Jetting what base to use

[EncyclopediaRonnie]

hey guys what is the best place to start im jetting a kx125 has stock pipes carbon reads. just rebuilt motor with steel sleeve and uped compression ration to aprox 10.1. actually is a tinny bit under.

in it now is

pilot:50

main:152

clip in 2nd or 3rd from top

stock is

pilot:50

Main:168

clip: not specified

or fmfs jetting guide states

pilot: 52

main: 158

needle clip: 3rd

air screw 1.5.


this is my 3 options im thinking ill start at the fmf guide and go from there.

also what plug to use b8es?? it had a 6 in previously


any tips more than welcome never tried jetting a bike before so this gonna be fun lol

cheers hagen.

 

[BSWIFT]

Have you read the jetting guide at the top of this forum? Your main seems way too lean now. How was the bike running before the rebuild? How is it running now? Always jet the engine for what it is telling you, not the specs. Need more info, average riding temps, elevation, humidity, etc..

 

[EncyclopediaRonnie]

umm it all changes illl ride anywhere between 100 meters above see to over 1000 above see almost. on a day to day chnage. with temp from summer at say 30 celcius and up to say 10 celcius in winter.

it ran good before comp was low so down low felt boggy but up top it hauled pretty good but lean in the mains was definetly my thoughts too.

bout to read the guide now im just puting it all backtogether new top end and wanna know where i should start from id rather be rich than lean???

 

[whenfoxforks-ruled]

What year is this KX? That plug is no where near proper.

 

[EncyclopediaRonnie]

my 93

 

[whenfoxforks-ruled]

The K model? NGK does not have a plug? They do not show one? Kawasaki seemingly does not run resistor plugs, but, R6254K-105 or a B10EG is the closest? You are running way too hot a plug. http://www.ngksparkplugs.com/part_finder/motorcycles/step3.asp

 

[EncyclopediaRonnie]

kawasaki dealer set me up with br9es today so shall roll with that for now sounds good he said it will be okay so.

also got some gets have pilots to cover everything and mains from 152,155,158,160.

 

[helio lucas]

now the hardest work, suck it and see :nod:

 

[whenfoxforks-ruled]

A keihn carb? That pilot seems huge, to me. But thats jetting. Nicely put Helio!

 

[BSWIFT]

Just remember to do one change and then test. Never make multiple changes at one time because you will not know what caused the good or bad result. If you were to get the pilot on the verge of being lean at your lowest elevation, the higher elevation should stay acceptable.

 

[EncyclopediaRonnie]

yeah its a pwk36 carb. foxforks.

bswift. not bad lil tip ill be hapily taking that on board. what circuit should i jet 1st pilot clip, mains or mains, clip, pilot??



thinking im gonna start at the fmf recomended jetting and work from there id rather be all a lil richer than lean.

any tips or things to look out for?

i can use choke to identify bogs etc as lean or rich corect?

 

[2-Strokes 4-ever]

New puppy here, not much sleep (thanks Okie for the Dog Crate Sponsor) so...

Establish the original, stock jetting specs.
Make sure bike is always fully warm before checking jetting.
We've been doing this long enough that we just do pilot and needle by sound, feel, and responce, main by plug-check.

Pilot first- Your airscrew should always be in the adjustment range from 1-2&1/2 turns out from fully seated. Establish an idle and turn airscrew to establish highest idle, then we go back in 1/4 turn. If you find this "zone" within the above range, then you're good. If not, going IN further means you need a richer pilot, and OUT further... a leaner one. If different pilot is needed, repeat procedure until correct pilot is found. The pilot is important, although it's main effect is in the first 1/4 throttle usage, it does effect the entire throttle range even though less and less the more you twist.

Needle next- Ride bike under a load at aprox 1/2 throttle. If a blubber is heard, go leaner on clip (raise clip position), if you sense a knock or pinging, move clip down to richen.

Main jet- Ride bike under a load at wide open for a few seconds. Pull in clutch, chop throttle, and hit kill button all at once. Check plug for color, what you want is a flesh color plug. Darker means you're rich, whitish means you're lean. We always establish the ideal color and then I go one size richer to ensure safe running if we encounter hard running in sand or mud.

After establishing the main jet it's a good idea to go back and check the needle in the midrange again.

Because I ride when it's 20*F - 90*F, I keep a chalk board in the shop to tell me my required jetting specs based on the season (temps) of the year. We change jetting three times a year depending on temps.

