which YZ exhaust cams work in POST(!) 2012 WR450F

Be there done that (reset my WR400f's and a buddies WR426F's exhaust cam to YZ timing and loved it)

My WR450F '03 was left stock with regard to YZ-cam or timing change because

I didn't want to purchase a YZ cam nor did I want to loose e-startability.

 

Now I've got me a 2012 WR450F EFI and am wondering which of the zillion posts on that topic I should believe.

For instance when someone claims "a 2006 YZ450 cam is the best one for any modely year WR450"

he might be correct THEN, but was in fact referring only to non EFI engines.

 

So what is the current - 2015 - take on which YZ cam "works"

(e.g. doesn't kill the engine, the e-Start- ability, and adds power)

in 2012/13/14 WR450F engines?

 

 

compatibility:

The chain pitch is identical on all 450 (2003-2014) so basically that is no issue.

 

WR generations deducted from intake cam part nubmers;

 

- WR generation 03 - 05  intake 5TA-12170-00-00 ex 5TJ-12180-10-00

as the intake cam is identical on all WR450s AND YZ450s from 03 till 05

http://www.boats.net/parts/detail/yamaha/Y-5TA-12170-00-00.html

the YZ exhaust cams outght be interchangable

 

-WR generation 06 intake intake 5TA-12170-10-00 ex 5TJ-12180-20-00

only for 2006 WR and YZ

YZ06 in 5TA-12170-10-00 ex 5TA-12180-10-00

 

- WR generation 07 - 13  intake 5TJ-12170-00-00 ex 5TJ-121800-20-00

here the YZs do differ even in the intake cam:

YZ07 in 5TA-12170-10-00 ex 5TA-12180-10-00  WR ex 5TJ-12180-30-00

YZ08 in 2S2-12170-00-00 ex 2s2-12180-00-00  WR ex 5TJ-12180-30-00

YZ09 in 2S2-12170-00-00 ex 2s2-12180-00-00  WR ex 5TJ-12180-30-00

from here on YZ with EFI + reversed cylinder

YZ10 in 33D-12170-00-00 ex 33D-12180-00-00

YZ11 in 33D-12170-00-00 ex 33D-12180-00-00  WR ex 5TJ-12180-30-00

YZ12 in 33D-12170-00-00 ex 33D-12180-00-00  WR ex 5TJ-12180-40-00

 

Please respond IF your ACTUALLY DID THE CHANGE, and do specify whch YZ cams you've tested.

 

deduction:

5TJ is "WR specific" modification of 5TA YZ part.

the '06 ex cam with -20- suffix brigdes from pre-07 to 07-13 generation

 

reasoning:

While tinkering with the ~300€ GYTR Power tuner might be fun and have nocticable effect,too,

I strongly would like fix the "cam issuse" first.

The original '98 engine was a YZ MX attac weapon that was deliberately detuned for WR usage by:

- CDI rev limiter down from 11500 to 10500 rpms

- higher cylinder foot gasket to reduce compression ratio

- more flywheel weight for low rpm tractability, and less flame out stalling

- and advanced (e.g. earlier!) exhaust valve open phase to beeld off power!

Which means the early WRs did deliberaytely blow some power into the exhaust (hence the red glow) instead of turning it into mechanical work.

In '99 there were people that upon comparison eagerly went back to glowing-header WR timing as they didn't like the YZ power.

Personally I was trilled at getting power for free w/o sacrificing off-road low end tractability and lovee my WRYZ400F as did my buddy love his YZ-timed WR4236F

 

 

thx

Rowdy

Edited by WRF-Rowdy

2006 - 2008 YZ ex cam: all have to have the decomp pin ground down to have a working decompression system on a WR.

There is a thread on the subject. Something like 1.28mm removed. 

All 2007 and later motors have essentially the same head so they all need the same mod to the YZ EX cam pin.

My 2008 is being done as we speak with a 2007 YZ EX, as the HotCams cam set sucked (peaky).

 

2006 is more agressive (longer duration profile) and 2007/8 are the less so.

Thx. a lot for the info, I dived into TT serach function and did catch up, knowledged wise.

