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Discussion Starter · #1 ·
So i see a lot of people talking about this 3 boost port cylinder ( i also have this kit) but i have never seen anyones review of it, all i have noticed so far without having tried it is that the two piston ring pins are pretty much centred with the outer boost ports, is this an engine failure waiting to happen?
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It's going to have a really bad blow by problem

You can flip the piston around and drill new windows to make it work or just send it as is
 

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Take a picture of the inside of the cylinder. I have never seen a cylinder with 3 boost ports separated like that. At least flip it around. I thought he weren't supposed to flip them around but what do I know. I would probably buy another piston without windows and drill a wide hole for the middle boost port.
 

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Take a picture of the inside of the cylinder. I have never seen a cylinder with 3 boost ports separated like that. At least flip it around. I thought he weren't supposed to flip them around but what do I know. I would probably buy another piston without windows and drill a wide hole for the middle boost port.
Yeah it's supposed to be thicker or even have a brass slug under the exhaust port side where the arrow is as a heat spreader but I have pulled many of them apart where the Piston was in backwards ( yes even from the factory ) where the Piston and cylinder were completely worn out without showing any signs of burn through.

I have even pulled them apart and well you know what they do they like to wear out on the exhaust port side with major scratches and gulling polished off the scratches put new rings and flip the piston and have gotten even more time out of them 🙂

So ideally no I would not flip the piston but in this case he might as well use up those bad parts run it lean and mean and who knows with all that weight taken out of the piston he might actually get a good balance Factor lol might turn out to be a really powerful engine lolz
 

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Discussion Starter · #5 ·
Yeah it's supposed to be thicker or even have a brass slug under the exhaust port side where the arrow is as a heat spreader but I have pulled many of them apart where the Piston was in backwards ( yes even from the factory ) where the Piston and cylinder were completely worn out without showing any signs of burn through.

I have even pulled them apart and well you know what they do they like to wear out on the exhaust port side with major scratches and gulling polished off the scratches put new rings and flip the piston and have gotten even more time out of them 🙂

So ideally no I would not flip the piston but in this case he might as well use up those bad parts run it lean and mean and who knows with all that weight taken out of the piston he might actually get a good balance Factor lol might turn out to be a really powerful engine lolz
why would there be blow by? The boost ports arent higher than transfers and cylinder pressure has to be practically null by the time piston opens tranfer ports by then only thing that can blow by would be the air fuel mix towards the cylinder but okay that doesn’t really matter ? What you think
 

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why would there be blow by? The boost ports arent higher than transfers and cylinder pressure has to be practically null by the time piston opens tranfer ports by then only thing that can blow by would be the air fuel mix towards the cylinder but okay that doesn’t really matter ? What you think
It will go between the ring gap and right into the triangle window and cook the wrist pin bearing just like what my first engine build did when I made the same mistake but on a side note it will run for a while 🙂

If you flip the Piston then the ring gaps and the triangle are on the other side where they will not affect anything then you can drill a new round hole to line up perfectly with your boost port I would use the center boost port and not use the outside ones but cut the center one a bit deaper to increase low end torque without affecting the upper RPM range too much.

I don't know maybe these can help
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Well now that I think about it I'm wrong you cannot flip the Piston it will not work with Windows in it :-( you might try a new 44 mm piston flip it and then drill in the boost ports that you want to use. Then you can still use that cylinder Pistons are only $10 on eBay.
 

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Yeah it's supposed to be thicker or even have a brass slug under the exhaust port side where the arrow is as a heat spreader but I have pulled many of them apart where the Piston was in backwards ( yes even from the factory ) where the Piston and cylinder were completely worn out without showing any signs of burn through.

I have even pulled them apart and well you know what they do they like to wear out on the exhaust port side with major scratches and gulling polished off the scratches put new rings and flip the piston and have gotten even more time out of them 🙂

So ideally no I would not flip the piston but in this case he might as well use up those bad parts run it lean and mean and who knows with all that weight taken out of the piston he might actually get a good balance Factor lol might turn out to be a really powerful engine lolz
I have also seen them backwards. Lol. Never thought to reuse them backwards for more time. I do have some older pistons!! 🤣🤣
 

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Well now that I think about it I'm wrong you cannot flip the Piston it will not work with Windows in it :-( you might try a new 44 mm piston flip it and then drill in the boost ports that you want to use. Then you can still use that cylinder Pistons are only $10 on eBay.
I was also thinking that about the windows. Facing the exhaust port.
Still haven't seen a cylinder head like that.
 

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Definitely carve the center boost Port deeper and abandon the two outside boost ports get a brand new piston and flip it so that the ring gaps are on the other side so they cannot snag on the boost outside ports then drill a round window.

That cylinder does not have the decompression notch and will be rather powerful.
 

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Discussion Starter · #15 ·
Definitely carve the center boost Port deeper and abandon the two outside boost ports get a brand new piston and flip it so that the ring gaps are on the other side so they cannot snag on the boost outside ports then drill a round window.

That cylinder does not have the decompression notch and will be rather powerful.
Wont it snag the exhaust port? Wich is even bigger?
 

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Discussion Starter · #16 ·
Definitely carve the center boost Port deeper and abandon the two outside boost ports get a brand new piston and flip it so that the ring gaps are on the other side so they cannot snag on the boost outside ports then drill a round window.

That cylinder does not have the decompression notch and will be rather powerful.
Im am also going to lose those fins on the transfer ports, the old ones didnt have em.
 

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Shove the piston in backwards and use a flashlight and look and see if the ring gaps will clear the exhaust port...

They make more RPM if you leave some of the finger separating the ports in.

But at this point you have nothing to lose you can either try it and see how long it will last 😉. Or start over with a new cylinder...
 

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Discussion Starter · #19 ·
Thanks guys for your help, but yeah im gonna take my time , winter coming and i got a polini 4.2 that ive been having fun with :)
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