet, slide
High end = 3/4 to full throttle - jet needle, needle jet, slide, and main,
WOT = main only

If your engine is screaming at 1/4 throttle, you are lean. The main jet has nothing to do with low end/small throttle opening plug fouling issues, and neither does the needle. That is the pilot and airscrew you need to look at.


Posted by: Brettsauto---------------------

I ride from sea level to 3000ft, and have just spent the last 12 months experimenting with jets, needles, pilot jets and different carbies. The short version of the story is; that when jetted close up top it was to rich down low and at idle ,( 220 was more of a problem then the 200, ).Tried different slides , R.B Design A/S carby, not even 35 pilot fixed the problem. So I started going to a to different L1 lengths with different tapers, which brings the large diameter of the needle in to the main jet at idle, this affects idle and bottom end. I am currently running a , DCP needle in the middle clip, 42 pilot, 52 main and the AS at 7/8 of a turn. Running the best it ever has , and real nice plug colours too.
Just to try an explain why this different needle size works, is that even at idle, air pass by the main jet, thus pulles fuel through the circuit, and if this circuit is to rich at this throttle opening[ idle ]. Even though it is not the primary circuit at work ,to much fuel can be entering the engine, even before you consider the idle circuit , making it very hard to adjust.
Before changing needles , I tried evey pilot down to a 35. It would improve the idle { not as well as the needle did}, but it would become rich again off idle to 1/4 throttle.
The 220 was worse then the 200 , simply because more air passes through the carby at idle , pulling more fuel with it.
Hope I have helped and not confused the matter even more



Text Version Home





vBulletin Copyright ©2000 - 2009, Jelsoft Enterprises Limited.
vB Easy Archive Final ©2000 - 2009 - Created by Stefan "Xenon" Kaeser