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SK racing carburetor 45 tuning... jets....

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Hello folks,

 I searched and there is really not much info in regards with these carbs.

i picked up a set of these carbs. Installed the triple and tuned. Here is current setup.

 

E88 l28

N42

Cams

triple sk carbs 45

170 air

130 main f9

50 idle jet

45 accelerator pump jet

 

The problem is im running rich during cruising, yet in wot my afr is good and when leaning of coarse it's fine.

I believe only when cruising, in which my afr is like 10.5-11.

The car feels good, but it just im like i need to gas up everytime.

 

Do you guys know or any tips i can solve this problem?

 

 

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What's your idle AFR and what's the F# of your idle jet? Both the idle and main circuit affect cruise mixture strength. I've attached Keith Franck's white paper on tuning Webers (SK is essentially the same), it should explain some things about sidedrafts that none of the tuning books nor manuals talk about.

Weber_DCOE_Tuning_White_Paper.pdf

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Interesting, I'm not familiar with that naming convention. If we assume that the 50 is the fuel orifice and 100 is air, I'm surprised at how soggy your cruise is. How many progressive holes do these carbs have?

 

Do you have pin gauges or some way of measuring small orifices? Drill bits could be a good substitute, double-check with a caliper. See if you can measure the hole diameter in the idle jet (part with 50/100 engraved in it) as well as your progression holes.

 

Also measure your float level using Keith's method and let us know what you get.

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2 hours ago, Leon said:

Interesting, I'm not familiar with that naming convention. If we assume that the 50 is the fuel orifice and 100 is air, I'm surprised at how soggy your cruise is. How many progressive holes do these carbs have?

 

Do you have pin gauges or some way of measuring small orifices? Drill bits could be a good substitute, double-check with a caliper. See if you can measure the hole diameter in the idle jet (part with 50/100 engraved in it) as well as your progression holes.

 

Also measure your float level using Keith's method and let us know what you get.

 

Im going to get more info about that when i get home.. btw, where can I buy a float tool or the optical fuel gauge seen kn kieths guide?

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Keith sells all of his stuff here: https://www.webstore.com/user,pgr,82598,owner_id,other_items

 

However, I don't think he makes the optical tool anymore. You can make one yourself using polycarbonate rod stock (I think 1/4" should work but measure your e-tube well to be sure) and a plastic sleeve. Alternatively, I've also used the depth gauge of a caliper.

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Posted (edited)

If you plan to make your own, here is a quote from Keith:
 

Quote

You'll need for the optical level measuring tool 1/4" to 5/16" clear acrylic or polycarbonate rod. The ends need to be lathe face cut with a sharp toolbit and then flame polished.

 

Use polycarbonate, as acrylic will lose its transparency after enough contact with gasoline.

Edited by Leon

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Posted (edited)

Usually a rich cruise is due to fuel level set too high.  DO NOT follow the 25mm level Keith D. Franck states. It does not work for our cars. Also do not follow his 12.5 A/F across the board.

 

Weber Spec and SK Racing/OER Spec is 29mm.

 

F2 E-Tube is your friend.

 

This page will help you out: http://240260280.com/Tech/Carbs/Weber/DCOE Theory Operation and Tuning.html

 

post-26437-14150825750279.jpg.1e4b1b51b8619a9a5a80e621ee18bcf7.jpg

 

855295514_29mmFuelLevel.thumb.jpg.1641cc5a8bdb3e6dd10700a1cab42033.jpg

 

 

Edited by Joe King

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Cool,

 

Once I receive the jets and tool. I’ll update you guys.. thanks Leon, Ryan And Joe king. Very informative.

 

I may have to reach to you all in a week.

 

What do you guys recommend for wideband? 

Im still checking my Afrs via tail pipe.

 Is there a kit I can purchase?

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I do it with the engine running for the most representative results. Here's my process to setting floats:

- Warm up the engine, make sure it's in good tune and not shaking at idle

- Pull one main jet stack out of each carb

- Measure and record float levels, take multiple measurements for greater fidelity

- Shut off the engine and remove the float covers

- Use a caliper to measure the distance between the float and float cover with the float tang just touching the float valve

- Adjust the above measured distance by the difference in measured and desired float height, it's a 1:1 relationship

 

All it typically takes is one iteration when using this method. SKs and OERs that have externally adjustable float levels still need a course adjustment on the tang but are more forgiving due to said adjustment.

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Leon, you got me lost starting removing float covers.

 

how ever i use this oer sight tool.  I placed the in specs with sk/oer of 29-31. 

I noticed my exhaust burning my eyes afterwards, and my engine temps getting higher and now my engine overheating. So i might have to revert back.

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 clockwise to raise float level, counter-clockwise to lower float level.

If you use the OER sight tool, you stick the tool inside the orifice of where the emulsion tube sits, you put your finger over the hole on the tool, and pull the tool out. Observe where the fuel is sitting, and make adjustments accordingly.

 

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Hello fellas, so i was able to put the fuel float level to specs.

 

So i have synced the carbs, how ever one of my carbs i think is bad.

On the same carb reads 4 then 5.

any guess what’s the problem?

 

next is im thinking of rebuilding the sk carburetors. I have an sk 45mm. I think it’s Chokeless.

Which kit should i buy? found this link http://lupinusflower.ocnk.net/product/20

 

Thank you.

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What do the other cylinders read on the flow meter?

 

If the others read 5, then you possibly have a vacuum leak, bent throttle rod, or misaligned butterfly. If the others read 4, then you likely have either a bent throttle rod or misaligned butterfly.

 

Remove your progression hole covers to diagnose a bent throttle rod. Use smoke or spray for vacuum leaks. If everything comes up inconclusive, then a butterfly is misaligned.

This assumes proper valve lash and even cylinder compression.

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