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mikuni tuning UL80

Moderators: Curt!, Pa



Posts: 64

Joined: Wed Nov 18, 2009 7:40 pm

Post Wed May 02, 2012 6:57 pm

mikuni tuning UL80

even'n folks, i've been reading this board for 5 yrs while i pieced together a 39 UL, thanks to all the folks on this board for all the valuable info i've learned here, i have a UL bobber.....slightly stroked for quench, T&O flywheels, the heavy pair. ported and relieved, mallory ign, wishbone frame with a modern springer and late harley rear wheel with disc brakes, kinda a bike version of a street rod. i have several bikes from a stroked shovel to a twin cam dresser with well over 100k on the clock. the UL will be run as a daily runner . i'm using a mikuni VM 38 and need a baseline for tuning, main jet is a 400 and too rich, at full throttle it stumbles badly, i have panics tuning booklet and he suggests a 330 main, i ;m wondering if any folks on this board may have experience with the 38's on a ul, any info from needle and needle jet to pilot jet. as a hot running engine i don't want to be overly lean but slightly rich under load if preferred, thanks for any help. all yeah this is my first rocker clutch and tank shifter, at 800 miles on her i'm getting the hang of it and liking it quite a bit but those first couple hundred miles were full of real thrills...toe to go, kept doing that backwards, yeah have a good laugh, later Mark Andrews


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Posts: 1600

Joined: Thu Jun 27, 2002 12:01 am

Location: Interlaken, NY USA

Post Thu May 03, 2012 4:51 pm

Re: mikuni tuning UL80

I've been using the VM38's for years, been very happy with them. The 330 main is about right, I've used 20, 25, and 30 idle jets, depending. Usually, the carbs I find at swap meets have been set up originally for sporty's or big twins and have worked well with the slides and needles they came with. Usually the are originally from Sudco, who do the original setup. I've played with slide cutaway, but found the original ones work best. Don't remember the number just now, but can check if you like. With the right pilot for your machine, they are first or second kick machines, with out bothering with all that primer kick nonsense that Linkerts seem to require. Yes, "the opinions are mine, and your results may vary" :-).

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