Titantium Valves for WR 400



11 replies to this topic
  • Clark_Mason

Posted July 17, 2000 - 03:06 AM

#1

Does anybody make and install Titantium valves and lower spring rate valve springs for a 99 WR 400?? any knowledge in this area would be appreciated?

Thanks

Clark

  • PSC

Posted July 17, 2000 - 06:03 AM

#2

Clark,

I guess that in the most likely event that no one has them off the shelf, that the best place would be a bike performance tuning shop (i.e. drag bikes etc) that could make them up for you. They would probably have the know how to recommend the correct valve springs as well.

Here is what Yamaha claim in their release blurb for the YZ250F i.t.o the titanium valves

"The three intake and two exhaust valves on this 5-valve engine are made of titanium to reduce spring load by about 30%, thus achieving outstanding response"

PSC

  • Hick

Posted July 17, 2000 - 07:35 AM

#3

How about retrofitting them from a 2001 YZ? I've read that they will come with Ti valves. I don't know about the WR, but the parts should interchange, right?

Would Ti valves necessitate diff. spring rates due to weight? Diff. seat material due to hardness?

Worth retrofitting to my 2000 426?

  • PSC

Posted July 17, 2000 - 07:56 AM

#4

Hick,

I would assume they could be interchangeable if the stem & head sizes remain the same. Knowing some of Yamaha's prices makes me believe however that it could be cheaper to have them made up.

I would also consider them for my 426 especially if Yamaha's claims prove founded. It would be interesting to hear from anyone who has had practical experience in comparing std vs Ti valves (ie drag racer).

The valve springs will have to be "softer" to enable the full power gains .

From the yamaha blurb on the 2001 426

"-Reduced horsepower loss with adoption of titanium valves, etc.
The three intake and two exhaust valves on this model's 5-valve engine are made of titanium to reduce spring load, thus contributing to outstanding response. Also, revision of the carburetor settings has improved performance characteristics."

They have also installed a lighter camshaft as the valvetrain stresses are now lower.

PSC

  • Vincent

Posted July 17, 2000 - 11:02 AM

#5

These are all things Suzuki is wishing they would have done on there new thumper. I've been reading that while they have been trying to make the bike a motocrosser, the motor tends to explode the valve train at anything over ten thousand rpm!! Ouch!! Shoulda run titanium...hehehe.

  • Taffy

Posted July 17, 2000 - 11:34 AM

#6

Clark

i caught up with an old post from someone from a bike mag & you & i've waited some time to post this knowing you couldn't let it go!

in it the guy said that you shouldn't bother with bigger valves because it would push the point at which they worked on your bike up a few thousand revs.

well (deep intake of breath) i'm going to disagree!!!your bike may be 'undervalved'.

the moment that Yamaha put the bike out to 426 they either had it overvalved as a 400 or it's now undervalved as a 426.

how do you tell?

someone does big valves let them tell you their figures.

Clark, i know we don't have to teach you how to suck eggs , so i will address this to everyone...

there is a right sized inlet & exhaust for your bike, so the standard sized valve head should be flowed by a proper flow engineer after a basic 'clean up' is done.

the CLEAN UP/blueprint is cutting the valve seats thin, cleaning the seat area, shaving the back of the valves, aligning the inlet manifold to the head, cleaning around the valve guide area, blemishes & the carb to inlet for rubber intrusions. also ditto the exhaust port.


after this 'clean up' which you clark have now done it should be flow tested. the valves will be pulled out completely & flow of air checked. then with the valves fully open, & finally with the valves fully open +.5mm (& more if good) using .5mm lifters at the cam to shim. if the bike works better with the valves open +.5mm you can try high lift cams for more mid to top.

if it doesn't make diddly squeek you can try longer duration (torque cams?) knowing that there is no point in high lift cams. the correct valve timing is ultra critical, & i'm not talking one tooth!

by the way a standard mod on all production racers in the 90's was to have .25mm (+ or -) taken off the base circle of the cam. this was simply the manufacturers quietening ramp & was cheap & quick, given that it takes months for yoshimura et al to develope a new profile.

one simple way to see if you can get a performance lift is to guage where the difference between your 'cleaned up' & a standard head comes on the dyno. from these figures you can figure where big valves would help.

usually bigger valves give more torque not top end- given that the engine needs them. they slow the airspeed down if they are too big. you want the right size that the engine demands.

i read a dirtbike mag that tested somebodies YZ with 'big valves' but they wouldn't disclose the CC!!!

this same mag described the steering head angle as very steep, BUT DO NOT GET ME STARTED ON THAT AGAIN!!!

titanium valves? go to the car world they'll be everywhere i should have thought, certainly will be to order. get the uprated 2001 valve springs.

don't forget your valve to valve & your valve to piston clearances. also how deep the big valves sit in the head.

i had my own ti con rods home made 10 years ago for the duke & i know a little about it. if i remember rightly it weighs just 56% of steel or is it 69%?

