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Brent Harper
Joined: 30 Mar 2003
Posts: 892
Location: United States, Texas, Lubbock
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 Posted: Fri Oct 29, 2004 10:29 am Post subject: |
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| Why don't we just say 42mm maximum for both the 250 and 450. GO, NO-GO. It seems that would be the simplest way of teching this. Otherwise we end up with arguments over polishing and how much metal was removed. I was also wondering where the 39mm max for a 250 came from anyway? Can't 125's run any size carb? |
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2919
Location: United States, New York, Ossining
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| Posted: Fri Oct 29, 2004 4:38 pm Post subject: Re: 2005 WKA Unlimited Rules Updated |
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John, as far as the 450's, the "electronics" is a throttle position sensor. OK now, there is NO electronic fuel metering device in these carburetors. The ONLY reason for the sensor is to retard the timing in a low RPM, high throttle position, ie. 3rd gear plunking around in the woods, whack the throttle wide open.
Stock OEM Specs as follows:
Honda CRF450, all years 40mm Kiehin
Yamaha 05 YZF 450, 39mm Kiehin
A couple things to consider about after market carbs.
After market Kiehin FCR's come in 37mm, 39mm, 41mm
The List price for an 04 YZF450 carb, 5TA-14101-00-00 is $889.58
The list price for an 04 CRF450 carb, 16100-MEN-671 is $614.87
The list price for a aftermarket 39mm FCR Kiehin w/TPS 016-927 is $593
The list price for a aftermarket 41mm FCR Kiehin w/TPS 016-937 is $623
Honda 04 CRF450 engine assemblies S0010MEB004, retails for $4140.75 and does not include Ignition box, coil, wire harness, and carburetor.
I don't think anybody else offers an engine kit, so for a Yamaha, you would need to buy a bike or maybe ebay it.
42mm max, that's it, same as last year.
Chris R. |
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John Ferreira
Moderator
Joined: 25 Jul 2001
Posts: 605
Location: United States, New Hampshire, Londonderry
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| Posted: Fri Oct 29, 2004 7:48 pm Post subject: |
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| Brent Harper wrote: | | Why don't we just say 42mm maximum for both the 250 and 450. GO, NO-GO. It seems that would be the simplest way of teching this. Otherwise we end up with arguments over polishing and how much metal was removed. I was also wondering where the 39mm max for a 250 came from anyway? Can't 125's run any size carb? |
Where did the 39mm come from?
It was the carb supplied with the original WKA Rotax 250 class. 38mm Round slide for the 244 and 39mm Flat slide for the 257.
Why not 42 mm - go-no-go
When it came to reviewing class speed and safety with the committee and the trustees, - when we were doing the rules for the ENTIRE Unlimited class, a limit was set on what they wanted to see for max performance. A decision was made that those parameters (carb, mods, fuel, pipe etc) where what they were willing to live with. And that was the base line. LAST year, we realized that the way we teched carbs per the WKA manual - our specified 39mm carb would not pass tech. So - we set a max DIMENTION size of 42mm knowing that no point in most 39mm (oval carb) was greater than 42mm. We did that to get us thought 2004. Problem is, slide carb are made oval for metering and throttle drivability - for BIKES. We mostly run WOT. So - making a 42mm round carb will definitely improve the base line that we set.
Otherwise we end up with arguments over polishing and how much metal was removed.
I am going to make this one REAL simple. If the tech man thinks you removed too much material in polishing - then you are illegal. Worried about it - do not do it. You all know what a 39mm - readily available - mass produced carb is ...and most are more than polished enough.
Can't 125's run any size carb?
--let me ask the guy who wrote those rules - oh that's me  ..
Yes then can - both 125 Laydowns and 125 Shifty Sprint. WHY?
Law of diminishing returns ...bigger is not going to be better on a 125 ... but on a 250 - yes it will make a difference.
John |
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2919
Location: United States, New York, Ossining
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| Posted: Fri Oct 29, 2004 7:57 pm Post subject: |
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John, if the 450's are being allowed a 42mm carb, do we have to limit the manufacturer and model? That's only going to drive the price of the engine packages up.
Chris R. |
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Don Engebretsen
Joined: 23 Oct 2001
Posts: 123
Location: United States, Tennessee, Eads
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| Posted: Fri Oct 29, 2004 9:25 pm Post subject: |
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John:
As far as I know Chris is correct about the Yamaha...$900.00 carb, throttle position only, and I had to buy a bike to get my motor. Anyone can buy a TM 42 or TM 45 Mikuni for about $400.00 retail and a bit over $300.00 at dealer prices. Mine came with a carb, but I would rather run the Mikuni.
I personally would like the carb size and manufacturer to be open for both the 250's and 450's (no FI). If that is impossible, I vote for 42 mm with aftermarket allowed in the 450 class and I defer to you for the 250 carb size.
Right now I have a bored stock carb and both the TM 42 and TM 45. Too bad I don't have something I can run in WKA!!!! I don't care what the next rule change is... I am holding off on buying the Dominator 1050.
Regards,
Don E. |
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