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I cleaned up the casting and opened the exhaust a hair on one head and the one I'm runnin now is big ported and I smoothed out the combustion chamber

the smaller port seemed to run better, 78 was the highest speed I've seen with it but my valves were floating.. Saw 76 with the big port head but could only do it drafting
 

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I cleaned up the casting and opened the exhaust a hair on one head and the one I'm runnin now is big ported and I smoothed out the combustion chamber

the smaller port seemed to run better, 78 was the highest speed I've seen with it but my valves were floating.. Saw 76 with the big port head but could only do it drafting
When you say smaller port, do you mean using the stock head and valves and just doing the exhaust porting with the 125cc cylinder and stock heads?!!!!!

And with the Big head porting do you mean with the bigger intake valve, porting of the exhaust chamber and head valve seating and spark plug area plus using a BBK such as 140,160, 170,180cc with aftermarket cam?!!!!

duel valve springs should reduce valve floating
 

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Discussion Starter #5 (Edited)
I am going to be running the Kitaco 133cc light bore kit 10:1 CR, Kitaco type 1 cam ( +1 lift DUR 223/226). So, I'm just not sure it's really worth the money.
Just trying to improve the 6000 -8500 rpm range a little.
 

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Worth the money is a relative statement honestly

do you have a few hundred dollars to spend? Then yes
if you don't have the money and your hustling dollars on the corner at the light then you should prob say it's not worth the money
only you can decide the "worth" of it
so do it and decide for yourself lol
 

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Discussion Starter #8
I found flow bench data (Brian S) that says the stock head will flow enough for 136cc to 8500. So, at 133cc, I think I'll just stay with the stock head. Look's like the larger BKK's need larger ports.
 

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I would like to know what the flow data was for the stock head? Any info? Whats considered good enough for a 136cc to 8500rpm? What volumetric efficiency? A lot of naturally asperated motors can exceed 100% volumetric efficiency with the right set of cams or cam.
 

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I found flow bench data (Brian S) that says the stock head will flow enough for 136cc to 8500. So, at 133cc, I think I'll just stay with the stock head. Look's like the larger BKK's need larger ports.
Seems like the kitaco and takegawa BBK of @180cc are finding that out the hard way, with no real extra speed as they don't come with a bored head.
 

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Found the stock head flow info.
Lift mm - intake - exhaust
.5 - 7.6 - 3.4
1.0 - 13.5 - 7.3
1.5 - 18.5 - 12.3
2.0 - 24.2 - 17.7
2.5 - 29.1 - 22.0
3.0 - 33.9 - 26.2
3.5 - 38.9 - 28.2
4.0 - 43.2 - 29.0
4.5 - 46.6 - 30.9
5.0 - 49.1 - 32.1
5.5 - 50.3 - 33.1
6.0 - 50.7 - 34.0
6.5 - 51.1 - 34.6
7.0 - 52.2 - 35.2

According to volumetric efficiency the 125cc at 110% was like 22 cfm. If thats the case the head way out flows the engines efficiency. Now with that said I am sure I am missing something somewhere. Back to the research.... :)
 
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