carbs

[triumph 69]

 has anyone here tried using the mikunis hsr flatside carbs for a performance boost on these bikes

[John U.]

I'd say, just offhand, that you'd be into some major fabrication to get 6 carbs of a different size or configuration to fit within the available space, connect to the existing (or remanufacture alternate) intake tubes and airbox, and fabricate new throttle linkage. My brain hurts just thinking about it.

[Ricky-D]

has anyone here tried using the mikunis hsr flatside carbs for a performance boost on these bikes

You're assuming there would be a boost.

 

***

[triumph 69]

  Hiperformance flatside carb over a vacuum operated carb and you think their would be no
  performance gain

[Blackduck]

There was a bike modified with 2 sets of carbs off four cylinder units, they loped off 1 carb if I remember correctly. Do not remember what carbs they were.
There were pictures in photo stash of it, Purple colour and used for drag racing.
Well modified and very quick.

[fstsix]

If you are thinking after market this would be a option, Also i have a Mikuni 45 HSR flatslide on my bike, and would say, I will run anybody heads up that has a Kehin on their Blower, Big improvement!!. I have a 911 Carrera, fuel injected, i was looking into doing this Weber setup on my bike, but went with the Blower, price wise the downdraft Weber would be cheaper @ $650.00 per side, but you would have to fabricate the tubes for a manifold, it would be awesome and no vacuum slide, you would loose some low end torque but would gain more top end. if you are into performance this would be a option.http://www.motormeister.com/suz/carb_access/carburetors.htm

[Ricky-D]

  Hiperformance flatside carb over a vacuum operated carb and you think their would be no
  performance gain

That's what you call it! 

The carburetors on the Valkyrie are not vacuum operated! Yes, the slide opens with vacuum but the action of the venturi control is manually operated with the butterfly by the operator.

The only hope of gain would be at WOT and you could probably get it to idle also.

Of course, I know all this is only conjecture and wondering out loud.

Would those be chrome or plain?

***

[Mikey]

If you put on chrome flatslides I'm sure it'd be faster! Wouldn't the flatslides open easier? JW

[fstsix]

The carburetors on the Valkyrie are not vacuum operated! Yes, the slide opens with vacuum but the action of the venturi control is manually ?

[98valk]

has anyone here tried using the mikunis hsr flatside carbs for a performance boost on these bikes

no performance gain unless your on the track, with a highly tuned race engine and u know how to use flatsides.
the Valkyrie carbs are constant velocity (CV) carbs.
http://www.drpiston.com/Cvcarbs.html

what would give a performance boost would be larger CV carbs, as stock are sized for best overall street operation. And bigger carbs require airbox mods and larger exhaust headers.

[Robert]

If fuel injection provides for small gains how much gain do you think another carb would do? Aside from all the bs and cost to make another one work.

[fstsix]

HP Increase Mikuni. http://www.mikuni.com/fs-products_guides.html

[98valk]

HP Increase Mikuni. http://www.mikuni.com/fs-products_guides.html

WOW!!
who would have guessed that they wouldn't just show the HP gain with only a direct carb swap and no other mods.

[fstsix]

HP Increase Mikuni. http://www.mikuni.com/fs-products_guides.html

WOW!!
who would have guessed that they wouldn't just show the HP gain with only a direct carb swap and no other mods.

Just think,? what would happen if you added a excelerator pump, just curious what year was your artical ? 1987 .: One way to deal with this is by adding an "accelerator pump" which provides a shot of fuel as the throttle is opened.  But there is another way which has been adopted for use in almost all modern carbureted street bikes:

[fstsix]

Had read this years ago, Also see BonneValk Land speed record holder.http://www.v-performance.com/products/air_fuel.html http://www.timskelton.com/valkyrie/gen_interest/bonnevalk.htm

[Robert]

I know that on some engines that carb changes are a real gain but that is not the Valk. If you are sighting the Bonneville bike then that thing is meant to run flat out and then yes I could agree that a carb change may help but under most circumstances that you and me would encounter there is virtually no gain and at a great cost. Hp to cost factor would have to be way up there. If you ever looked at the intake of the Valk you would notice the that the outlet of the carbs is quite a bit smaller than the intake runner that's its plumbed to. If yo increase carb size for high end then you may have bad idle because the velocity and amount of air that goes through the carb may not be enough to really give good idle. Like I have always said a engine is a balancing act to much on one side offsets the other. If you are going to go through that expense then put fuel injection on it that has ignition too so you can get rid of the stock icm and make your own maps. This will give the best gain and from there you can do any mods and redial in the system and the cost will be a bit higher but the hp gain will be better. Driveability will be better too and you can open up the intake then any mods done after this will be easier. Why live with the weak points that the bike came from the factory with? OH a Harley is not a Valk I know obviously but the week point in that engine is the carb after the mods you need a carb change because you only have one or two carbs to let all that air into the engine. The Valk has 6 and breathing is not really a major issue. HP takes air and gas if you have 2 openings to let air in as compared to 6 and you are talking about roughly the same hp then the openings would have to be bigger on the 2. So if you go from stock to bigger with more hp then of course there will be a gain. I would like to see that same thing done on the Valk with no other mods and then we will see the true hp gain. Since I have done all the mods on my Valk according to the sales people I should have somewhere around 150 hp well that would really be great if true but in the real world that just dosent happen To give you a idea Jeff K has a blown Valk with some nice work and just about every bell and whistle under the sun on it and I think it pushes 150 to 165 hp now Jeff please forgive me if I am wrong so if Jeff with a blower , fuel injection aftermarket ignition gets that much how much will just a carb change do? Dollar per hp there just no better deal than a blower.

[fstsix]

I believe Jeffs HP Max was with a S&S Carb Not FI from the notes he has posted on his Dyno charts, with all due respect  


View Profile Email Personal Message (Online)
   
   
Re: Dyno results
« Reply #9 on: September 17, 2009, 01:58:45 PM »
   Reply with quoteQuote
Quote from: fstsix on September 17, 2009, 01:56:08 PM
Jeff K. Was that with the S&S carb or fuel injection ? Just curious.

S&S super G

Got the flat spot out but my mileage dropped to 17mpg  Shocked