How fast is a motocrosser?

S

sturd

PR Addict
We decided to find out, though our bikes are now dirt trackers. The boy needed to practice starts with lights, just like the pros use at the dirt track and for $15 bucks we made a dozen or so runs each at Thompson Raceway last night.

2006 YZ250f - 13.97 @ 89mph
2004 YZ450F - 13.24 @ 96mph (ran out of gearing though, bouncing of the limiter)

And just for completeness
1974 RD60A - 24.29 @ 53.8 mph
 
That is fastet than I thought they would go. Interesting info. Stock gearing? Engine mods?
 
Both had highest gearing we own for them. The 250 was just barely high enough, the 450 was still undergeared. The 250 has hi-comp piston, race gas, pipe. The 450 is 100% stock (except for the front wheel which is a 19" for the dirt track tires), 93 octane pump gas.

The RD60 has a pipe I made :->
 
And this thing isnt even jetted right


I drag raced my friend with my YZ125 vs his cbr 250 back in 05. Smoked him til I ran out of gearing.
 
Anyone remember the Dirt Rider issue I believe it was where they ran a CR500 down the strip with a CBR500 I think it was? Something is trying to tell me the CR topped 100mph...
 
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The CR SMOKED the CBR ... badly.

Even with a rolling start for the CBR the CR still beat it badly.
 
Would like to get my 1984 CR500 Husky to a strip sometime . It has a 6 speed transmission and I never had it anywhere I could catch top gear . These bikes were desert favorites . In an article I found in an old magazine , they were purported to top out between 110 - 115 mph . Only drawback is that there is no place to bump start the monster SOB at a drag strip . It is almost impossible to kick start cold . A buddies 490 Maico is the same way . After about 20 minutes of kicking , cussing , and sweating we would do " the walk of shame " and push them to a hill to bump start . Hence , we became known as " the over the hill gang " . Most all of the big bore 2-strokes from the 80's could haul butt in a straight line until the gears limited them out . Stopping them was a whole nuther issue , my Husky has drum brakes ( as they were are laughingly called ) .
 
I had a friend who had an '84 Honda CR500. The year before they were liquid cooled I believe. Whenever someone asked if they could take a spin he'd say, "If you can start it, you can ride it". Peeps seldom rode it. ;)
 
I drag raced my 85 cr500, put the smallest rear sprocket my rear hub would allow. the biggest front. I ran out of gear way before the finish my best time slip was 11.92 101mph... big was totally stock with 70 mx races on it
 
Jim598 said:
I drag raced my 85 cr500, put the smallest rear sprocket my rear hub would allow. the biggest front. I ran out of gear way before the finish my best time slip was 11.92 101mph... big was totally stock with 70 mx races on it
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Are you talking 1/8 mile strip or 1/4? That would be pretty impresive out of a dirt scooter on the quarter, I think my fastest time on my 750 gixxer on the qt was like a 11.1 or .2.
 
Jim598 said:
1/4 mile, still have the time slip
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I'm not calling you out on it, I just was saying that is impresive. I wonder what one could run with that gearing stretched out like a hill climber, that would be cool to see. Did you have any trouble keeping the front end down? lol
 
I ran one of my buddies rear road racing slicks, got way to much traction..everything else was stock. had to take off easy and slip the clutch, then I would short shift into third and could hold it open the rest of they way... one of my good friends made a pass on it and he used the rear brake and slipped the clutch to hold the front end down.no matter what you did it wheelied in every gear...p.s. I crashed it that night..lol still had the knobby on the front and I was slowing down trying to turn in the first exit...dumb
 
Jim598 said:
I ran one of my buddies rear road racing slicks, got way to much traction..everything else was stock. had to take off easy and slip the clutch, then I would short shift into third and could hold it open the rest of they way... one of my good friends made a pass on it and he used the rear brake and slipped the clutch to hold the front end down.no matter what you did it wheelied in every gear...p.s. I crashed it that night..lol still had the knobby on the front and I was slowing down trying to turn in the first exit...dumb
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Nice, I've never seen or even thought about running a dirt bike down the 1/4. I live right down the road from a drag strip, got the little gears in my head turning now. lol
 
I also just looked 1/4 times for cr500's on you tube. saw several different ones.. they were saying anywhere from 11.50s to 12.20s... I don't see how you could get much better than what I did with out wheelie bars and different transmission gearing
 
Remember that dude on Pass Time wrecking the street bike hot dogging... Yes, me and a street bike probably wouldn't mix all that well and the strip and a MX bike undoubtedly wouldn't I figure...
 
Jim598 said:
I also just looked 1/4 times for cr500's on you tube. saw several different ones.. they were saying anywhere from 11.50s to 12.20s... I don't see how you could get much better than what I did with out wheelie bars and different transmission gearing
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Stretch it out 10" and lower it I bet you could pick up a half second easy with a few passes, put a holeshot device on, throw a diff clutch in and run an evening of test and tune and I bet low 11's are achievable. lol
 
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