To ease things for other seekers: this post

http://www.thumpertalk.com/topic/1063462-decomp-pin-grind/#entry11287793

of greyracer513 explains it all in beautiful brevity.

 

Thus: That grind-it-down is the cheap way around purchasing a YZ cam, IF it's a '03-'06 WR exhaust cam.

 

That means a 2007 and onward WR cam won't be much fun, because having the lower, YZ-type decomp pin,

but in the correct position for (advanced) WR timing, retarding these newer cams to YZ timing will close the valve too late

and one would have to add material to the pin to enable e-start in retarded position, right?

 

Hence, if one wants peerless e-start-ability + YZ timing

- for WRs from 2007 and onward one needs to buy a YZ cam,

- pre-2007 WRs can avioid that by grinding off some material from their stock WR cams and retard them.

 

 

If that is true, I'm really interested to hear from anyone who can compare the power output of

 

stock exhaust cam retarded one tooth   vs.  '03-06' YZ exhaust cam  in a 2012 EFI WRF.

 

preferrable w/o messing around with the power tuner at the same time, yust the cam swap's effect!

 

 

I can check the "WR2012 stock cam retarded effect" myself, leaving the autodecomp issue aside

(back then when the TT600 decomp cable had snapped we'd kick start 600cc w/o the help of that decomp thingies)

but am truly eager to hear about the effect these "high lift '03-'06' cams" would have on the 2012 WR.

 

 

Rowdy.

2006 - 2008 YZ ex cam: all have to have the decomp pin ground down to have a working decompression system on a WR.

There is a thread on the subject. Something like 1.28mm removed.

 

Why is that? YZ cam already have the rounded pin, one can't grind off YZ pins, not?

 

 

There is a thread on the subject. Something like 1.28mm removed.

But they were speaking about the early WR decomp exhaust cams, the ones with the longer square, pins.

These buggers, when put into YZ timing position would over-decomp the compression stroke, killing the E-start feature.

Grinding down the square WR pins will turn them into YZ pins, and E-start should work as before, right?

....they were speaking about the early WR decomp exhaust cams, the ones with the longer square, pins.

These buggers, when put into YZ timing position would over-decomp the compression stroke, killing the E-start feature.

Grinding down the square WR pins will turn them into YZ pins, and E-start should work as before, right?

 

Not how I read it. 

 

2006 - 2008 YZ ex cam: all have to have the decomp pin ground down to have a working decompression system on a WR.

There is a thread on the subject. Something like 1.28mm removed.

 

Simply rounding the pin doesn't directly address the length of the pin, and the key to the whole question is the point in the crank's rotation at which the decomp pin rolls out of contact with the lifter and lets the valve close.  Check this using a degree wheel.  In a stock YZ450, it reseats the lifted exhaust valve at roughly 20-25 degrees BTDC.   Later than that, you may not have enough compression to start.  Too much earlier, and the starter won't turn the engine through compression. 

 

I haven't researched the matter enough to know, but your question as to why this should be necessary is understandable, since the two engines are essentially the same, and it therefore seems reasonable that the YZ cam would sit in the head in the same way on either one.  But the experience of those who have installed the cams in WR's and made them work speaks for itself. 

 

Notice, too, that grinding only the axial tip of the rounded pin won't change the timing of the decompression event.  Because of the angle at which contact is made as the pin rolls off the lifter, the center of the pin doesn't touch anything at that point, so it's the "bottom side" of the pin that need the work.

Okay, (sorry for the second thread, I'll stick to here)

let me try to clear things up in my mind and show all know how I collected on the net in one place.

 

I'll state something and you are invited to agree or falsify it. ;)

 

- the 1.2 mm  grinding off is only done (only doable) on the very long, square pins of '03 - '06 WR exhaust cams

- we'd do that grinding because yamaha compensated the too early decomp valve opening (closing too early) of advanced stock WR cams timing

 by making the pin longer e.g. opening the valve during more crank degrees, hence closing it later as well

- YZ cams at YZ timing work nicely with regard to decomp in YZs , otherwise the YZ-MXers won't be able to start them

- YZ cams at YZ timing in a '12 WR (maybe post '07) do not allow e-start due to lack of compression

- even YZ cams at YZ timing need some grinding when used in WRs with the intention of e-startability

- the amount of YZ pin grinding necessary for WR e-start use is unkonwn, and should be established by measuring crank angle for valve closing after decomp action, as you outlined in one of my other threads

- the reason why YZ cams installed with YZ timing in WRs prevent e-starting is unknown as of yet

 

Please feel free to comment on each statement.

