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Motor differences between CRF450vsCRFX450??
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Posted by: rcers---------------------

Ive got 2 friends that both bought 06 Honda 450's.One bought a 450F and the other bought a 450X.The X is alot more tight single track friendly than the F. What are the differences between the 2 motors(Besides happy button)?What can be done to make the F motor like a X motor?Any help or insight would be greatly appreciated.THX

Posted by: big dutch---------------------

there is not much difference its basically the same engine with diffrerent gearing. if u want a 450 x to be the exact same as a 450r all u have to do is cut the pink cord

Posted by: Rich Rohrich---------------------

The R and X 450s are vastly different engines.

Here's the short list of differences :

Big cam timing differences:
<table border="1" cellpadding="2" cellspacing="0"><tbody><tr><td>Intake valve:</td> <td>CRF450R</td> <td>CRF450X</td> </tr> <tr> <td>opens</td> <td>15¹ BTDC</td> <td>10¹ BTDC</td> </tr> <tr> <td>closes</td> <td>50¹ ABDC</td> <td>45¹ ABDC</td> </tr> <tr> <td colspan="3">
</td> </tr> <tr> <td>Exhaust valve:</td> <td>CRF450R</td> <td>CRF450X</td> </tr> <tr> <td>opens</td> <td>55¹ BBDC</td> <td>50¹ BBDC</td> </tr> <tr> <td>closes </td> <td>15¹ ATDC</td> <td>15¹ ATDC</td></tr></tbody></table>

The CRF450X cylinder head has intake valves that are 1.0mm smaller in diameter (35mm vs. 36mm on the R model). The exhaust valves are also smaller (30mm vs. 31mm on the R). The 450X also has a smaller intake port than the 450R to increase the intake velocity which helps part throttle running.

The exhaust system on the 450X has a longer headpipe (688mm versus 662mm for the R), and the internal diameter of the 450X pipe is also smaller (38mm versus 41mm).

The X crank is built slightly different mostly for reliability and the trans gears are a lot beefier in the 450X as well.

Transmission ratios are also different :

<table border="1" cellpadding="2" cellspacing="0"><tbody><tr><td>
</td> <td>CRF450X</td> <td>CRF450R</td> </tr> <tr> <td>1st gear:</td> <td>2.230 (29/13) </td> <td>1.800 (27/15)</td> </tr> <tr> <td>2nd gear:</td> <td>1.625 (26/16)</td> <td>1.470 (25/17)</td> </tr> <tr> <td>3rd gear:</td> <td>1.235 (21/17)</td> <td>1.235 (21/17)</td> </tr> <tr> <td>4th gear:</td> <td>1.000 (19/19)</td> <td>1.050 (21/20)</td> </tr> <tr> <td>5th gear:</td> <td>0.826 (19/23)</td> <td>0.909 (20/22)</td></tr></tbody></table>

The radiators are bigger on the X model and the suspension is sprung heavier and valved differently than the 450R.

I'm sure I'm missing something, but the basics are here. So I guess it takes more than cutting a wire to turn a 450X into a 450R.

Posted by: Vic---------------------

Honda doesn't do anything the easy way.

Posted by: AJ Waggoner---------------------

X to R -
valve and valve springs, cam timing is different,,
exhaust different from header to silencer..
and the airbox is vastly different..
carb jetting is different,
stator/rotor , wiring harness, CDI, susp is differtent, susp linkage rates and linkage are different
actually therte is quite a long list.

all add up to quite a bit of difference in performance
as one is geared at a completely different set of riding conditions than the other.

one isnt "better" than another? just manufactured and designed specifically for different markets and applications?

as posted - to make an R into an X , is a VERY long long away around..towards a specific goal.

it's much more common to want an X to have a bit mote "umph" ??
and to add in some R engine components,
as well as and modify the airbox,carb jetting and exhaust for improved (or mote R like hp) performance.
and yes the mentiuoned wire mod..

this direction isnt so difficult,and an X can be livened up fairly easily..
with just the airbox mod ,electrical mod, and jetting etc.

but honestly to completely change either model ,truly into the other,
is very pricey ,
and not cost effective. (easier to sell one and buy the one you want)

Posted by: AJ Waggoner---------------------

if you have an 450X you want to liven up,
your local Honda dealer should have a *wrench report*
that details the airbox mod , jetting specs, and other suggested things from Honda.

Posted by: HajiWasAPunk---------------------

I don't know squat about mechanics, but I recently rode a 250x and compared to the 250f is was real sled. I thought they were the same other than the lights and and electric start but there are some very noticeable differences in power. I'm stumped as to your statement that the x is more tight track friendly? I would have thought just the opposite?

Posted by: Okiewan---------------------

The 250X vs my 250R is a COMPLETE joy to ride in the tight stuff.

Posted by: HajiWasAPunk---------------------

Okie, I guess you're saying it handled better? I didn't notice that but I'm a novice in every since of the word.

What makes it better in tighter situations?

Posted by: dirt bike dave---------------------

Quote:

Originally Posted by HajiWasAPunk

What makes it better in tighter situations?

I have not ridden either a 250X or an R, but most stock MX bikes lack the smooth power delivery and plush suspension that you want when riding nasty trails.

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Motor differences between CRF450vsCRFX450??

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