XR400 Dyno Run

[skipn8r]

I have a Gordon'ed '99 XR400 with the following:

Snorkle out

Uni with cage

Header ground flush

Jetted 52/155

Float set 14.5 mm/19 mm

A16A needle in middle position

Krizman Magnum exhaust tip

Denso Iridium IX24 plug

Phillips 91 octane fuel

Honda 20W-50 75% synthetic oil with moly

Dunlop 756 tires F/R

14/45 sprockets

Got a chance to run on a dyno and got this. The dyno numbers were corrected for atmospheric conditions, but not for drive train losses. Temp was 91 degrees, low humidity and 5,300 ft elevation. The run was made in 3rd gear. The Uni had about 3 rides since last cleaning, so it was a bit dirty.

Max power is 26.3 HP at about 7,000 RPM. Max torque is 21.2 ft.-lb. at about 6,000 RPM. The air/fuel ratio measurement indicates lean below 7,000 RPM and slightly rich above. At idle with the pilot screw 2-3 turns out, the air/fuel measurement still indicated slightly lean. Time for a 55 slow jet.

[ob1quixote]

How did the knobbies do on the dyno? Do you think they were spinning?

How much did the test cost?

I wouldnt mind running one on mine, if it isnt too expensive! Maybe I could find a street tire.....

Robert ?

[Randy_Olaughlin]

That is a nice curve. Being up 5300 ft might lower the numbers?

[skipn8r]

There was no obvious slipping, but after the test, there was the distinct smell of burning rubber. I suspect a street tire would be much better. The cost was low. Our local Honda dealer had a deal that if you spent $25 on parts, they'd cover the dyno run. I had to pay an extra $20 for the air/fuel ratio measurment. The dyno operator said if I wanted to spend some time, he'd do as many runs as we could fit in an hour for $60. Don't know if that includes A/F measurement.

[skipn8r]

The dyno guy said that the numbers were corrected for altitude, so this is supposed to be what my bike would put out at sea level properly jetted. To be honest, I was expecting a little closer to 30 hp.

[YoungGunXR]

Somebody had a dyno run done on his 250 with knobbies and then with a street tire. I think he said there was about a 30% differnce in power between the two. My friends 125 two smokers are putting out around 30hp and my bike just smokes them in accleration and top speed. So my bike should be pushing more that 30 hp. Also I dont think the 650 cant have twice the power of my 400. Its faster but not twice as fast. (650 puts out over 60 hp at the wheel ?) I want to have my bike dynoed. I will buy a cheap street tire to test it on. Every once in a while they have free dyno runs down here.