porting new top end ht bicycle engine 80cc

GoldenMotor.com

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
5,844
109
63
SoCal Baby!!!
www.facebook.com

ivan H

Member
Oct 8, 2011
622
1
16
australia
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
 

truckd

Well-Known Member
Oct 19, 2010
2,837
134
63
palmdale calif
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??
 

young grease monkey

New Member
Sep 20, 2011
362
0
0
Chicago
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.
 

movinfast

New Member
Sep 17, 2012
21
0
0
az
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
 

ivan H

Member
Oct 8, 2011
622
1
16
australia
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
 

truckd

Well-Known Member
Oct 19, 2010
2,837
134
63
palmdale calif
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
 

Attachments

ivan H

Member
Oct 8, 2011
622
1
16
australia
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
 

truckd

Well-Known Member
Oct 19, 2010
2,837
134
63
palmdale calif
Re: porting new top end ht 80cc

All of the fasteners/bolts have been up graded as well and yes the head bolts will be Allen keyed, the head was just placed on the engine for photogenical purposes.
I don't know if you have visited my thread Blood Thursty but you can see what the bike looks like(1911 Indian BTR) so this engine has to be right & tight!! and will be starting another shortly after this build
 

dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
Re: porting new top end ht 80cc

wow! how about that. venice motor bikes is one shop to say mod's are needed for this part to work properly. instead of making a sale. one honest dude. way to go Norm!
 

headtrama

Member
Jul 8, 2010
886
2
16
california
Re: porting new top end ht 80cc

All of the fasteners/bolts have been up graded as well and yes the head bolts will be Allen keyed, the head was just placed on the engine for photogenical purposes.
I don't know if you have visited my thread Blood Thursty but you can see what the bike looks like(1911 Indian BTR) so this engine has to be right & tight!! and will be starting another shortly after this build
the head bolts should be studded , To tell you the truth I have never had a issue with the stock head studs. Get yourself some open head nuts and torque them down to 13 pounds . Spray the head gasket with copper coat and you shouldn't have a problem.