smokeysevin
Novice Class
ZX12r-STX15f hybrid motor
Posts: 82
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posted April 24, 2013 03:01 PM
Rev limit on stroker bike
Hey guys I have a bit of a weird motor, its based on a zx12r but its in a Jetski, I have a 69.2mm stroke and a 83mm bore. I know most guys can spin a zx12r up to 11 or 12,000 rpm with the 55.4mm stroke. anyone with a 1427 or other stroker motor how high do you spin your engine and what did you do to make sure it doesn't spin apart?
Thanks
Sean
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1498 cc
69.2mm stroke
83mm bore
  
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted April 30, 2013 07:24 PM
Sean It depends on what you are doing- the length of time it's up there. I doubt that there is any benefit to spinning a 1427 much above 11.5. We used to run the prostocker to 13++ , But that's only for a couple seconds. Karl's LSR 1427 ran well shifting at 11.5 or so. In a ski where you need good torque and I'd say prop it for 10+ and it would be a bear.
The weak point in a high rpm- long stroker is the bottom of the piston pin boss which fatigues due to the high piston speed. It's all about cycles- time spent at the highest rpm.
DOug
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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smokeysevin
Novice Class
ZX12r-STX15f hybrid motor
Posts: 82
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posted May 01, 2013 07:54 AM
quote:
Sean It depends on what you are doing- the length of time it's up there. I doubt that there is any benefit to spinning a 1427 much above 11.5. We used to run the prostocker to 13++ , But that's only for a couple seconds. Karl's LSR 1427 ran well shifting at 11.5 or so. In a ski where you need good torque and I'd say prop it for 10+ and it would be a bear.
The weak point in a high rpm- long stroker is the bottom of the piston pin boss which fatigues due to the high piston speed. It's all about cycles- time spent at the highest rpm.
DOug
Mr. Doug that is exactly the issue, I had always heard that on this motor not to spin it past 8500 with stock rods and 9000 under any conditions because it would tear the piston pins out of the pistons regardless of manufacturer. I don't have the benefit of a transmission so in a circuit race (close course) It might only be at 8500 rpms for a few seconds but in an endurance or offshore race it will be there ranging anywhere for 15 minutes to 4 hours, you just can't spin a motor that fast for that long without issues. I like to get opinions of the bike guys because my motor is so similar (even more so now that it is built). I may be entering a series of drag events with it in which case it might be okay to pitch for 9-9300 because it is a 1/8th mile race but even still that is essentially run in one gear.
Thanks,
Sean
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1498 cc
69.2mm stroke
83mm bore
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entropy
Moderator
Posts: 8671
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posted May 03, 2013 03:07 PM
quote:
Sean It depends on what you are doing- the length of time it's up there. I doubt that there is any benefit to spinning a 1427 much above 11.5. We used to run the prostocker to 13++ , But that's only for a couple seconds. Karl's LSR 1427 ran well shifting at 11.5 or so. In a ski where you need good torque and I'd say prop it for 10+ and it would be a bear.
The weak point in a high rpm- long stroker is the bottom of the piston pin boss which fatigues due to the high piston speed. It's all about cycles- time spent at the highest rpm.
DOug
actually, Doug, when you set the record for lastest NA Kawasaki in the world, i geared it for 224mph+/- at 12,500rpm, and you crossed the traps at Loring at 12,380rpm.
The bottom end & pistons weren't the limiting factor, it was the head falling apart (valve spring resonance) at about 12,800.
I lost 3 heads finding out that 12,500+/- was the limit.
That said, i don't know how long the bottom end would last at that rpm bc i rebuilt it routinely.
karl
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted May 05, 2013 06:37 AM
Ah, memory fails me. But, As you would note, it made GREAT torque in the 11's and for Mr Smokeyseven's boat, trying to run in the 12k's would be a suicide mission. The valve springs are the weak link in the chain in the "short term", but if you were able to "fix" that, I'm pretty sure the pistons would give up after an hour or so of WOT! Don't you think?
Does that record still stand?
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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smokeysevin
Novice Class
ZX12r-STX15f hybrid motor
Posts: 82
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posted May 06, 2013 09:44 AM
I have 65# carpenter springs in my setup and ferrea valves, I think that with the big stroke on mine the pistons speeds are already way up there, anything past 9k would end up with a piston somewhere it shouldn't be. Either that or I would egg shape the rods and lock it up. I have great oil pressure because the pump was modified at the factory to output more than the zx12r pump. The piston speed on a stock zx12r at 12,000 is right at 4360 fpm, with my stroke that happens at 9500 rpm. by those numbers I am playing it safe by limiting mine at 8500 but like mentioned bikes only stay at WOT at full rpm for a few seconds while I need mine there potentially for minutes to hours. Where did you guys make peak torque on that bike?
Sean
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1498 cc
69.2mm stroke
83mm bore
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entropy
Moderator
Posts: 8671
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posted May 07, 2013 02:42 AM
quote:
Ah, memory fails me. But, As you would note, it made GREAT torque in the 11's and for Mr Smokeyseven's boat, trying to run in the 12k's would be a suicide mission. The valve springs are the weak link in the chain in the "short term", but if you were able to "fix" that, I'm pretty sure the pistons would give up after an hour or so of WOT! Don't you think?
Does that record still stand?
yup, yr record stands.
Jim Gilnack's hot rod got close, but no cigar.
Shane Burton had plenty of plans but never did anything with em.
karl
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted May 07, 2013 10:44 AM
Cool! I didn't realize that. Likely it will be there for a while..........
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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KZScott
Needs a life
high on speed
Posts: 7235
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posted May 08, 2013 04:01 PM
quote:
quote:
Ah, memory fails me. But, As you would note, it made GREAT torque in the 11's and for Mr Smokeyseven's boat, trying to run in the 12k's would be a suicide mission. The valve springs are the weak link in the chain in the "short term", but if you were able to "fix" that, I'm pretty sure the pistons would give up after an hour or so of WOT! Don't you think?
Does that record still stand?
yup, yr record stands.
Jim Gilnack's hot rod got close, but no cigar.
Shane Burton had plenty of plans but never did anything with em.
karl
Someone else is  
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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KZScott
Needs a life
high on speed
Posts: 7235
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posted September 04, 2013 06:14 PM
quote:
quote:
quote:
Ah, memory fails me. But, As you would note, it made GREAT torque in the 11's and for Mr Smokeyseven's boat, trying to run in the 12k's would be a suicide mission. The valve springs are the weak link in the chain in the "short term", but if you were able to "fix" that, I'm pretty sure the pistons would give up after an hour or so of WOT! Don't you think?
Does that record still stand?
yup, yr record stands.
Jim Gilnack's hot rod got close, but no cigar.
Shane Burton had plenty of plans but never did anything with em.
karl
Someone else is
called that one
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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