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Steve Perdue
Joined: 07 Dec 2003
Posts: 97
Location: United States, Washington, Algona
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 Posted: Wed Sep 19, 2012 1:33 pm Post subject: |
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What about the frame?? I heard from testing it bends the average frames after several uses.So a new thicker frame will have to be made.
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Keith Bridgeman
Joined: 24 Aug 2001
Posts: 1335
Location: United States, Minnesota, Farmington
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| Posted: Wed Sep 19, 2012 1:37 pm Post subject: |
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New engine that costs $5,999. The Swedetech, SRS and DDR version then will be about $9,999 for a stock one. yeah!
Now that SKUSA has cleared out some time in the supernats they can add is as an experimental class. I bet 20 would show up the first time no matter what the cost.
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Merlin / Maxter KZ |
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Keith Bridgeman
Joined: 24 Aug 2001
Posts: 1335
Location: United States, Minnesota, Farmington
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| Posted: Wed Sep 19, 2012 1:38 pm Post subject: |
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| Steve Perdue wrote: | | What about the frame?? I heard from testing it bends the average frames after several uses.So a new thicker frame will have to be made. |
Yeah, the 30mm frames that are now popular in shifter karts will not work well.
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Tim Pappas
Joined: 25 Jul 2001
Posts: 792
Location: Burkina Faso,
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| Posted: Wed Sep 19, 2012 2:20 pm Post subject: |
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| Steve Perdue wrote: | | What about the frame?? I heard from testing it bends the average frames after several uses.So a new thicker frame will have to be made. |
As long as you don't use a Tonykart you will be okay. I heard that they only last 3 races with a Yamaha Can. 
We put over 500 laps on with one on a standard 30mm chassis with no problem. While it does make a bit more torque, the engine makes marginally more horsepower than a stock moto and a fair amount less than a KZ or open moto and they don't have any problem with 30mm chassis.
There is going to be all kinds of misinformation about these engines depending on which side of the street you are on. Take it all with a grain of salt.
We don't build or sell engines and have no skin in the game except we to have spent some time with this engine package. Some people will like it, some won't. The future of the engine as a race package is in the hands of the organizations and HPD. It does make a great recreational engine as long as it is left stock.
Oh, my popcorn is done. Gonna get a bowl and watch this fester.  |
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Matt Kaiser
Joined: 19 Sep 2005
Posts: 25
Location: United States, Nevada,
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| Posted: Wed Sep 19, 2012 3:29 pm Post subject: |
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I think EFI is a great idea. Even with the added expense.
No tuning on the fuel I would guess?
For guys like me, even with software, etc, carburator tuning can be scary. Trying to maximize performance, without destroying the engine, specifically if you are trying to kart on a budget or not karting every weekend. Just hop in and go (relative of course).
I would be interested to hear about that part, tunable, fire and forget, etc. |
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Jim Derrig
Joined: 22 Apr 2008
Posts: 1012
Location: United States, Washington,
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| Posted: Wed Sep 19, 2012 3:40 pm Post subject: |
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| Spencer Uzri wrote: |
I live in the PNW & don't know what track you're referring to with regard to a 2-stroke ban. PGP is supposedly in litigation with King Co. regarding their noise permit, but I don't think that's specific to 2-stroke engines. If anything, comparable-output 4 strokes are louder & their noise covers greater range (Sound range & frequency are inversely proportional, & it's obvious whether or not you know the math).
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PGP just sent out an email saying it is opening a new 4-stroke CRF 250 shifter class and the first race is Oct 13. They also are creating a 6.5 hp 4-stroke class. So it looks like the ban is specific to 2-strokes. |
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Jim Derrig
Joined: 22 Apr 2008
Posts: 1012
Location: United States, Washington,
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| Posted: Wed Sep 19, 2012 3:59 pm Post subject: |
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| Tim Pappas wrote: | | Steve Perdue wrote: | | What about the frame?? I heard from testing it bends the average frames after several uses.So a new thicker frame will have to be made. |
. . . .
We put over 500 laps on with one on a standard 30mm chassis with no problem. While it does make a bit more torque, the engine makes marginally more horsepower than a stock moto and a fair amount less than a KZ or open moto and they don't have any problem with 30mm chassis.
