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Post by 80sting440 on Mar 11, 2017 13:23:24 GMT -5
Now that I have a full season on my 36mm Power Jet carb, I have to say that it works better than I expected.
obj1 says that he uses them for his race sleds and that they run well, so I figured I'd pay attention!
Some other guys are more guarded and won't use them or they eliminate the Power Jet and bump up the main.
Here are some of the things that I've learned along the way:
-the main jet circuit added with the power jet circuit total to the main jet size of a regular Mik carb... eg. on mine I have a 300 main and a 155 power = 455 total...at least that's the way I have it in my head! 
-keep the power jet the same and vary the main as needed
-run the main one size up if you run without the air box
-yes!!! they do run well without that air box and piping!!!...I run mine with an air filter to keep dirt out. (the power jet air intake port is easily plugged with cat tail fluff!).
-mine was retrofitted with an aluminium cab around the carb at the dealership before being sold. This only makes the carb inaccessible and one tends to not service carb as you're always fighting with all of that plumbing and stuff around it!!!!!!!!!!!!!!!!!!!!!!!!!! 
phewwww...I feel better now  I just added extra venting and threw out all of that nonsense (my wife and I have an understanding...I don't keep stuff and she keeps ME!).
-this carb was designed to be more fuel efficient than a regular carb and it is! I get better gas mileage than I expected.
-the mid range runs leaner and my engine does not load up (run too rich) when it's warm out and therefore I don't need to jet down if I'm lazy  ...I just keep a rich main (which is way leaner than a regular Mik) and the added power jet adds extra cooling fuel at wide open throttle to cool down the pistons.
I like them enough to consider using one on any future project.
Rene
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Post by speedbuff on Mar 12, 2017 7:37:40 GMT -5
Good to hear the mikuni works good for you the piece you threw out is part of a highly sought after dealer installed kit. That just goes to show you one man's junk is another mans gold !What machine is it installed on ?
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Post by 80sting440 on Mar 12, 2017 8:20:45 GMT -5
Hello speedbuff.
It's in an '80 Sting.
I did donate the fan housing boot to an online buddy...the rest was mostly all hacked up in one way or another.
Like I said, my wife and I have an understanding... ...we just celebrated 25 years together last week...I'll keep her over "stuff" any day!
Rene
 
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Post by 75whip on Mar 12, 2017 11:14:30 GMT -5
Thanks for the info rene, I like the mikuni carb postings on here that mention jetting, and other info for using mikuni carbs. I have decided from now on im using mikuni or maybe tilly hd on my rockwell/cuyuna engines from now on. Im 50/50 with luck with the walbro wf. The info that is missed the most with the mikuni conversions is what needle jet and jet needle and cutout works best, everyone ask what pilot jet, and main jet are you using, and they are important but half of your throttle is controlled by the jet needle and needle jet. Im going to find a 77 sting here soon to have a partner for my 77 range whip, and I already plain on using a power jet mikuni on that.
Eric
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Post by 80sting440 on Mar 12, 2017 11:40:29 GMT -5
Thanks for the info rene, I like the mikuni carb postings on here that mention jetting, and other info for using mikuni carbs. I have decided from now on im using mikuni or maybe tilly hd on my rockwell/cuyuna engines from now on. Im 50/50 with luck with the walbro wf. The info that is missed the most with the mikuni conversions is what needle jet and jet needle and cutout works best, everyone ask what pilot jet, and main jet are you using, and they are important but half of your throttle is controlled by the jet needle and needle jet. Im going to find a 77 sting here soon to have a partner for my 77 range whip, and I already plain on using a power jet mikuni on that. Eric Check back in a few hours Eric and I'll have all of that info for you.
Rene
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Post by 80sting440 on Mar 12, 2017 12:21:38 GMT -5
Here's how I'm running mine.
Uni foam pod air filter
36 Mikuni Power Jet
pilot jet 35 (found a 40 to be too rich)
main jet 290, ( from 270 for 32 o F to 300 for -30 o F)
power jet 155
needle 6dh21
needle jet 159 p-8
needle clip 2nd from the top (tried one clip down...too rich)
slide 2.5
idle ~ 2500 rpm
I set my pilot air mixture screw so that after startup, the engine runs unaided (without choke or primer) after about 20 seconds. I readjust according to temps...usually 1/8 turn richer or leaner.
This setup along with a good spark and 40:1 synthetic oil mix = no fouled plugs!
If you have any more questions...ask!
Rene
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Post by speedbuff on Mar 12, 2017 23:11:16 GMT -5
Thanks for posting all youre specs it will be a great help to others .I just got some service manuals from a dealer it had all the jetting added that he went to from stock for his customers.I will have to compare to see where he arrived with final jetting for the sting is yours still cdi?
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Post by 80sting440 on Mar 12, 2017 23:29:45 GMT -5
Yes, the '80 and '81 Stings have cdi on their 440 Cuyunas.
Rene
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Post by speedbuff on Mar 13, 2017 9:12:22 GMT -5
Yes but many have been converted to point due to the cdi boxes being no longer available .I am not sure whether the timing curve changes from cdi to points ie is the cdi curve hotter?
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I just added extra venting and threw out all of that nonsense (my wife and I have an understanding...I don't keep stuff and she keeps ME!). 
...I just keep a rich main (which is way leaner than a regular Mik) and the added power jet adds extra cooling fuel at wide open throttle to cool down the pistons.