[This message has been edited by Taffy (edited 07-17-2000).]

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  • MotoGreg

Posted July 17, 2000 - 04:54 PM

#7

Would Ti valves necessitate diff. spring rates due to weight?


Yes, if the valve is lighter just imagine how much lighter it is at 11,000 rpm! At that speed it wants to float and needs a strong spring to keep it closed. Strong springs are harder for the engine to turn over robbing HP, just imagine how much you lose in frictional losses at high rpm! Posted Image

------------------
MotoGreg - The voice of a new millennium
'99 WR400 - 'cause thumpers rule!
'92 GSXR 7/11 (But I wanna trade it for a dope 916)
You can visit my photo album for $1 - ENTER AT YOUR OWN RISK

  • WFO_DON

Posted July 18, 2000 - 02:48 AM

#8

YES you are right moto greg you will need more valve spring with ti valves or they will float.More power more spring a friend of mine builds sprint car motors and uses ti valves ti rods large ring end gaps a hole bunch of tricks all to get mre power like 700 hp
in a small block chev.

------------------
DON STEMPLE
WASHINGTON ST
OFFROADER
99WR400, FACTORY EFFEX GRAPHICS,FACTORY CONNECTION FRAME GUARDS,
AIRBOX LID OFF,PROCIRCUIT T-4 PIPE,87 HONDA CR500.

  • PSC

Posted July 18, 2000 - 06:35 AM

#9

The valve spring is responsible for a number of things the most important been.

1. Making sure the valve is airtight when closed.

2. Making sure the valve tracks the cam profile.

When you replace steel valves with Ti versions (same size, but considerably lighter), the amount of force that is needed to be exerted by the valve spring to achieve the same objective (accelaration/tracking) becomes lower, so you use lighter springs (lower tension/springrate).

*IF* you change the profile of the cam to a more radical opening and closing ramp you will typically need to increase the springrate so that the valve will track the cam profile (for the same valve weight).

*IF* you increase the working RPM of the engine, the valves will have a shorter period of time in which to complete there cycle and so the rate of acceleration needs to be higher (achieved with a higer tension spring and/or lower valve mass). if the valve does not track the cam you get valve "float", which causes rapid valve wear (especially on the exhaust valve).

So effectively if Valve weight diminishes and max RPM remains the same (Ti valves in WR/YZ std rev limiter) the valve spring tension should be lower, resulting in lower valve train power loss and longer valve train life.

PSC

[This message has been edited by PSC (edited 07-18-2000).]

  • James_Dean

Posted July 18, 2000 - 06:43 AM

#10

My suspicions about the news is that a power increase may not be that much unless the cam profile ramps open and closed quicker. So the lighter weight valves may still require a stiff spring due to increased accelerations. There are other design considerations that may prevent higher rpms. Yamaha might boast reduced spring rates, but they could increase preload resulting in the same tension.
James Dean

  • Taffy

Posted July 18, 2000 - 01:11 PM

#11

PSC

spot on with the spring poundage. lighter spring for a lighter valve. less effort to open & close, Gee-Gee's saved.

the engine is already safe but Yamaha will want it to be doubly so. they need a safety margin & the ti valves will give it to you.

ti is obviously coming down in price over the years & is now a viable proposition for the big four-given that telling everyone sells more bikes as well!

it will allow a higher lift cam with a more viscous ramp & given that the extra size of an already light valve won't be much, allows bigger valves.

as mentioned before if only someone on this website was a top runner we would get more info & a lot of it would be mindblowing i'm sure.

check that the valve seat & valve guide material don't have to be changed to be compatible with ti.

also can someone check out what the TRX850 set up was & who raced them at the highest level. if the bike was raced & then dropped by a top tuner, they'll now want to cash in on that knowledge at the counter. how many valves, what size (& bore size of course) you could even find out if it ran a 2 into 2 what the bore size was for the torque pipe was etc etc.

  • MotoGreg

Posted July 18, 2000 - 04:18 PM

#12

WFO Don- Read my post again (or see PSC's) you've got it backwards. Posted Image



------------------
MotoGreg - The voice of a new millennium
'99 WR400 - 'cause thumpers rule!
'92 GSXR 7/11 (But I wanna trade it for a dope 916)
You can visit my photo album for $1 - ENTER AT YOUR OWN RISK




 
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