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I'd also note that the torque the chassis sees depends as much on gearing as on torgue at the engine output shaft. The rear tires' ability to transmit that torque to the ground also is a limiting factor. The CRF 250 is a 5-speed right? My guess is that the torque gain at the shaft is going to be offset at least partially by people running a taller gear ratio, partly to get more straightaway speed and partly because if they geared like a 2-stroke they'd just find themselves applying the throttle later and less coming out of a corner. |
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Howie Idelson
Joined: 18 Jul 2001
Posts: 1337
Location: United States, California, Pacific Palisades
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| Posted: Wed Sep 19, 2012 5:19 pm Post subject: |
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No more stress on the chassis then a CR125. The built motos were much more violent and we never had a problem. The CRF is smooth like Buttah.
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Howie Idelson
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2929
Location: United States, New York, Ossining
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| Posted: Wed Sep 19, 2012 5:24 pm Post subject: |
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| Jim Derrig wrote: |
I'd also note that the torque the chassis sees depends as much on gearing as on torgue at the engine output shaft. The rear tires' ability to transmit that torque to the ground also is a limiting factor. The CRF 250 is a 5-speed right? My guess is that the torque gain at the shaft is going to be offset at least partially by people running a taller gear ratio, partly to get more straightaway speed and partly because if they geared like a 2-stroke they'd just find themselves applying the throttle later and less coming out of a corner. |
There's a reason why 4 strokes are dominating motocross, and it wasn't because of HP, it tractability. Remember a 4 strokes power pulses are every 720 degrees, not every 360 degrees like a 2 stroke. Even if it had more torque and HP, it's only abusing the axle and frame 1/2 the time as a 2 stroke....
CR
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Spencer Uzri
Joined: 18 Apr 2006
Posts: 798
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| Posted: Wed Sep 19, 2012 7:46 pm Post subject: |
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| Jim Derrig wrote: | | Spencer Uzri wrote: |
I live in the PNW & don't know what track you're referring to with regard to a 2-stroke ban. PGP is supposedly in litigation with King Co. regarding their noise permit, but I don't think that's specific to 2-stroke engines. If anything, comparable-output 4 strokes are louder & their noise covers greater range (Sound range & frequency are inversely proportional, & it's obvious whether or not you know the math).
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PGP just sent out an email saying it is opening a new 4-stroke CRF 250 shifter class and the first race is Oct 13. They also are creating a 6.5 hp 4-stroke class. So it looks like the ban is specific to 2-strokes. |
Yeah, I just checked that out. Wave physics clearly shows that the regulation should favor 2's, but then it's King Co., so I shouldn't be surprised. 
Caveat: maybe it never was about noise...?
I suspect the issue isn't over.
| Chris Reinhardt wrote: | | Jim Derrig wrote: |
I'd also note that the torque the chassis sees depends as much on gearing as on torgue at the engine output shaft. The rear tires' ability to transmit that torque to the ground also is a limiting factor. The CRF 250 is a 5-speed right? My guess is that the torque gain at the shaft is going to be offset at least partially by people running a taller gear ratio, partly to get more straightaway speed and partly because if they geared like a 2-stroke they'd just find themselves applying the throttle later and less coming out of a corner. |
There's a reason why 4 strokes are dominating motocross, and it wasn't because of HP, it tractability. Remember a 4 strokes power pulses are every 720 degrees, not every 360 degrees like a 2 stroke. Even if it had more torque and HP, it's only abusing the axle and frame 1/2 the time as a 2 stroke....
CR |
The 4's dominate because they have become the dominant product. The market didn't really have much of a choice when all the factories were unanimously moving in that direction, although recently there has been some market "push back" in MX on the 2-stroke side.
Never the less, for comparable output, a 4 hits twice as hard every other cycle. |
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2929
Location: United States, New York, Ossining
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| Posted: Thu Sep 20, 2012 3:47 am Post subject: |
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| Spencer Uzri wrote: |
The 4's dominate because they have become the dominant product. The market didn't really have much of a choice when all the factories were unanimously moving in that direction, although recently there has been some market "push back" in MX on the 2-stroke side. |
Not true....
It wasn't until Doug Henry won a championship in 1998 on a Yamaha YZF400, that the other manufacturers took them seriously.
http://en.wikipedia.org/wiki/Doug_Henry_%28motocross%29
The CRF's were introduced in 2002, the last CR's were built in 2007, the dominance of the 4 stroke on the track is what sealed the two stroke fate.