 

 

Btw. looking at my pics in http://www.thumpertalk.com/topic/1140673-wr450f2012-which-yz-cams-perserve-wr-e-start-ability/?p=12453059

do you have any explanation why the position of the decomp mechanisms is one cam tooth apart, especially considering that one of them is a '12-WR exhaust cam

 

Can it be that kickstart decomps (YZ) need other decomp timing than e-start decomps?

 

Is there any e-start YZ450F with the engine not reversed?

Edited by WRF-Rowdy

My '08 with the YZ EX cam took a lot of trial and error on the pin grind to get it to always spin fast and always start.

Why is that? YZ cam already have the rounded pin, one can't grind off YZ pins, not?

 

But they were speaking about the early WR decomp exhaust cams, the ones with the longer square, pins.

These buggers, when put into YZ timing position would over-decomp the compression stroke, killing the E-start feature.

Grinding down the square WR pins will turn them into YZ pins, and E-start should work as before, right?

 

No.

 

The '06 + YZ EX cam in the 2007+ WR head all need a pin mod to even function and start.

I remember reading that the cam from a carb'd yfz should work when it's retarded a tooth.  Don't know if anyone ever tried it though.  Can't seem to find the thread but there was specs on the duration and lift of the decomp pins.

I remember reading that the cam from a carb'd yfz should work when it's retarded a tooth. Don't know if anyone ever tried it though. Can't seem to find the thread but there was specs on the duration and lift of the decomp pins.

That worked on the early YFZ450's. So it would end up being a WR450 cam timing when you were done. Don't do it.

It's funny all the talk about YZ cams isn't going to do much for any real HP increases.

YZ and GYTR cams have the same lift as stock WR cams and just end up moving the lobe centers around a little. If you want real power you need to have the head professionally ported and use a different cam than a YZ cam at least on the intake.

Edited by stevethe

Retarding the cam on the quad makes it like a YZ, not a WR.  Early WRs have duration and lift like a YZ.  I think the WR got a milder exhaust cam, maybe when they went to the aluminum frame, then it got a milder intake cam for 12.  I think GYTR cams have more lift than YZ cams, not sure though.

The later WR's ('06+) were hamstrung by their intake cams a good deal more than the exhaust cam timing did the older ones.  The old '03-'06 YZ intake cam would be an improvement.

 

But, the difference in the '03-'05 models was that the WR cam was ADVANCED.  Back before auto decomp and electric start complicated everything, the quick way to YZ cam timing was to RETARD the WR exhaust cam one tooth.

 

Those days are gone, however.  Understand that when you retard a cam, the events it controls happen later.  Since the decompression pin is a fixed component of the camshaft, that means that the lifting and reseating of the left exhaust valve will happen later, too.  Since each tooth on the cam sprocket equates to 22.5 degrees of engine rotation, and the YZ cam is designed to reseat the exhaust valve at 20-25 degrees BTDC, if you retard it one tooth, the exhaust valve won't be closed until TDC or just after, and your compression will be in negative numbers.

 

Oops.

 

So I don't know where you read, "that the cam from a carb'd yfz should work when it's retarded a tooth", but forget you read it.  It's wrong.

 

Edit:  In the case that you actually are talking about the cam from a Quad, and not just misusing the "YFZ" label as many do, there is very little difference between that and the original '03-'06 WR ex cam, but there again, retarding the cam one tooth will destroy your cranking compression unless you grind the decomp pin down.

there is very little difference between that and the original '03-'06 WR ex cam, but there again, retarding the cam one tooth will destroy your cranking compression unless you grind the decomp pin down.

