Thinking of doing the cam mod. Question is will it effect my top end much? Is it worth doing for low end , top end or what?

 

i definatly recommened doing the cam mod, i didn't really notice a loss in my top end, it gives you the same cam timing as the YZ450F dirtbike. it really opens up your quad you will love it!!! DO IT!!!!!!

 

Looks to me it would produce more on the low end. Any other mods I can do for the yfz? I've modded everything from the 200x three wheelers and 250r 3 and 4 wheelers and for the last 12 years or so it's just been banshee's so I'm just getting used the the 450 and so far I am impressed.

 

i don't know first hand what the mod does since i have not done it, but there are some dynos on this website www.gtthunder.com/yfz450 . if i understand correctly the "cam mod" we are talking about retards the exhaust cam therefore delaying the opening of the exhaust valves. i am just guessing here, but the stock ex cam timing has the valves opening up at bottom dead center (BDC) at the end of the power stroke this is basic 4 stroke technology. by retarding the cam you allow the piston to briefly begin the exhaust stroke before opening the valves. this would be the only place a loss in power could occur since the compression of the air would resist piston momentum. however, air unlike water can be easily compressed and the explosive force of the powerstroke should be little effected by a millisecond of resitance at the greatest momentum point of the powerstroke (BDC). the effect this has on the latter end of the exhaust stroke is much different. the timing of max lift and duration of total lift is now occuring when the piston and crankshaft start to lose more momentum. this allows them (piston and crankshaft) to lose momentum or inertia at a lesser rate. this all equalls a more free revving faster motor. hell for all i know the stock timing might open the exhaust valve before the completion of the powerstroke, doubtful but this might be part of the reason you see flames shoot out of exhaust with no spark arrestor, the gases don't complete burning before allowed to exit cylinder, the lean jetting will only emphasize this effect. anyway without seeing a diagram of the timing curve of a stock motor it is hard to know exactly what is occuring when you switch timing. sorry to get so technical. i am also considering doing the mod so let me know what you think if you DO IT!!

 

Yes, do it up. You will end up with a bit more power everywhere, at least it felt that way to me. I have seen dyno charts on the net that showed the cam mod providing close to the same power gains as buying an aftermarket exhaust cam. The mod is free if you can do the work yourself so it is worth it and can always be reversed if you don't like it. Geisdog, the YFZ motor is "detuned" from the YZ-F spec bike motor. One of the places they acheived this was by advancing the exhaust cam timing a bit. My feeling is that the bike motor is probably timed ideally, the quad motor does wake up with the mod done.

 

cool, any idea where to get info on the differences in lift of a stock cam and aftermarket cams

 

the more technical the better. I have advanced and retarded a lot of cams in a variety of engines but have not been inside the yfz yet. Just trying to save myself some time if it's not worth doing. On a single cam if you advance it it will help the low end and if you retard it you get a better top end but loose a little down low. Since we have dohc it's easier to keep both.

 

I'll keep this short & sweet......

YOU WON'T BE DISAPPOINTED AT ALL !!!!!!!!!!!!! [img]i/expressions/face-icon-small-wink.gif[/img]

I did mine when it was brand new, broke the motor in with it retarted, It ran great and still does...........[img]i/expressions/beer.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img]

 

I just got an 04 YFZ, anybody know where I can get info on this mod? I would not mind doing it if it has not been done already. How can I tell if it has been done, the guy said he did not do anything to it, but what does that mean now days.

 

ugly88, just google YFZ cam mod and you'll find it. You can tell if it has been done by looking to see if the timing mark on the cam matches the engine. If the exhaust cam doesn't match, it has been done.