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03-27-2005, 11:47 AM | #31 | ||
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Re: Re: Two vs. Four
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The most simple explanation of the 4s displacement advantage is they need it to be competitive. For example: we had a racer that got caught with an overbore kit on his YZF 250 and got bumped up to the 250 cc class from 125cc class. Needless to say he did not not fair too well on the track against the 250cc two strokes, often getting lapped. As to the CRF 450s and YZF 450s, they are not stock when competing against two strokes with AMA legal mods such as porting, Pro Circuit or FMF exhaust, V Force Reeds, etc which doesn't cost an arm & leg in dinero. A box stock Honda CRF 450 or Yamaha YZF 450 cannot beat a modified two stroke 250 on a AMA type track. For proof just check out the Supercross racing results....although they are factory works bikes, the two strokes dominate. When the regular season starts they will switch over to the thumpers because they shine on hilly tracks with long strait aways but the two-strokes always surprise everyone. Lets see how James Stuart will do this year riding a Kawasaki works KX 250 against all the thumpers. Reed and Carmichael will switch over to their works thumpers. |
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04-15-2005, 03:11 AM | #32 | |
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Re: Re: Two vs. Four
in addition to all that, if your working on your bike at home and truck it up the hills your going to have to second guess carb jetting for altitude, if its a significant difference.... i think a four stroke would be more forgiving in this respect.
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04-15-2005, 03:19 AM | #33 | ||
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Re: Re: Two vs. Four
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04-15-2005, 03:29 AM | #34 | ||
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Re: Re: Two vs. Four
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04-15-2005, 03:58 AM | #35 | |
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a link
ok, check this out...?
http://tec.avl.com/wo/webobsession.s...wMDMxMDY3.html a diesel two stroke motorcycle? |
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04-16-2005, 09:27 AM | #36 | ||
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Re: Re: Re: Two vs. Four
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Thats true. Two strokes are more sensitive to humidity, temperature and altitude versus four strokes. It's just something a two stroke owner has to consider and deal with. Doesn't hurt to keep jetting kits handy. I can swap out a needle, pilot or main jet in under 15 minutes and the manufacturer's shop manual has various charts to help you make an educated decision on jetting. |
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