I was in Rexburg Idaho the other day and decided to have my 450 dyno tuned since I knew it wasn't jetted right. All I had them do was play with the main jet, I didn't want the to go as deep as the needle since I am planning on putting my 490 big bore in soon. When it was all said and done my numbers were 26ft lbs and 32hp. All I have done is a DMC alien header and silencer and uni air filter. My gearing is 12/38 if that matters. Those number seem low from what I have been reading around here. Also these aren't dyno jet numbers, they are SAE. I was a little disapointed considering a buddy with an 06 raptor 700 with pretty much the same mods put down 44 ft lbs and 40hp. He is running 13/40 gears. Also what are the stock numbers for an 05 450, and are they dyno jet numbers?

I have been on that dyno and my 05 with a dasa, 12.25 piston, and hc stg 2, and no air box. made 44 hp. they said it was the highest reading stock bore they had on it ? your numbers seem low because they said a stock one makes about 38. how did it run? the numbers dont matter really, as long as it runs good.

I thought it ran way better than before they dyno'd it. But still with my fat ass on it I can't make it up chokecherry or devils dune. I let my 140lb friend ride it and it walked right up chokecherry. I guess I was mostly suprised at how low the torque was compared to the raptor.

How much do you weigh?

I went right up choke cherry w/ just a HMF slip-on.

What is you jetting right now?

Stock is 32hp.

I weight about 270lbs, I am running a 135 main jet, but when I had it dyno'd the mechanic figured I had a different needle. I am not sure which needle is installed as I have never messed with it and bought the wheeler used. Doesn't HRC make a jet kit that comes with a needle?

Yes HRC makes a Needle that also comes with a 185 main jet PN#16020-NLZ-651 and are in the $32 range available at any Honda dealer Your bike sounds like it is way too lean

What do you mean "these arent dyno jet numbers"? Was this not a dynojet dyno? If not, what brand was it? This seems about right for a dynojet. It takes a modded airbox, jetting, HC 2, and a pipe for an 05 to make that on an eddy current dyno. So if you got 32 on an eddy current dyno then thats pretty good for what you have.

Your gonna be in the 170-185 Keihin main jet area. The stock cams killin your numbers.

Sure those arent dynojet jet sizes?

sounds like he is using dynojet jets

jetting sounds good for what you listed for mods. the dmc has the same header as a stock,
the silancer isnt much if any better then the hrc tip, the uni filter isnt much better then stock, and you didnt mention the lid being removed, so if stock is 118-120 and your at 135 with just a slightly better exhaust then stock it sounds right. so does the 32hp. i have heard that lower gearing can show lower numbers on a dyno but i have never tryed it just to see.

maybe one of these nice fellers with a dyno can make some pulls with 12-38, 13-38 and 14-38 and report back to us.

What's the deal with a 12 tooth front sprockets, are you pulling a trailer? Through a hotcam stage 2 and a 13 tooth front sprocket and you'll be amazed from the results.

On an inertia dyno, gearing and tire size will make a difference as far as HP and TQ readings go. If he tested on an eddy current dyno gearing will make no difference, and it wont matter what gear you pull in. So to answer your question, yes low gearing should lower you number....if it on an inertia dyno.

Mr. Torque,

I have to respectfully disagree at least on the tire size making a power difference on an inertia dyno. I tried two drastically different sized dyno tires on a dyno jet and they were absolutely identical to each other. At least in RPM. I never looked at it in speed as we never do so I could'nt say for sure on that.

I dont know about gear changing resulting in differnt readings. I never tried changing gearing on the dyno. I thought that would also yeild no difference, again at least in RPM.

King, I had this debate with an honest to God dyno Guru quite some time ago. Here is a statement that came from one of the top tuners in the country that has tuned thousands of fast cars and bikes, and he tunes on both types. Heres what he said.....

Inertia/accelerometer style dynos measure the acceleration rate over time (point A to point B). If you change the numerical "gear" you test the vehicle in then you will change the acceleration rate of the vehicle and the "Calculated HP" due to manipulating the amount of torque output available at the wheels.

On a proper dyno that actually measures the torque, it will not. Here is the math....


HP = Tq X RPM divided by 5252

Gear Ratios
1.) Divide RPM
2.) Multiply TQ


Using the formula above.

Example:

An engine produces 100 ft/lbs at 1000 RPM

100 ft/lbs X 1000 RPM = 100000
100000 divided by 5252 = 19 HP

The engine produces 19 HP!


The transmission is in a 3.0:1 gear ratio

100 ft/lbs x 3.0 = 300 ft/lbs at the transmission
1000 divided by 3.0 = 333.33333 RPM

300 ft/lbs X 333.33333 RPM = 99999.99
99999.99 divided by 5252 = 19 HP

19 HP Available at the transmission
The engine still produces 19 HP!


You have a 3.73 final drive (rear end)

300 ft/lbs X 3.73 = 1119 ft/lbs at the rear end
333.33333 divided by 3.73 = 89.36 RPM

1119 ft/lbs X 89.36 RPM = 99999.99
99999.99 divided by 5252 = 19 HP

19 HP Available at the final drive
The engine still produces 19 HP!


The engines HP never changes, only the torque output and speed thus changing the acceleration rate.

Inertia style dyno = yes the gearing will change the calculated HP

Proper actual measurement dyno = no it will not change the "actual HP"



Now, I dont claim to know it all about inertia style dynos, but im not one to take anyones word for it so I tried it on mine, and there is no HP change. I remember trying it on my drag cars several years ago and his statement definitely holds water on automotive dynos. I have yet to test it on an ATV/MC dyno but i will...soon.

Yea but can you back that up with any real info??

LOL J/K

No doubt the theory in there and you have a strong point, but unless what I saw was a fluke, I had zero change. I guess Ill have to revisit this experiment next time Im on the rollers. Like I need to test more stuff...lol Im up to like a 3 day testing session as of now!

Thanks for typing out all that info.

i have seen no difference on my dyno between 4th and 5th. maybe slight torque difference thats it.

I didnt type that, he emailed that to me quite some time ago. As I stated earlier, it does hold water on automotive dynos. As far as ATV/MC dynos, Im gonna try it out for myself. I dont see why it wouldnt be the same on them, unless there is just so much more of a margin on what cars make vs. ATV's. I know for a fact it doesnt change on my dyno, but there again I tune on it almost everyday and I know it like the back of my hand and I rarely have time to visit other dynos and really havent had the desire to.

what about the loaded dyno (eddy current) operators loading the engine for 'quick release' to produce an extra surge in power,... ? DOH!

thats good to know. i have a separte chain that i use for dyno tuning and always tune with 14-39 just to know for sure the gearing isnt effecting my numbers.

Havent seen that one happen. I have seen torque spikes when dropping the clutch wide open, but its the same I have seen on inertia dynos. I cant see that happening in the order that you are speaking of, but I could see letting the bike run hard then "quick loading" one to create a torque spike.

Hey Gary, Mr.Torque- I see what you mean gary and torque and that is some good info but sredrum and I have done a little experiment with my 480 and had 20's on it and then put on 18's and seen very little if any change as well with our dynojet dyno. And King you may be on to something there with the speed versus engine rpm, we always use engine rpm and never the speed setting. Would be a cool experiment to try someday.