CR
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Jim Derrig
Joined: 22 Apr 2008
Posts: 1012
Location: United States, Washington,
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| Posted: Thu Sep 20, 2012 7:33 am Post subject: |
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| Spencer Uzri wrote: |
Yeah, I just checked that out. Wave physics clearly shows that the regulation should favor 2's, but then it's King Co., so I shouldn't be surprised.
Caveat: maybe it never was about noise...?
I suspect the issue isn't over.
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Hearing is more subtle than that. The human ear is not remotely linear with respect to frequency range. Google "Fletcher Munson curve." Basically, we are very sensitive to mid range frequencies, with our sensitivity peaking at approximately 4000 HZ. Right were a baby's cry makes plenty of volume. Coincidence? Evolution suggests not. We hear something in that frequency range and it bugs the hell out of us.
Low frequencies carry a long way but we hardly even notice them. So that lowrider caddy cruising by with the bass up to "earthquake" is as much a curiosity as an annoyance.
Anyway, my guess is that a 2-stroke's frequency distribution includes plenty of volume in the sensitive range of human hearing.
Still, the ban is idiotic and clearly was a political maneuver designed to appease the same sort of people who build in airport flight paths and then complain about the noise. |
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Spencer Uzri
Joined: 18 Apr 2006
Posts: 798
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| Posted: Thu Sep 20, 2012 1:40 pm Post subject: |
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| Jim Derrig wrote: | | Spencer Uzri wrote: |
Yeah, I just checked that out. Wave physics clearly shows that the regulation should favor 2's, but then it's King Co., so I shouldn't be surprised.
Caveat: maybe it never was about noise...?
I suspect the issue isn't over.
. |
Hearing is more subtle than that. The human ear is not remotely linear with respect to frequency range. Google "Fletcher Munson curve." Basically, we are very sensitive to mid range frequencies, with our sensitivity peaking at approximately 4000 HZ. Right were a baby's cry makes plenty of volume. Coincidence? Evolution suggests not. We hear something in that frequency range and it bugs the hell out of us.
Low frequencies carry a long way but we hardly even notice them. So that lowrider caddy cruising by with the bass up to "earthquake" is as much a curiosity as an annoyance.
Anyway, my guess is that a 2-stroke's frequency distribution includes plenty of volume in the sensitive range of human hearing.
Still, the ban is idiotic and clearly was a political maneuver designed to appease the same sort of people who build in airport flight paths and then complain about the noise. |
Frankly, sitting on the road by PGP at the edge of the velodrome, the "roar" of the 2-strokes was all mundanely noticeable. I drive past, towards the big track, & you couldn't really hear them at the main SIR/PR entrance. At the Monroe fairgrounds, go outside behind the bleachers on the main fairground entrance & you can't ehar the 2's; the volume of the 4 was clearly more noticeable.
I used to live about 2-3 miles away from a local MX track (which I also used myself way back then), & I could just hear the 2-strokes when outside, but not at all inside the house. Up here in Arlington, I live near (within miles) of a off road recreational area used by MX & ATV riders, & I can hear those 4's from over the mts - not that I mind, just saying.
I'm familiar with Fletcher Munson. It speaks to sensitivity, which is valid, but range is still an issue all it's own. Noting that volume is an "evening" factor, a low-frequency sound emitted at higher volume (eg. 4-stroke 250 v. 2-stroke 125) may be perceived to be more more equally annoying - for lack of a better phrase - by the human ear. So, if the 250-4 is loud enough, even though it's half the frequency of a 125-2, according to Fletcher-Munson, it could be perceived with similar disdain. Was the noise actually miked & compared using the curve? Somehow, I doubt it. I think someone complained & a blanket ban was thrown down.
I guess what I'm saying is that a "sensitive" noise that virtually no one can hear is a red-herring. The noise ordinance "violation' is a ruse. Again, it's King Co.
Last edited by Spencer Uzri on Thu Sep 20, 2012 2:55 pm, edited 1 time in total |
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2929
Location: United States, New York, Ossining
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Craig Sender
Joined: 20 Apr 2002
Posts: 18
Location: United States, Washington, Kent
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| Posted: Thu Sep 20, 2012 2:57 pm Post subject: |
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| The reason 2-strokes are prohibited at PGP from my google search (pacific grand prix conditional use permit) Indicates that during the permitting process for the kart track in 2005 it was communicated that 2-stroke karts would be phased out by late 2008. The reason for that statement was either a mistake, misinterpeted or worse an assumption. The end result was that Jan 1, 2009 2 stroke karts would be prohibited at PGP. |
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