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YAMA1978

Speed............Anyone?

18 posts in this topic

Does anyone know (approx.) how fast a 2000 426 with stock gearing goes (14-49). For argument sake the road surface is tightly packed gravel. I've heard people say a high as 90mph but I dont know if that story will hold water. I use my bike for mostly trails but a few sections are flat and i just can't resist pushing her to the limits. I ride with friends who own 1995 rmx 250, 2000 kx500 and a 1989 yz 250 (all stock gearing). From 1st gear to 5th i kick ass but by the time i reach high rpm 5th people are catching up, I even lost a race between a 1989 yz 250. Losing to a kx 500 is understandable but my bike just seems to lack high speed even though it does not bog or stumble at high rpm. Ive never had the chance to actually clock myself but I have an idea what 90 mph feels like on my street bike watching objects zoom by.

Coming from a xr 250 to a 426 is a great jump but for some reason i was expecting more. Don't get me wrong i love the bike, it is reliable and has tons of power on the lower to mid range I just wanted to know if there might be something internally wrong with my bike. I guess I cant have the best of both worlds (speed and accelleration).

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im a complete noob but i would think it would go alot faster than that.. ive had my fourwheeler clocked ( riding next to a pickup ) at about 82-83 and my 426 feels a heck of alot faster than my fourwheeler in every respect... its got a 15 tooth front sprocket but that couldnt make more than a 7-8 mph difference. i would think 90 would be reasonable.

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When I was in Colorado I had to stop by Thunder Valley (didnt have my bike, just looking the track over) and I was talking to the owner and he said there was a double on the track that the pros hit at over 90mph... but I thought he was full of $hit. Any way that could be true? I mean... I dont think he had anything to gain by lieing...

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Given stock gearing, and the fact that the power falls off sharply above 10000 rpm, your top speed with perfect traction would be something like 85 mph, although it could pull past that to maybe 88. Then you have to knock about 10-15% off for wheel spin on the gravel surface, so now you're looking at more like 72-77.

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Mid 70's is correct and if you try and gear it higher you will find out the thing need more hp to get 90. It just isn't all that aerodynamic.

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I had a 1989 YZ250 and have a 1990 YZ250WR and I can tell you there is no way that the YZ was catching you in top gear with stock gearing unless it was the WR model. The WR model is good for 90+ in 5th gear but the acceleration in 4th and 5th is weak. If I am not mistaken the RMX was also an off-road model and might have tall gearing. Go up one tooth on the front, shouldn't hurt acceleration much and will give you a few MPH on top end. Can't help you with the KX500. :thumbsup:

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About the thunder valley thing, I'm no pro but I do ride there once a week and I never need to use 4th gear on the track. I clear most jumps in 2nd but a few in third (03 yz450). The only jump out there that you really could go wide open would be in the old layout, the uphill triple (that was really a double). That one would be plausible for high speeds.

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I've got an 01 426 with 14/48 gearing and I was clocked (by a KTM speedo) at 76mph and the bike had a bit more. Gotta love the dry lake bed outside San Felipe in Baja :thumbsup:

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I've had my bike up to 85 with a gps. My bike has 14/48 gearing and its an 04 with a 4 speed. If you are not jetted right you will not hit the rev limiter in last gear.

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06' 450, stock gearing, wide open on hard packed gravel road, 79 by gps. Had it against the rev limiter for about 10 seconds, it wouldn't hit 80. On pavement I had it to 84 by gps, wide open, flat surface, no wind, 190# rider.

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2002 YZ426F, all stock except for a K&N Air Filter.

Spent a day drag racing over intermediate soil with a friends speed-radar setup at the 280ft. mark of a 350ft strip. He uses the speed-radar setup at local private airport for monitoring aircraft speed on the runway so it's proven to be accurate.

Best run (180lb. rider) was 78 mph with the stock 2002 YZ426F with constant wheelspin.

My daughter's (105 lb. rider) best run was 64 mph with a stock 2003 YZ85 with constant wheelspin.

The best run for the 400 + cc 4-wheelers was 67 mph.

The bike should pull around 80 mph on concrete.

NOTE: Be cautious of headshake at these speeds, these bikes don't deal very-well with long periods at high rates of speed.

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I think gray would be just about right on. I've got my bike geared stock right except for BK mod now and pull about 87 according to gps on asphalt, but I start hitting the rev limit about there.

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