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JC - Tri Fuel Carb Adjustment


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  #1  
Old 02-08-2008, 07:36:37 PM
Ted_Cool Ted_Cool is offline
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Default JC - Tri Fuel Carb Adjustment

Hi All,

Now that my JC is running well on propane, I plan to try gas. I see that the carb has both idle and main jet adjustments for the gasoline side. Since the governor brings it to 1800 rpm right away, does the idle circuit play any role? How would I adjust it? My manuals don't have much info about the carb, so I'm hoping one of you knows the procedure.

I'm guessing a vacuum gauge will be my friend...

Thanks !
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Old 02-08-2008, 08:05:42 PM
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EricWood EricWood is offline
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Default Re: JC - Tri Fuel Carb Adjustment

Set it as you would any other small gas engine carb. Start it, idle it down by hand, adjust idle speed screw for an appropriate idle speed if necessary, then adjust idle mix screw out until engine speed starts to drop, then back in until running smooth, and as you guessed, you can use the vacuum gauge to look for an optimum setting.

Then let it "snap" to rated speed, and check response. Little sluggish, try a little richer. Belch of black smoke and falter, try a little leaner.

Then, adjust the high speed mix the with the same procedure.

These engines run just off-idle at no load/light load, so they do pull fuel across the idle circuit during those high vacuum periods.

eric
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Old 02-19-2008, 12:38:47 PM
Ted_Cool Ted_Cool is offline
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Default Re: JC - Tri Fuel Carb Adjustment

Thanks for the advice - That worked pretty well!

I'm hoping to use a vacuum gauge to get a good final adjustment, but I don't see any ports to hook into. Has anyone here done that?
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Old 02-19-2008, 01:53:24 PM
Ben Clarke Ben Clarke is online now
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Default Re: JC - Tri Fuel Carb Adjustment

Hi Ted
Some of the tri-fuel carbs did not come with the internal pieces (float etc.). Be sure you have them before you pour the gas to it.
Ben
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Old 02-19-2008, 11:15:35 PM
Ted_Cool Ted_Cool is offline
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Default Re: JC - Tri Fuel Carb Adjustment

I did take a chance hooking up the gasoline without checking the carb first, and I seem to be lucky. After sitting unused for 36 years, the fuel pump sucked the gas up like a champ, the bowl filled, and when the engine started sputtering, I shut off the propane. A few more sputters, and it started running pretty well! I fooled with the needles a little bit, and it seems pretty good. Propane seems a little smoother, overall. I've been starting the set on propane, then cutting over to gasoline to excersize it. That way, I don't have to fool with the choke. So far, so good!
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