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DirtDevilbt 09-29-2006 12:32 AM

I don't know if slicks were used or not but I had my bike dynoed yesturday after putting it back together. I love the fact my jetting was that close, didn't have to jet at all lol. It's not a race or drag bike so good usabe power is what I'm after. First one hp, second is tq. Never mind the other lines on the torque chart. Mine is 42hp and 30tq. What do you think? The mods are as follows:

HH 12.25:1
2002 CRF cam
Pulse Charger standard core
Mild Porting
KW springs and stock mm valves
UNI filter
Stock carb
VP 103


sredish 09-29-2006 12:35 AM

that seems a little lower than I would've expected. First dyno I think I've seen with the 02 but was pretty sure it makes decent power..... :dunno: who did the porting?

DirtDevilbt 09-29-2006 01:00 AM

A local guy here in town that only does engine building. He does a lot of the engines for championship road race bikes, 2/4 stroke dirtbikes/quads, and work on championship jetskies/seadoos. You could call him a flowbench nerd, lol.

Sheepless 09-29-2006 11:32 AM

I would say it's a bit low as well. :dunno:
Must be a stingy dyno or like you said, slicks werent used.

I have almost the same setup- 12.25:1 BW, mixxer port/polish, standard core PC, uni, hrc kit, HC2, kibblewhite springs and valves and make 47.xxhp

Curious what jet are you at? Altitude?

You said you just put it back together, what did you tear down? Did you replace the rings?


Vader 09-29-2006 11:49 AM

hmmm... you have a very nice linear curve, and your jetting looks pretty good. I guess the wild cards are the dyno tires and porting - find out about the tires for sure. Also, why does the last graph say "slip-on" if you are running a PC exhaust, r is that just a different bike's set up?

DirtDevilbt 09-29-2006 05:19 PM

The tear down was suspension/ maintanence
Piston, rings, valves, spring, porting all have about 10-15 hours
Burbank would know best what altitude it was at since he's local otherwise it's a comlete guess, bout 50 miles off the coast. :dunno:
Slicks were used

50 pilot
Woodward screw 1.25 turns last I remember
Dynojet needle pulled up one from center
165-170 main, can't rmember

The two lines at top are mine, the other crazy one is a 450r done earlier that week with a pipe/filter and no jetting, lol. My torque is good but it's delivery is nothing different from the HRC/HC2 dyno's I've seen. Kind of depressing when it's supposed to be a small block torque motor, then not see the kind of HP others do. Donno, wish there was another dyno I could try.


DirtDevilbt 09-30-2006 12:59 PM

Would using vp 103 make a big difference than say using 91 pump or even mixing the two? I know it's more octane than I need but with the cam I figure it's insurance. I see a lot of dynos of similar set ups running 91, with a slightly off dyno and too much octane be the caulprit?

Sheepless 09-30-2006 01:32 PM

The VP isn't "needed".

Maybe the VP is too excessive, diminshing your output? :unsure:

miller 10-06-2006 11:17 AM

i ride the top of the fence in compression with a custom setup of 12:5 to 1 compression... i run 93, but I couldnt resist trying others....when I slapped in some 110 (not sure if it was citgo or sunoco, but it wasntVP) and I didnt change anything else , the motor revved slower, and it felt FAT and actually made alot more heat than the pump gas 93... i run a 175 to 180 main depending on temps and humidity...I also ran 50:50 mixes with 110 and 93, still felt fat and hotter....the bike still feels fastest and runs coolest on good ole 93 shell without ethanol..... id say thats where you need to be.... But IMO Id say you dont need race gas at all....

i know there alot of people who run race gas on stock comp and up to 12:25 or so, even though they dont need it...but should the main jets go up or down if you switch from pump 93 to 100 or 110 ...?

DirtDevilbt 10-06-2006 01:38 PM

Race gas will take a smaller main I believe however I've seen contradictory evidence that it should take a larger one. Only one size either way I think.

When I went with the piston I immedaitly used 91/c12 mix so I wouldn't know if the main would go up or down. It went down with compression that's all I know. It's ran really good with 91/c12 mix and straight VP103. I'll need to get some new 91 and try it.

GPracer2500 10-06-2006 02:47 PM

Jetting up/down for a different fuel could go either way--it just depends on the fuel. Octane rating has nothing to do with it. The place to start is by looking at the specifc gravity specification for the new fuel. If it's lower than the base fuel than it's very likely you'll need to go with larger jets. If the SG of the new fuel is higher then you'll need smaller jets.

Specific gravity is a measurement of density (or weight). Pure water has a SG of 1.0. Everything is referenced to that. Since A/F ratios are a measure of air to fuel by weight, the weight of the fuel matters. The volume of fuel isn't the only consideration.

Most pump fuels are in the 0.750 range (meaning it's 75% as heavy as water). VP C12, for example, is 0.717. That's about a 5% difference. In order to keep the A/F ratio the same between the two fuels than you'd need 5% more C12. By my calculations, 5% more fuel flow comes out to about 2 jet sizes (i.e. from a 180 to a 185).

Now, that example assumes the two fuels being compared have similar chemistry. If one of them is oxygenated than that complicates things. If the pump fuel is oxygenated (MTBE or ethenol) than it requires slightly richer jetting in and of itself (vs. a conventional gasoline). In some cases it might be enough to offset the differences in specific gravity.

Really, you'd have to know alot about the make-up of two fuels you're comparing to make an accurate judgement about jetting changes. There's no set-in-stone rules about needing to jet up or down. It just depends on the particular make-up of the two fuels being compared. And octane rating doesn't really factor into it--it's other characteristics of the fuel that matter.

When you're being specific about jetting, performance, etc. "race gas" or "110" is far too general a term to be useful. What applies to one race fuel won't apply to another--there's just too many ways they can (and do) differ. To often we focus on octane rating. That's just one of MANY characteristics that distinguish one fuel from another. All octane rating tells us is resistence to detonation--nothing else.

miller 10-06-2006 03:27 PM

cool , the guys at one of the local shops sell me 110 for less than 6 bucks a gallon...however they told me it was Sunoco 110, it is reddish in color....thats about all I know, and they did not have any more info to tell did make more heat with the same jetting though. i didnt run it very long...

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