Mikuni Help
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Road Master
Joined: May 2018
Posts: 783
Likes: 179
From: Bay Area
Mikuni Help
Hey guys. I just picked up another fxr and Im looking for a little bit of clarity. Its still 80 evo with thunderheader and EV 27 cam. It has a Mikuni 42 on it which is foreign to me. Came from MN to me here in CA so could have been tuned right up there but def not here haha. Runs ok, idle seems to be fine but any hard throttle and wants to die. Crack full throttle and not let go right away it will.
Pulled the main jet and its a 160. Two of the bowl screws are stripped so I havent been able to open it up to see about everything else. Mixture screw is one turn out, anything more or less and it idles rough or wants to die.
Ignition wise its a S&S HI-4N set at mode 5 and advance rate at 9. Coil is the Andrews red 3 ohm coil (dual spark I think?)
thats the details I have now hoping someone can tell me the typical killer combo for this set up. The jets and parts arent expensive but shipping takes forever so Id rather order everything and spend an extra $5 for something I might already have then have to wait another week to order another piece.
Pulled the main jet and its a 160. Two of the bowl screws are stripped so I havent been able to open it up to see about everything else. Mixture screw is one turn out, anything more or less and it idles rough or wants to die.
Ignition wise its a S&S HI-4N set at mode 5 and advance rate at 9. Coil is the Andrews red 3 ohm coil (dual spark I think?)
thats the details I have now hoping someone can tell me the typical killer combo for this set up. The jets and parts arent expensive but shipping takes forever so Id rather order everything and spend an extra $5 for something I might already have then have to wait another week to order another piece.
Club Member
Joined: Sep 2010
Posts: 15,429
Likes: 7,122
From: Beyond Fucital
There's a Mikuni manual online you can print. Also there a write-up for jetting for better mileage.
I just installed a HSR42 on my 94 Softail. Same setup as you.
Andrews cam EV27
S&S ignition, single fire coil
Good right out of the box
The tuning book explains the adjustments for jetting to fix your issue.
I just installed a HSR42 on my 94 Softail. Same setup as you.
Andrews cam EV27
S&S ignition, single fire coil
Good right out of the box
The tuning book explains the adjustments for jetting to fix your issue.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,095
Likes: 7,622
From: Poolville
A 25/170 should be more than enough for what you have in that. Unless there is at least a 5,000 ft elevation difference between the previous owner and you, I highly doubt that that's the issue, most likely dirty carb just needs a good cleaning... Also not a big fan of the high four ignition.. Known to have issues.
Seasoned HDF Member
Joined: Oct 2007
Posts: 8,852
Likes: 2,493
From: Decatur, Alabama
So I put a Mikuni on my ironhead and it wouldn't run worth a crap. I pulled it off, took it apart and dunked it in a gallon can of carb cleaner you can get at any auto parts store. It has a little basket to hold small parts too. After a 3 hour soak, cleaning in water and blowing out dry with compressed air, I put it back together and it ran great with no adjustments.
So before you do any adjusting on that carb, dunk it in that cleaner first. I've tried cleaning them using the spray cans and it doesn't work like this stuff does. Not very expensive either.
carl
So before you do any adjusting on that carb, dunk it in that cleaner first. I've tried cleaning them using the spray cans and it doesn't work like this stuff does. Not very expensive either.
carl
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,095
Likes: 7,622
From: Poolville
Thread Starter
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Road Master
Joined: May 2018
Posts: 783
Likes: 179
From: Bay Area
Thanks for the replies. Yea I have been reading the manual and it gets a bit overwhelming after awhile haha and I cant ride it right now due to rain.
just took the carb apart and Im going to clean it real good.
found out
pilot jet is a 25
needle is a 97 on the third (middle) clip
needle jet is a 6 series (Y-6)
just took the carb apart and Im going to clean it real good.
found out
pilot jet is a 25
needle is a 97 on the third (middle) clip
needle jet is a 6 series (Y-6)
Seasoned HDF Member
Joined: Apr 2010
Posts: 9,562
Likes: 7,916
From: Long Island, New York
Those stripped screws on the bowl are for a Japanese phillips head screw driver, standard screw driver will strip them every time. Do a search, people sell allen head replacements so you can get them on and off again with all of the BS. I had to use a vise grip to get mine off, not fun.
PS have the same setup in my '97, worked just great out of the box, good luck.
PS have the same setup in my '97, worked just great out of the box, good luck.
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Road Master
Joined: May 2018
Posts: 783
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From: Bay Area
Ok cleaned the carb up good, put in a 165 main, kept the 25 pilot and moved the needle up so the clip is on the 4th down
at idle the mixture screw seems to be best at 1.5 turns.
im not using VOES and it was just cut before so it forced the hi-4 to use the retarded version of the curve. I grounded the wire now so it used the advanced version. Havent been able to ride it yet but in the garage it seems to respond pretty good. Except if I hit the throttle off idle hard it sometimes gives a backfire in the carb.
I need to test ride it and see if theres pinging but the carb backfire has me confused.
at idle the mixture screw seems to be best at 1.5 turns.
im not using VOES and it was just cut before so it forced the hi-4 to use the retarded version of the curve. I grounded the wire now so it used the advanced version. Havent been able to ride it yet but in the garage it seems to respond pretty good. Except if I hit the throttle off idle hard it sometimes gives a backfire in the carb.
I need to test ride it and see if theres pinging but the carb backfire has me confused.
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Seasoned HDF Member
Joined: Aug 2008
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From: Ohio
There's a Mikuni manual online you can print. Also there a write-up for jetting for better mileage.
I just installed a HSR42 on my 94 Softail. Same setup as you.
Andrews cam EV27
S&S ignition, single fire coil
Good right out of the box
The tuning book explains the adjustments for jetting to fix your issue.
I just installed a HSR42 on my 94 Softail. Same setup as you.
Andrews cam EV27
S&S ignition, single fire coil
Good right out of the box
The tuning book explains the adjustments for jetting to fix your issue.
A pop out the carb is a lean condition, back fire could be a timing issue but most likely lean