Hope this helps, now I must take our new dog out before he poops on the carpet... :whoa:

 

[EncyclopediaRonnie]

sweet as massive help makes alot more sense.

i asume i can do the pilot and needle doing plug checks aswell?

ill be jetting hopefully this week so ill be doing it in my middle temp range so hopefully its semi decent in all temp ranges i see alotta sand so ill definetly get mains sweet then go 1 size up for saftey.

hope the dog didnt get the carpet

 

[whenfoxforks-ruled]

The main jet is the only circuit scientifically read by cutting the plug threads off. The rest is seat of pants tested, and checking the plug for wet or dry. If you have doubts, and the choke can not verify which direction is correct, make drastic changes. A pilot 3 sizes smaller will not seize your bike, should not, for a few seconds to check it. Remember the over lapping carb circuits? Thats the biggest reason to start at the bottom, not the main. Make sure its warmed up, and cleared out for a good feel/read on the plug. Cold and loaded up tells you nothing. If you get into an area that does not effect the desirable change, even after drastic changes, there is a mechanical problem someplace else trying to confuse simple jetting. On a side note, the proper installation of a wide band O2 sensor is scientific also, throughout the throttle range. Around 500 hundred US dollars, and a good welder. Also, the ES series plug is not the best for a decent top end revving bike, imo. The EG, EV, or the R6254K-105 plug is much better, after you have the jetting sorted out. I am still baffled why this bike does not have resistor plugs recommended, and yet the dealer sold you 1?

 

[helio lucas]

On a side note, the proper installation of a wide band O2 sensor is scientific also, throughout the throttle range. Around 500 hundred US dollars, and a good welder.

infortunatelly even those o2 sensors are not 100% accurate on two strokes.
kart racers usually use EGT (exhaust gas temp) and CHT (cylinder head temp).

Remember the over lapping carb circuits? Thats the biggest reason to start at the bottom, not the main.

and the reason to re-check the circuits...

vintage bob, just to complement your very good post, the bike should not use resistor spark plug if it has already a resistor cap or ignition may fry. i guess the dealer forgot to check they´re parts list!!!

 

[EncyclopediaRonnie]

i have the ability to check exaust gas mixes but not super acurately. welding a bung in for an o2 sensor is childs play for me lol the rest of it becomes effort ahahahah.


imm gonna go with 2 strokes for evers advice/ method keeping in mind what you guys have said on plug reading circuit overlaps etc. aim hoping this week proves to be the tuning time cause the rear shock is finally rebuilt. not as easy as 1st thought lol.

 

[EncyclopediaRonnie]

forgot plugs can some 1 please slow down and explain wtf is goin on here cause im semi lost now. i get the hotter colder thing but resistor cap? and resistor plug??? ignition may fry? also semi unrelated can bike ignition be timed with a timing light or nah?? just move on plate n see what goes on? thinking i should check mine before jetting

 

[helio lucas]

hey ronniepedia, slow down... ;)

some older ignition systems caused many interferences with electronic devices, one exemple is when old bikes travel along the road by my house, happen lots of interference on my television.
that was cured with spark plugs with some electrical resistance. bike manufactures start to include that resistance on the cap instead of spark plug. this was even more confusing. now you can mix both...

if you happen to have a bike with digital ignition, then the use of both non resistor spark plug and cap may cause interference on the ignition and fry it. if you use both resistor type, the ignition may fry putting too much load on it...

you really need the service manual to be sure on what to use, because each bike is different.
the proper way to timing the ignition is described in the service manual as well.

check eric gorr web site "foward motion". on the bottom of main page he provides outsanding articles and tips for each model bike. really...

:cool: :cool:

link: http://www.eric-gorr.com/

 

[EncyclopediaRonnie]

well i had a b6es and the ignition didnt die so im gonna roll with taht or is the br9es where the resistor part comes in? the stock plug is like ngk-625something-105 or something like that gotta look it up again

 

[BSWIFT]

Go with the br9es or br8es. The "r" stands for resistor. The lower the number the hotter the plug. A 6 is very "HOT" for that engine.

 

[whenfoxforks-ruled]

The years I checked from NGK showed some 10's, Even the 8 would make me nervous. Ignitions being different, even the resistor part. The 9 should be fine. I made jokes about guys running with no crank oil seal and b6 plugs! Now I have to change it to a 4?

 

[EncyclopediaRonnie]

welll still no where near geting this bike in 1 bit and compression is stioll no where near where i want it so verry anoyed now