Mod question?

[sheetwright]

How much can someone really gain by machining the head, and adjusting the cams on a stock Nytro with an exhaust system, and controller? Is it worth it, and how dependabll is it on a 4-stroke?

 

[shadow44]

Don't know if this helps Bill, but Hurricane did a stroker this past season ( 6mm overbore I think..or 1150cc ), with head porting, full exhaust and I assume his airbox mod.. I think Dave said he got 165HP out of it...I would imaging there would be no reliability issues, but that may depend on whether you are milling to bump compression or just porting it. I've only heard of one guy using different cams ( on HCS ) and he claimed he was pumping out 160ish hp..but he never said what exhaust he was running.

 

[yukon yamaha]

I just had the head on my nytro cut down twenty thou and i spent the time to port and polish it..... I have a pcv & auto tune, intake, plugs, header, mpi pipe, and let me tell you it rips! I ran empty 8bu weights before and would pull 8900 all day long... I had to load the 8 bu's with 2.44 gram weight and i still was sitting on the 8800-9000 rpm range.... The snap off the liine was crazy, not sure about the top end I have not had a chance to run it on a lake yet. My gearing is 23/40 no reverse and it still hits hard on the bottom end! If you are good with a wrench I really think that shaving the head is so so great! Stock comression is 11-1 and with the head work it went up to 12.2-1, I will be running premium all the time... Any thing after 12.4-1 I would be adding some race just to be on the safe side......Local machine shop 148$$$ to shave the head, so very cheap

 

[Capt.Caveman]

Do you really need to add race fuel with that high of compression?

 

[yukon yamaha]

No i dont think you would have to but anything over 12.4-1 i dont think it would hurt to put a splash in, better to be safe than sorry