motor?

[bigz-71]

i was talking to a friend of mine the other day about the yfz and the 450R. i was wondering why would honda not make it five valves like the yfz? and why would honda also make it a single overhead cam? isnt the yfz going to have a lot more engine rev? i am not too good with motors but i would think the more valves the faster the motor would rev. i would like someones feedback on this issue.

[robby26wi]

The CRF head will outflow the YFZ head and it all about rotating mass and efficiency...The crf-trx cam set up is way lighter and way more efficient..Dont let the big blue kid ya about there 5 valve head being the latest technology..They had the 5 valve head in the early 80's

[lukester720]

The rev limit on the R is 10,300rpms the yfz is 10,750 not to much of a difference. The honda is 42 hp stock the yfz is 37 hp, the honda has 47 to 48 hp with hrc kit the yfz with the lid off, pipe, and jetting 47 hp. On the yfz you can do the cam mod which will give you about 2 more hp. I am curious to see what adding a full exhaust system to the R will do for it. It made a huge difference on the yfz but I don't know about the R. Although hondas exhausts don't usually restrict their motors as much as other companys I think honda may had on this quad. On one of the posts I've read on here in the past a guy said that loren duncan of duncan racing said the R only needed a pipe to be fast so I guess we will wait and see.

From what I am gathering the Honda has a stronger bottom to mid...that is what I like....launchin' out of corners with a more torquey motor...most passes are made comin' out of a corner.

[bigz-71]

my 400ex has a lot of bottom and mid power. i like that way.

[Maxx_Action]

Err.....

sorry to contradict you here, but the YFZ is almost 42 RWHP stock. See this link:http://www.gtthunder.com/dynoyzf450stock.html

When Jetted, lid removed, full system, and cam mod it is over 49 hp: http://www.gtthunder.com/YfzDyno8.html

And I would suspect doing some mods to the intake (K&N, Straighter intake tube) might give it another horse and a half or so when jetted to compensate for the additional airflow.

I think that the Honda will probably make similar numbers, but I might tend to disagree a little also on the statement that 4 valves are as good as five. I think that would be true if the valve area were the same, however I think HOnda's idea was to make that quad a little more "trail" friendly by goin with more stroke, thereby more low end torque, less rev capacity.

I am not saying one is better than the other, just stating the differences SO DON"T GET YOUR BRAND LOYAL FUR UP AND START FLAMING ME!! Please? :D

Maxx

[bigz-71]

i am not trying to create an up roar in here. i just basically wanted to know everyone opinion on the valves. i would think five would be better than four.

[trx440]

If more vavles were better then Honda would have done a 6 valve. Hell they did oval pistons.

Often times more is just more. Look what Harley has done in Dirt Track with 70's technology.

[biohazard1.2]

Originally posted by trx440
If more vavles were better then Honda would have done a 6 valve.
:confused:
You really believe this?

You might want to freshen up on your knowledge of Internal Combustion Engines, cams and thermodynamics.

[2004TRX450R]

the whole point about 5 valves over 4 is that each valve has less mass of air around it. So when it opens it takes less time to get the air moveing. This better response time in getting everything moveing results in more air in the cylender and more power. That isn't saying that it is in every situation a better performer. The ports in a 4 valve head are generally larger and can flow more over all air as there is less valves and dividers in the port. Of course all this depends on head design.

[trx440]

Originally posted by biohazard1.2
:confused:
You really believe this?

You might want to freshen up on your knowledge of Internal Combustion Engines, cams and thermodynamics.

No and yes, kinda-sorta.

Why is the GSXR1000 a better engine than the R1? Explain that to me and I will entertain debating this with you.

Remember, in the end you have to conclude that the R1's engine with the 5 valve design produced more than 10hp less than the GSXR's engine with a 4 valve design.

[BigAl]

The valve design has a lot less to do with the way the engine runs, than other things do.

The honda has less compression, and a longer stroke, as well as the butterfly carb. All these things add up to an engine with a milder hit, and a smoother power curve. It may well make as much or more horsepower than the yamaha, but it may feel slower. That doesn't mean it will be.

Yamaha developed their 4-stroke motor to have a 2 stroke feel, trying to convert 2 stroke mx riders. That is why they started with a very short stroke, and a very light flywheel. The dual overhead cams allows an engine to rev higher and faster because there is no linkage (rocker arms) to mess with.

Honda developed a system with 1 (as compared to 4 or more in the past) very light rocker arm, to try and compete with the revability of a DOHC design.

The 5 valves is good, but as much of a sales pitch as anything.
Hondas "unicam" design is good also, however it is also just a sales pitch. Many people felt that the YZ "BIKES" were too top heavy, so Honda tried to fix that problem by going with a single cam on top of the engine, therefore reducing weight high in the chassis, giving the "BIKE" a lower center of gravity.

I am happy to post here without the flames, but I'm sure it won't last long.

[biohazard1.2]

Originally posted by trx440
No and yes, kinda-sorta.

Why is the GSXR1000 a better engine than the R1? Explain that to me and I will entertain debating this with you.

