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New Top end with HC piston ride report.

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After 92 hrs of riding on original top end and 1 minor valve shim @ 70 hrs, I freshedn up the top end. the new parts consisted of a JE Hi Comp piston, 5 valves and springs (old were still in spec from previous shimming), cam chain, clutch springs. Also new was the DLR Cycleworks head work which involved a 3 angle vavle job and minor flow work to remove casting flaws in both intake and exhaust. The verdict: a different bike.

The flow work changed the jetting requirements. the jetting was much too rich. I dropped 1 MJ size and leaned the needle out 1 clip and leaned the F/A screw. I think I need to lean the PJ out 1 more as it's still feeling a little fat right off the bottom.

The piston has given the bike the ability to jump farther on jumps right after a hairpin corner. Previously, I needed to hit the same corner perfectly and clutch bike heavily to clear jump. Now, I can make a minor mistake on corner and roll the throttle on and clear this jump. I was concerned about the new piston impeding the motor's ability to rev thru the rpm's. Early on in the day this was playing true but that was due to the fat jetting. Once that issue came around this thing pulls thru the rev's perfectly.

In summation: if you get a little tired/bored of your current bike, do some major mod's as this will change the personality of the bike enough to make it feel like something completely different and it will cost much less than a new one.

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sounds good chris.

what CR are you supposed to be at now?

what fuel are you running?

what clearance is the piston in the bore at?

what pipe is on the bike?

let me whisper "vortex" in your direction. :thumbsup:

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Yet another person judging some ones riding ability without even seeing them ride. :thumbsup:

AGREED!!!

I think it's great OLDNBOLD! My 03 is coming up on the need for some top end work and this just may be the route I go as I have moved to Colorado from Georgia and the poor little thumper lost some of it's pull just from the altitude change. I think this would be a good alternative to a 450. Thanks for the report.

OWENLO :ride:

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AGREED!!!

I think it's great OLDNBOLD! My 03 is coming up on the need for some top end work and this just may be the route I go as I have moved to Colorado from Georgia and the poor little thumper lost some of it's pull just from the altitude change. I think this would be a good alternative to a 450. Thanks for the report.

OWENLO :ride:

Or you could just buy a 2006 YZ450F, that people says FEELS 20 pounds lighter than a 250F and you would have more power than a 250F with some motorwork at a high altitude. Then you could write a ride report comparing the two bikes. See and it would be a win-win situation. :thumbsup:

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After 92 hrs of riding on original top end and 1 minor valve shim @ 70 hrs, I freshedn up the top end. the new parts consisted of a JE Hi Comp piston, 5 valves and springs (old were still in spec from previous shimming), cam chain, clutch springs. Also new was the DLR Cycleworks head work which involved a 3 angle vavle job and minor flow work to remove casting flaws in both intake and exhaust. The verdict: a different bike.

The flow work changed the jetting requirements. the jetting was much too rich. I dropped 1 MJ size and leaned the needle out 1 clip and leaned the F/A screw. I think I need to lean the PJ out 1 more as it's still feeling a little fat right off the bottom.

The piston has given the bike the ability to jump farther on jumps right after a hairpin corner. Previously, I needed to hit the same corner perfectly and clutch bike heavily to clear jump. Now, I can make a minor mistake on corner and roll the throttle on and clear this jump. I was concerned about the new piston impeding the motor's ability to rev thru the rpm's. Early on in the day this was playing true but that was due to the fat jetting. Once that issue came around this thing pulls thru the rev's perfectly.

In summation: if you get a little tired/bored of your current bike, do some major mod's as this will change the personality of the bike enough to make it feel like something completely different and it will cost much less than a new one.

Good write up. I know when I put a Hi Comp Wiseco in my wifes bike she noticed the bike pulled alot harder all the way thru the power curve. I had some jetting issues after the piston swap too. I finally got a JD jet kit for it and all the jetting problems went away.

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i too love my HC piston, though i went with the single ring wiseco.

I think this would be a good alternative to a 450.

never will a 250 come close to the torque a 450 puts out....never

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There you go... Tempting me! Now you have only added another reason for the jump to the 450, A ride report. Now if I can only convince my wife of that. HAHAHA!!!

I know the 450's are hard pulling MONSTERS due to riding my buddies CRF450. I just like how easy it is to ride the 250's(not always holding on for dear life). I am still tempted though. HHMMM???

OWENLO :thumbsup:

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Did you measure the piston? I am curious if the JE piston has some slop. Piston cylinder clearance?

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#1 its not a 2smoke u only have to rebuild topend once every 1-2 years OR MORE

#2 it sounds like you need to start ridin some more and stop moddin out the bike for no reason

then ull be able the clear the same jump with a bone stock bike :thumbsup:

I have just taken ownership of a brand new 06 250f... because i race and power is half of the equation i have installed a high comp piston, shaved the head and a better cam in the bike. Not to mention vortex ignition and a w/b pipe. While the above loser thinks you don't need to rebuild them i have the opinion of if you want to win races you need to have the best available bike.

And as for the mods... keep doing it you will learn to get faster around the track because of the extra horsepower!..

Clearly big blue rider is a 2 stroke bandit.. and the saying goes "riding a 2 stoke is like riding a fat chick, only fun until your mates find out"... !! :ride:

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sounds good chris.

what CR are you supposed to be at now?

what fuel are you running?

what clearance is the piston in the bore at?

what pipe is on the bike?

let me whisper "vortex" in your direction. :thumbsup:

supposedly 13.5 :1 (DLR did all the work and he mic'd it to compare with stock and could find no noticeable diff in the piston vs stock. I have no idea where the extra compression is coming from)

fuel: pump 93 octane

piston to bore clearance unknown ( I didn't ask DLR what it was and I don't know if he checked)

pipe: CHM P4-R

gearing 13/49

temp 95+, 60% humidty, 600' ASL

What's been whispering in my ear is "Subtanks, subtanks, steering stabilizer, steering stabilizer....)

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Did you measure the piston? I am curious if the JE piston has some slop. Piston cylinder clearance?

I know I had a hard time getting a HC piston from both Wiseco and JE. I tried for about 3 weeks with both companies saying the latest and greatest was on backorder indefinetly. I had to settle for last week's latest and greatest from JE. Both compaies were havin problems in their production of the newest piston. The area they were trying to save weight from was causing problems in the production process.

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I don't race motocross but I race in the woods.Just got through installing sub-tanks & steering damper.All I can say is-- WOW! Ruts & chop are gone! Wonderful stuff.

Ahhhhhhhh, you're killing me. These voices are getting stronger.......

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I know I had a hard time getting a HC piston from both Wiseco and JE. I tried for about 3 weeks with both companies saying the latest and greatest was on backorder indefinetly. I had to settle for last week's latest and greatest from JE. Both compaies were havin problems in their production of the newest piston. The area they were trying to save weight from was causing problems in the production process.

I'm in Australia and got a Wiseco high comp for my 06 and man is it worth the money over the standard one!... I replied earlier and did similar mods and this bike has heaps of power to burn compared to my moded 03!!

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