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Old 07-20-2010, 07:15 PM
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Default 1991 CR500 Need more power for the sand


I know the 500 has plenty of power stock but I would like more for the sand dunes and drag racing. The bike runs great, good compression, fmf fatty pipe. The reeds are old so i would like to replace them. Whats the best reeds for this bike. It has a flywheel weight, would I benifit from removing it? Any other bolt on mods you can think of. I have a cr250 for the dirt so if the 500 is over powered thats fine with me.
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Old 07-20-2010, 07:34 PM
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If the flywheel is heavier than stock that would make it rev slower. I'd at least go back to stock or a lighter than stock one. I justgot some Boyesen reeds for my 91 CR250. Look into the Boyesen Rad Valves also.
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Old 07-20-2010, 09:46 PM
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86, or 87 cylinders work well for that. get an 85 head (more compression).

use as light a flywheel as you can for sand, without stalling on the starts. Plan to go up on your octane. your bike would like leaded fuels. drop the pj carburetor for a pwk that is larger. the kaw 500's came with a 39.5 that is really good. there are 40mm ones available. for sand dragging bigger is better and you can make that one bigger (cubic inches). I don't like those for any other riding, but hill climbs and dragging it works well on.

you can mill any of the heads to work fyi.

Porting is next, and unless you want to buy some cylinders and play with raising the exhaust port and then the transfers I would leave that to someone who knows that engine. if you want to try it, just start by raising the ports by using a spacer under the cylinder. .030" to start with and 010 after that is where I would start. then you will need to mill the top of the cylinder to get back to the original deck height. sooner or later the head will get milled even more.

speed is power, power is money. how fast do you want to go?
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