2007 vs 2009 YZ250F Jetting

Long story short, I had my 2007 YZ250F recovered this fall after it was stolen over 2 years ago.  In the meantime, I bought a 2009 YZ250F and was happy with how it ran on stock jetting and adjustments on the fuel screw.  After I got my 2007 freshened up enough to ride, I can notice better power/response above 1/2 throttle and an overall free-er revving engine compared to my '09.

 

Judging by the condition the stolen '07 was in when I got it back, let's assume everything is still the same as it was 2 years ago... stock (but I do need to check).  Valves are on the tight end, but in spec.  Fresh gas in each bike.  The '07 is louder and could use new exhaust packing, but not ridiculous.  My '09 has ~80 hours on it.  My '07 had about that many when it was stolen but the hour meter was ripped off of it, so no clue how many are on there now.

 

The only difference in jetting specs in the manuals is the needle and clip position.

NFPR, clip 5 on the '07

NHKR, clip 4 on the '09

 

I'll probably sell the '07 eventually, disclosing what's happened to it, but I'd like to get my '09 running just as well first.

 

Location: Iowa

Elevation: 1000 ft

Main: 178 (on both)

Pilot: 42 (on both) at ~2 turns out

Leak Jet: 70 (on both)

Riding Style: Low B Class, Hare Scrambles, some MX riding

 

Correct me if I'm wrong, but I don't think there were any engine changes between these years other than going from a 12.5 to 13.5 comp ratio piston, which should help the '09 if anything, right?  So where should I start on my '09?  I'm thinking drop the needle (then test), swap needles (stock positions, test again), drop leak jet size and tune AP circuit (and test again), but what are your thoughts?

 

Thanks.

Edited by yz250f_spud

my first thought is a hi comp piston gives more snap in the bottom end but a low comp one will rev freer in the hi end.

why not try the 09 out with the 07 needle in it?

Actually there were a lot of changes to the '08 motor/frame, and suspension.

The '09 just had more refinements.

 

 

The newer motors are better for race pace, but are actually a tiny bit slower (stock).

The older head has a more aggressively ported head.

 

You need a 50 leak jet, an upgrade apump linkage spring (merge racing or tokoyo mods) and it will wake up dramatically (either bike)

you say the 07 was freshened up?  does that mean fresh topend?  mention it because 250f's always run better freshened up even if you didn't think it needed it.   With a new top end on your 09  it may feel better?

my first thought is a hi comp piston gives more snap in the bottom end but a low comp one will rev freer in the hi end.

why not try the 09 out with the 07 needle in it?

Makes since, and mirrors what I feel on the bike pretty well.  I found some info on the needles in the manual.  The two needles are the same, except the one is a 1/2 clip richer/leaner.  

 

You need a 50 leak jet, an upgrade apump linkage spring (merge racing or tokoyo mods) and it will wake up dramatically (either bike)

I have a 50 leak jet that I can add, and I am familiar with the O-ring mod.  Just wanted to make sure I wasn't missing something else first.

 

you say the 07 was freshened up?  does that mean fresh topend?  mention it because 250f's always run better freshened up even if you didn't think it needed it.   With a new top end on your 09  it may feel better?

By "freshened up" I meant I repacked every chassis bearing, changed all fluids, filters, replaced broken parts, and overall cleaning.  It was in pretty rough shape when I got it back.  The valves were in spec which is usually a good indicator of engine condition, so I didn't bother to go any farther into the engine yet.

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