 

Yeah, they were saying the decomp pin on the quad was smaller because the quads had a lower compression piston and a bigger battery than the WR.  But I haven't heard of anyone actually trying it.

Edited by chewbaccauncircumcised

That worked on the early YFZ450's. So it would end up being a WR450 cam timing when you were done. Don't do it.

It's funny all the talk about YZ cams isn't going to do much for any real HP increases.

YZ and GYTR cams have the same lift as stock WR cams and just end up moving the lobe centers around a little. If you want real power you need to have the head professionally ported and use a different cam than a YZ cam at least on the intake.

It's not such much a quest for excessive power, although the difference is/was striking.

 

Personally I hate the dreaded WR timing because it means the exhaust lobe opens 22,5° earlier than the engine was designed for. :rant:

(Closing the exhaust 22,5° earlier, creating less overlap, didn't imporve idling and going back to YZ timing incurred no problems for idle as well.)

 

Stock WRs simply blow out usable combustion pressure instead of putting it to work, at each and every revolution.  :banghead:

 

The only thing it does is create is an extremely hot header pipe, complete with all injury-options and the discomfort of a hot right tigh/leg while riding. :thumbsdn:

I find it stupid to to PowerTune a bike that deliberately wastes available power per design, that excessive heat we feel does go down on milage, too.

Like tuning a V8 where someone has permanently disconnected spark plug #8.

We ride WRs  AND heat the environment/frame/leg a little more than anybody else, just because.

The sensible sequence would be fix the timing first and then PowerTune if you need to. :naughty:

 

Back in '99 Rich Rohrich of the news group r.m.d. was publicly wondering about the crayz lobe timing the stock WR had compared to YZs.

As far as I recall he was the first one to retard a WR cam back to YZ timing, from then on everyone did it, me on my 400, my buddy on his 426 etc.

 

I'm definitely going to YZ timing and if only to get rid of the heat and help the milage. 

Thanks to all the info in here  I think the YZs have much different decomps as they are kickstart only bikes.

They want maximum decomp/no compression  as one good kick appears to reach decomp decativation rpm anyhow.

The WRs need fine tuned decomp with a litte amount of compression (and charge !) remaining so the spark can ignite stuff at way below decomp deactivation rpm.

 

That theory would explain why the YZ cam at YZ timing in my WR had the e-start churn away happily w/o finding any charge to work against or ignite.

Edited by WRF-Rowdy

It's not such much a quest for excessive power, although the difference is/was striking.

 

Personally I hate the dreaded WR timing because it means the exhaust lobe opens 22,5° earlier than the engine was designed for. :rant:

(Closing the exhaust 22,5° earlier, creating less overlap, didn't imporve idling and going back to YZ timing incurred no problems for idle as well.)

 

Stock WRs simply blow out usable combustion pressure instead of putting it to work, at each and every revolution.  :banghead:

 

The only thing it does is create is an extremely hot header pipe, complete with all injury-options and the discomfort of a hot right tigh/leg while riding. :thumbsdn:

I find it stupid to to PowerTune a bike that deliberately wastes available power per design, that excessive heat we feel does go down on milage, too.

Like tuning a V8 where someone has permanently disconnected spark plug #8.

We ride WRs  AND heat the environment/frame/leg a little more than anybody else, just because.

The sensible sequence would be fix the timing first and then PowerTune if you need to. :naughty:

 

Back in '99 Rich Rohrich of the news group r.m.d. was publicly wondering about the crayz lobe timing the stock WR had compared to YZs.

As far as I recall he was the first one to retard a WR cam back to YZ timing, from then on everyone did it, me on my 400, my buddy on his 426 etc.

 

I'm definitely going to YZ timing and if only to get rid of the heat and help the milage. 

Thanks to all the info in here  I think the YZs have much different decomps as they are kickstart only bikes.

They want maximum decomp/no compression  as one good kick appears to reach decomp decativation rpm anyhow.

The WRs need fine tuned decomp with a litte amount of compression (and charge !) remaining so the spark can ignite stuff at way below decomp deactivation rpm.

 

That theory would explain why the YZ cam at YZ timing in my WR had the e-start churn away happily w/o finding any charge to work against or ignite.

