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9oz or 11oz FWW for high altitude

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I have a 2004 YZ250 2-stroke and only ride trails in the Colorado mountains. I typically ride at an elevation of 9,000 to 11,000 feet. Because of the altitude the bike probably has approximately 25% less horsepower than at sea level. The bike is jetted for my elevation. Should I get a 9oz or 11oz flywheel weight. I'm afraid to get the 13oz because the bike has less power at my altitude. My goal is to make the bike easier to ride on tighter single track trails.

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I have run a 13 oz and it has worked fine. With the Rekluse I use the 9oz. Because of the loss in HP at high elevations I tend to notice the flywheel less because I'm normally reving the bike more. The 13 is nice to fight stalling. I don't think you could go wrong either way and dought you will notice much difference.

What I do recommmned is getteng the head milled to raise the compression or buy a Phat Head. I did this to a 2003 KX and it worked really good in the mountains.

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Just a thought, but if you do consider a head mill to boost compression as celler recommends, do a search here for squish or head mod. first, lots of positive feed back on this. If you have your squish gap corrected? to around .050", it will increase your compression ratio also, and at our altitudes should still run on pump gas. This way you'll gain two pluses for the price of one! If I understand what I've read, correcting the squish gap improves the effecency of the burn of the air/fuel mixture thereby reducing ping/detonation, that provides for better jetting which can increase power/response and help reduce spooge. An increase in compression should increase power, more so maybe at low end. All that for @ $80 sounds like a bargin to me, or to good to be true. At any rate I haven't done it yet, but I intend to! :confused:

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Squish band is a nice mod but I also like my GYTR off road flywheel. It was $78 and has definitely reduced stalls and made it somewhat more tractable/gained some traction.

I feel more comfortable lugging it on tight uphill hairpin turns on the narrow goat trails. I usually ride these standing up and so a stall sucks because I would normally be pushed forward and borderline over the bars once the stall happens.

This is happening WAY WAY less now with the GYTR offroad flywheel. It is 8 ounces or so. I feel NO power less either.

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Just a thought, but if you do consider a head mill to boost compression as celler recommends, do a search here for squish or head mod. first, lots of positive feed back on this. If you have your squish gap corrected? to around .050", it will increase your compression ratio also, and at our altitudes should still run on pump gas. This way you'll gain two pluses for the price of one! If I understand what I've read, correcting the squish gap improves the effecency of the burn of the air/fuel mixture thereby reducing ping/detonation, that provides for better jetting which can increase power/response and help reduce spooge. An increase in compression should increase power, more so maybe at low end. All that for @ $80 sounds like a bargin to me, or to good to be true. At any rate I haven't done it yet, but I intend to! :confused:

This idea is well worth listening to. At 4000 feet of elevation I lose about 15% of my compression. Your losses at 9000 would be incredible. The power is improved. The bike is also much easier to jet correctly.

If I ever get to low elevations a new head is cheap. Race gas was, but not anymore.

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