125-200cc Need Cafehusky counseling...WR125 problem.

This seems long, but please stick with me...

Please don't go away without putting your 2 cents in...I need a brain storming session, which means there a no stupid ideas!
I have inherited a 'Blah', a complete cutting out when the throttle is cracked, not a bog. It almost seems to come and go. A roll-on of the throttle seems ok, but that's not going to help in a race.
Trying to set up the '09 Wr125 for Hare Scramble racing for my son.
In Pennsylvania, around 500' elevation, temps all over the place.
So far...Engine wise.
- FMF Fatty/TC2 combo
- I do have Walt's springs, Stock and a blue right now.
- Power valve adjusted to just cover top of slot
- Maxima Super M 36:1
Now for the good stuff...
Raced the bike once with the Mikuni, was not really happy with the performance.
Couldn't beat the price for the chance of predictable power, so I bought the pre-jetted 38mm PWK from Moto...
Did a lot of reading, pm'd Kelly and started with.
180 main, 45 pilot, red needle 4th clip down, # 7 slide - major 'blah'
Tweaked this jetting all over the place and 'blah'
Brainstorm - Talk to Drew Smith, PA rider...runs the Mikuni. Put his jetting specs in and throw the Mikuni back on see what happens...
450 main, 50 pilot, 6dey15-74 needle 3rd clip down, #4 slide - same major 'blah' - same place.

Am I destined to continue chasing the jetting or are we looking at something else here?

Float levels, flywheel, electrical (I did wrap the lead for an hour meter to the plug wire), Power valve...

Whatever

I know this is a really open subject, but I thought the masses might have a ''been there-done that'' I missed...

If the "blah" was in the same place for both carbs, I would be looking at other causes.

Spark Plug? Try replacing it with a resistor plug or R type. In 2004 my new CR 125 would just die when riding at high rpm's. My dealer was there as well and we tore the carb off and checked a bunch of stuff, turned out the bike had the wrong plug from the factory.

Got a pm within the first 10 minutes...

Pa rider, same bike, same carb...kind of, sort of same problem.

Is trying a very thin needle...thinks it needs a lot more gas...

He'll be doing some testing today, maybe we'll see an update.

Really need to fix this - does not instill any confidence at all that the power will be there when you need it...

No stupid ideas... Okay then, this thread is screamin' my name...


I've was messin' around on the 'net RE jetting techniques etc... I came across this jetting method. This method is foreign to me, and I haven't tried it yet; but may be old hat for some. If someone has/uses this chime in...

If it's a valid method maybe it'll help you w/ your bike....

JETTING

For whatever reason it becomes necessary to re-jet a carburetor, it is without a doubt a nightmare if you do not have a procedure to follow. The following is nothing more than a technique, procedure, steps or whatever you want to call it to help identify and isolate the carburetor circuit involved.

You can only begin re-jetting your carburetor if the following conditions are met:
1. Top end is in good condition.
2. Bottom end is in good condition. Crank seals.
3. Spark plugs, air filters, reeds and so on.

If your bike's motor is not mechanically sound, then all the jetting in the world will not help. With all of the above conditions met, you should be able to jet your carburetor following these steps:

Step 1: DETERMINE THE CORRECT NEEDLE AND OR NEEDLE JET.
Step 2: DETERMINE THE CORRECT PILOT (slow)JET.
Step 3: DETERMINE THE CORRECT MAIN JET.
Step 4: DETERMINE THE CORRECT NEEDLE TAPER AND CUT AWAY.

Step 1: DETERMINE THE CORRECT NEEDLE AND OR NEEDLE JET.
Whether or not your carburetor is a MIKUNI or a KEIHIN, it does not matter. This is the most important step in jetting your carburetor--period!
1. Remove the main jet.
2. Place needle clip in mid-position.
3. Start motor and run it on the stand.

Condition: Motor running and main jet out. Needle or needle jet is correct: Carburetor should run clean to approximately 3/4 throttle. From 3/4 throttle to full throttle, the motor should start to break up as a result of too rich condition.
Correction: None needed.

