Hello all,

davej, (and others also) I do have kind question on AFR readings. I did purchase also Innovate gauge and planning to start carb tuning as season starter once desperately expected spring comes. As previous season end I did change my setup to RC1980 filter and Barons jet kit. I am newbie with AFR gauges and so expecting nice things to be learned in here.

My initial question concerns on ambient temperature effect to AFR. I am planning to use gauge only as measurement tool and get it off once tuning is done. I live in cold climate and expect carb tuning to happen at 40-50F temps due early season. Typical on season temp, where most of riding happens is around 70F.

How much I should adjust my AFR targets due this expected delta 20F on temps? 0.2? Or even higher.

I have read more or less all existing writings on this forum concerning AFR details and several cases there mentions on effect of ambient temp. Secondary extremely helpful detail would be also some rule of thumb on how much one step in main jet effects on AFR. And same case similarly with needle. I bought Barons kit due I got educated, that Barons needle is easier to tune than stock.

I am dreaming to be able to hit very right spot with AFR due gas is damn expensive here (north Europe). Record has been 8USD/gallon. I cannot go to safe side against lean.

If you guys are willing to chat more, I would like also to speculate with my AFR targets. Yes, there is plenty of good numbers existing already in this forum and based on those I have set my targets already. Previous season, with stock carb jetting, stock air cleaner and drilled pipes (maybe stage2, not sure due it was done by some previous owner) setup I reached 50mpg as average. I know, that it is lean and I was lacking power due that. I think I afford to go little bit up perhaps to 42mpg or so.

Thank you already!

You have some good questions some that I can't give an exact answer for because I have never tuned for those low temps. Although I would still start with the standard jetting recommended for a 1600 and tweak it from there. (167.5 - 170 main jet,37.5 pilot jet, needle clip in 4th groove and pms @ 2- 2.5 turns out) The cold weather shouldn't have a real effect on the general jet sizes and needle setting. I recommend that you try to achieve a AFR of around 13.5 for idle,13.5 - 14 AFR for lower speeds up to 4th gear (35 - 45mph), 14.5 AFR for upper cruising speeds but you can go as high as 15afr. I always liked to stay closer to 14.7 but 15 is still OK but a little on the lean side and not much mpg gained from it. I don't know of any "rule of thumb" for main jet difference but I will tell you that anything more than a mikuni 170 main is too large and with a aftermarket air filter and exhaust you want to choose between a 167.5 or a 170 main jet Choose the main by going to WOT and the main you want should drop your AFR to no lower than about 12AFR (if it dips into the high 11's for just a second it would still be OK but 12 is my preference) and no higher than about 12.5 and use a 37.5 pilot jet. needle clip in the 4th groove but you can play with the washers from under the spacer to change the needle setting by 1/2 step for each washer added or removed from the bottom of the plastic spacer. (example) clip in the 4th groove w/plastic spacer and 1 silver washer is considered to be in the 4th groove. Remove the washer and now you are at groove 3 1/2 which is a 1/2 step leaner, If you use 2 washers under the spacer you would be at groove 4 1/2 which is obviously richer. Changing the main jet has more of an effect on WOT and don't show much difference at cruising speed, changing the needle clip position will show an immediate effect in all ranges with the exception of idle. Going to the larger pilot with help for a smooth transition between circuits and in lower to mid cruising speeds. Happy tuning to Ya!!

Hi FPB, yeah, that's as close as I could get. I bought it at a police dept auction of old police bikes and then proceeded to chop it as that was the rage back then in the early 70's. But I left the carb and carb cover stock so the picture you see is the original carb cover. Oops, having trouble reformatting the pic so I can post it.
Tried twice and now when I click edit it won't give me the option of posting a pic. I can tell you that the cover was original and it was smooth on the outside unlike the one I found online that has the circular grooves in it but it is a pretty close approximation. PM me your email address and I'll send you pics. BTW, it had the 6 volt ignition which I upgraded to 12 and changed the countershaft sprocket to a higher gear ratio for expressway driving..
You will see in the pics that I did a major chop on it. Paint, king queen seat, springer, Sportster tank, etc. And yes that is me with the long hair which also was in fashion back then. LOL!Father_Pobasturd wrote:
[quote]Get down wit cho bad o-mage 666. I had a '49 EL, Mine had the "bell" cover. Is that as close as you could get, or is that not the new one pictured?

