Carburetor and Fuel System
Title: Mikuni
carb tuning
I am still pretty new to this bike and panheads. I had it at a shop for some other work. They "tuned it up" for me. Big mistake. I'll start another thread aout the electrical. Anyway, they did the tuning with the choke on. So I'm starting over from scratch.
Thamks for any and all replies.
Post by DanM on Jul 28, 2005, 11:05pm
Check out Victorylibrary.com- he has a booklet on tuning the Mikuni. I had one when I ran one on my 45 and it was very good. Here's the add from his site:
Mikuni Tuning for Harley-Davidsons”; for the Mikuni round-slide VM type carburetor. Want more performance from your Harley-Davidson Knucklehead, Panhead, 45, or U-Series? Already have a Mikuni carburetor, but don’t know how to adjust it? Doesn’t run “right”, and won’t respond to the changes you’ve made? Can’t make any sense of the original Japanese“instructions”? Looking for an affordable alternative to replacing or rebuilding your tired Linkert? This booklet will help you! Click the cover for a complete list of contents.
Dan
Post by Mbskeam on Jul 28, 2005, 11:58pm
hello
on my carb a VM 38 stock was:
main jet #330 now #280
pilot #30 now #22.5
needle #166 Q2 left this alone
jet needle 6DP1 left this alone
air jet 2.0 now 0.5
throttle valve 2.5
this is on a 74" pan with drag pipes.As you can see there is a diff. from there set up to mine, hope this helps.
this set up will give you that med. tan on your plugs
mbskeam
The only thing that I feel.......will be the RECOIL
Post by Mbskeam on Jul 29, 2005, 12:01am
hello
oh....
air screw in will richen idle mixture
out it will give more air= lean
mbskeam
Post by 63panhead on Jul 29, 2005, 4:37am
Thanks for the replies. I thought that I would be lean with the jets I have. Doesn't look that way, thanks mbskeam. I must have a fundamental problem that needs to be fixed before tuning. Have an adapter for checking intake leaks with Mikuni?
Post by 63panhead on Jul 29, 2005, 3:20pm
Installed 25 pilot jet and 330 main jet. Tightened manifold fittings. Started second kick. Ran fine with choke on. No more missing. Turned off choke. Still ran OK for a minute then started to pop through the carb. Made adjustments to air bleed screw and idle speed. Still pops through the carb. Died, wouldn't restart. Will try again cold. Any ideas?
Post by Mbskeam on Jul 30, 2005, 12:42am
hello,
if you have to keep the choke on with this carb, then I think that you have a intake leak.pull off the carb and test manifold.
what manifold do you have? are you running the adator and the rubber sleeve?.
on mine I welded the adaptor to the carb to get rid of the sleeve, then you can run the stock style intake.
I have the mik tunning book and it did help some but,
I just played with the jets to get it where I like it. with this set up it gets in the low 40's MPG. Ifin I keep the fun factor low.
mbskeam
Post by 63panhead on Jul 30, 2005, 10:21pm
Mbskeam,
I have the rubber adapter from the mani to the Mikuni. I tinkered with some things and have bike running somewhat OK now. I think that I did have a manifold leak but I tightened all the fittings on the manifold and it made a big difference. It will run without the the choke now. However, it pops through the carb. It does it while idling and while riding.
Post by sleeper on Jul 31, 2005, 5:10am
63-
Hoping you don't have an intake leak, is asking for trouble. It still does Not run right. That's an indication for further testing..
If it were my bike, I would test the intake in the correct air pressure fashion, as described here. This will tell you how bad your leak is, & where it is at..
Otherwise, yer pissing up a rope. Stop the leak, & you would be amazed how nice & easy to tune your bike can be..
PS: Every carb needs a carb support.
JUst hanging there, hitting bumps is asking for it to start a leak, after ya just fixed them.. If you do..
JMHO
Post by 63panhead on Jul 31, 2005, 10:57pm
Thanks. I'll look into it and post what I find.
Post by 63panhead on Aug 5, 2005, 1:52am
Thanks for the help. I took apart the intake manifold and cleaned up the gasket mating surfaces and replaced the O-rings. I also installed new spark plugs. My pan is running great now. Starts first kick and I rode around all day, no problems until I ran out of gas...oops. I will look into supporting the carb better. Any suggestions on a bracket for a Mikuni carb?
Post by Mbskeam on Aug 5, 2005, 2:11am
hello,
thats good to hear,
what jets are you runnin?
now dont forget to turn off your gas when you park it.
dont want you to have the good morning I had today,
forgot to turn off the gas last night and when I get out into the garage I smell gas ......
as I was pushing it out the door, gas is coming out the breather port....oh this is not a good sign
well, filled the front cyl full (hydro lock) pulled plugs and out came the fuel. then took off the oil return line, and ran it into a container, pulled the gas filed air cleaner and kicked some more.
finally got it runnin and it spit a buttload more out the breather, ran it untill the oil started to come out and not gas from the return line.
I get to change the oil now,
I wonder if this is the pans way of getting back at me for ridding another bike, just lick a women scorned I tell ya.
mbskeam
Post by Mbskeam on Aug 5, 2005, 2:13am
oh....
after this weekend I can take a pic. of my hanger bracket for ya
mbskeam
Post by 63panhead on Aug 5, 2005, 6:24am
mbskeam-
Sorry to hear about your gas problem. I have a new Mikuni now, the old one did the same thing as yours. I think the needle valve seat was worn. I haven't left the gas on since changing carbs but gas does not run out of my air vent tubes now when I stand the bike up. It always did with the older carb. I am running a 25 pilot and 330 main jet; 166 Q2 needle, 6DP1 jet needle.
