Another 66cc wide intake porting thread

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maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
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memphis Tn
This one is a wide port jug with the rectangular transfers rather than the "eyebrow" type.
Starting point intake

Exhaust

Transfers


bottom of transfers
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Getting started by knife edging bottom of transfers at case


Also smooth casting lip in top of transfers


 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
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memphis Tn
Also opened up entire transfer tract from top to bottom thinning the cylinder wall at the top for better flow (bigger hole)



It's hard to see from the pics, but with piston in place, the transfers are substantially bigger now with same amount of port open.
I maintained basically the same angles for the outlets but widened the flow area.
Also matching to the cases for best transfer flow.
Start

After matching
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
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memphis Tn

next the intake gets hogged out


About 2mm wider overall.

Exhaust gets the same but about 4mm wider overall.

 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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memphis Tn
Ready for assembly


Getting a 40mm zl crank and innards from a stripped case victim.
That was ALMOST as much fun as RIDING it will be!
 

snorks

Member
Jan 16, 2009
41
8
8
Africa
Looking down into the case it appears the bearings protrude into the case leaving alot of area around the bearings?
Would it be possible to stuff that area with epoxy or machined aluminium to minimise the crankcase volume?

Cheers
Simon
 

kevo

New Member
Jan 4, 2015
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Murrieta ca
Are they "40mm" intake cylinders any good for the 40mm stroke motors? I'm a new but I thought the port timing was designed for the GT5 short stroke high piston pin motors. Looks like that jug should flow real good
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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memphis Tn
No idea kevo. Have not tried fitting it to a 40mm stroke engine yet.
Should work though the compression might need a second gasket or base spacer.
There's always a way if you REALLY want it to fit....
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Edited;
The wide port jug in this thread is currently sitting like the last pic since I have too many engines waiting now...The 40mm zl rod engine already has a jug so no reason to swap yet and zl rod motor is already back together after a case swap. I simply forgot to check if this jug fit it. Sorry.
 
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