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4Takt

XR650R: Is the Rev Limiter doing this?

7 posts in this topic

My XRR is unplugged, full Moriwaki exhaust , drilled side panel, Edelbrock carb, 15/48 gearing, Maxxis IT Cross tires.

I aired it out on some dirt roads today. At exactly 94mph (according to my Trailtech speedo) the bike starts to stutter as if it is running out of gas. Back it off just a little, say to 90mph, and it will run fine all day long. No other problems whatsoever.

Is that the rev limiter?

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I have the same gearing and I can hit around 92mph, been told this gearing is close to 100mph, if not over. I am doing this at 6100 feet, so me thinks you might have an issue, although I doubt it is the limiter.

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I have the same gearing and I can hit around 92mph

So what does your bike do when you hit 92mph? Just not go any faster?

Mine seems to pull strong towards 94, like it had the power to go faster, but at exactly 94 it starts cutting out.

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Mine hits 92 in the dirt(meant to clarify), and around 96-97 on the pavement, it just stops accelerating, no sputter, just runs out of steam. You figure at 6100 feet I am down about 20% in rated HP over a sea level bike though.

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Why not adjust the carb to give it more gas, and see if it helps? Depending on the plug maybe its bogging from to much fuel? Either way you can adjust easily enough.

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If, when this happens, you let off the gas a little & the bike surges forward a bit then your main jet is too lean. Go up one size & retry.

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I'd check it with a tach, or possibably you could tap it out in 4th and see if it feels the same. The cdi doesn't know what gear it's in, so when it hits the rev limiter, it would sound and feel the same. Jetting up will tell you something, and a trailtech speedo may be a little off, might be going faster than indicated!

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