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turboXR250

Dyno run on XR280

6 posts in this topic

Just went up to the shop were my bike stays, they recently put in a dyno. Just for fun we put my 280 up on it this morning. Before I tell you the numbers let me tell you some of the variables against my bike. Knobby tire, hopped a lot on the drum. Old gas, at least 3 months old. Other than that my bike is fresh, has Eddelbrock carb, XR's only 78mm piston(284 cc I think), oversized valves, cam, port and polish head, etc etc. A stock 2001 cr 250 made 35 hp at rear wheel with knobby. My bike made a whopping 21.5 hp at rear wheel. :):D :D :D We were very surprised it was so low, but on comparison to the cr it is not so bad. It would have been good to run a stock xr 250 to see what it does. The good point of the bike is that the power is very smooth and the torque which was only 15 ft lbs was peaked at 3500 rpm and ran flat to 8000 rpm. Max hp was at about 8000 rpm and then everything started to fall off. It redlined at just over 11,000 rpm.

Again my bike runs strong and these may sound low but in reality they are probably not bad, it is rear wheel hp and it is about 62% of the cr 250 which is supposed to make around 50 hp at the crank.

Just thouhgt you might be interested and also I would like to no if anyone else has ever dyno'ed their bike and what you got?

turbo

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Kinda funny, the first thing I did was check out the numbers(guess it's the 'rice' in me :)) I saw 35 and actually said "what the fox (racing that is wink)". None the less I think a stock 250 makes what I've heard 12hp or so. Now how do I get my xr4 to push 40 hmm

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40 hp at the rear wheel may be kind of tough out of a xr400. You will definitley have to go bigger!! I had a 440 that felt really strong but never dyno'ed it. Stock on a 400 at crank is 33hp by Hondas book. Rear wheel is probably 22 or 23 hp. It would take a ton to get 40. Good Luck!!!! :)

turbo

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Rob Barnum Dyno'ed my XR416 w QS carb, heads ported, and WB e series pipe at 31.1 hp with a knobby. He stated that a knobby causes about a 30% reduction in measured power as compared to a "Dyno tire." So the XR416 dyno test converts to about 40 hp.

That being the case, your 21.5 hp converts to just under 28 hp which sounds right in the ballpark for a 280.

Our XR320 dyno'ed at around 31 with a dyno tire.

Rh

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Thanks for the info, :) I feel better now. That 30% is what I kind of figured after doing some math knowing what the cr did and what it was supposed to do.

Thanks again.

Turbo

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Turbo the numbers sound correct. I had my 280 on dyno with the following results

Dyno results (measured @ the wheel ) are,

SAE Max. Horsepower - 23.8 (7100-7800rpm)

SAE Torque (ft.lbs) - 18.2 (6200-6500rpm)

I put a street tire on the back to avoid the hop and the wheel slippage that you experienced. The above numbers are with a UNI filter installed. The K&N filter produced an extra 1.1 hp.

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