curmudgeon666 wrote:
Hi FPB, yeah, that's as close as I could get. I bought it at a police dept auction of old police bikes and then proceeded to chop it as that was the rage back then in the early 70's. But I left the carb and carb cover stock so the picture you see is the original carb cover. Oops, having trouble reformatting the pic so I can post it.
Tried twice and now when I click edit it won't give me the option of posting a pic. I can tell you that the cover was original and it was smooth on the outside unlike the one I found online that has the circular grooves in it but it is a pretty close approximation. PM me your email address and I'll send you pics. BTW, it had the 6 volt ignition which I upgraded to 12 and changed the countershaft sprocket to a higher gear ratio for expressway driving..
You will see in the pics that I did a major chop on it. Paint, king queen seat, springer, Sportster tank, etc. And yes that is me with the long hair which also was in fashion back then. LOL!Father_Pobasturd wrote:
[quote]Get down wit cho bad o-mage 666. I had a '49 EL, Mine had the "bell" cover. Is that as close as you could get, or is that not the new one pictured?

WTF??? Is this an inside joke? Was there another pic other than your Rosdstar?

Hi Spydr, I mentioned that my choice of a retro carb cover was because I used to own an old Panhead with a similar cover and FPB said he had a similar one back in the day and I tried to post pics but of mine but ran into problems and told him to PM me his email address and I would send them to him via email which I did.Spydr wrote:
curmudgeon666 wrote:
Hi FPB, yeah, that's as close as I could get. I bought it at a police dept auction of old police bikes and then proceeded to chop it as that was the rage back then in the early 70's. But I left the carb and carb cover stock so the picture you see is the original carb cover. Oops, having trouble reformatting the pic so I can post it.
Tried twice and now when I click edit it won't give me the option of posting a pic. I can tell you that the cover was original and it was smooth on the outside unlike the one I found online that has the circular grooves in it but it is a pretty close approximation. PM me your email address and I'll send you pics. BTW, it had the 6 volt ignition which I upgraded to 12 and changed the countershaft sprocket to a higher gear ratio for expressway driving..
You will see in the pics that I did a major chop on it. Paint, king queen seat, springer, Sportster tank, etc. And yes that is me with the long hair which also was in fashion back then. LOL!Father_Pobasturd wrote:
[quote]Get down wit cho bad o-mage 666. I had a '49 EL, Mine had the "bell" cover. Is that as close as you could get, or is that not the new one pictured?

WTF??? Is this an inside joke? Was there another pic other than your Rosdstar?

Good! Thank you davej for this instruction! My original AFR targets were on this area, except high cruising speeds 14.5. I was hesitating on that, but of course this is beneficial at MPG point of view. I will target on there now.

Currently as starting point I did set up 167.5 main, Barons needle at 3rd groove, 37.5 pilot and PMS 2.5 turns open. Once tuning starts at coming spring I should not be far from optimum already.

BTW, have you been tuning accelerator pump? I tested shortly Innovate gauge in garage before covering bike to winter sleep and recognized, that AFR changes heavily once you flick throttle. I have already notified acceleration pump article at RSC and decreased duration adjustment 2 turns as wild guess. Even though mixture seems to get very rich for short period due this pump operation. Is it somewhat overshoot?

3rd groove is too lean go right to the 4th if you want to play from there do it by adding/subtracting washers from under the spacer. Set the acc pump to start squirting immediately and squirt to between 1/2 - 2/3 of the way thru the throttle twist.

Ok. Thanks davej, on these! I will concentrate on this acc pump now during winter. Also probably go to 4th groove already even without testing now same time. Tank removal for needle adjustment is not that fun.