Condition: Needle or needle jet is too rich. Carburetor runs clean to approximately 1/2 throttle but breaks up before 3/4 throttle as a result of too rich condition.
Correction: Mikuni replace needle jet with next leaner and test again. Keihin replace needle with next leaner diameter and test again.

Condition: Needle or needle jet is too lean: Carburetor runs clean beyond 3/4 throttle and has an erratic throttle response.
Correction: Mikuni replace needle jet with next richer and test again. Keihin replace needle with next richer diameter and test again.

The emphasis here is to find the correct needle or needle jet diameter, which will allow more fuel to pass than is needed but not so much that the needle itself has no control below 3/4 throttle.

Step 2: DETERMINE THE CORRECT PILOT JET.

1. Make sure the bike is warmed up if at all possible.
2. Main jet out.
3. Needle clip in mid position.
4. Turn air screw all the way in then 1/4 turn out.
5. Start motor and run it on the stand.
6. Adjust idle so the bike will just barely idle.
Condition: Motor running and main jet out.

PILOT JET CORRECT:
With one hand on the throttle maintaining RPM at approximately 1/8 throttle, turn air screw 1/4 turn at a time clock wise until you bottom it out. Motor should become slightly erratic and you should have to play with throttle to maintain RPM. Start turning air screw counter clockwise, 1/4 turn at a time until you have reached 2 3/4 turns out. Between 1 1/4 and 2 1/4 turns, your motor should have reached its highest RPM maintaining a steady throttle. Adjust air screw again between 1 1/4 and 2 1/4 until you have determined highest RPM. Quick throttle response should be clean without bog.

PILOT JET TOO RICH:
RPM does not reach a peak between 1 1/4 and 2 1/4 turns, stays the same or keeps rising out to 2 3/4 turns.
Correction: Mikuni replace pilot jet with next leaner and test again. Keihin replace pilot jet with next leaner and test again.

PILOT JET TOO LEAN:
RPM does not become erratic and motor maintains throttle when air screw is turned all the way clockwise.
Correction: Mikuni replace pilot jet with next richer and test again. Keihin replace pilot jet with next richer and test again. Remember, with a steady throttle approximately 1/8, there should be a distinct difference in RPM from 1 1/4 turns to 2 1/4 turns if the pilot jet is correct. The emphasis here is to find a pilot jet that will run crisp without bog and without the main jet.

Step 3: DETERMINE THE CORRECT MAIN JET.

The main jet selection process is easy once you have the correct needle diameter or needle jet. You now only have to correct a rich condition from 3/4 throttle on up and you know what a rich condition sounds like. Your pilot circuit is correct and without bog.
1. Replace main jet with one that is at least two sizes smaller.
2. Needle clip in mid position.
3. Start motor and run it on the stand.

By replacing the main jet with one that is too small, you are looking for a condition that is too lean. You adjust your main jet from a too small to lean condition.
Condition: Motor running and main jet in.

MAIN JET CORRECT:
Carburetor should run clean and crisp to full throttle.
Correction: None needed.

MAIN JET TOO RICH:
RPM reaches a peak slowly with a deep sound. Excess fuel and oil mixture at end of silencer. Spark plug fowls easily and is dark in color.
Correction: Mikuni replace main jet with next leaner and test again. Keihin replace main jet with next leaner and test again.

MAIN JET TOO LEAN:
RPM reaches a peak quickly but erratic. A quick full snap open of throttle causes the motor to hesitate BEWAH sound or a complete bog. Motor sounds like it has a ring to it. End of silencer white. Spark plug is white in color.
Correction: Mikuni replace main jet with next richer until the BEWAH bog just barely goes away, then replace the main jet with the next richer and run it. Keihin replace main jet with next richer until the BEWAH bog just barely goes away, then replace the main jet with the next richer and run it. The emphasis here is find a main jet that is just rich enough to allow you snap the throttle wide open without the motor bogging as a result of the main being too lean. Should be a quick crisp throttle with no hesitation.

Step 4: DETERMINE THE CORRECT NEEDLE TAPER AND CUT AWAY.

