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Old 07-11-2019, 11:12 AM   #1 (permalink)
IronButt
 
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Jake707SBFMC wants to know Dino or Syn?
Jetting Questions

Ok trying to fine tune the Ultima 131 a bit. I put on an AFR gauge so I got a little data.

First, carb is a bored G with thunderjet. Current jetting is:
Main - 0.82
Inter - 0.33
T Jet - 135

First question, what determines which jet is being used, RPM or throttle? Meaning, if Im in high gear putting away at 3k rpm but barley 1/4 throttle is that running off the main jet or interm?

Second question, related to the first, if barley on the throttle cruising on the freeway, not bogging the motor above 2500 RPM but maybe 1/4 throttle, the AFR gauge shows in the 10-11 range, hell going up to Tahoe it even got in the 9s a bit and I think caused the motor to sputter? But if I crack the throttle all the way open it goes up in the 13s and 14s.
Would that mean Im running too rich on the main jet?

I had it tuned beginning of the spring but had to swap out the Ultima carb for a real S&S and had Scott at Hillside bore it out while I was at it. Also planning to have head work done over the winter so don't want to pay another $450 for dyno tuning if I can dial it in close myself for now.
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Old 07-11-2019, 11:26 AM   #2 (permalink)
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Uncle Salty is still riding a stock bike Uncle Salty is still riding a stock bike
This recent thread appears to be relevant to your application. It'll give you something to read while you're waiting for a qualified person to answer. ('cause I'm not)
https://www.v-twinforum.com/forums/e...42838-jet.html
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Old 07-11-2019, 12:51 PM   #3 (permalink)
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Uncle Salty is still riding a stock bike Uncle Salty is still riding a stock bike
I'll toss in my opinion but keep in mind although I have tuned EFI cycles and carbed autos, I haven't tuned a carbed cycle. Sounds like you're a bit rich down low (10-11, even 9 parts of air to 1 part of fuel) and getting lean when you open it up (13-14 air to 1 fuel). My EFI Road King is around 13-13.5 to 1 at lower RPM, 13.5-14 cruise at light throttle and 12.5-12.8 at higher RPM open throttle. That's just a general view but you get the picture. 9 to 1 is rich, 14 to 1 getting pretty lean on an air cooled motor.
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Old 07-11-2019, 12:59 PM   #4 (permalink)
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ecir45 is reading this now saying WTF is this? ecir45 is reading this now saying WTF is this?
rpm not throttle position tells what circuit you're in, read pdf below.

https://www.zippersperformance.com/i...stallation.pdf
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Old 07-11-2019, 03:19 PM   #5 (permalink)
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tall terry is still riding a stock bike tall terry is still riding a stock bike
you may be 1 size rich on the main,,, with a t-jet,, the low speed jet should be close,,,

what size is the air bleed on the thunderjet? it should come I at around 4500rpm,,,
a large engine can use a 190-200 air bleed,,, bringing the t jet in later..
did the folks who did your thunderjet,,, do the full package? or just bore it and add the t jet..
I sometimes send a new G carb to zippers,, cost is in the $300 range for the full package,,,

as an example or 2
my modified S&S 113,, uses an 80 main, 35 intermediate with 3/4 turn out on the af screw,, and a 165 t-jet with a 200 or bleed.. it rolls like a CV no stutters sputters, just acceleration
another 117 S&S,, I also modified used a 32 low speed, 78 high speed, 165 tjet and a 175 air bleed

the 113 makes 137hp the 117 is in the 145hp range,,, and is just like mine,, smooth as glass and wicked quick.
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Old 07-11-2019, 05:03 PM   #6 (permalink)
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Thanks guys

How do I check the air bleed on the T jet?

Not sure what the full package would include but I sent him the G carb he board the throat and bored in the T jet, then put in rough guess of jetting.
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Old 07-12-2019, 10:40 AM   #7 (permalink)
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I had a couple hours between jobs yesterday so I watched a video from s&s on jetting and tuning which helped a bit but didn’t cover the thunder jet piece.

I also put on the larger filter Scott sent with the worked G. I’ve been putting it off looking for a backing plate to run the external breather kit I have plus I need an end cap. But I said F it and slapped it on. Looks like 10#s of sh*t in a 5# sac with that cover but it works. Hopefully it doesn’t leak between the filter and backing plate.

