Main jet setup on big bore stroker 100 cui with s&s super B.

[viking-bob]

Hey guys
I have a shovel with carb issue I rebuild the engine last year and now I must readjust the jets. As I drive the bike to around 2800 rpm. It stalls big time.

By now I have an idle jet: 031 and main 073. I must put in a bigger main but how big, any suggestions?

Here is the setup:
100 cui (1620 ccm.)
Big bore s&s cylinder, s&s crank, Andrews C cam, dual spark plugs with dyna's ignition, black dyna coils, Accel yellow power cables for half Electronic ignition with new advance kit optimised inside founding, s&s oil pumps, s&s super B carburator, a 3 / 4 "drag pipes open, new energy one clutch with aluminium release plate and Barnett springs.

//viking-bob aka. lars

[junior]

couple of thoughts....

one area overlooked in issues like this is ignition impedance matching. first be sure that the coil impedance matches the ignition primary resistance (in most electronic ignitions @3 ohms).

next, depending on throttle plate position it is entirely likely that even at 2800 rpm under a light/medium to medium throttle you are still running off the pilot jet. before beefing the main i'd poke the pilot up a notch and then verify the air screw setting (make sure its warmed up fully).

let us know-

s

[viking-bob]

Hey junior
I haven’t thought about that, but you are right that could be an issue, so I check it. The ignition primary resistance is fine. It reads exact 6,1 ohms (on my $12 multimeter) on both coils and it should be 5 ohms witch is what Dyna recommends to street use. Nice.........

The airscrew I have set to 1 1/4 turns from button and if I try to open- close more it stalls. So airscrew should be ok, but I will try to install a 032 pilot and check the result.

At 2800 rpm the throttle is open not more than 1/5- 1/4 and if I give more it stalls (won’t take the increase in air) later today I go on a ride and shoot a small film to upload on you tube for you all.

To my knowledge the main jet takes over around 2800- 3000 rpm. Therefore I think it is that one. BUT i'm absolutely not sure on that one.

//Lars

[Relic]

!00 cube shovel? That B carb ain't big enough, Bro. Over 80 cubes they get a bit twitchy. You really have to play with that sucker to get it right.

[junior]

that's true, bud- but he might start with a .033 to .035 pilot and maybe a .085 to .090 or so main first before throwing the baby out with the bathwater. it sounds like he might be overseas (forgive me if you are not in norway or some other viking-related place), and putting a 44mm keihin or a super g might be really costly for him. heck- you are familiar with that for sure.

oh- and bob- the transition from pilot to main is more like 5/8-3/4 throttle or better on most carbs in my experience....

hope all is well for you, relic....

j

[Heretic]

Ok, I am in a bit of a hurry at the moment, but I have the S&S E off my old 103 inch pan in my garage (used STD heads, so breathed like a shovel, but looked like a pan)....I will check what jets are in it....

I don't have a flow chart handy, but I am pretty sure 38mm is the best for anything up to 96 cubic inches, and 40mm would be the optimum size for 100 cubic inches. Anything larger, and you lost intake velocity.....If it is used more as a bar hopper than a touring bike, it can be beneficial to size the carb a little small for better throttle response.I know that clips a little off the top end, but how often do you really ride at full throttle?

[rwpatton]

At !00 cui The B is at its flow limits but still capable. I run a B on a 98cui stroker shovel. I run .035 intermediate and a .080 main. I also added a thunderjet third circuit. IMHO a must. Air bleed jet at 150 and thunderjet at 124. Runs like a scalded dog and breaks shit. Always!

FWIW

RW

[Heretic]

At !00 cui The B is at its flow limits but still capable. I run a B on a 98cui stroker shovel. I run .035 intermediate and a .080 main. I also added a thunderjet third circuit. IMHO a must. Air bleed jet at 150 and thunderjet at 124. Runs like a scalded dog and breaks shit. Always!

FWIW

RW

you are close to the jetting for the triple X perpped carb on my 127 incher there. I have dual thunder jets though

[viking-bob]

Hey again
This weekend as I set off to shoot the small film to youtube the bike was DEAD. Ok I know I did some shit with the ignition switch (cheep after mark model) No problem, I just hotwire the bike.... So said, so done. Out on the road and making ready to shoot the film, holding the camera with my left hand and giving throttle with the right hand, run the bike to app. 2800 rpm nice and easy. Turned the throttle to max and bam the bike jumped forward and almost kicked my sorry a.. Off..... The problem was a bad ing. Switch...
But reading all the post inhere I still will try to give the bike bigger jets...

I have one question for you all what octane gas do you run on in the US? (I run on 95-99 octane gas.)
And how much $ does a Thunder jet kit cost in the us?

//Lars

[Heretic]

On my hot rod, the hot wire to the ignition does not run through the switch. I have relays wired into the 12 gauge main wire lead to the ignition/ coils. The original ignition wire is still run through the switch and the handlebars, but now it just triggers the relay. I also have a second relay wired in, that shuts off power to everything but the ignition and the starter relay when the starter button is depressed. That way I do not have multiple power draws on startup. The power meter on my dakota digital h runs off my coil hot lead, so I know if ignition power is down. The rest, I really don't worry about. if something happens and I don't have power to my Ipod, I can still get home, if I have ignition