Spare_Parts
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Oh boy. Gonna be a bunch of arguing again....
Porting
- Thread starter Carcher
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Deleted member 12676
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I havent seen any of the recent cylinders. I know there are different manufacturers so I am wondering how much they differ amongst themselves.
That is scary to hear they have 170 psi since that is skirting the threshold of reliability, especially for cheap chinese bearings.
Of course a more flat topped exhaust port gives more peak power. My recommendations are more slanted towards commuters than racers. I commute on mine and like a very broad powerband and for that the round top exhaust is best.
That is scary to hear they have 170 psi since that is skirting the threshold of reliability, especially for cheap chinese bearings.
Of course a more flat topped exhaust port gives more peak power. My recommendations are more slanted towards commuters than racers. I commute on mine and like a very broad powerband and for that the round top exhaust is best.
Street Ryderz
Well-Known Member
Those are Grubee's current spec's and most follow those.I've said this before but I personally run at 185 psi and have setup peoples engines at the same with stock bearings and no issue.Folks whom inquire about porting are more likely looking beyond that of a commuter and trying to get all they can from it, alot of us are using scooter pipes that are 2 and 3 staged with very broad band widths compared to the dirt bike pipes and others.4k band widths can be had easily.Port area's and timings should match the other components used meaning that carb size and pipe length along with flange dia/header dia all have to work properly together when considering the porting needed.
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Deleted member 12676
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Here's a page of mine about exhaust port shape and durations that some people may find helpful: http://www.dragonfly75.com/moto/portshape.html
FNTPuck
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My current 2stroke is 190psi, and although the bottom end only has about 130miles on it since its mostly a test bike, almost every one of those miles are WOT for long straights testing and it has zero issues so far. I sold a mountain bike with 180psi about a year ago and last I heard (few months ago) it had over 800miles on it with a 230lb rider daily commuting. I haven't seen a sub 160psi motor since I switched to only using 40mm kits.
The newer triple40 motors are getting a lot nicer than the old stuff...the bearings, ports, and jug-to-jug consistency are all much better quality and closer in spec between one another.
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Deleted member 12676
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I think what we should all take into consideration is that motorized bicycles log a whole lot less miles than does a regular motorcycle. My mind is more geared to motorcycles and so with a higher mileage ride such things as engine compression become of more negative importance. But Im glad to hear that for most people the high compression is not much of a negative factor. Im giving the benefit of the doubt to those advocating high compression with the hope you arent hiding from me that the high compression is causing a premature loss of cylinder chrome plating. Higher compression causes more outward pressure of the rings onto the cylinder.
J
Jase
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Maybe just post the info here. afterall the question is on this site not that other site. Ive read about 5 threads today that all had links to this site. Why? makes me learry as fuch. Wonder why mods on here allow such things.
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