Cylinder Porting

ronin62715sv

New Member
Jul 17, 2018
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I have this new cylinder body with a steel bore and 40mm intake port. I was thinking about cleaning up and refining the ports on the cylinder body and was wondering if removal of this small metal divider in the exhaust port would mess up anything. I was thinking it’s there to keep the piston rings from catching on anything but other than that I don’t know what it’s there for. Would it be fine to remove it?
 

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javy mcdees

Active Member
Jul 30, 2018
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Like to find some more steel liner jugs just put mine on and runs so much better than the plated cylinders. I cut out the divider widened the exhaust at the cylinder, raised the intake a bit at the cylinder side left the rest of the ports alone and cleaned up what I could of the transfers. runs great low speed take off no pedaling needed. kinda nice. good street power so far. top end is not there yet. for daily commute it is a killer deal. Love the steel liner cylinders, just got to find a source and buy a few. Who sells any? been looking.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
Like to find some more steel liner jugs just put mine on and runs so much better than the plated cylinders. I cut out the divider widened the exhaust at the cylinder, raised the intake a bit at the cylinder side left the rest of the ports alone and cleaned up what I could of the transfers. runs great low speed take off no pedaling needed. kinda nice. good street power so far. top end is not there yet. for daily commute it is a killer deal. Love the steel liner cylinders, just got to find a source and buy a few. Who sells any? been looking.

I think www.zedamotorsports.com sells steel lined (big bore) piston & cylinder kits.

Also... The divider in the exhaust port is to keep the rings from snagging on the port edge: keeping it in there is a good way to allow you to make the exhaust port super wide for more top end power.
 
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javy mcdees

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Jul 30, 2018
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killed the iron cylinder yesterday ex side of piston scored the cylinder below ex port, may clean up. Piston got hot enough, may be my fault too running it 100:1 with stock RT jet. Had her turning in the upper rpm range just a short time but the cylinder was dry when I cracked it open. think I should add a bit more oil and maybe a little more piston clearence for iron cylinder. The plated one I have now just runs different than iron, iron pumps more air seems like to me. Yea found the iron jugs on ebay gonna oeder a few more, who makes a high end piston for the CG?
 

javy mcdees

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Jul 30, 2018
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update, honed the cylinder built new engine broke top ring, shattered after about 300 miles, piston in backwards. cylinder had no real damage, built a another engine with a b piston and AF80 rod and the same iron liner and that engine has now at least 500 miles probably 60 miles today runs real strong loud exhaust note low rpm power and at cruise speed the engine is strong keeping a steady speed even with a good headwind. drilled 6 holes in the piston on the ex side ring gaps face intake side now. The iron liner makes better power than any alum cylinder I have used in the past. This cylinder I cut down the deck surface and the piston almost reaches the top, no measuring just guess work. quench is tighter now and the motor responds real good to it.
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javy mcdees

Active Member
Jul 30, 2018
143
58
28
49

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