Remember, in the end you have to conclude that the R1's engine with the 5 valve design produced more than 10hp less than the GSXR's engine with a 4 valve design.

BIGAL...good post!


I do not know dik about either of those bikes....I never got into street bikes...had a near death experience on my Harley (old lady ran me into a ditch...thank god there was water in it!)SOLD IT!

I am fully into offroad....

I will not debate what I do not know about...though that does not stop some people.:D

[eddings]

There is a point to where the low end torque is too much. Example the raptor, it has more torque than any other quad, but that makes the front end too light to launch off the line. I love the yfz for the ability to launch off the line without too much worry about the front end poping up. There are pro's and con's on both sides. A higher top end will let you stay in a gear longer without shifting and could save you some time in certain instances. I know I can launch the yfz in the sand in second gear with no problem. It has plenty of low end and tons of top end power, but opionions vary, and this one is mine.

[hotex]

When we flow bench tested the CRF450R and YZ-F heads, the head from a 1998 YZ400F had more flow than the 02 CRF did, the exhaust port was the culprit. The intakes produced nearly identical flow rates with the slightest advantage to the Yamaha. Porting the cylinder head on the Honda helped make it slightly better than the Yamaha was stock.

Running an 04 CRF450R and 04 YZ450F on a dyno proved Yamaha has a torque and HP advantage over the CRF too, EVERYWHERE. The YZ450F is VERY abrupt in it's power delivery though and the throttle response compared to the Honda is staggeringly quicker. This makes the YZ a little more difficult to get the machine hooked up coming out of corners, it takes a fair amount of throttle control to keep the tire from just getting blown away. That is what makes the Honda such an effective tool for the less faster riders, it's much easier to control, making it more effective for the less finese type rider.

In the AMA Supermoto series this year, the fastest 2 bikes belonged to Matt Pursley and Doug Henry, both on YZ450Fs. They were pretty consistently the fastest bikes on the track. Then a hoard of Hondas and a few KTMs. When the Honda is built right, it is seriously fast and effective, that's a tough combination to beat, just ask McGrath and Ward!!!

Tony

[Bretmd94]

Originally posted by Maxx_Action
Err.....

sorry to contradict you here, but the YFZ is almost 42 RWHP stock. See this link:http://www.gtthunder.com/dynoyzf450stock.html

When Jetted, lid removed, full system, and cam mod it is over 49 hp: http://www.gtthunder.com/YfzDyno8.html

And I would suspect doing some mods to the intake (K&N, Straighter intake tube) might give it another horse and a half or so when jetted to compensate for the additional airflow.

I think that the Honda will probably make similar numbers, but I might tend to disagree a little also on the statement that 4 valves are as good as five. I think that would be true if the valve area were the same, however I think HOnda's idea was to make that quad a little more "trail" friendly by goin with more stroke, thereby more low end torque, less rev capacity.

I am not saying one is better than the other, just stating the differences SO DON"T GET YOUR BRAND LOYAL FUR UP AND START FLAMING ME!! Please? :D

Maxx

Once again GTthunder and their extremely generous dyno throwing everyone off.

Everyone please dont take every dyno number you see into consideration. Every dyno will give different results. I have seen several dyno sheets that rate both the raptor and yzf in the 37hp range stock. The only hp comparison that is usefull at all in comparing two bikes is when they are done on the same dyno.

So two different bikes dyno'd on two different dyno's means absolutly nothing. I have no doubts that GTthunder will dyno the 450r at around 42 hp also. They need to get their dyno replaced. All the numbers on their website are like 5 hp higher than everyone elses.

just stating the odvious so people dont go around ranting about how they saw the YZF get 42 hp stock when they dyno their friends 450r at a local place and it only has 37hp.

[Maxx_Action]

HEy Bret...

here's another couple of runs, but these bikes had the K&N filter, running 175 mains, and 13:! compression and race gas. Pretty impressive, and these aren't from GTThunder

www.nzjensen.co.nz/images/Dynoruns.jpg

But like you said, the Honda is probably gonna be right on the same pace....

Maxx

[Honda Jay]

# of valves is in a way errelavent, but the flow rates, head design and porting or what cut the numbers. you could have lots of tiny valves (if possible, less that likely) and it still doesn't mean it is going to rev or make more power.

look at the hot motors of the ford pushrod 5.0 and the chevy LS1, they are only 2V/Cylinder and they are some of the best motors out. forget yammies when the torquey honda passes it:devil:

[lukester720]

Maxx here are a couple for you.

www.yfzcentral.com/sparks.htm
www.ctracing.com/yfz450.htm

But hey there just numbers I'm sure we could find websites saying that they are 50 hp stock if we really wanted to waste our time. But I feel 37 hp is a more accurate number and that is why yfzcentral uses it.

[Woody_YFZ]

I don't know how related this is to the valve discussion and I don't proclaim to know anything about them, but one observation that I made was that Ford took their 5.4L V8 and added a 3rd valve on the exhaust port (I believe) and that alone added 70 ft. lbs of torque and 35hp to their motor, so it seems to me there must be something to it, though again, I really have no idea, just an observation.

