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New Pro Circuit head........ What now?

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Alright, installed new rings a couple weeks ago. Broke the bike in using the mototune method and it hauled ass. After 2 hours I broke an intake valve.....that was interesting. When I put a top end next time, I am going to check the valve clearances after every ride for the first 5 hours. 👍

Ok, done with this useless info and on to my question. Bike is an 07 CRF 450 completely BONE stock with 20hrs. After breaking the intake valve I decided to just buy another head (so I could make fontana this weekend) and have a back up. The head was from an 06 CRF 450 and was ported and polished by Pro Circuit. It has about 40hrs on it. My question is, will I have to rejet or do anything to the bike in general to have it race ready this weekend?

Also, anybody have any reccomendations on what I should do in the future for the bike to reach its full potential given that it has a PC head on it now?🤣

Thanks.

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the procircut head is more or less a clean up nothing should change

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Should I expect an increase in power how it sits now? If so, where do you think Ill notice it? Also, would it be best to run race fuel now? Just curious.

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as stated above, you may not notice any diff. From what i found on this site, the 2002-2006 head has slightly larger exst. valves than the 07-08 head making a tad more power up top, but the 07-08 head with it's smaller exst. valves makes slightly better low-mid power vs. the 06. I have an 04crf450 and opted to buy a new 08 head with all ss. valves (had the spring kit already) as i do mostly fast trails and only some mx..

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Man, all I expect from it is to run at least as good as it did before! I bought it for significantly less than it would have been to put new intake valves in the stock head. If it runs like it did before Ill be happy.👍

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as stated above, you may not notice any diff. From what i found on this site, the 2002-2006 head has slightly larger exst. valves than the 07-08 head making a tad more power up top, but the 07-08 head with it's smaller exst. valves makes slightly better low-mid power vs. the 06. I have an 04crf450 and opted to buy a new 08 head with all ss. valves (had the spring kit already) as i do mostly fast trails and only some mx..

Thats great information, but kind of sucks at the same time since I really liked that low-mid power!!!

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Stock to stock, 07/08 head makes more power everywhere. The 02-06 head is only better if you intend to build a fully modified 60hp+ monster.

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you should notice a difference, i did and my 07 toatally smashes my brothers stock 08. does yours have 4 titanium valves with copper burilium seats?

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you should notice a difference, i did and my 07 toatally smashes my brothers stock 08. does yours have 4 titanium valves with copper burilium seats?

this means absolutley nothing to this subject since he doesnt own your brothers bike or your "FREAK" bike.

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you should notice a difference, i did and my 07 toatally smashes my brothers stock 08. does yours have 4 titanium valves with copper burilium seats?

I don't know if the valves are Ti, but the seats are copper looking. I don't want to psych myself out too much. Ill just wait to see how it runs on race day.

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im sure you will notice a difference from the work they have done to it .i have dynoed heads that made nothing in peak power gains but had better over rev and the customers thought they had gained 5 hp by seat of the pants .Im finding that most pro racers on a 450 are using the power between 5000 and 8000 rpm the most the big gains from there on up only help in the long woop sections and the hole shot thats why the 07-08 heads worked better for mx there smaller port volume makes them more responsive in that rpm range an average rider may not want that much response you may feel the bike is eazyer to ride and still has more over rev .

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