my 416 dyno

[bayou boy]

yesterday I got her dynoed...first run 36.57 hp 26.65 torque. my mods are JE 10:8:1 416 bore, C&D head work, hot cam old stg 2, HMF sport series full system, 39mm fcr, ehs racing air box lid. 165 main

[bayou boy]

last run...38.08 hp 27.56 torque. we took off the lid and ended up with a 175 main. not bad I think for a basic 416 on gas. I am happy. he told me he had dynoed an 05' 400ex stock for a reference a few months ago and it pulled 25 hp.

[chad502ex]

a/f on second run tagg'n 16 seems too lean. I'd watch runn'n it open for long drag runs with 16 a/f,...

[bayou boy]

he told me that too..I am going to put a 178 in it it should fatten it up a little bit. I probably should have did one more run with a 178. look at the air fuel on the first run it is crazy

[bayou boy]

lol forgot to post it

[cory]

Bayou boy, where did you dyno your bike? They have a dyno around Houma?

Did you ever run it again with the bigger main? You'll probably pick up a couple more HP just on the richer main jet!

Who did you get to do your bigger valves? LATER....

[bayou boy]

the dyno is moto madness he is in jennings. a lil west of lafayette he is the guy that brings the dyno to clash of the titans. yes i did jet up to a 178. have to jet down for the summer though it gets a lil lazy. i do not have bigger valves.

[400eXr1d3rZ]

I want my quad dynoed :( , after i get some money and get a 450r carb, and port and polish :D

[cals400ex]

what needle and clip position are you using?

[bradley300]

why would he want a bigger main? its already way too rich at 8000 rpm? the main might make the lean part better, but its going to make everything else worse?

[honda250xrider]

Originally posted by bradley300
why would he want a bigger main? its already way too rich at 8000 rpm? the main might make the lean part better, but its going to make everything else worse?

ok, but wouldnt the fact that at 3000 rpm with wot it would be lean because the engine isnt needing the amount of fuel needed but at 8000 it is starving. I would rejet to a higher main jet and just ease the throttle next time on the dyno to full throttle maybe this isn't how you do it but to me what your saying bradly is that you wouldnt rejet? I'd hate to be running wot with it being that lean.

[cory]

Desired air fuel ratio hovers around 14.7:1 for efficient internal combustion. At 8000 rpm, he's around 16. 16 parts air to 1 part fuel is more air to one part fuel. So 16:1 is way lean. 8000 rpm is near WFO, so the main jet needs adjustment to compensate....

You are forgiven.....

[bayou boy]

lol....this post has more replies in 2 days than it did when i posted it a year ago. as far as the needle and clip position too be honest i really dont know. i had bought a cheap fcr off ebay and sent it to colby to set up. i bolted it on and got it dynoed. we never had to mess with the needle or clip position. in the summer i do need to drop the main down a size or too....it is real humid down here and with the 178 it feels a lil lazy in the hotter months

[MXin700R]

14.7 is true Doech(?) but only when the engine is not under load. When under load it needs to richen up. Most top tuners shoot for 13-13.5 but thats gonna vary from engine to engine. Mine and other 700s like to be a tad rich for optimal power, 12.7-13.0

[cory]

I might be mistaken, but on a dyno....don't you have it under load??? My bikes show minimal variation between a/f ratios regardless of a load (gear ratio, 3rd gear pull, 5th gear pull, whatever) but I'm not a pro....just based off past experience.

[cory]

Did you mean stoichiometric? And...just by past experience....richening the mixture below 14.7 only helps cool the engine combustion (under high load, lower EGT). I've never seen a performance increase by richening under a load unless you are referring to the increase in power from the cooler temperature? Only so much oxygen in there...added gas is only gonna cool it off and get wasted....and maybe prevent detonation.

[sandmanblue]

Originally posted by cory
Did you mean stoichiometric? And...just by past experience....richening the mixture below 14.7 only helps cool the engine combustion (under high load, lower EGT). I've never seen a performance increase by richening under a load unless you are referring to the increase in power from the cooler temperature? Only so much oxygen in there...added gas is only gonna cool it off and get wasted....and maybe prevent detonation.



You will find that it is well documented that the best afr is going to be right around 13.5:1 for power. ANYTHING leaner than that will not only reduce power, but stimulate detonation and increase the temps to a point that other damage will occur.

Second, in order to measure the torque produced by the quad, the dyno has a drum of a certain mass (weight for you newbies), and accelerating that mass LOADS the engine, and the rate at which the drum increases in speed is what calculates the rear wheel torque being produced.

So going back to the original dyno runs, this guy was dangerously lean and I certinaly hope that after almost a year, he's fixed that.

Also, look at the afr chart. He increased his jetting from a 170 to a 175 and it did not affect the lower rpm afr. IMO, you need to go a lot further than a 178. How about a 190 or so...