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Old 07-31-2010, 09:30 AM   #1
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Default mod crank

here is a mod crank that i done.not all the way done with it. tell me what you think good bad what ever you want to say. tell me what you want to see if you say dad to make it good.
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mod crank-dsc02588.jpg   mod crank-dsc02589.jpg  
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Old 07-31-2010, 09:37 AM   #2
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taking mass out of the counterwieght is a bad idea... even tho it will increase the low end response of the engine it will also hamper high RPM performance and increase vibration and lower the RPM where the engine starts to resonate... So you will have a quicker spool up but less top end with more bad vibrations....
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Old 07-31-2010, 09:38 AM   #3
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Default the pic

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Old 07-31-2010, 09:45 AM   #4
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Sorry to say but it is a waiste of time. So far I can see the size of the hole and timing is not changed..... Only fancy looking cut-out things always looks nice but does not do a lot to an engine.
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Old 07-31-2010, 09:46 AM   #5
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Dosnt look to bad try your best not mess with the balance. What kind of silicone putty did you use looks nice came out nice and smooth. Was it self leveling. Some guys say that guys like us do nothing but hurt engine useing dremels to mod motors but i think if you do the right mod it donst take much to see a increasement in power and dosnt hurt anything. Its took me years of playing with these motors to learn where and what to do to these motors. I did some mods that guys swear the motor well never run again but they Scream So hard and they get great gas mileage. Thanks Speedyrob
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Old 07-31-2010, 09:52 AM   #6
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taking mass out of the counterwieght is a bad idea... even tho it will increase the low end response of the engine it will also hamper high RPM performance and increase vibration and lower the RPM where the engine starts to resonate... So you will have a quicker spool up but less top end with more bad vibrations....
i like what you told me. but i really was not loking for top end. next there is no way to balance a single piston motor but you do need counterwieght for top speed if i was racing on road. i was mostly trying to get better run times.
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Old 07-31-2010, 10:02 AM   #7
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Dosnt look to bad try your best not mess with the balance. What kind of silicone putty did you use looks nice came out nice and smooth. Was it self leveling. Some guys say that guys like us do nothing but hurt engine useing dremels to mod motors but i think if you do the right mod it donst take much to see a increasement in power and dosnt hurt anything. Its took me years of playing with these motors to learn where and what to do to these motors. I did some mods that guys swear the motor well never run again but they Scream So hard and they get great gas mileage. Thanks Speedyrob
it is a sirio longstroke 5+2 so it came it the silicone putty. for the people that dont think cuting groves in the outer crank dose anything it increase pressure in the crank wich lest you run less fuel. a high counterwieght crank is only help to speed. balance dose noting i can put a heavy flywheel on if i want to stop vibration but it will ear up what iam trying to do the motor has more power than it need. the only thing i need is fuel mileage.

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Old 07-31-2010, 10:10 AM   #8
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it is a sirio longstroke 5+2 so it came it the silicone putty. for the people that dont think cuting groves in the outer crank dose anything it increase pressure in the crank wich lest you run less fuel.
Actually it doesn't increase pressure in the crankcase.... And even if it did that would be a bad thing.... These engines operate with both pressure and vacuum in the crankcase, if the blades you cut increase pressure like you say, they would also reduce the engines ability to make vacuum , which would reduce the engines ability to intake a fresh charge into the crankcase.... regardless at the RPM these engines operate the crank more or less becomes on solid mass , any cuts you make would have no effect other then reducing mass....reducing mass can help low RPM response, but hurt high RPM stability...so its a trade off....
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Old 07-31-2010, 10:12 AM   #9
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it is a sirio longstroke 5+2 so it came it the silicone putty. for the people that dont think cuting groves in the outer crank dose anything it increase pressure in the crank wich lest you run less fuel.

no way to really balance them, however there is a definite increase in vibration with a lighter counterweight, the higher the RPM a engine operates at the more mass is needed in the counterweight to keep vibrations in check.......
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Old 07-31-2010, 10:15 AM   #10
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The less weight you have the less you have to balance....
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Old 07-31-2010, 10:16 AM   #11
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it is a sirio longstroke 5+2 so it came it the silicone putty. for the people that dont think cuting groves in the outer crank dose anything it increase pressure in the crank wich lest you run less fuel.
Cutting the grooves in the face of the counterweight like that does nothing but increase turbulence, increase harmonics and increase lower crankcase volume.

If they do anything at all, the increased turbulence can manage to keep the fuel atomized at lower RPM but that's about it.
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Old 07-31-2010, 10:23 AM   #12
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The less weight you have the less you have to balance....
I agree ! reducing piston and rod weight tho not counterweight !
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Old 07-31-2010, 10:27 AM   #13
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Cutting the grooves in the face of the counterweight like that does nothing but increase turbulence, increase harmonics and increase lower crankcase volume.

If they do anything at all, the increased turbulence can manage to keep the fuel atomized at lower RPM but that's about it.
I am even skeptical of that, with the RPM these engines operate at any grooves or channels would just go into cavitation and the crank would become one solid mass for the most part.....Now this is only my theory as the equipment needed to test this properly is out of my reach.... I do however own a dyno and have played around with some of this stuff only to find negative results... I do however see that a ligtened counterweight does allow the engine to spool faster in a low load situation, but has no effect on a loaded situation...in other words once the tires break traction they will just spin even more violently.... The faster the rate of aceration the more effects a lightened rotatin mass has... in a drag car that runs 0-45000 RPM in 1.6 seconds a lightened internal mass plays a huge role...but in a heavy offroad it has no effect other then when the tires break traction....
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Old 07-31-2010, 10:33 AM   #14
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Actually it doesn't increase pressure in the crankcase.... And even if it did that would be a bad thing.... These engines operate with both pressure and vacuum in the crankcase, if the blades you cut increase pressure like you say, they would also reduce the engines ability to make vacuum , which would reduce the engines ability to intake a fresh charge into the crankcase.... regardless at the RPM these engines operate the crank more or less becomes on solid mass , any cuts you make would have no effect other then reducing mass....reducing mass can help low RPM response, but hurt high RPM stability...so its a trade off....
every thing you say is good but wind the piston is over the port there is not enought pressure in the the crank to stop vacuum. it would have more vacuum if it dose anything because it would increase back pressure in the pipe.
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Old 07-31-2010, 10:37 AM   #15
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It would make a purdy paper weight though.
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