 

A whole lot of assumptions going around here. Which I have never heard. As I have said before the difference between the cams is the lobe centers. So you may find a slight performance improvement in the RPM band but don't look for a horsepower increase. As for a hot exhaust pipe well they will both get just as hot. The 2012 and the 07-11 share the same cams and both bikes and idle fine, the 07-11 starts fine? You will not increase your gas mileage just because you put a YZ cam in.

There has been Dyno time on a YZ and GYTR cams, the same operator knows every spec of the WR and YZF cams as well. If you are looking for a real power increase you need to ditch the YZ intake cam and get appropriate porting for a real cam with more lift and duration to take advantage of the porting.

Edited by stevethe

A whole lot of assumptions going around here. Which I have never heard. As I have said before the difference between the cams is the lobe centers. So you may find a slight performance improvement in the RPM band but don't look for a horsepower increase. As for a hot exhaust pipe well they will both get just as hot. The 2012 and the 07-11 share the same cams and both bikes and idle fine, the 07-11 starts fine? You will not increase your gas mileage just because you put a YZ cam in.

There has been Dyno time on a YZ and GYTR cams, the same operator knows every spec of the WR and YZF cams as well. If you are looking for a real power increase you need to ditch the YZ intake cam and get appropriate porting for a real cam with more lift and duration to take advantage of the porting.

I'm not convinced yet. Just keep in mind that WR timing does cancel the (downward) power stoke 22.5° before the YZ timing does. :thumbsdn:

That IS throwing away torque, you will note that as "less power" on any dyno comparison,

when all other parameters are left unchanged, nothing more nothing less.

 

If uncertain simply do a throught experiment and "picture" a WR timing that is TWO teeth advanced (45°). If you look at typical four stroke cam timing diagrams like http://en.wikipedia.org/wiki/Valve_timingyou can see that "two teeth" advance would cancel the power stroke (by opening the exhaust valve) when the crank is a measly 90° past TDC!  That will show up on any dyno and in any drag race.

 

 

 

 

If you are looking for a real power increase you need to ditch the YZ intake cam and get appropriate porting for a real cam with more lift and duration to take advantage of the porting.

For me the power increase is a welcome side effect, gained while restoring the engine's original efficiency. :rant:

 

When something blows off a fixed precentual portion of your power stroke, you simply have to crack open the throttle a litte bit more, to generate the same net torque at the clutch. :naughty:

That means a litte bit more fuel consumption. Maybe not enough to measure it in real life on 10 MX laps, but it is common knowledge that WR timing makes the header glow bright red, while YZ timing does not.  BTDT on my '98 WR400F. That energy used for red glowing the header must be put in (fuel) and is not used for propulsion.

 

It is literally a V8 with on cylinder having the spark plug disconnected, (except for the fact that in this case the increased fuel consumption is not ued to make the header glow :rolleyes: )

 

 

To prove the real power gain (10% ~4hp) from YZ-timing a '98 WR400F,

and to compare it against the stock '03 WR450F see attached Dynoruns:

WR-DynojetRuns.PNG

The fat lines are the '03 WR450F with WR timing

The thin blue line ist the '98 'WR400F with WR timing

Red and green are my '98 WR400F with YZ timing (red being the version with open airbox) :jawdrop:

 

You can see that YZ-timing a WR400F practically turned it into a WR450F above 7000 rpms. :thumbsup:

You can also see the huge torque plus the WR450F has ober the WR400F between 4000 and 6500 rpms.

I can't imagine why anyone would want to run a WR other than with YZ timing, back then!

 

Stay tuned, I plan to subject my '12 WR450F to the same measurements,

if my buddy's workshop still lets me acces their dyno.

Edited by WRF-Rowdy

Jesus you are mixing up years, models, types, cams, heads, ignition timing, pipes, and putting it all on the responsibiltiy of a cam change between models that are not even compatable.

 

 

Good 

 

Luck 

 

With

 

That

GYTR cams for the WR will drop in and work if you want to pay.  Or experiment with another cam and reshaping decomp pins.  I got no experience with that.  Nobody on the forums is going to help you.

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