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horsepower question

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ok so this might be a stupid question but its something I don't get at all. so my bone stock pushes around 35 hp. but supposedly a 250 2 stroke dirtbike motor pushes 45 hp. I don't get how this happens. how can a motor make 10 more hp but yet is 100cc less?

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A 250 2 stroke motor is a high performance race motor and it's 2 stroke. It takes roughly double the cc's for a 4 stroke to equal a 2 stroke. If you have a 250r, it's because the newer 250 2t's have gradually gained peak hp over the years. 

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bone stock banshee, sorry. and the banshee is a 2 stroke to. im sure that might change the answer

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well I know the dirtbike weighs less. but the weigh of the bike doesn't affect the horsepower does it? that just means the hp to weight ratio is better isn't it?

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Banshee's are tame stock. Pipes alone add 25% more hp for example. It's not hard to squeeze power out of them, there's a much higher potential for HP being a twin. 

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Its the mild state of tune atvs come with

Yep, same reason 450 quads put out horsepower in the mid 40s whereas modern 450 MX bikes are nearing the 60hp mark stock.

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and why i can go 100 hours on my 450 quad for a top end or 25-50 on a bike. my 250f is far stronger than my kfx450, its sad.

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and why i can go 100 hours on my 450 quad for a top end or 25-50 on a bike. my 250f is far stronger than my kfx450, its sad.

if you look at it grime a bike perspective. A 450 lasts longer than a 250 because they don't rev so hard. If a 450 puts out even less hp, they can go even longer in between rebuilds. In theory.

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if you look at it grime a bike perspective. A 450 lasts longer than a 250 because they don't rev so hard. If a 450 puts out even less hp, they can go even longer in between rebuilds. In theory.

For a given displacement, say a 250, the 2t rev limiter is typically lower than the 4t rev limiter.  While the 4t puts out less power it can still produce very usable power above 10,000 rpm. Whereas the 2t is outputting essentially nothing at the same RPM.  So, for a race bike the 4t will generally be revved just as hard as the 2t.  For an example of this take a look at the specs for the KTM 2t and 4t 250s.

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Because littler bikes can stroke more than big bikes it takes longer for a 320or350 to get more strokes and etc. So the little bike has a little more top end and can stroke more times than bigger cc bikes

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 2t rev limiter is typically lower than the 4t rev limiter.  

 

2 Strokes don't have rev limiters (unless a custom ignition is installed). Their RPM range is limited by the exhaust, stroke, port duration/layout, and piston size.

 

For example, a stock CR500 will be lucky to ever see over 6,800 RPM. A buddy of mine, who is an experienced CR500 tuner, has a 500 that will rev past 13k rpm

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I understand the self-limiting of 2t engines and misspoke, but my point was that for similarly sized engines, a 4t revs just as high as a 2t and is actually under significant load at high RPMs.  Revs are not a good indicator of rebuild frequency when comparing 2t and 4t, but that's just my opinion.

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