Big bore kits talk



Street Ryderz

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Oct 14, 2016
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Ok guys I fitted the 48mm cylinder on that 38mm stroke engine I was talking about. It fits the only thing I’m worried about is the top ring is it supposed to come above the port at tdc?
You've got me confused,the top ring would be well above any port at tdc.
 

Will'smotobikes19

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At TDC the dome is slightly above the cylinder by maybe half a mm or a mm. Way less than the other engine. I still think it might need a gasket. At BDC almost half the intake is still showing and that's when It needs to pick up the fuel for the next fire cycle right? The port looks different than on stock cylinders it's like a rounded square but it's also for a reed valve and windowed piston. For my frame I may have also to use one of those X ports to clear the frame with the exhaust.
 

Street Ryderz

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At TDC the dome is slightly above the cylinder by maybe half a mm or a mm. Way less than the other engine. I still think it might need a gasket. At BDC almost half the intake is still showing and that's when It needs to pick up the fuel for the next fire cycle right? The port looks different than on stock cylinders it's like a rounded square but it's also for a reed valve and windowed piston. For my frame I may have also to use one of those X ports to clear the frame with the exhaust.
This pic shows how the dome protrudes above the top deck of cylinder and that's fine.The intake port for a windowed piston/reed setup should be open at bdc to get its max intake duration.
 

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Will'smotobikes19

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Oh cool might have the big bore installed on the engine soon. The ring's are thinner than stock and a little tricky to compress. Motor's never been run it's the one I put Japanese bearings in I put SBP 8.8 studs on it too. Got a spare magneto off my neighbor since my wires were ripped off and a cdi. I'll have to see about fitment. Probably going to order that X-port so I can use a banana pipe and might have to figure something out to redirect the air filter to the side. Do you think it would be capable of 40mph with the OZ reed valve and 23mm intake along with the banana pipe and the 48mm cylinder? Oh and a Mikuni VM18
 

Street Ryderz

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Joined
Oct 14, 2016
Messages
3,004
Oh cool might have the big bore installed on the engine soon. The ring's are thinner than stock and a little tricky to compress. Motor's never been run it's the one I put Japanese bearings in I put SBP 8.8 studs on it too. Got a spare magneto off my neighbor since my wires were ripped off and a cdi. I'll have to see about fitment. Probably going to order that X-port so I can use a banana pipe and might have to figure something out to redirect the air filter to the side. Do you think it would be capable of 40mph with the OZ reed valve and 23mm intake along with the banana pipe and the 48mm cylinder? Oh and a Mikuni VM18
The banana pipe I'm not to sure about,the Oz reed with the VM 18 on that cylinder can easily do 40 even with a straight pipe LOL.If you get it setup and tuned right and had a real pipe it can make 5-6 hp no problem,I myself would not recomend that x port etheir as it restricts port area you can use and just puts more stress on the studs or fasteners used hanging the weight and vibes out further,But just saying that's me I know some folks do use them.
 

Will'smotobikes19

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Apr 9, 2018
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I'll have to get one of the $99 buck pipes that looks like a dirtbike pipe I am excited. If I'll be going 40+ I'll probably get those shouldered axles and use both mags, Was thinking of a 203mm disc in the front instead of the 180 that's on it.
 
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