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Opinion on Jetting & mods

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Hey.. This is for an 05 250x. 1st, lets deal with the mods. I'm not sure what exactly THE 'airbox mod' is. I gather it has something to do with cutting a huge hole in the airbox. I'm not a real big fan on putting these big holes in any airbox. Is this what the mod is ?

Also, I have two options, I can pick up a cheap R muffler(silencer alone) off Ebay or I can just drill out the baffle on the X muffler. I kinda prefer the R muffler cuz it looks better, lighter, and sounds better imho. Which is the better muffler and what are the power differences with each ?

Thanx in advance!

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I have a stock 06 and just did the JD jet kit with the recommended mod to the air box, along with the AP kit as well. I did a 50+ mile single track ride this past weekend and all I can say is WOW. I'm just sorry for waiting so long in doing this mod. The bike is just so much more fun to ride and eaiser to control.

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I have a stock 06 and just did the JD jet kit with the recommended mod to the air box, along with the AP kit as well. I did a 50+ mile single track ride this past weekend and all I can say is WOW. I'm just sorry for waiting so long in doing this mod. The bike is just so much more fun to ride and eaiser to control.

On your 06, what jetting did you go with?

Also, what mod do they recommend for the airbox, and were can I find pictures or something like that describing the mods?

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crf250X 14,

try this... place a straw in your mouth (this will be the only way of breathing) plug your nose with a clothes pin and start to run... in a VERY short time you will be gasping for air... this is what we call 'lean'.

If we were to give you a bunch of straws or better yet, one big straw, the air you require to run efficiently would be available to you on demand.

This is the idea of 'opening up' your air box. If you research the 'R' air box you will see there is a huge difference in how they operate (the 'R's being much more 'open') As long as the air filter is snugged up securely to the carb you will do NO damage to your machine... it will be like giving it a nice big straw!

Van.

please do not actually try the above mentioned breathing experiment with a straw... I don't want to read in the captions 'Man suffocates with straw in mouth':applause:

later... later...

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Ok, I will be controversial.

We have a Closed Course modified/JD-kitted/pro-circuit ported 250x. My brother has a stone stock 250x.

Stock isn't so bad, really. In fact, his stock bike has MORE bottom end snap off idle than my modified bike. I do prefer the modified bike overall, and it does have more kick in the mid-upper range. Still, stock is pretty decent for a stock, quiet 250F off-road bike. Also, his bike 's air filter stays clean for about 3X longer than my bike. (I also note that dirty filters and dirt getting into the intake is sometime blamed for the early model valve issues.)

Overall, I would recommend stock for trail riding, and modified for racing... just like Honda says.

Lastly, "drilling" the stock muffler wont help performance. It will just "sound" faster due to higher decibels.

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Ok, I will be controversial.

We have a Closed Course modified/JD-kitted/pro-circuit ported 250x. My brother has a stone stock 250x.

Stock isn't so bad, really. In fact, his stock bike has MORE bottom end snap off idle than my modified bike. I do prefer the modified bike overall, and it does have more kick in the mid-upper range. Still, stock is pretty decent for a stock, quiet 250F off-road bike. Also, his bike 's air filter stays clean for about 3X longer than my bike. (I also note that dirty filters and dirt getting into the intake is sometime blamed for the early model valve issues.)

Overall, I would recommend stock for trail riding, and modified for racing... just like Honda says.

Lastly, "drilling" the stock muffler wont help performance. It will just "sound" faster due to higher decibels.

That's exactly what I why i don't really like the airbox mod..cuz of the dirt. I guess i'll do it though, maybe not as much though.

As for the muffler, so if the stock drilled makes no difference in performance, does the R muffler do anything? And also if anyone knows, can the R dual mufflers fit on the 250x ?

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Drilling the stock does make a difference.

The R twin cans will work but with extensive mods, subframe, remove battery, remove overflow tank, change rear fender and side panels and airbox. Probably the whole thing would cost more than $ 2000...

