Flatslides on Twinshocks

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sherpa
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Flatslides on Twinshocks

Postby sherpa » Sun Feb 06, 2011 11:24 am

Hi, I was going through some old magazines during a big cleanup at our house and came up with some interesting facts regarding the introduction of the flatslide carburetor [note our 2011 manual of motorcycle sport on page 210, has published the cutoff date for twin shocks as the 31st December 1986]
Australian Dirt Bike, March 1982, page 15 ,while testing a Suzuki RM250Z Quote ' the motor is fed by a new mikuni carburetor similar in appearance to a Lectron but would more accurately be described as a box slide carburetor'
Dirt Bike Rider, May 1982, page 30, Specifications for Suzuki RM list the MIKUNI VM Flatslide as the carburetor
Australian Dirt Bike, November 1984, page 19, photo of mikuni flatslide fitted to Suzuki TS125X, also mentioned in specs
Dirt Rider, August 1985, page 58, Specifications for Suzuki RM list MIKUNI VM Flatslide as the carburetor
Dirt Bike Rider, December 1985, page 17 , when testing the new Yamaha Range Quote 'Along with the new inducion system theres a new flatslide carburetor'.
Dirt Bike Rider, April 1985, page 19, when testing the new Honda range, Quote' the new Flatslide Keihin '
Dirt Bike, March 1986, page 66, Spec sheet for Honda CR lists the carbuetor as a Flatslide Keihin
So that should clear up any misconceptions about when this type of carburetor was first produced.



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Re: Flatslides on Twinshocks

Postby brownie » Sun Feb 06, 2011 4:48 pm

G'day
This a sticker on my toolbox, it came with a carby I bought in 1976 the carby and the bike are long gone only the sticker survived.

Pretty sure I bought it to put on a 159 Sherpa

Ross



Geoff Lewis
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Re: Flatslides on Twinshocks

Postby Geoff Lewis » Sun Feb 06, 2011 7:42 pm

Hi All, It would appear that it is ok to use a flat slide carb in twinshock. It would be up to the individual to decide whether the performance gain is worth the expense. Consider that most trials engines may not benefit significantly from such a conversion and may gain more benefit from a rebore and careful rebuild and proper and thorough jetting.However it may look pretty trick!
Regards Geoff.


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sherpa
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Re: Flatslides on Twinshocks

Postby sherpa » Sun Feb 06, 2011 9:18 pm

Geoff an OKO which is for all intents is a Keihin copy is only $170 which is cheaper than replacing the slide, needle and needle jet on an Amal, which wear out that quickly that you are faced with this cost almost yearly. After all you really want to encourage people to compete at a reasonable cost.



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Re: Flatslides on Twinshocks

Postby OKOAustralia » Mon Feb 07, 2011 9:46 am

Just a word of warning...although flatslides can provide fantastic benefits...'chucking' one at a semi-worm twinshock may not be so cost effective....why?

The flatslides, in limited situations, can be oversensitive (read pain in arse) to tune if your motor is not in good shape..this is because there are many other external factors to consider other than engine condition...eg exhaust, ignition etc

So before you get a flatslide, make sure you have good compression, clean exhaust and good ignition and the bike is tuned well....this way you will reap the rewards of a flatslide carb

Failing this, you are probably better off with a roundslide...as they tend to be less sensitive to engines with wear etc

We have had good test results with our 'speed carburettor' the OKO 3000....no its not a flatslide, its a roundslide, but it tends to be more effective for those who wish to replace a worn carb and in the process improve ride ability etc...this design is especially applicable if your bike does not have reed valve induction...not to say a flatslide won't work on eg a SherpaT though....we have sold many for this purpose and the results are often staggering...except for once......but that was an ignition failure problem brought on by the extra power the motor could produce with the flatslide ....ignition couldn't handle it

just thought we'd let you know......

Cheers
Denis
OKO Australia
http://www.oko-australia.com.au



brt650
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Re: Flatslides on Twinshocks

Postby brt650 » Mon Feb 14, 2011 8:26 pm

Hello Sherpa,
I read with interest about the flatslide carbs on twinshocks. Does this mean I can have one on my 350 SherpaT and ride it at a Aussie comp?
Or will I have to take another carb just in case someone reads the rule book differently?
Thankyou for your research Sherpa.
Cheers
brt650



sherpa
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Re: Flatslides on Twinshocks

Postby sherpa » Tue Feb 15, 2011 2:27 pm

Flatslides are legal according to rules and regulations that are published in The 2011 Manual of Motorcycle Sport, page 210



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Re: Flatslides on Twinshocks

Postby Scorps » Wed Feb 16, 2011 7:09 pm

Howdy Y'all,

Having spent a lot of time researching this, you CANNOT use a Keihin PWK flatslide. These carbies were not manufactured until 1989 - I have talked extensively with Keihin on this matter, and have email correspondence somewhere that proves such.

In light of this, OKO carbs are a visual match for a Keihin, but since a Keihin is ineligible, so is the OKO.

Do not get confused in thinking that because flatslides existed before 1986, you can use any flatslide.....

The only reference I could find to flatslides at the time was what was available on some early RM's - being the the Mikuni VM. It would also appear a Blue Magnum would be fine too....

Sherpa, I could not find reference to flatslide carbs being legal on PG 210 of the MOMS. It still lists the Carb as a major component on pg 209, and as such, it must be visually indistinguishable from an item that could be purchased pre 1986.

Cheers,
Your friendly neighbourhood KawiMan,
Scorps


Children are smarter than any of us. Know how I know that? I don't know one child with a full time job and children.
1981 Fantic 240 Professional
1976 Kawasaki KT250 (x2)
1975 Kawasaki KT250
1975 Kawasaki KT250

David Lahey
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Re: Flatslides on Twinshocks

Postby David Lahey » Wed Feb 16, 2011 9:31 pm

Further to Scorps mentioning flat slide carbies from RM Suzukis, I have heard that the flat slide carbies from some early 1980s Suzuki two stroke road bikes were used on trials bikes in the early 1980s. I'm thinking it was the RG500 or the RGV250 that had suitable carbies. The info I am recalling was from Richard Marken who used them on Bultacos.


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sherpa
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Re: Flatslides on Twinshocks

Postby sherpa » Thu Feb 17, 2011 8:02 am

Hi , sorry I did not mean to imply that any flatslide carbie could be used only ones that were manufactured before december 1986 as per my original post. I will scan some of the articles I have and post them in the next day or so.




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