Ok heres the think, this started with the new yzf and the 450r, well i thought 5 valves are better than 4! (correct me if im wrong)! Next i got to thinking, every one says twin cams have more hp But i thought the lighter the valve train the faster revs and more revs u get? help me out! i am very interested in the yzf450 and think it should be a better quad then the 450r but that 4valve and single cam have got me thinking! eny imput would be great! thxs

 

ANYONE?? ANY AND ALL IMPUT WOULD BE GREAT! THXS

 

Well hey if no one knows the answer thats ok! but hey i gots a nother question for u guys! the honda 450r is actually 450cc and the yfz450 is actually only 439cc! Is this true? If it is true then , dats big differance! now if the yamaha out performs the honda, im going to Laugh at those honda boys!

 

2 cams are better than 1. 10 or 11 cc's aren't going to make much of a difference.

 

The one thing that 4 valves are better than 5 is that when you start doing work on the head there is more room in a 4 valve head for massaging the combustion chamber. The 5 valve head is pretty busy . all the angles are flat. Possible Not as good a 4 valve head with the combustion chamber reworked if needed.

 

One should not just look at the number of valves and cams on the YFZ450 and the 450r. It’s open for debate, but I believe the 450r will have less power than the YFZ450. When Honda release the 450r it might have similar or more HP than the YFZ in stock standard form, but after a few mods the YFZ450 will have more power than the 450R.

Why you ask, here are my thoughts.

What do we know about the two bikes. I will start with the basics. 1st Yamaha always puts on a crappy pipe and air intake system on their quads. They also messed with the exhaust cam on the YFZ450. All of this is to limit the power on the bike. Honda tends to add better pipes to their quads, so in stock standard showroom form the Honda might have the same HP or maybe more than a stock standard YFZ450. Put a good pipe onto the YFZ450, do the cam change and fix the breathing on the bike and the YFZ450 make a massive amount of power (Stock Motor). The Honda motor will not have the same HP even after doing the same mods to the 450r.

Why you ask me again.

1st the YFZ450 have a higher compression piston than the 450R, It has five valves and should breath better than the 450r. Also most people say that a dual cam produce better HP results. This alone tends to indicate that a YFZ will make more HP with a stock motor. Now people can dip into the motor, and make the one do better than the other, but it will require some tricks. One also needs lots of cash. Most peopel add a pipe and new aircleaner. Then much fewer people add a new piston and cams, maybe even head work. Most ATV riders never go all out and make a drag machine. I beleive you will have to spend more money on a 450r to get it to make the same power as a more stock Yamaha. The Yamaha have more technology as a standard working for it.

Then the Yamaha is lighter than the 450R and one can make it even lighter if required. So a lighter bike, higher HP, then I would tend to go for the YFZ450.

Lets see if I am right.... its only a couple more months to go, before we get our hands on a 450r and see the real proof.

 

Just thought I would throw this in. Four valves will actually out flow five smaller valves. Yamaha wrote a paper about this and the test they did with different head designs. They said that the reason a five valve head will out perform a four valve head is due to the design of the head. With five smaller valves you can make the head design much more efficient and that is where you get more power from.

 

450r- 450cc, 42mm carb, uni cam (less friction)+ lighter. The 450r will be lighter too.

yfz- 430cc, 38mm carb, DOHC (more friction)+ heavier. a little more comp.

More vloume+ more air= more power+ less friction with moving parts= more power and reving.

** Its just a hypothesies that the 450r will be light but it probably will because it has lighter parts and less parts....

 

Dual cams will give you more hp at higher rpms. kind of like the ltz/kfx 400 twins, dual cams yeilds less low end torque, this is your trade-off.

The yfz is a 439cc. this was done because at the time of mfr the pro requirements were 440cc or less. That was upped to 450 just as the yfz was in final pre-production. The honda had a lot more time to deal with this change and so could take advantage of this. The 11cc could make a difference if the engines were more similar. Just as a 26cc bore makes a big difference in a raptor (660 to 686), 1/2 that could make some noticable change. However, being that the engines are quite dissimilar, (honda single cam 4 valve vs yami dual cam 5 valve), the displacement alone shouldnt make or break honda's possible superiority.
'

 

Here's the scoop guys... do with it what you will.

Dual cams don't neccissarily make any more power than other types. What they do is allow for less moving valve train parts to be used. In other words, DOHC only has a valve (and related keepers,retainers, so on) to move. A conventional SOHC engine has rocker arms to move in addition to the valves.

The DOHC engine will arguably have more physical weight than a SOHC. BUT, with less moving valvetrain mass (the parts moving inside the engine), this allows for the DOHC engine to run more reliably at higher rpms before you start having problems with valves floating.

I a SOHC engine, to offset the effect of the additional valvetrain mass, you'll see stiffer valvesprings and lighter aftermarket titanium valves and so on to try and offset the extra weight of the rockers. Basically when it comes down to it... there is more high rpm potential in the DOHC.

As far as 4 and 5 valves........ Ideally... 5 valves have more potential to flow more air. Simply based on surface area in the combustion chamber.

Hope this makes a little sense!