Anyway. Adjusted the AF mixture some and marked the screw so I can MSN’s sure it’s not turning in it’s own. This seems to have helped some but I think I need to spend more time and swap some jetting still.
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Old 07-13-2019, 11:39 AM   #8 (permalink)
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I watched a S&S video on tuning the Super E & G carburetor this morning. Tuning those isn't that much different in principle than the automobile carbs in the past. The A/F ratios they used are in the ballpark with what I did on my Road King except I'm a little leaner while cruising at light throttle. Interesting video.
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Old 07-14-2019, 06:28 AM   #9 (permalink)
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Quote:
Originally Posted by Uncle Salty View Post
This recent thread appears to be relevant to your application. It'll give you something to read while you're waiting for a qualified person to answer. ('cause I'm not)
https://www.v-twinforum.com/forums/e...42838-jet.html
Well that started out good with some informative information but went to hell.
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Old 07-14-2019, 04:01 PM   #10 (permalink)
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ecir45 is reading this now saying WTF is this? ecir45 is reading this now saying WTF is this?
Jake you figure your air bleed size yet, should be on the left side of the carb above S&S Super.
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Old 07-14-2019, 06:31 PM   #11 (permalink)
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Originally Posted by ecir45 View Post
Jake you figure your air bleed size yet, should be on the left side of the carb above S&S Super.
No haha. I been looking at the dam thunder jet wondering what else there could be for air bleed size. What’s funny is I just watched that video again and the mentioned an air bleed in the spot to look st once the bowl is off. Some are fixed and some are replaceable ?

I think my G is the older style or it at least has the older style choke “T” handle not the arm lever you pull up so not sure if mine is a fixed size but I’ll pull the bowl this week. Took her on a 9 hour ride up the coast so letting her catch her breathe and my a$$ relax haha
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Old 07-14-2019, 07:35 PM   #12 (permalink)
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see the pdf I posted above tuning a tjet is not the same as a regular S&S carb, disregard that video. The original location you described above should now have a screw plugging that hole. The air jet is external in the location I described above. look at top left of S&S Super printed on side of carb, clearly visible if you look there.
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Old 07-14-2019, 09:31 PM   #13 (permalink)
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Quote:
Originally Posted by Jake707SBFMC View Post
Thanks guys

How do I check the air bleed on the T jet?

Not sure what the full package would include but I sent him the G carb he board the throat and bored in the T jet, then put in rough guess of jetting.
The air bleed for the T-Jet is on the base of the jets main body. Look at the base, regardless of what color the body is, there will be a raw aluminum slice at its very base. There is at least one very small hole, that is the air bleed for the T-Jet. To change its size requires a set of very small drill bits.

Depending on your Super carb, the bleed for the main jet is either internal/fixed, internal/replaceable or external replaceable.

If the main jet air bleed is external, it will be on the rear portion (towards the back of the bike) of the carb looking at it from the side. The air bleed for the main jet uses jets with the same thread pitch as the T-Jet. Be careful as there are two very different types of jets that will screw into those holes and work, but they have very different numbering conventions. Some will easily get the too confused.
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Old 07-14-2019, 09:48 PM   #14 (permalink)
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tall terry is still riding a stock bike tall terry is still riding a stock bike
get the instruction sheet for the thunder jet from zippers,,, it thoroughly explains how the tjet,, and the rest of the carb circuits work once the tjet is installed... read it nd understand it before you try tuning it like an unmodified super G.

my zippers carb had these mods..
throat bored
a bowl vent machined into the carb body,, the original vent plugged.
a
an air bleed installed,, and the original plugged.
a high flow needle and seat installed
thunder jet installed and bowl drilled for the fuel supply.
a few other mods but I dont remember..
I used a 5/16 fuel line and petcock..
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Old 07-14-2019, 09:59 PM   #15 (permalink)
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ecir45 is reading this now saying WTF is this? ecir45 is reading this now saying WTF is this?
turbo cleared this up. main jet air bleed is the one I think terry way questioning it size above being it usually replaceable unlike the tjet air bleed that is fixed.

As terry said read the zippers manual again again and again.

https://www.zippersperformance.com/i...stallation.pdf

Last edited by ecir45; 07-14-2019 at 10:03 PM.
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