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MountainMax

How much Horsepower is in the motocross factory racer 450's

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I was wondering how much more HP the factory 450 racers make over the stock yz's which i was told is around 51HP ? anyone have any specs on them??

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I think the general consensus is you can get 60HP out of 450 before rideability goes out the window. Some of the dirttrackers get a little more but at what expense I don't know. I had an 04 YZ450 that had porting, Hi comp piston, valve work, cams on U4 that made 58 on the dyno. But Dyno readings are relative. I think the spread of power is more important. What would you rather have. 60HP for 1000 RPM or 55HP for 4000 RPM. Flat power curves is what makes the 450's so easy to ride.

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Most factory 450s aren't pushing as much horsepower as they can get out of them. The big thing in the 450 class is to spend money to make it smooth and ridable. Most factory 450s are about 55 horse, but it is very smooth and useable. Any Joe nobody can make a 450 put out over 60 horse if you spend the money and send it to the right engine builder, but it probably won't be as fast as a factory 450 with less power. The lites class is a different story, most of the money in those bikes oes towards making power.

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I know a few dirt-trackers personally and they can get about 64-67 hp but you want to talk about a lot of $$. About 10 grand in the motor alone.

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well i was reading a dirt bike mag and they said reardons bike here in aus was putting out 55 hp and the stock does 50 so obviously its not all about hp.. he wont the comp here and is heading over there, and all this done with a pretty much stock bike compares to some of the others.. some testers even said the bottom end was really crap but some usable...

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Ron Hamp, who has been working with some of the top finishing National flat trackers in the country for several years, has stated that the head on the big YZF has been the limiting factor, and that he considers the fact that he has now extracted 62 hp from a YZ450 to be a major accomplishment. Given that his bikes win national championships, I'd say that claims by anyone that they have a YZ450 producing significantly more than that are highly dubious.

Numbers like 55 are somewhat easier to achieve, though, and as has been pointed out, the real focus of the pro bike builders is in lowering the lap times. If 2 more hp contributes to that, they'll do it. If it interferes, they won't.

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250's were making mid 50's as well. They just didn't have the bottom end, or the long spread of power like a 450.

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Only maybe 1 or 2 hp more than an old factory 250 two stroke, but that power is for a much wider range of RPM. We are talking over 45 hp for a 5000 RPM spread whereas the old two strokes were over 45 hp for about a 1500 RPM spread.

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