OldMiniBikes hi comp head for predator212 questions

johnatthebox

johnatthebox

New Member
#1
#1
found out my rtc-6 valves wont fit in the new head.
Besides the 5.5mm stem valves, is there anything else I have to order to make this work? the spring perch looks different?
 
johnatthebox

johnatthebox

New Member
#2
#2
oh, and while Im at it......does anyone know how small i could get the combustion chamber on the rtc-6 head by having it milled? since the rtc-6 has bigger valves, would a little porting plus milling make it a better head to use?
 
Prowler08

Prowler08

New Member
#4
#4
The RTC6 head is the same 22cc head as all the other except it has 5mm valves with 27/25 valves, you can fit a 28.5mm valve in there but you need to ream the guides to 5.5mm, also the RTC6 head has locks to hold the spring and cap in place where as a stock Honda or clone has slip on retainers...
You can mill the head down .09-.1 and get the compression same as a 14cc head... But if you mill it that much you will need shorter lifters or shorter push rods... And keep a eye on piston to valve clearance..
 
johnatthebox

johnatthebox

New Member
#5
#5
Prowler08 said:
The RTC6 head is the same 22cc head as all the other except it has 5mm valves with 27/25 valves, you can fit a 28.5mm valve in there but you need to ream the guides to 5.5mm, also the RTC6 head has locks to hold the spring and cap in place where as a stock Honda or clone has slip on retainers...
You can mill the head down .09-.1 and get the compression same as a 14cc head... But if you mill it that much you will need shorter lifters or shorter push rods... And keep a eye on piston to valve clearance..
Click to expand...
ok.........in your opinion- which would make more power-- the 14cc head or the rtc-6 milled down(something safe like .o5?) Do the slightly larger valves trump the added compression? Do they have similar flow characteristics?
 
Prowler08

Prowler08

New Member
#6
#6
You would have to do a lot more work to the 14cc head to make it flow like the RTC6, would be a lot easier just to mill the RTC6 head to get the compression you want, it already has larger valves, and you just have to upgrade valve springs which already will fit the retainers in the RTC6 head.
 
johnatthebox

johnatthebox

New Member
#7
#7
Prowler08 said:
You would have to do a lot more work to the 14cc head to make it flow like the RTC6, would be a lot easier just to mill the RTC6 head to get the compression you want, it already has larger valves, and you just have to upgrade valve springs which already will fit the retainers in the RTC6 head.
Click to expand...
How much do you think i can have milled off before i need to get shorter lifters or pushrodds?
 
Prowler08

Prowler08

New Member
#8
#8
Every engine is a little different... But I would say if you mill more than.050-.060 you defiantly will need to measure, check and adjust accordingly...
This is where cut to length push rods come in handy..
 
naterater

naterater

Member
#9
#9
im thinking about the valves on my two predators , need to upgrade the lifters, rods, valves ,springs . atm im running 18lb. springs with upgraded retainers and stainless steel valves, im getting around 58-64 mph outta it depending on the sprockets . i want a 90mph bike . i wanna race stock cars at the strip in sac and win. lolol
 
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