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the '05 head on the '04

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so the '05 head bolts right on to the '04? if you do this conversion, what else should be changed? ignition? jetting?

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well if you get the 05 head and your getting the 05 head you would need to change the ignition for sure. not sure of the jetting but you might also need a new rev box.

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just put the 05 head on your 04 use the 04 cam thers no need to change the ignition .the 05 heads look just like the 04 heads that i was filling in and reporting ,they just dont flow as well but with the reduced cross section of the port it will help your low to midrange power.

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I will be getting the 05 head.But in the mean time i took off the head and decarbonized the valves(which have no ware)And decarbonized the ports and polished them.Came out pretty good.Is there such a thing as too smooth?.

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I'm not sure so I'd like to hear what RHC or Rich has to say about this, but I think you only want to smooth out or polish the exhaust ports. The intake ports should be rough (i.e. 60 or 80 grit coarse cartridge rolls) to create turbulence and mix the air/fuel better.

BTW, I am also going to be putting an 05 head on my bike and decided to try and port my 04 head for fun using tips from mototuneusa.com

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thanks for the comments....i think it would be interesting to see how the '05 head alone with the '04 cam and ignition would change things. maybe you'd have lots of bottom and top?i think i'll try it when mine wears out.

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It would be cheaper to send your 04 head to Eric Gorr and get it ported.

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So would it be less costly to buy an '05 head and have it ported or just have an '04 head ported. I'm talking about an extensive port job.

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So would it be less costly to buy an '05 head and have it ported or just have an '04 head ported. I'm talking about an extensive port job.

Which head to go with would depend entirely on the type of power you are looking for.

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For sx/mx I would like more hp from 6500 on up but I would prefer not to give up much more low.( Dr.D cost me a little) I don't want a narrow peaked max hp. I would still like to keep a fairly broad power band that pulls harder and farther.

As far as the '04 vs. '05 head I thought it might be more economical to purchase and flow the '05 than to fill and shape the '04.

How about some specifics from the builder/tuners what effect would a extensive port job have on hp throughout the powerband?

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You can find a lot of info on 4 stroke Porting vs. Oversizing vs. Stroking and all the combinations there of in the CRF 450 and 250 index. Most of it is written by the knowledgeble guys that do it for business.

Usually the ideal power bands for MX and SX are different. Just read the write ups on the "Bikes of the Stars" in the magazines on how their power is set up for MX and SX. Also, gearing has to be considered to utilize the power band to its maximum. I don't have a tach on my bike so I don't know what rpm I prefer the meat of the power to be in. I'm no pro so I go by the "seat of my pants" dyno! 😢

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