This is why I decided to do Dyna runs, more important to me than the Tq and Hp figures was the air fuel ratio's (AFR)

So, I started doing my mods way back when, knew nothing about motors, knew nothing about carbs....basically knew nothing.

so, did my BAK, set-up the carb, ported.
all seemed fine, had absolutely no issues from my first stab at all this. About 6 months later, one night at a bike nite, there was a mobile Dyna, figured what the heck lets see. Of course now, after yrs of reading, talking to the pro's (Bob Yost, the Head tech @ Mikuni)and a few others, I know a bit more. But any way.

my first run WOT was lean approx a AFR of 15
my idle was lean and my mid-range cruise was lean.
How was I to know? All ran fine (or so I thought)

these AFR figures below are from a number of sites I have come across over the yrs

Cold Start (first 30 sec) 11.5-12.5 (choke)

Idle 12.8-13.5

Part Throttle Cruise 13.0-14.0

Wide Open Throttle 12.5-12.8 (values down to 11.5 may be used to reduce detonation

(btw a AFR of 13.5 is needed to get max Tq)

If you don't have the "DATA" then how do you really know?

Lets take this hypothetical situation
say your main jet is a 165 and you go to a 170, sure, you'll see a difference by the seat of the pants, but.....what if the 165 was an AFR of 16 and going to a 170 brings it down to 14, but, how do you know, you never did a AFR run, yes, you felt a seat of the pants difference, but still way lean, lean, that you might not get that 13.5 afr thats needed for Max Tq. Lean in that it is causing excessive heat too and possibly detonation as well.

If you notice from the above chart, (not including the start afr) between the 3 ckts, there is only a 1.5 change in afr from it's leanest to it's richest. (leanest @ 14...richest @ 12.5)

Over the yrs, not in only my runs (about 10)and seeing data sheets from others, it appears to me that a afr of 13 at cruise speed (65mph as per Mikuni)yields 40mpg, and at 14 yields 50mpg.

Mikuni uses 65mph on as much on a straight road with no winds. I've noticed over the yrs that it does not take much in playing with the throttle to kill mpg. If you really want to know what the best mpg you can get is to do a long cruise and hold the throttle steady. Yes, it is a very mundane ride, been there, done that, but it will tell you what the best mpg's you're gonna get.
I've done quite a few like this
149 miles @ 65mph yielded me 49.7mpg
121 miles @ 80mph yielded me 40mpg
this tells me as well, as more throttle is applied I am getting richer which is the direction I want to go

Any way, take what ya need, toss the rest
















)

Great info!
I want to take mine in for a Dyna run to dial it in too. I'm sure my adjustments are off cause I've been adjusting by the seat of my pants

Steven

Erbman, you know what i took from it? When i can actually upgrade to the 42 i'm headed to ur house to make sure it gets set right. (if u dont mind helping out a carb idiot). My wife has family in riverview and would have a reason to go visit them.

I think you are absolutely correct. And going lean I think is what causes Gas Puking. It goes lean and heats up and when stopped pukes.

Mine did that for over 45K miles, because of the intake leak on the Ben Herr Manifold, Odd once I ditched that I have no more puke. Because, I am not running lean.

With the Ben Herr I was running lean intermitently After a while I could actually tell as well as the passenger.

So be sure you have a sealed system before dumping money on a DYNO or results will be all over the map.

just give a holla. actually you are not far from me anyway as it is.

Very well spoken Neil .... yer talking CV40 right?

You should do an elborate write up in detail on a HSR42 for 1600/1700 or have you already done this

You did do a elaborate write up for the CV40 on a 1600/1700 Roadstar 141841.1


also noted not many out there... can afford a A.F.R. meter and let it just ly around till someone needs one, most just get close to yer readings and let it go by the seat of there pants!

Just a thought one can purchase a A.F.R. meter, Rent it out with a large deposit "rufundable" if the unit is in good working order when received back to the owner. Renter pays shipping cost. also if the renter damages componets and accessories they can be purchased by the user....



Samson

MS1700 wrote:
I think you are absolutely correct. And going lean I think is what causes Gas Puking. It goes lean and heats up and when stopped pukes.

Mine did that for over 45K miles, because of the intake leak on the Ben Herr Manifold, Odd once I ditched that I have no more puke. Because, I am not running lean.

With the Ben Herr I was running lean intermitently After a while I could actually tell as well as the passenger.

So be sure you have a sealed system before dumping money on a DYNO or results will be all over the map.

yes, lean could be a reason for the puke, it's causing excessive heat.
And yes, for sure want to be rid of any leaks. Usually the carb pilot ckt ends up compensating by making it richer than where it needs to be. Vacuum is strongest at idle and diminishes somewhat as throttle is applied. The stronger vacuum will pull in more outside air and lean the ckt from the leak area..

A few yrs back, when riding I would get lean condition symptoms, but at idle, using starter fluid, absolutely no indication of any leaks. I changed jetting about 3 times, finally, upon a visual examination I found my leak. The original boot that came with the Nemesis carb had a tear right at the edge of the clamp, but at idle, it stayed closed, but riding and the bumps and the dips in the road would case that tear to open and close. Mind you, this was not a small tear, it went around the boot 1/3 of the way. Since I went with radiator hose, have not had one issue

Well Neil I'm still waiting for you to come up here to work on my 42................lol

Well Samson, I've noticed the same results as far as mpg to those AFR numbers with both stock and 42hsr carbs. I've done by far a lot more testing with the 42 than the stock carb. I didn't have the stock carb for more than a yr, it developed a leak coming out of the carb throat and damaging the filter in my Bak. Had the float lowered twice, no help. Changed the needle valve and o-ring, no help. After 3 months and trying various fixes, went with the 42.

I did more than my share of different jetting in the 42, just for the "lets see factor" Some where in the neighborhood of 25 different jettings, and 8 to 10 AFR runs.
I've also ran 4 different filters.
I also tried all the "A" setting on the Dyna3k as well have even hard wired the retard sw. to work with the use of a VOES, and even tried all the retard settings. (big waste of time) I also ran the 42 with no mods, with a VOES and now with the TPS mod.

Never once doubted your expertise..........knew you had more knowledge and brains and a bald head to prove your theory behind all the maaddness. lol


Samson