trx450r motor vs crf450r

[kazpr]

What is different about the crf that makes it have 10 or so more HP? Just curious as friend was telling me it did. Thanks alot Scott

[Honda]

I posted this in an earlier thread.

I wonder why this is?

I think we need to examine the specs on both motors (TRX vs. CRF) to see what the major diffrences are. Surely thay are not all that different and should respond similarly once modded.

The CRF has a 12.0:1 compression ratio, compared to the TRX's lower 10.5:1.

The CRF also uses a slightly smaller throttle Body at 40mm compared to that of the TRX at 42mm. The TRX's throttle body also incorporates a TPS Switch. More on that in a minute...

The CRF has a Bore of 96.0mm and a stroke of 62.1mm
The TRX has a bore of 94.0mm and a stroke of 64.8mm

I can tell you that after bumping the compression on the TRX to the CRF's high 12.0:1, you will have a totally different machine. More power, and power that works better with the HRC cam, and it will also respond better to mods because of the increased pumping volume. I would put money on it, that with a higher compression piston alone, the YFZ would not be able to pull away from the TRX like we have been hearing.

The Bore and stroke is not a big factor. The CRF will rev easier because of it's shorter stroke and larger bore. The TRX will produce more torque, torque that understandably Honda thought the TRX needed to turn the extra weight and traction produced by two tire's instead of one.

The CRF uses a 40mm Throttle body, that is not influenced in any way by electronic control. The CRF should have better throttle response because of it's smaller bore and the fact that the computer does not really on a TPS to feed fuel into the motor.

I am also wondering whether or not the TRX's power output has been influenced by the additional Emissions systems. That could explain why it does not respond to modification as well.

Overall, I believe the problem lies with the Compression ratio being so low. Honestly, a higher compression piston would really wake the TRX up, and make it more responsive to mods. Why Honda dropped the compression is beyond me. Possibly, they dropped the compression because of reliability concerns, since a higher compression piston would require the motor to be serviced more often, and would make using a high grade fuel necassary. Honda knows we are not going to leave our quads alone, they probably are also skeered as heel of being sued over and over again as they had been in the 80's. I think they designed a great reliable quad for a large majority of people. Honda has produced a foundation which all of us can now build upon. The Legend of the R would not have been such a legend if not for the aftermarket's support.

Now who makes a HCP upgrade?

Class is Dismissed!

[kazpr]

Tks alot honda I am new back to this sport after 9 yrs. About to get my new 450r in a couple of weeks and am so pumped :)

[Honda]

Me too Mang!

My last quad was an 88 250R. That was back in 1991.

Welcome Back!