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Thread: mikuni hsr 42mm

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    Default mikuni hsr 42mm

    I picked up a mikuni hsr 42mm carb for my sporty. Does anyone have any experience with these they want to share? It was super cheap so I snagged it. It came off a 96" big twin so I'll have to re jet for my bike which is a ported 1250. I'm gonna open it up today and see what size jets are in it.

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    Quote Originally Posted by metalheart28 View Post
    I picked up a mikuni hsr 42mm carb for my sporty. Does anyone have any experience with these they want to share? It was super cheap so I snagged it. It came off a 96" big twin so I'll have to re jet for my bike which is a ported 1250. I'm gonna open it up today and see what size jets are in it.
    It's to big for your sporty........

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    Quote Originally Posted by Tattooo View Post
    It's to big for your sporty........
    Nope, not too big. 1200+ XLs will turn way more revs than a big twin, and need big carburetion to do it. The HSR 42 may actually be on the small side, depending on the head porting and cams.

    Jim

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    Quote Originally Posted by Tattooo View Post
    It's to big for your sporty........
    For once, I'm gonna' have to disagree with the esteemed Tattoo.

    It's a super common upgrade on 1200 XLs, and they work quite well.

    FWIW, there's a really good booklet from Mikuni on getting these carbs dialed in available online.

    Download link:

    http://www.mikuni.com/pdf/hsr_tuningmanual_021003.pdf

    If you spend the time to dial it in, you will be rewarded with throttle response like a freaking light switch when you trust the grip WFO

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    Quote Originally Posted by JBinNC View Post
    Nope, not too big. 1200+ XLs will turn way more revs than a big twin, and need big carburetion to do it. The HSR 42 may actually be on the small side, depending on the head porting and cams.

    Jim
    You can't say it isn't to big then say it depends........... But I'm sure you know more about the new bikes than I do....

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    Quote Originally Posted by thecarfarmer View Post
    For once, I'm gonna' have to disagree with the esteemed Tattoo.

    It's a super common upgrade on 1200 XLs, and they work quite well.
    Your more than likely right..... What I was going by was a 38 was just right for an ironhead...... I can't be right all the time..... LOL

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    Quote Originally Posted by Tattooo View Post
    You can't say it isn't to big then say it depends........... But I'm sure you know more about the new bikes than I do....
    Reread what I said. I said it's not too big, and may possibly be TOO SMALL depending on heads, cam, etc. We raced these motors for over a decade in XLs and Buells, so I learned a little bit, yeah.

    Jim

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    Quote Originally Posted by JBinNC View Post
    Reread what I said. I said it's not too big, and may possibly be TOO SMALL depending on heads, cam, etc. We raced these motors for over a decade in XLs and Buells, so I learned a little bit, yeah.

    Jim
    Reread what I said....... {But I'm sure you know more about the new bikes than I do....}

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    I have no experience for the HSR42 on a Sporty, but I be learnin'
    Here is a horsepower gallery for 883 and 1200 with various upgrades, with 3 examples of the HSR42 mixed with other mods on 1200's (86HP, 94HP and 103HP):

    Performance and Technical information on engines for Harley-Davidson motorcycles.
    http://www.nightrider.com/biketech/h...orty_stock.htm

    and info from the same site, "to describe the way to perform a 883 to 1200 upgrade;...The attention to detail in this article is excellent...This rebuild consists of choosing Wiseco dished 9.5:1 pistons, X-Hasting rings, Harley-Davidson base gaskets, Bartel’s .027 head gasket kit, Andrews N2 Cams, Yost Power Tube and normal Stage I modifications (i.e. Screamin’ Eagle (SE) air cleaner, slip-ons, 45/180 re-jet, SE coil, SE 1200 Ignition module and the Vance & Hines SS2R racing exhaust system)."
    http://www.nightrider.com/biketech/x...200_page00.htm

    oh, wait, still more:

    2017 Thread: Mikuni hsr 42 tuning need help
    "...this is a 97 sportster bottom end with 10.5-1 compression pistons, and 04 sportster heads with after market valve springs. Also has screaming eagle cams with 546 lift I believe. The cams are a high RPM range cam. It has drag pipes..."
    http://www.chopcult.com/forum/showthread.php?t=48736

    Testing the Mikuni HSR42 Easy Kit for Sportster
    https://www.streetchopperweb.com/tes...-for-sportster
    Last edited by TriNortchopz; 04-28-2019 at 8:52 PM.

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    ^^^^^ So it could be to big depending on the modifications to the motor...^^^^^^


    So well we shall see......... A carb on a drag bike can be useless on the street..... I know that for sure......

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    I’m in to know what jets are in it now, have a 96” project that I picked up a 42 for

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    It's going on a 94 1250 sporty with the 883 heads that have been ported, 10.5-1 and thunderheader. The hammer performance guys recommend them for bikes that have their kit. It was cheap so I thought I would give it a shot. I just opened it up and it has a 30 pilot, 155 main, and I believe it's a 95 Needle? was hard to read. clip in the middle for the guy who was asking. If it ends up being too big for my setup now hopefully it will work in the future when I change the cams and put on the thunderstorm heads I have. Things I've read have kinda been back and forth so Ill get some jets and put it on and see how it goes and report back.

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    Yes let us know..... Post a pic of the plugs if you can when you can.........

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    My buddy runs one of these on his 900cc triumph bonneville without issue

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    How'd he feed two cylinders from one Mikuni? Custom intake?

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    My buddy runs one of these on his 900cc triumph bonneville without issue
    Quote Originally Posted by farmall View Post
    How'd he feed two cylinders from one Mikuni? Custom intake?
    I see dual HSR42 kits for the Triumph twin:
    Click image for larger version. 

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    The 800GT Carburetor kit was specifically developed for the new series Triumph Bonneville’s. The kit is designed by and manufactured exclusively for BONNEVILLE PERFORMANCE. It consists of twin 42MM HSR Mikunis (pre-jetted for your bike), CNC machined billet manifolds, airbox adapters, and top and bottom braces.
    Click image for larger version. 

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    https://triumphbonneville.org/mikuni...08-bonneville/

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    Yeah that’s it. I forgot they run 2. But either way, it’s a great running bike and he’s had it on there for a long period of time.

    I did have a friend who had a hopped up big twin, maybe 88” evo FXR and ran a 42 HSR and got considerably worse fuel consumption than I did on my stock 80” with a CV. Even with a 1200 and cams on my sporty chop and CV, I get 50mpg easy. While the HSR are probably good carbs, fuel mileage takes a hit.

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    Quote Originally Posted by brooklynbomber View Post
    (snip...) While the HSR are probably good carbs, fuel mileage takes a hit.
    I couldn't speak to that - when I put the carb on my bike, it was at the same time as swapping in a 1200 with aftermarket cams and porting, from an 883.

    After the swap, I can't seem to keep out of the throttle so I don't have any idea what mileage the bike would get if I was riding it like a normal adult

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