Mikuni Tuning
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Mikuni Tuning
I finally got tired of trying to get my Zenith to work right, so I got a couple of Mikunis on Ebay. I downloaded the manual to see what setting I should start with, but it doesn't say anything about a start position. It does tell you how to make adjustments once the bike is running, but I'm not having any luck. I also had a guy at work give me a CV Mikuni form his 95 sporty. It is missing the choke cable, but other wise it is all there. Should I try to use it instead? I have 2003 softail controls and switches, so I am leaning toward using the CV Mikuni, but the throttle cable mounts are only 1/4~1/2 inch from the bottom of the tank. Any suggestions or ideas would be appreciated.
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Joined: Feb 2006
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From: Houston Texas
RE: Mikuni Tuning
I would use the latest model Mikuni you have. If the throttle cable fouls the tank you may be able to insert a spacer between the carb and manifold to move the carb out some, hoping for some more room.
My old Mikuni has a throttle cable with a 90 degree elbow in it and it clears the tank underside (barely). This old carb was made in 1974 and is long out of production.
I have attached a photo of the elbow to give you some idea of what I am describing here........pg
[IMG]local://upfiles/8331/BA5A7ADAD17A492881146E2F5CADF321.jpg[/IMG]
My old Mikuni has a throttle cable with a 90 degree elbow in it and it clears the tank underside (barely). This old carb was made in 1974 and is long out of production.
I have attached a photo of the elbow to give you some idea of what I am describing here........pg
[IMG]local://upfiles/8331/BA5A7ADAD17A492881146E2F5CADF321.jpg[/IMG]
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RE: Mikuni Tuning
I have the Fat-Bob tank, so adding spacer in wouldn't help me any. I'll try to put it on tomorrow and post a pic of the problem. I would prefer to use it, just for the dual throttle cables.
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Joined: Feb 2006
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From: Houston Texas
RE: Mikuni Tuning
ngf.....
Yeah, I know the problem and that is likely compounded by the fat-bob tanks. Air space is scarce between the manifold and the underside of the tank on a Sportster.
If you want to run two cables then the problem happens twice. My old Mikuni is a conventional slide carb and has the strong return spring inside above the slide. This uses a single throttle cable as you can see from that photo I attached to my last post.
I know the government mandated two cables some years back because it was done to'prevent hung throttles' on motorcycles. Give me a break! In fifty years of riding I have never had a hung throttle.
Perhaps your two cable Mikuni will not work unless you have both attached and hooked up? I do not know about that one. If it needs two, well then...you have no choice. Space is going to be a problem however. Send the photo(s) if you get it installed and maybe one of us has something to offer in the way of a solution to the problem.........pg
Yeah, I know the problem and that is likely compounded by the fat-bob tanks. Air space is scarce between the manifold and the underside of the tank on a Sportster.
If you want to run two cables then the problem happens twice. My old Mikuni is a conventional slide carb and has the strong return spring inside above the slide. This uses a single throttle cable as you can see from that photo I attached to my last post.
I know the government mandated two cables some years back because it was done to'prevent hung throttles' on motorcycles. Give me a break! In fifty years of riding I have never had a hung throttle.
Perhaps your two cable Mikuni will not work unless you have both attached and hooked up? I do not know about that one. If it needs two, well then...you have no choice. Space is going to be a problem however. Send the photo(s) if you get it installed and maybe one of us has something to offer in the way of a solution to the problem.........pg
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Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: Mikuni Tuning
OK, that's more than enough reason to run two cables. The challenge is to get the cables close enough to be able to route them in the space close to the frame bar. Obviously easier said than done.
The only thing I can think of is to have elbows on the throttle cable(s) ends, but even with that these elbows will have a quite generous bend in them to necessitate movement of the inner cable(s). Send some photos if you can take some, so we can see what you are faced with..........pg
The only thing I can think of is to have elbows on the throttle cable(s) ends, but even with that these elbows will have a quite generous bend in them to necessitate movement of the inner cable(s). Send some photos if you can take some, so we can see what you are faced with..........pg
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RE: Mikuni Tuning
I'm heading out to the shop shortly. I have two of the older slide Mikunis. Just like the one you have in the pic. I want to use one of them, but I can't find a documentation on how many turns out the throttle screw and air screw should be to start the adjustments. I have pics up soon.
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RE: Mikuni Tuning
I got some pics to help us out. I am thinking I can use a dremel and trim the guidepost for the newer CV carb and possibly make the bend. The Mikuni slide has an accelerator pump on it. Thats what the red circle are showing. I don.t have it hooked up at the moment. I want the carb to run without it before I hook it up.
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Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: Mikuni Tuning
Just turn the air screw in until it seats, and then back it off one and a half turns. This will allow the bike to start. After it warms up you can finish the adjustment of the air/fuel and idle settings.
I would suggest you pop out the slide and check the position of the needle rod that seats in the main jet. This should be in the middle slot. If yours has 5 notches then put it in notch #3 from the top.
You cannot get any parts for these carbs anymore, not even a float bowl gasket....so be careful with all of the carb parts and gaskets. looking forward to the photos.................pg
PS: The Mikuni slide carb is the best and smoothest running carb I have ever dealt with. I bought mine in 1975 to be able to start my Sporty which had the horrid Tilotson carb on it from the factory. I used to kick for sometimes half a day before I could get it going. The Mukini fixed that problem. A one kick machine... every time.
I would suggest you pop out the slide and check the position of the needle rod that seats in the main jet. This should be in the middle slot. If yours has 5 notches then put it in notch #3 from the top.
You cannot get any parts for these carbs anymore, not even a float bowl gasket....so be careful with all of the carb parts and gaskets. looking forward to the photos.................pg
PS: The Mikuni slide carb is the best and smoothest running carb I have ever dealt with. I bought mine in 1975 to be able to start my Sporty which had the horrid Tilotson carb on it from the factory. I used to kick for sometimes half a day before I could get it going. The Mukini fixed that problem. A one kick machine... every time.