High comp piston vs. std in a CRF450R

[Spokes574]

I am getting ready to install a piston in my Y05 CRF450.
I was thinking about adding a high compression piston but am a tad bit confuse.

-Are there diff. compression options for high compression pistons?

-Is pump gas going to be required?

-How is jetting affected?

-I heard I would lose top end?

-Is it worth it? How is the overall power? I would preffer lots of power in 3rd so that I can essentially just leave the bike in 3rd all day long.


what do you think?

Spokes574

 

[Rich Rohrich]

The CRF450 LOVES compression, and makes great torque in the mid range with it. If the bike is jetted correctly you should be able to run pump gas all the way up to 13.5:1 compression. The exception being hot dry desert type conditions. Those dry 95+ degree days would require some help on the fuel side.

Most riders can't tell the difference on the top end, but they notice the roll-on torque changes.

Jetting is too bike specific to be able to say which way it will go for sure, but it is common to be able to lean the jetting a bit with an increase in compression.

Overall it's money well spent.

 

[cthowards]

I too am in the process of installing a new piston, rings, Kibblewhite valves and springs, etc.

Do you have any specific recommendations on the brand of high compression piston for the CRF450?

Also, will the Kibblewhite valve and spring setup have any noticable impact (reduction) on horsepower?

Thanks!

 

[Rich Rohrich]

I too am in the process of installing a new piston, rings, Kibblewhite valves and springs, etc.

Do you have any specific recommendations on the brand of high compression piston for the CRF450?

JE & Wiseco both have high quality kits.

Also, will the Kibblewhite valve and spring setup have any noticable impact (reduction) on horsepower?

Most people see an INCREASE in high rpm power with good quality valves and springs like the Kibblewhites because the valves close properly instead of bouncing on the seat and bleeding off cylinder pressure.

 

[cthowards]

Thanks Rich.

I am going to have a local shop install the valves and springs and inspect the seats, etc. I already have the Kibblewhite valves and will be purchasing the Kibblewhite springs. The shop indicated that I did not have to go with the Kibblewhite springs but that they could offer alternative springs that would not rob horsepower or cause the valves to slam against the seat.

I believe the shop to be reputable, but they also have a MX race team so perhaps they push for maximum performance and not so much for durability (which is what I'm looking for). In any event, I am convinced that the Kibblewhite valves and springs are the way to go. Thanks for being so firm and consistent in your recommendations as it seems as though it is very easy to get lead in the wrong direction on what valves and springs work best.

 

[Rich Rohrich]

Thanks Rich.

I am going to have a local shop install the valves and springs and inspect the seats, etc. I already have the Kibblewhite valves and will be purchasing the Kibblewhite springs. The shop indicated that I did not have to go with the Kibblewhite springs but that they could offer alternative springs that would not rob horsepower or cause the valves to slam against the seat.

Do yourself a favor and use the Kibblewhite springs and retainers. Make sure they cut the seats. I've taken apart well over a hundred CRF heads and I've yet to see one that DIDN'T need a valve job, and that includes a few new cylinder heads.

If the seats are properly cut and the parts are installed correctly I think you'll find the Kibblewhite stuff to be an excellent value over the long haul. :cool:

 

[oldrnyzr]

Buckets

Rich..... allong the same lines, do you still recommend changing the lifters to Kibble as well....???? :nod:

 

[Rich Rohrich]

On the CRF450 you don't need to change the buckets unless there is abnormal wear. The Honda buckets are very well made and most riders will never break one. For pro level Dirt trackers and SuperMoto guys who see lots of sustained high rpm running the Kibblewhite buckets are good insurance.

The RMZ/KXF 250s are the only bikes that you have to run hardened buckets with the stainless valves and springs. The OEM buckets are known to fail even with the stock springs and valves on RMZ250s.