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High altitude help

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Im new to Denver area, been riding the local mx tracks. Jetting is dialed in, good color on spark plug, no bog anywhere. No engine mods and have stock gearing 13/48. 06 crf450r. Im really missing the low/mid range hit it had at sea level. I know these bikes suffer power loss at altitude, but whats everyone doing out here. Im thinking go up about 2 teeth in the rear and possibly and exhaust down the road. Does anybody know any quick cheap solutions?

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maybe advance the timing a bit. idk what you have access to but if you could mill the head or shave the block a little to gain some compression it might help too

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A bump in compression would certainly help. It is usually done with a piston as opposed to shaving anything off. Your 06 is probably ready for a top-end anyway. Between a compression bump, a fresh topend, and going through the head, you will restore performance, probably similar to what your tired 06 did at sea level.

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What is your jetting?

A 50 tooth rear sprocket will feel snappier, because it is, but a 48 will give you faster lap times on an mx track.

Altitude is a power killer.

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im sure my top end is tired like u guys are saying, i bought it new late in 07 so its got hours, appreciate your thoughts

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Easiest thing to do is play with you pilot jet and needle position. Main jet should be 158-162 depending in temps. Go a size down on the pilot to start. I'm at 6000 feet and went down a pilot size and to a 162 for winter riding. Needle is dependant on your mods. A high comp piston will help but it is more involved than jetting, stock is 12.5 and a 13 or 13.5 will work on pump gas at elevation. Not too far off though if you know how to work on your bike. Rember you lose 3% of a hp for every 1000 feet you got up in elevation.

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