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Scooters - 50cc => Agility 50 => Topic started by: scooterman11 on June 30, 2012, 10:22:44 PM
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I put a 70 cc big bore kit on my agility 50, and i dont have a new gasket i used a dremel to make the cylinder hole bigger, will I be ok doing this with my stock head gasket
please let me know
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It's Kind of ok... Aluminum i'm guessing. It's really better than nothing. You could try a light coating of "flange sealer" to both sides. I'de bet it would work till you can get a proper one. Just check the clearance/squish before firing it.
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i would just go onto Ebay and get 4 lots of 80cc gaskets they are the same size as the gaskets that come with a 72cc kit. that way if things do go wrong and you have to tear the block again you have pleanty of gaskets spare to do the job.
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Do you have a harbor freight there .they sale a kit that you can cut out and make your own gasket.
some of your auto stores sale it too,
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With a 70cc you could probably use the unmodified 50cc gasket since the cylinder head stays the same.
Just check that there's enough clearance between the top of the piston and the gasket at top dead center (also taking into account the compression of both gaskets by tightening the cylinder head nuts of course)...
With the 72cc cylinder that I own it's not a problem, but yours may be different...
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as far as i know and from what i have read, using the original head with the 72cc cylinder makes what i've found out to be a "squish zone" because the head still has the smaller combustion area with the valves which leaves quite abit of flat surface around the edge of the cylinder, affectivly squashing the space. i'm a little concerned and excited about what i might get.
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As far as I understood the squish area is important because it creates turbulence as the piston reaches top dead centre, which gives the mixture a more uniform distribution for improving combustion and minimizing chances of detonation.
Our cylinder heads are practically flat at the outer edge of the original combustion chamber and completely flat for the part between the 50cc and the 72cc diameter, so a 50cc gasket will change nothing to this shape compared to a 72cc gasket, except for a small extra ridge halfway into the squish area and a tighter squish clearance at the edges, which will only help increasing turbulence...
I wouldn't be surprised if the difference between a 50cc and a 72cc gasket on a 72cc cylinder isn't even measurable with a dyno...
The only two problems I could think of are that the piston might hit the gasket at TDC, and that the inner edge of the gasket (which has a narrow ridge pressed into it to compensate for non-straight surfaces) isn't supported by anything so it might leak a bit - but then again the same goes for dremeling this edge away...
edit : corrected some results of early-morning / before-coffee brain malfunction.
edit 2 : thinking of quitting my dayjob to try out everything for real that I have a theory about.... ;D
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thinking of quitting my dayjob to try out everything for real that I have a theory about
I tried that once, my theory was it would be a great idea. Turns out my wifes theory is it isnt such a good idea. Still working the day job :D
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I wouldn't be surprised if the difference between a 50cc and a 72cc gasket on a 72cc cylinder isn't even measurable with a dyno...
The only two problems I could think of are that the piston might hit the gasket at TDC, and that the inner edge of the gasket (which has a narrow ridge pressed into it to compensate for non-straight surfaces) isn't supported by anything so it might leak a bit - but then again the same goes for dremeling this edge away...
edit : corrected some results of early-morning / before-coffee brain malfunction.
edit 2 : thinking of quitting my dayjob to try out everything for real that I have a theory about.... ;D
i dont have any worrys there, i only have 80cc gaskets because they are the same size as the gaskets which came with my 72cc cylinder kit. ooooooooh squishy power.
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Mono is exactly right about the piston hitting the smaller gasket. The use of a 39mm head requires a 47mm gasket. I have had interference issues with 39mm gaskets. Things change at rpm's...
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Mono is not going to quit his dayjob ;D