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Test day at the track- KX250 perfection


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I did some extensive testing Friday at the track with some new parts I got. Its the first time I could do some back to back exhaust, reed, and ignition comparisons. Hopefully it can help you out with some purchases. 2005-2007 KX250

Here's a list of the parts I tested:

New OEM reed assembly

Pro Circuit pipe and 304 silencer (new)

Stock ignition vs Pro circuit (jd)

Fmf factory fatty and Powercore silencer

Jetting: I have the jetting dialed. Its so crisp I wanna record it and put it as my ringtone. The pilot was the key. If I went to straight racegas or AVgas I might go even leaner but for now its perfect. The only thing I would experiment with a bit more would be the needle but I haven't had a chance to get a hold of a leaner one yet. So far it feels spot on.

Bike: 2007 KX250

Pilot- 40

Needle (stock)- Very top pos

Main- 152

AS- .5-1 turn out

Elevation 1100ft 50-60 degrees

50/50 mix Torco 110 and 91 pump, Yamalube @ 25:1

Alright, first of all I wanted to a do a Vforce vs stock test first but when I pulled it I found some cracking and some petals not sealing. Any idea that was the cause of my poor low end??? Hmmmm. Any who I put in a new stock reed cage with the FMF pipe and powercore w/ the JD ignition as my baseline.

1st run: WOW. There is the low end that I was missing! Nice and crisp from the bottom all the way to the top. Better low end and more top end are what impressed me most. Not bad. Too bad I didn't have a fresh vforce to compare.

2nd run (just the 304 silencer): Even better. It looks like the 304 is slightly longer than the Powercore so I expected a little better top end pull, which I think I got and a little more low end. It felt even more responsive. Nice.

3rd run (PC pipe with 304): Now the PC pipe is the plated, not works so I was really hoping it would not beat the FMF. Not a big fan of the plated pipes. The PC pipe is amazing. It was such a noticeable improvement everywhere that I just rode the rest of the day and stopped testing. It was perfect. Low end was great, midrange was fat and meaty and the top end was endless. I really don't know how it can get any better. It was a perfect day. I don't know what else I can say.

Before I got done I put the stock ignition for a quick run just to see how the JD worked. It felt down on power pretty much everywhere. Put it back on and power was back. Gonna keep that thing on. I also have an extra one for sale if anyone wants to try it.

The last test I wanna do is re-ring my RC piston with the TiN coated ring. It should be here in a few days.

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Hey now that was a top notch write up.๐Ÿ‘ I also had a little(read HUGE) reed prob that was fixed by installing the stock reeds/assembly. I had a Boyesen RAD VALVE assembly that had seen better days,although EXTREMELY high miles as this was during a 2+ year riding 200 + miles/week stint,anyway,put stock back in,fired right up and they are still in.

SO. would you believe that I DID NOT even put locttite on the RAD vavle reeds when I put the damn thing in? How the hell did it not take my cylinder out I'll never know but the screws stayed in place. A sinking feeling overcame me when I was taking the screws out to install the new screws that came w/the carbon fiber RAD valve reeds. I must have been in a hurry back then OR probably just ignorant.

Anyways.I too am running a pro circuit pipe,fmf turbine core s/a,and stock gearing @13/47.I was sooo impressed w/my KDX 200 and the lugging that it did in 1st gear that I am almost hesitant to re-install the RAD valve. I will.

It is a little rich right now,clip @#2.Did not seem to run this rich w/the RAD valve set up.

My question,finally-could it be possible that my bike will lean out upon putting the rad valve back in? I was running the clip in the middle w/the rad valve but dropped it one w/the stock reeds because of this new tendency to run a little rich.

I assume it will take a little experimentation anyway and i have become adept at snatching the carb off as well as the top to raise and lower that damn pesky clip.

OH yeah.FRP has the needle that he says clears up the bog when running the air box mod along w/a pipe and silencer.Anyone running this new needle that he offers? If so any comments?

thanks in advance-

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25:1 ? really ?!

Yup. I stay between 24:1 and 26:1 depending on how I feel. No spooge at all.

๐Ÿคฃ

Haha I know right? I wouldn't try a 152 on pump that's for sure.