[RIDER11X]

Nobodyelse builds five valve motors because Yamaha has it under a patent#. I think we will finally have two production machines as evenly matched as MX bikes usually are...........equaling GREAT RACING! Enjoy!:cool:

[SickSixD R]

I have the YFZ and am happy with the bike.....Ijust did the YZ450F cam,pipe, CFM AirBox, Jetting/Kit Plus other BS Mod's Nerf's and what knot....i love the power this bike puts out....i have a 265R,Sold Raptor,2 Banshee's and a Z400 there all modded or were Modded....and not one of these bikes come close to the YFZ...well 2 me.

My Friend carey is getting the 450R when it gets here...we have money down on one of the 3 that are coming to Tampa Fl,
o cant weight....i think its going to be just as good if not better then the YFZ.
Honda has the upper hand seeing as how long they took to put out the 450R.

-Paul Tampa Fl,

[2004TRX450R]

Originally posted by Woody_YFZ
I don't know how related this is to the valve discussion and I don't proclaim to know anything about them, but one observation that I made was that Ford took their 5.4L V8 and added a 3rd valve on the exhaust port (I believe) and that alone added 70 ft. lbs of torque and 35hp to their motor, so it seems to me there must be something to it, though again, I really have no idea, just an observation.

They added a second valve to the intake side makeing it 3 valvs total. 2 intake and 1 exhaust. That wasn't the ONLY thing they did. The cam timeing is also going to be different and other things to go along with the 3rd valve. All this together makes the increase in power. Can't wait to see the new '05 Lightning with the 3 valve engine in it. supposed to be at or over 500hp. That increase from 380 isn't just from the extra valve though.

[bigz-71]

Originally posted by 2004TRX450R
They added a second valve to the intake side makeing it 3 valvs total. 2 intake and 1 exhaust. That wasn't the ONLY thing they did. The cam timeing is also going to be different and other things to go along with the 3rd valve. All this together makes the increase in power. Can't wait to see the new '05 Lightning with the 3 valve engine in it. supposed to be at or over 500hp. That increase from 380 isn't just from the extra valve though.

500 horses from a stock truck. that is awsome. i cant wait to see it. i have alway wanted a lighting. maybe one day i can afford to get one. i have plenty of time for things like that.

[RIDER11X]

The whole battle used to be maximum flow a nd light weight valve trains. And the battle never really changed. Yamaha went with the 5 valve system to primarily to lessen weight per valve by running smaller valves but more of them, yet still retaining good flow characteristics. Weight per valve is important, hence the titanium material used to make their valves. I do like the daul cam set up better than the Unicam that Honda has, for the fact that there are no rockers, better design IMO.

[holeshot19]

i like it idea of less parts

Originally posted by eddings
There is a point to where the low end torque is too much. Example the raptor, it has more torque than any other quad, but that makes the front end too light to launch off the line. I love the yfz for the ability to launch off the line without too much worry about the front end poping up. There are pro's and con's on both sides. A higher top end will let you stay in a gear longer without shifting and could save you some time in certain instances. I know I can launch the yfz in the sand in second gear with no problem. It has plenty of low end and tons of top end power, but opionions vary, and this one is mine.

The Raptor's problem with the front coming up is 50% chassis...50% rider. I can dump the clutch on a second gear start on hardpack and keep the gas on and the front end just where I want it...just off the ground....with clutch control.

[eddings]

Originally posted by HRC450R
The Raptor's problem with the front coming up is 50% chassis...50% rider. I can dump the clutch on a second gear start on hardpack and keep the gas on and the front end just where I want it...just off the ground....with clutch control.


Exactly, alot of clutch control. I bet you can launch better on a yfz with the same mods better than you can on a raptor by far. That has to do with bike geometry rather than rider ability. Sure you can keep it on the ground, but can you be competitive with the yfz and 450r. I don't think so. Thats my .02 worth.

[r450rr]

more vavles and more parts is just more to tear up... if honda stays competitive with less then, i will love it.... and thats what they intend to do with it... so i hope it is exaclty the same or better than the yfz and still maintain less parts..

[joedirt]

yamaha has the 5 valve head pattened. Honda has the uni-cam Head pattened. Just the Jap. builders though. It's all about flow. One isn't better then the other. did you ever wonder why Honda has the only round bearing carrier out of the Jap. builders. Pattens Pattens

[RIDER11X]

Originally posted by joedirt
yamaha has the 5 valve head pattened. Honda has the uni-cam Head pattened. Just the Jap. builders though. It's all about flow. One isn't better then the other. did you ever wonder why Honda has the only round bearing carrier out of the Jap. builders. Pattens Pattens
I prefer a round carrier over a 5 valve head anyday!:D

[RiPPiNiTuP7]

Originally posted by RIDER11X
I prefer a round carrier over a 5 valve head anyday!:D

i prefer a 5 valve head and when i feel like getting a stronger swinger i will grab a round housing carrier for it too:devil:

its cool, you can always upgrade to a 5 valve head...ah crap n/m on that one:(