Author Topic: Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?  (Read 618 times)

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Offline soldierofortune

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Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?
« on: Thursday, November 01, 2012. 12:14:24 AM. »
Dear All,
Bike : softail heritage 2002
Carburator : Mikuni HSR 42
Current Exhaust : Longshots original by VnH
Previous Exhaust : SE Stage 2 slip ons

Question : Is it really needed to have bigger jets on my HSR 42 ?
Will the current jet sizes be compatible with the exhaust system ?

Facts : after installing the VnH, i have noticed a difference in performance and the bike feels more active.
However, after reading all the reviews, i became suspicious and want to investigate more about getting bigger jets , such as
Main : instead of 160 , get 165  and so forth

I live in the UAE '' Dubai'' , and it is a bit of hassle to get a clear demonstrations and feedback from the Mechanics!
Therefore, your expert feedback is highly appreciated.
Hoping to hear from you and get rid of my confusion!

SOldierofortune

Offline Northside

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Re: Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?
« Reply #1 on: Thursday, November 01, 2012. 07:27:03 AM. »
It sounds like the carb is pretty close if you notice a gain in performance.  Get the Mikuni HSRTuning Manual.  It will tell you how to get optimum performance out of your carb.  The very best way would be have it dynoed by a guy who is proficient with Mikunis, but that's hard to find even in the U.S.  If you are handy with a screwdriver and have the Mikuni Manual you can get it to run very well.

Offline Hillsidecyclecom

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Re: Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?
« Reply #2 on: Friday, November 02, 2012. 03:20:43 AM. »
Dear All,
Bike : softail heritage 2002
Carburator : Mikuni HSR 42
Current Exhaust : Longshots original by VnH
Previous Exhaust : SE Stage 2 slip ons

Question : Is it really needed to have bigger jets on my HSR 42 ?
Will the current jet sizes be compatible with the exhaust system ?

Facts : after installing the VnH, i have noticed a difference in performance and the bike feels more active.
However, after reading all the reviews, i became suspicious and want to investigate more about getting bigger jets , such as
Main : instead of 160 , get 165  and so forth

I live in the UAE '' Dubai'' , and it is a bit of hassle to get a clear demonstrations and feedback from the Mechanics!
Therefore, your expert feedback is highly appreciated.
Hoping to hear from you and get rid of my confusion!

SOldierofortune

We worked with those on more occasions than I can remember.
My suggestion is to see how the bike runs, and pull a plug after a couple hundred miles.
You may need the 165, but many run fine with the 160.
Gotta' play it out as the bike will tell you.
Scott
"If I parrot or google information, folks will suspect I really know."

Offline mkd

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Re: Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?
« Reply #3 on: Friday, November 02, 2012. 06:03:25 AM. »
soldier! if you are close to sea level you may need to change the pilot jet and or main jet but if the mikuni has the same internals since new i would guess not.stock out of the box they are set up to deliver lots of fuel and support more than a stock evo or twin cam motor.if the bike cold starts without the choke your low speed jetting is probably on the rich side.i'm at 850 ft above sea level and have installed leaner than stock pilot jet,needle and accel pump on my stage 1 evo.how it starts cold,how it runs while warming up as well as how long it takes to warm up are indicators as well.coughing out of the carb when cold or at steady cruise means it's on the lean side,starting without the choke,short warmup,black soot out the tailpipe, being able to run without the choke soon after starting,and poor fuel mileage are signs of too rich.keep in mind that the slow speed or pilot mixture screw controls the air and not the gas.turning the screw in richens the idle mixture by reducing air,turning the screw out leans the idle mixture by increasing air.

Offline soldierofortune

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Re: Does a Mikuni HSR 42 must have a bigger jets if installing a VnH longshots?
« Reply #4 on: Sunday, November 04, 2012. 03:56:49 AM. »
Thank you all for the input, it is getting clearer now :)
 i am in the stage of testing the bike on different levels, hopefully in couple of weeks will reach a conclusion and will let you know what is the outcome!
what i noticed is that the bike consuming more fuel than b4! but what the hell ,  it feels alive :)
Soldier of Fortune