2000=big NONO..lol What is the difference when ya drill the stock other than sound ? And what about the R muffler ?

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I don’t have the 250 x but. On my crf 450r if I put my DB reducer in my muffler it chokes my bike. It run way better with it out "same as a baffle" I think the 05 crf 250r muffler should work it’s a single pipe. Not 100% sure?

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The sound doesn't really increase but the flow rate does. Allows the rpms to build much faster, feels alot snappier (if that's a word).

I don't know much about the R muffler. Is it a free flow muffler? Which gives better performance, X drilled or R?

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I am wondering if someone (Agent? or anyone else...) could place in order the modifications needed to make a 250X a top performer. I would hate like heck to have a fellow rider spend $ on a muffler without doing anything to the carb/air box for performance. I have long been a proponent that when doing carb work, the air box is a must do! Here's the way I see it in order of priority...

1) Re-jet/air box

2) Accelerator pump (AP o-ring)

3) Cam

4) Exhaust system

You could stop after #1 and see a huge power gain... 2, 3, and 4 will give you slight to moderate gains. Everyone wants to mod out their X for performance (to be like a race bike ®) but doesn't realize how the R actually runs. They have relatively the same engine (different tranny... etc) but here you go

Stock 2005 250X // pilot jet 40, main jet 130

Stock 2005 250R // pilot jet 42, main jet 172

Same carb // Keihin/FCR-MX37

The other main difference is the... A I R B O X

My bike went from a nice machine to a ripper after the JD mod and Hotcam... and I only ride trails and hares... IMHO

Van.

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aftermarket pipes are more hype than anything else.People think is an easy way to get hp when all it does is move it around the curve.Like Smith said,your not gonna gain anything through a pipe without doing the other mods that benefit a pipe.An aftermarket pipe is only icing on the cake to a properly tuned and jetted bike.Halen, your right in your list of beneficiary mods.

With my bike jetted and ccc mods the 05R pipe made everything come together and only cost 75.00.The X can is a baffle spark arrester designed pipe.That means wither or not you drill or remove the whole baffle it is still a restrictive pipe.But a great pipe for what it is meant for.The sparky will never burn out.

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I suggest this order of mods to the 250x:

1st. airbox mod and JD kit w/AP "o rings" and a ZIP TY fuel screw.(this is an all in one mod)

2nd. radiator guards (flatland)

3rd. skid plate (flatland again)

4th. bark busters ( acerbis are good and reasonably priced)

5th. better tires front and rear

6th. suspesion tuning to fit your weight/ riding terrain.

7th. riding lessons to get the most out of the AWESOME bike you just built!!!

8th. buy a display case for all your trophys!!

Just my .02:thumbsup:

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8th. buy a display case for all your trophys!!

Dad, how are you gonna get trophies if you're riding in the same class as me this season? :applause:

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Ok, time for Part two of the thread. I'm gonna get the R muffler and open up the airbox. What is the correct jetting for me. I'm not gonna buy the JD jetting kit. I'm gonna just nuy individual jets(cheaper). But which ones.

I ride from 0 - 7,500ft. in 60* - 100* temperatures.

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Agent Smith is right.With my R pipe and air box mods I ran the same thing he say's except for a 155 main.Thats just what I started with and never tried any thing bigger or smaller.My air screw ended up being 1 to 1 1/2 turns.

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Don't forget, you can start at the 2 turns out position, but need to tune it for different elevations, temperatures. I turn the idle up a bit, then turn the Koube T-handle down until the bike stumbles, then I turn it back up for maximum rpm and then just a bit more, and reduce the idle. The real way is to stop it when it first stumbles, and count the turns in, Then start it again and turn it up until it stumbles on the other end. Turn is off and count the turns in again. Then set is somewhere in the middle of the two measurements. It should fire right up like mine does. When cold, I give it 5 turns of the throttle before hitting the E-button, and it fires right up. :applause:

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Where can I order these parts for cheap ? Which main should I use if I don't get the needle ? According to Rick Ramsey, i thought i should be running a 132 main jet..

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