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MX, SX & Off-Road Discussions
Dirt Bike Mods & Maintenance
A few questions about fuel delivery in an oldYZ490
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[QUOTE="zoommx, post: 702841, member: 22864"] I bought a '82 yz490 as a winter project for the upcoming spring post-vintage ultima 500 class. Yes, even after reading a few items about their various shortcomings. Well, I just got to the top end, and it is only at +.5mm over right now (much to my surprise and happiness); I'll have to mic later to see if I need to bore it. Now for the questions: 1. the jetting confuses me. I just want to verify that it was completely wrong before I go further. The Yamaha motors online parts lists these std.: 50 pilot, 6F16 needle, 440 main. What I found in carb.: 40 pilot, 6F16, clip in top position, 200 :scream: MAIN!!! The only test ride I did was get it running and shift through the gears to make sure tranny was o.k. It WAS hard to start. I am leaning to someone not really knowing how to jet and dropped a 200 in, not that the Yamaha site is wrong or that the main could be that far off. 2. It has steel reeds, Who votes that I replace them with fiber?...i.e. Boyseen. 3. It has a boost bottle. do they really DO anything or should I toss it and plug the hole? Thanks, Roger [/QUOTE]
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Dirt Bike Mods & Maintenance
A few questions about fuel delivery in an oldYZ490
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