This step in the jetting process can be made very simple if you remain close to stock. However, your needle taper is adjusted for 1/2 throttle to 3/4 throttle. Start off with a rich taper (shallow taper angle) and keep going leaner (steeper taper angle) until it will not maintain constant RPM at 1/2 throttle (runs erratic). Go back to the leanest taper angle that ran the smoothest at 1/2 to 3/4 throttle and that should be the correct taper. The needle taper final test should be under track conditions with the greatest effect entering and exiting corners. Do not change the needle diameter or needle jet size during this process because that has already been determined. Adjust taper and throttle cut away only.

Throttle cut away affects from idle to 1/4 throttle. The correct cut away will maintain steady 1/8 throttle with quick throttle response. Generally the stock cut away is very close. Experiment with different cut away until it maintains the best response to 1/4 throttle.

QUICK TIPS:
Keep it simple, buy the optional OEM needles or needle jets that are available, as this may speed up the taper selection process. Don't skip any steps or you're just guessing.

FINAL THOUGHTS:
That's it, if you spend the time jetting correctly, the benefits you will gain definitely out-weigh way the time spent. Take the guesswork out of jetting by following a procedure that has been given or one you have laid out yourself. Keep the black magic process out of your tuning tricks and you will be better off for it.There's a specific step RE the needle. I've not tried the listed steps yet.

The stock plug cap is a major POS, replace with NGK waterproof. can lead to intermittent running

Are you sure the powervalves have been replaced?

Is it sputtering like its rich? My bike was pig rich at 180, 178,175 172, with RED needle in leanest position and 45 pilot. 32:1 motul 800.
This was while I was in canada this summer 500-1500 ft.
Ended up at 170m 40 pilot red needle 2nd from top, felt like it was still a tad rich. Granted I am running a 144 kit though, and have a RB designs divider plate.

Check grounds to frame as well.

Don't get me wrong I love these bikes, I'm on my second tiddler, but it seems like by the time you get the jetting sorted it's time for a top end?????

blah sounds like its not getting on the pipe - too rich
You are running
180 main, 45 pilot, red needle 4th clip down, # 7 slide - major 'blah'
id first try needle 2nd clip from top
- to lean it out
isnt it summer? needs less fuel as air not as dense.
possibly leaner main

if its worse then you know you are heading in wrong direction

Thanks for the replies... we are all over the place too lean...too rich!

The jetting technique is one I have never seen, very interesting.

I just got another pm, New Jersey/New York rider - running the stock Mikuni.
410 main, 30 pilot, power up needle?( DEY?) middle clip, # 4 slide... That sounds really lean, but he said bike runs great.

I am tracking the thread, just out putting some new windows in the garage...

Please keep talking.
Thanks

I'd go with the NGK T5B plug cap and a new Iridium plug, for starters. And check the reeds for cracks and cage for leaks.

Then check the power valve for proper operation. It may be stuck open or not opening. Or, it could just be too high. Check the static height to make sure it's not too far open to start with.

Might even make a little vid of your son riding around the yard and post it. Might help to nail it down if we can see and hear it running.

I'll look through the service manual about setting the power valve.
(Unless someone wants to explain the procedure)

I have had the gov. out messing with Walt's springs, I tried to pay close attention to the home position of the shaft indents, I don't think I have this installed wrong...

I would think if the gov. is installed a tooth off the indents would be way off...but...

I will pull the reeds and inspect, the process of elimination does not bother me...

The pm I got earlier from the NJ/NY rider...

Rider is over 200 lbs and senses no bog with the jetting they have in!
Just raced an NJ sand hare scramble and says plug looks great.

Mine is lucky if he's 130 with gear...Will round up some jets on Monday and see what we got...


What do you think the equivalent jetting would be for the 38 PWK to match the Mikuni 410m, 30p?

I must have lucked out, PWK and its been awesome. I dropped the needle 1 clip today and its so perfect.

Hope you get it sorted.