Hey now that was a top notch write up.๐Ÿ‘ I also had a little(read HUGE) reed prob that was fixed by installing the stock reeds/assembly. I had a Boyesen RAD VALVE assembly that had seen better days,although EXTREMELY high miles as this was during a 2+ year riding 200 + miles/week stint,anyway,put stock back in,fired right up and they are still in.

SO. would you believe that I DID NOT even put locttite on the RAD vavle reeds when I put the damn thing in? How the hell did it not take my cylinder out I'll never know but the screws stayed in place. A sinking feeling overcame me when I was taking the screws out to install the new screws that came w/the carbon fiber RAD valve reeds. I must have been in a hurry back then OR probably just ignorant.

Anyways.I too am running a pro circuit pipe,fmf turbine core s/a,and stock gearing @13/47.I was sooo impressed w/my KDX 200 and the lugging that it did in 1st gear that I am almost hesitant to re-install the RAD valve. I will.

It is a little rich right now,clip @#2.Did not seem to run this rich w/the RAD valve set up.

My question,finally-could it be possible that my bike will lean out upon putting the rad valve back in? I was running the clip in the middle w/the rad valve but dropped it one w/the stock reeds because of this new tendency to run a little rich.

I assume it will take a little experimentation anyway and i have become adept at snatching the carb off as well as the top to raise and lower that damn pesky clip.

OH yeah.FRP has the needle that he says clears up the bog when running the air box mod along w/a pipe and silencer.Anyone running this new needle that he offers? If so any comments?

thanks in advance-

Thanks man! I loved my old KDX, that thing was a rocket for such a little bike. I knew that I would need new petals on the V-force when I pulled it since they had been in there for more than a year. I should have known that was my low end problem.

If you put the reed valve back in I'm not sure what it will do, possibly go leaner or maybe richer. Just put it back in and see how it runs. I had a PC pipe and silencer on my KDX and the thing ripped but I could lug it any gear very impressive bike.

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whats the pro circuit ignition worth. my bike is running preety awsome right now as well. i am running the fmf pipe, diferent gearing. it idles perfect, and is very crisp. i get no spooge. have been running mine at around 40:1. on 94 pump gas with motul.

wouldnt mind tryingt he ignition if it 1s not to spendy$$

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wouldnt mind tryingt he ignition if it 1s not to spendy$$

PC blows them out for $100. I bought one a while back but it arrived DOA. I tried contacting JD in Italy to get mapping software, etc but he never returned my emails. Thankfully PC took the unit back, which was another nightmare trying to explain the situation to an airhead secretary: (chewing gum noises) "ok, sooo like you installed it on your bike and like it didn't work? But it was like new right?"

Oh My effing God! ๐Ÿ‘

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whats the pro circuit ignition worth. my bike is running preety awsome right now as well. i am running the fmf pipe, diferent gearing. it idles perfect, and is very crisp. i get no spooge. have been running mine at around 40:1. on 94 pump gas with motul.

wouldnt mind tryingt he ignition if it 1s not to spendy$$

Sent you a pm

PC blows them out for $100. I bought one a while back but it arrived DOA. I tried contacting JD in Italy to get mapping software, etc but he never returned my emails. Thankfully PC took the unit back, which was another nightmare trying to explain the situation to an airhead secretary.

For the 05-07? I remember trying to get one for my 03 a few years ago for 100 but the 05-07 ones were almost retail. I talked to an engine builder here who has experience with the JD and he says you need to send them back to PC where they take care of the re-map. This was for the 4-strokes so I'm sure the 2-strokes are similar.

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Dude, PC takes them back and that's it. They don't "re-map" anything. Smokers are in the Clearance section unless it's brand new model.

Dude,

How do you re-map? You either send it back to PC or Italy. Which one is it? Whats the use of a programmable ignition when you can't program it?

I did not find any ignitions for the 05+ on PC's website. Do you buy one for your 05 or 98? Did you use it or send it back?

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The unit I bought for my 2000 didn't work when I got it. Dead On Arrival. You can purchase the cables and software to re-map the unit yourself. The only company I got in touch with was in Spain (IIRC) and they wanted the equivalent of $1100 US for the disk and cables. One the bike is like 3 years old they just blow them out for $100 to get them off the shelf (heard right from a tech guy at PC). They don't order in any new ones either, so when they're gone, they're gone.

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