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
Motor differences between CRF450vsCRFX450??
- Thread starter rcers
- Start date
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.;)
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.;)
AJ Waggoner
Crash Test Dummy
- Nov 5, 1999
- 4,368
- 34
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)
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)
AJ Waggoner
Crash Test Dummy
- Nov 5, 1999
- 4,368
- 34
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.
your local Honda dealer should have a *wrench report*
that details the airbox mod , jetting specs, and other suggested things from Honda.
HajiWasAPunk
Member
- Aug 5, 2005
- 807
- 0
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?
HajiWasAPunk
Member
- Aug 5, 2005
- 807
- 0
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. :nod: What makes it better in tighter situations?
dirt bike dave
Sponsoring Member
- May 3, 2000
- 5,349
- 3
HajiWasAPunk said:
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.
