CRF's Only Forums

hey guys,

I have an 05 450r that i recently decided to tear down and do a full build like i have always wanted, the motor originally only had a 12,5:1 wiseco and a slip on (fmf).

On this run i was looking at a hod rods complete bottom end kit, 13.5:1 wiseco, goin with stainless steel intake valves, head porting, a stage 2 hot cam, and full fmf exhaust with a megabomb header. Now i need somebody well informed to give me their opinion on that combo and answer a few questions here. (if you got a few minutes)

when i get the stainless steel valves installed will the machine shop have to do seats as well? how do you think the stock clutch will hold up here? With all the mods here are a new tensioner and timing chain gonna be smart to do as well if they have never been replaced. and if yes would it be better to go with an oem tensioner or an after market mechanical tensioner?
and any other warnings or tips for this build i would appreciate, i'm a mechanic but i don't work on bikes for a living.

thanks.

Welcome to CRF's Only.

The megabomb is an excellent header and will mate with the FMF slip on you have.

The Hot Rods bottom kit is excellent and contains the main bearings and all the seals and gaskets you need to do the install.

The Wiseco is a good piston and the increased compression will increase power everywhere.

The SS valves will increase the valve durability over the stock valves. I recommend the Kibblewhite brand. Also, you must have the valve seats professionally cut to maximize performance and valve durability. We offer these services as well as performance porting.

You should consider upgrading to a 2007 CRF450R head. This has superior porting and is a better place to start when porting. The reason is Honda increased velocity flow by decreasing port volume. So, increasing port volume of a 2005 head, while improving performance of the 2005 head, won't approach the performance of the 2007 head. If you can only afford one or the other, get the 2007 head. We offer the '07 head with KW stainless valves installed with our performance CNC valve seat blending and port bowl work. Much of the performance gained from a port job is above the valve guide in the port bowl and valve seat.

On the cam, I would need to know more about what type of riding and skill you have to make a recommendation.

Stock clutch will be fine if it's within spec.

I do recommend replacing the cam chain if it has a lot of hours. Like any chain they wear and stretch. since the cam chain is what keeps everything from colliding it's cheap insurance.

The manual cam chain tensioner we offer is recommended for all motors. Again, cheap insurance.

While you are doing this motor work, consider updating teh carb with the updated AP kit and replacing the floating valve seal on the slide. We have how-to articles for both:

http://crfsonly.com/howto/keihin-fcr-ca ... rf450r.php

http://crfsonly.com/howto/keihin-fcr-ca ... rf450r.php

Also, replace the plastic hot start nut with the Pro Circuit/Zip Ty we stock. It's not necessary but makes servicing the carb much easier and prevents a damaged hot start from causing ride time issues.

http://crfsonly.com/howto/keihin-fcr-ca ... rt-nut.php

Ken

Ken,

Thanks again for the info, i guess this brings up a few questions. So a ported 05 head still will not flow as well as an 07 head is what i'm getting here correct? How well do the parts in my list hold up? I want performance as well as durability. If the durability is compromised here are there any changes you would make to the parts list?
As far as my skill level i am an intermediate rider, mostly splitting my time between trails and track depending on who i'm riding with that weekend. the only reason i selected the hotcams stage 2 is i saw the most significant gains across the board on hotcams website dyno charts. what cam would you recommend?
now looking at the 07 had assy's on the site those come with all oem stainless valves right?
When breaking a motor in like this with everything new is there a special way beside the 2000 rpm for 20 minutes method to break the cam in? just a lil nervous with all the new parts in there then having to do this for the cam, any suggestions?

thanks again,
Brandyn

the '07 unported head will perform better than a '05 ported head for most all requirements. so, if you can only afford one get a new unported '07 head. then when you can afford porting you'll be starting with a better performing head.

the parts on your list are very durable. the main durability issue is with the valves and stainless steel valves with the seats prepared the way we prepare them will provide maximum valve durability. also, it's critical the KW stainless valves be installed with the KW spring kit, seals and new cotters(keepers). if not, durability will suffer significantly. the piston and crank you selected are just as durable as the stock components.

the hot cams is a good cam and would work well for your riding and durability goals.

the '07 R heads we offer come with either the KW stainless valves or the TRX OEM valves. personally I prefer and recommend the KW valves. these are designed for the higher rev limit of the CRF450R. the TRX spring package is designed for the lower rev limit of the TRX.

when breaking in a motor with these new components, or a brand new motor, the method is the same. your primary purpose is to seat the rings. so, follow the method listed in our how-to section.

ken