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High Performance Bicycle Engine Tips and Motorized Race Bicycles We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds


porting new top end ht bicycle engine 80cc

We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds


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  #1  
Old 06-26-2012, 01:27 AM
sleepy hollow sleepy hollow is offline
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Default porting new top end ht bicycle engine 80cc

Killed my old top end from running without an aircleaner, dumb choice, what mods should i do to new top end to gain performance
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Old 06-27-2012, 12:24 PM
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MotorBicycleRacing MotorBicycleRacing is offline
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Default Re: porting new top end ht 80cc

Quote:
Originally Posted by sleepy hollow View Post
Killed my old top end from running without an aircleaner, dumb choice, what mods should i do to new top end to gain performance
Hopefully you didn't damage the bottom end too.

Dave Rust builds the fastest 66 cc bikes on the track and is
the only seller that I know of that offers a professionally ported
cylinder.

http://www.arrowmotorizedcycles.com/...cylinders.html
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Old 06-27-2012, 07:22 PM
ivan H ivan H is offline
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Default Re: porting new top end ht 80cc

Hi, u didnt say whether u wanted 2 port 4 increased top end performance (where u'll loose bottom end performance), or 4 increased low & mid range performance (where u'll loose top end performance). Which ever way u go, 2 increase in 1 area means loosing in another. Then, 2 get the most out of ur port job, all other aspects of ur motor have 2 b made 2 compliment ur port split & duration, so they all work in conjunction 2 achieve ur goal. Cheers
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Old 07-09-2012, 03:18 PM
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Default Re: porting new top end ht 80cc

Does anyone know what the numbers mean on the piston? I have 2 PK 68.5/80cc engines and there is a #4 on one piston and & #5 on the other piston and just got a puch head 70cc Hi Hi compression and need to know what theses #'s are and the difference between the piston's if any??
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Old 07-09-2012, 10:48 PM
young grease monkey young grease monkey is offline
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Default Re: porting new top end ht 80cc

If you do a complete overhaul you will see gains across the rpm range. Only working on the top end will force you to compromise.
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Old 07-09-2012, 11:05 PM
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Default Re: porting new top end ht 80cc

Sooo! I'm Taken it no one knows what the #'s on the piston mean ??
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Old 09-26-2012, 12:53 PM
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Default Re: porting new top end ht 80cc

they are the piston dome size i belive. you will have to through calipers or a mic on them to see if the diameter is different
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Old 09-26-2012, 05:49 PM
ivan H ivan H is offline
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Default Re: porting new top end ht 80cc

Hi, as ur uping the compression it'd b adviseable 2 at least upgrade the small end bearing. Measure between the piston pin bosses, NTN does a 10x14x16.5 if it'll fit it'd b best, otherwise use 10x14x15 bearing, but Young Grease Monkey gave good advise, tear it right down & do it properly. Cheers
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Old 09-26-2012, 07:42 PM
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Default Re: porting new top end ht 80cc

Completely torn down PK 69.5/80cc
New...
Wrist pin bearing
Cylinder ported/intake and exaust also re-surfaced
Crank bearing
Pro racing expansion chamber
Dellorto 15mm carb
Puch 70cc High High compression head
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  #10  
Old 09-26-2012, 09:26 PM
ivan H ivan H is offline
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Default Re: porting new top end ht 80cc

Its always a good idea 2 replace all the fasteners with Hi Tensile Automotive grade socket head (Allen Key) fasteners. Torque case fasteners to 75 inch/pounds. Cheers
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