hey dudes (and dudettes),
I figured I better write this while it's all fresh in my head. There were some interesting things, I'll try to remember them all.
First I'm pretty sure it was a Dynojet 250.
Next, we did the stock run (with Boyesen water pump cover and impeller- more on that later). Turned up 29.6 hp, 17.2 ft/lbs of torque. Not too shabby. Less than what the pipe vendors say as stock figures, but hey, what the heck. Then put the M4 pipe on, it jumped to 32.2 hp, 17.5 ft/lbs of torque. We did no jetting changes; in fact, the bike ran a little bit rich on the main with the stock pipe, so adding the M4 pipe put it right where it was supposed to be. The best part was that it made more for way longer. It mimics stock midrange, then after about 8 grand it just keeps going up (where the stock just kinda gains less hp more slowly until about 11 and then starts tapering off). We didn't actually have a space shuttle there for comparisons, but it was pretty loud. Then again, so was the stock pipe! Both of them you could feel in your chest. We wore noise-headsets. Outside the dyno room I heard a pull with the M4 and it sounded rad.
Here's an interesting tidbit; the dude likes to run the bike until it starts making LESS hp. I guess it has something to do with finding "real" hp numbers, I don't remember the specifics. Anyways, he was mercilessly doing pulls, and he's like "what's up with this thing? Are you running some kind of synthetic or something?" I'm like "no, why?". He says he can hardly get it to get hot and lose power! I told him about the Boyesen water pump cover and impeller, and he says it's doing it's job!
On that same topic, he says he will sometimes see 1/2 hp increase in power from using synthetic oil. He highly recommends AmsOil synthetic. I have some, and now I can be fairly well assured my bike is broken in! I'll use it next change.Anyways, I have to say, time was terribly limited. I asked for their least busy day, and I got unlucky, it was a zoo. I was bummed, but got limited dyno resources. So I could only add the Vortex to the M4 and see what it would add.
So anyways, I have mixed reviews on the Vortex. Well, first, it does add power, almost 1 hp (.8 according to Hitman Motorsports dyno in St. Paul, MN, http://www.hitmanmotorsports.com). With the M4 pipe at 32.2 hp, the Vortex jumped to 33.0 with the Vortex set to #5 (trail, one of the "closest to stock" settings). With it set at it's default setting (Power), it made 32.9. Consistently. It was very strange. Maybe my switch is backwards, where the top setting is the "whatever you chose on the box" setting. I dunno. We were very short on time. I would love to get more dyno time to test the other settings to prove this point. Maybe it would be better with a modded motor, dunno, maybe Power is a rad advance or something that my basically stock motor can't use, whatever, #5 put out more power (.1, very measly) than the Power setting! Sucky. Wish I could switch those two now. Anyways, don't jump to conclusions, maybe I had my switch hooked up backwards or something so that was the power setting. I dunno. Clearly more investigation is needed. Either way, the Vortex definitely does make more power (almost 1 on my bike). Would love to have tried traction as well.
Anyways, one thing I can tell you I learned about her jetting was that it was always super lean right when he wacked the throttle open from way down low (3K or less). It would almost die. He thought it was because the carb on the '03 YZ250F is a flat-slide, and wacking it open too quickly floods too much air. He says that's why you need to roll it on. I agree, it worked better when he did that, and if it's true, it makes sense, I have to do that on my roadrace bike with flat-slides. However, I'd like to just try a richer pilot jet just for kicks to see if it would richen it up enough to make up for that. He's probably right, the pilot won't help, but there's just certain things you've got to find out for yourself. On the air/fuel ratio meter, way down low when he'd first get on it, it would spike super lean. You be the judge. I am going to try to add a richer pilot jet. From what I hear, people are doing that anyways. I can't tell you yes it worked or no it didn't due to limited dyno time, but I am already making a list of what I need to do next time! Hopefully I can prove I did the right thing, otherwise I can prove I was wrong!
Anyways on to the PowerNow. Once the subframe was off, installation was a breeze. Just took a few minutes. Beautiful piece.
That's about all I can tell you about the PowerNow. This is where I start getting confused. It seemed like it made the main slighty rich (still lean spike way down low when he'd first open it up tho, like before). Even with my M4 pipe and Vortex, I think I could have gone down a size on my stock main. Lacking the time to do so, I can't tell you how it all worked out in the end. I'm hoping to continue this chapter in the book called "My 250F" another day. Very tired after 10 hours today! Anyways, this wasn't something you could feel on the dyno, he really couldn't let it drop below 3 grand, and then he'd always try to get it wide open as soon as possible. You can't feel throttle response on the dyno like that. So I need more "real-world" testing in that venue. It did start like a champ tho. I think I am going to drop my main a size and up my pilot a size and see when I can make another appointment!
Also note that it is cold here in MN, about 20 degrees outside. We opened the door when we dyno'ed (just a small "human" door), so it dropped to around 55-60 or so I would guess (maybe down to 50). So while my jetting was just fine for that weather, if it gets above 80 I would want a 1-2 size leaner main jet (1 if no PowerNow, probably 2 sizes if using the PowerNow).
here's a pic of the dyno sheet I walked away with; stock, M4, M4+Vortex: http://12.218.13.249...YZ250Fdyno2.jpg
Sorry not more info! Maybe more next time.
