Protec head milling

Jakobi86

Jakobi86

Have a protec rec head for 701. Compressions at 150 and wondering if it's ok to mill it to bump compression. Has anyone done it and if so how much? I believe when milling, squish is what I want to watch out for... What is that clearance I'm looking for? Thanks!


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brylon644

brylon644

Location
buffalo ny
What motor are you putting it on? I had the same problem a while back on my 61x. I found out from protect that they have heads to fit specific motors. They told me the head that uses orings are for 61x and 62t. The head that uses a stock gasket is for a 760 motor. You can run any head on any motor but, I had the 760 head and gave me no bump in the compression on my 61x. Call protec they may be able to tell you how much to mill. They were very helpful when I called.
 
Quinc

Quinc

Buy a Superjet
Location
California
150 is low, either your cylinders are ported, or it might be time for a new top end or at the least piston rings.
 
jetpilot36

jetpilot36

Location
Fort Worth
i had a stock 760 head with 760 cylinders. i just took it to the local automotive shop and tole them .40. bumped me up to 180psi. ran perfect going on 11 seasons now.(knock on wood)
 
VXSXH20

VXSXH20

Sionis Industries
Location
Mid-Atlantic
Check the diameter of the domes. That may be a 650cc 6m6 style head. a 650 protec head will run 78mm across in diameter,
A 61x 701 rec head will run 82mm across in diameter. the rec heads are grooved with an provison for the Oring. Early Rec heads had one threaded mount hole near the front cylinder for the exhaust bracket. Later and subsequent model heads have more mounting spots, two front and some atop the rear cylinder as well. The 6m6/61x/62t head in its produced form from protec should yield approx 175 psi on a healty stock bore cylinder. And run at perferred 91 octane fuel. This IS ALL QUOTED from Carl Brown at protec. I went thry all of this last year and looked up my notes just for you buddy!

that being said test your compression on a stock head and then install the protec. see if it changes. If it does not , it is very likely your cylinders may need attention..
 
Dartman

Dartman

Location
usa
IMO
o-ringing a stock head is asking for failure.
2nd, even with milled heads you can't control squish clearance/msv very well when the Yamaha OEM headgasket is .052 compressed *
just buy a ADA head setup for a yamaha

*not based on the 760 metal headgasket*
 
Jakobi86

Jakobi86

Never planned on o ringing the stock head, the guy above mentioned that the protec has provisions to be o ringed... And being an aftermarket head, I'd assume the domes are different shape,
Which correct me if I'm wrong, but would make it easier to manage the squish while still removing material to bump compression. However it may be, sounds like I need to confirm my porting and ring/cylinder condition before anythingn
 
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