125-200cc 09 WR125 jetting and fuel mileage comparison (2 WR125's)

Norman,

I am going to pull the pv cover off and hook up my rpm gauge tomorrow. I was going to do it today but I ran out of time. Up until now I have just gone off my seat of the pants feel and some calculator extrapolating from a gearing chart.

Tomorrow I will also give you a speed in all gears when the bog hits and when it finally opens in all gears. I don't know if it helps but I am trying to find a solution, it has to be something that can be remedied. If the guys who bikes run well rode my bike, you would come back shaking your head. The fact that you don't have this problem is at least encouraging for me.

Walt,

I grew up riding and racing 125's and believe me this is not the switch they used to be except in one area.

Norman,

Ok, I finally got to do the rpm test. The current top of my mid-range pull is between 6250 and 6300 rpm. The power valve opens at 7800 rpm. It opens all the way immediately no progressive transition. If you try rolling on in one gear, you can't get it to climb up to the pv opening in either 5th or 6th gear. This is on a county dirt road. Pulls crisply up to the top of the mid-range but will not climb above that point without completely abusing the clutch.

My guess is that Husky has gotten a few govenor springs that do not meet their specs. I pulled my complete power valve assembly and govenor apart and everything operates smoothly and easily except the govenor spring is incredibly stiff.

Oh well, I have gone on line and purchased a batch of springs of various compounds and wire thickness's with a wide range of compression loads and static compression pressure vs progressively stiffer as compressed. A little spendy but I will be the ginny pig for those of us with the problem.

I thought about removing some of the stock spring on the outside circumference, but decided to just go with actual springs manufactured to have different compression values.

Walt

I swapped to the #5 slide and went down to a 30 pilot. Woke the bike right up at sea level, but at elevation it felt the same as it did with my initial setup. Odd that I went leaner on the slide and the needle, yet it felt the same, but with half a turn in on the air screw the bike ran much better in the mid-range (thanks for the tip on the air screw Kelly). It still doesn't run as well as Kelly's bike and has done an odd (and scary) thing a few times on WOT runs after about 20 seconds or so where the motor just dies, then comes back to life 5 seconds later.

I'm going to try a 32.5 pilot instead of the 30, and a 470 main to replace my current 460 but it is getting closer. It's amazingly finicky on the jetting, I don't really have any experience with jetting as all of my other bikes tend to run fairly similarly, summer to winter, sea level to mountains. By the time I get this right I may just be a jetting guru

This bike is a ton of fun but I have to say if I didn't have Kelly giving me jetting tips to help me get closer to the correct jetting this would have been a very disappointing experience. Too bad Husky doesn't do a better job with their power up jetting, or if the bikes are this finicky they could have at least included a wider variety of jets in the power up kit.

I remember when the four strokes mx bikes came out years ago you used to always hear people say that while they didn't feel as fast, you actually went faster on them. That is probably true, but since I'm not racing I am having a ton of fun "feeling" like I go fast on my little 125 once it gets up in the powerband. It corners so well (and I corner so poorly) that every time I hop on someone elses four stroke I end up blowing corners on it. To everyone whose bike I have thrown off the trail recently, please accept my apologies. I'm working hard to break the habit before I break any more bikes

Kelly,

I have ordered several different springs for the Power Valve govenor. I believe the stock spring is supposed to have about a 60lb per inch rate(~23 lbs to actually open the pv all the way). I have ordered springs that vary between 30 and 55 lbs per inch rates. They should be here tomorrow or Wednesday and I will report back on pv opening rpms respectively.

I have done as much with jetting as I can for my elevation and while it is better, it still has the bog. I spent a lot of time this weekend with an airstrike PWK(I have a huge variety of jets for those carbs). No matter what combination of jets/needles it never really ran any better than the TMXX with the best combination that I have. I am pretty sure that the bog I am experiencing from ~6500 rpm to ~7700 rpm is related to the pv not opening in a progressive manner. Mine goes from closed to wide open in about 50 rpm(really hard to gage this accurately because it revs so fast).

All my jetting changes helped raise the mid-range pull and nothing I did helped the upper end of the bog(this is why I believe it is a pv spring rate issue). I had the needle and main jet both collectively and seperately rich and lean with no effect on the upper bog.

One thing I am a little irritated with is the inability to find alternate needles for the new TMX. I can find part numbers but no availability The new TMXX works far better than the old TMX and is on par with the airstriker pwk from my seat of the pants gage. OBTW the 38mm pwk is overall about 1/2" wider than the TMXX. The intake boot was able to take this for my experiments but I wouldn't want it like that long term.

Walt

PS. Did I mention that working on the WR125 is an absolute joy. I love tinkering and this bike just makes it so easy to access almost everything.

Have you looked at needles for a yz125? It sure looks like the same carb.

NWRider,

It is the same carb as on the 09 YZ 125, however if you try to buy a needle for that from them there are only two available. 6BFY42-73 and a 6BFY42-74. The stock needle in ours that it won't run with is the 6BFY43-74. These needles have essentially the same taper and only one mm difference in length. My kit needle that works fairly well is a 6DEY15-74. It has a much steeper taper and is richer at all positions than the stocker.

Kelly,

I wonder how much your pipe and SA effect the running of your motor. Oh ya we are supposed to get new pipes. When I first was jetting mine I tried it with the #5 slide, but wasn't getting anywhere with the bog. I had better luck with the #4. At this point I am going to put off doing more jetting work until I experiment with the PV springs.

Keeping the faith I can get mine to run like yours.

Walt

I am surprised there are only 2 needles for such a popular bike. I guess that is the advantage of the Keihin, lots of needles.

I wonder if JD makes a YZ needle.

NWRider,

They list about 10 but they are all on back order except those 2. This is similar to what you find when you go looking under Mikuni carb part sites. I find it amazing that Mikuni puts out a carb that is OEM equipment on a popular model like the yz 125 and then doesn't follow up with availability for parts and jets/needles. I guess this might be why they lose so much business to Keihin.

Walt