I fought this same problem since day one, for whatever reason, some of the bikes need more fuel. if you roll on the throttle, it is ok, but if you whack it open it dies. Got the mikuni working with 480 main and needle in richest clip.
I then got the PWK kit from Kelly and had the same problem. Blue needle fourth clip and 180 main still would die with quick throttle opening. I now use a NOZF needle from my KTM and 180 or 185 main and it runs good.
I feel confident if you give it more fuel, problem will go away. Try a bigger main or a noze or f needle. Have you tried the blue needle?, it is richer. Also check your compression, mine is at 162.
I origionally was convinced it needed a bigger pilot, and that did help, but was only helping a little. I discovered you could go from 0 to half throttle with good results, but if you go from closed to full open it would die, and I am talking like I hit the kill button.
I also tried lean settings, and it was much worse. i wouldn't worry so much about what others use for jetting, just go to extremes to see what works.
I have a 36mm pwk from a KTM coming, I am interested in seeing what it will do.
GP

I had an issue couple of weeks ago, the bike would not rev at all. Turned out I had forgot the plastic bag over my air filter :O
Sometimes it's just a little something that cause a big problem..

I looked for the plastic bag, Dang! - Not there…

Isn't it great to own a bike with so much personality!

They should come with a marriage certificate, not a title…Watch out…:smirk:

All good stuff! Just helps to confirm I'm not off my rocker with this one.

I will follow the guidance of those who responded. Good stuff.

Again no plastic bag, Dang!

I will...(Kind of sounds like 'I do', very scary)
- Check plug cap/plug
- Check compression
- Check power valve
- Check reeds

water racer,

I do have a pile of jets, may go to extremes, just to see. If not, your comment about not trying to match others may be the best. I think the bikes are very different and each one needs different levels of TLC. Best move sounds like - pick a carb, following a good jetting procedure and see where it lands.

I would really liked to get this sorted out - the boy will need some peg time and I would really like to see him remain on the Husky.

Will keep you posted… and Thanks…

Any other suggestions are welcome...

there must be a simple reason for this ocurring on so many bikes - it is not reeds , compression or power valve or an issue with your bike in particular it is common with so many bikes _ Ive had two an both had this issue at different times
There must be some kind of common design fault

If you run rich you may solve issue at one throttle opening but will have a bike thats not running properly at other times which will mean less power
Try the needle height its the easiest way

I wouldnt run those settings on a 09 Wr125

410 main sounds like the older TMX which is a different version

mine ran ok with 450 main and 30 pilot with the mikuni

I am running the Keihin PWK now with 175 main and 42 pilot with air screw at 1 turn out (pilot is just a bit small) red needle at middle slot

PV adjustment bolt slightly above the middle area on the slot..some guys run it very close to the top with great results too


try taking the cover off the PV and watch if it moves when revved

and check the plug gap and or replace plug

something doesnt sound right

I can make mine do the bog if I crack it wide open under load at idle rpms. The 167 actually resists this more. The leaner the needle position the worse this reaction is on mine. I currently run the red needle in the 4th slot down with a 175 main and 42 pilot. When it cools off I will go to the blue needle in the same location. I have to really idle down the 167 under load going up a hill to get it to bog when you crack it wide open. The 144 will do this a little easier but you still need to be under load and very low rpms.

I actually can't make mine bog in normal riding and conditions. You really have to try. I am currently running the 167 with the linkage all the way at the bottom and the 144 with it adjusted half way.

Walt

Kelly,

I agree if it is a mid-range bog. If it is a just chopping the throttle open at a lower rpm then it isn't PV related. If the PV is opening too soon then it will bog whether you roll on or crack the throttle in the mid-range. I have found that the 08 and newer power valved top ends do not like to have the power valves opened more than about 3mm before 7000 rpm. The older style power valved cylinders are much more tolerant of changing the opening rpm. I don't get it and don't even understand why this is true. I have settled on a combination for my 144 that has initial opening at stock spring settings and then have added an inner spring that slows the total opening until later than stock and it is an awsome powerband. I also used a spare set of bad 09 power valves to regrind for the 144 minimizing the gap to minimum tolerances. It doesn't have the same low/mid that the 167 has but it certainly pulls like a raped ape across the entire power band with the linkage at half mast. Obviously I have done a lot more futzing than most would want to but I am trying to make an additional spring supplement that will allow some compromise for those with the linkage adjusted up. I hope to be able to send this to anyone with the kit as a free update this winter.

Walt