WR450F'12+ How to grind a YZ cam for e-startability

Hey awesome job and just wanted to say thanks for posting this. Now what I really wanna know is. hows the power? What mods have you made (i.e exhaust, tuner / map settings) and what do you think of the YZ cam?

See http://www.thumpertalk.com/topic/1141596-wr450f12-chicken-shed-dynoruns/?p=12465221

Power is lacking, compared to my '03 WR with then stock WR timing.

But as the regualrs have pointed out the post-06 intake cams have 1mm less lift, god knows why :banghead:

(old '05 cam is under way :p )

 

The most restrictive thing was the pea shooter :facepalm: , naturally.

Removing the snorkel only helped a bit.  I figure if yamaha restricts air intake by reducing intake cam lift,

you can almost do what you want at other places, the '03 will win.

 

I'm trying to be stealthy w/o lightlheartedly sacrificing power. Just 10 mins ago I tried the stock muffler

with spark arrestor but w/o end pipe, just the domed cap. :thumbsup:   Beautiful, deep sound, but a tad too load. :naughty:

 

The reason for YZ exhaust cam (and soon '05 intake cam) is that I liked the road performance

the old cam setup did give me w/o binning the stock '03 euro/aussie exhaust.

And, philosophically speaking, I don't see any reason why I should give up ponies that are readily there.

 

If one wants a less torquey bike, he should not ruin the engine by messing up the cam timing,

instead he'd better get himself a WR250F.  Buddy had one for many years, perfect offroad bike.

 

From what I've learned the last month about my '12 model,  I'll probably end up with

'05 intake cam, '06 YZ cam, and the 20mm exhaust pipe. Snorkel is undecided as of yet,

removing it makes it louder at medium power setting too, no good for inner city peace of mind.

 

I'm very partial to with regards to mappings, but I'll try "fuel -4 / ign +1 everywhere" on my ride into town,

just to see it it does anything noticable at all. :goofy:

Edited by WRF-Rowdy

08-09 YZ supposedly had the earliest intake valve closing for best low end power.  I think the steel frame years were the most top end oriented. 

08-09 YZ supposedly had the earliest intake valve closing for best low end power.  I think the steel frame years were the most top end oriented. 

Weird. If I'm in some really tricky environment, like a 45° side hill with loose gravel, that last thing I need is low end power.

But hey, to each his own, thankfully we do have a lot of OEM parts combinations to choose from. :thumbsup:

Edited by WRF-Rowdy

The lower torque hit is nice for pulling up wheelies and stuff in the higher gears.  I think you trade some of that with any of the YZ intake cams.  Depends on the type of riding you do the most.

08-09 YZ supposedly had the earliest intake valve closing for best low end power.  I think the steel frame years were the most top end oriented. 

 

Backwards.  The '03-'05 were the "gruntiest".  The '06, '07' and '08-'09 were each progressively more biased to top end power. 

 

Most people with experience on both of the '03-'04 and the '05 have a hard time believing they run the same set of cams.  The CDI mapping on the '05 makes it feel softer and much less aggressive ("sluggish" is a term often used).  Timing mapping is a very big part of how the bike responds, whatever the valve timing.  The '08 and '09 models also differ in the same way.  The '08 was soft in the mid range, but no one ever complained about that with the otherwise identical '09.

 

The weight of the gas cap sized flywheel on the YZ's feeds into it as well. 

I'm just going by what I read on the quad forum.  When they switch out the intake cam on the 06-09 carbed quads for the 08-09 YZ they lose some top end and pick up some low end.  The stock intake cam on those quads is the same as the 06 WR and YZ.  I dunno, haven't really tried it for myself.

Weird. If yamaha did not change the lobe angle on all its intake cams, (my current "knowlegde")

just the lobe height (1mm less from '07 onwards)  then I'd like to hear the rational,

how less lift would have given them more low end power, with erverything else unchanged, mind you.

Edited by WRF-Rowdy

The WR cams have like 20ish degrees less duration, I think.  Less overlap is better for low rpms, kind of like an RV cam vs a drag race cam.

The WR cams have like 20ish degrees less duration, I think.  Less overlap is better for low rpms, kind of like an RV cam vs a drag race cam.

Hmm. Less lift equals less duration got that.

But how the less time to intake the fresh charge (=less torque) can be overcompensated by less overlap

leading to way much less scavenging losses (=more power) is hard to picture, but I never rode any quad,

so I can't speak from experience, just state how backwards that sounds for an engine tuning layman like me.

I shouldn't really say there's more torque, I don't know.  The peak would come on at a lower rpm, more off idle torque, stuff like that.  At lower rpms, you don't need all that duration and lift.  The air is moving too slow to really fill the cylinder all that good anyway.  I'm by no means a  cam expert, just read a few posts on internet forums.

Backwards.  The '03-'05 were the "gruntiest".  The '06, '07' and '08-'09 were each progressively more biased to top end power. 

 

Most people with experience on both of the '03-'04 and the '05 have a hard time believing they run the same set of cams.  The CDI mapping on the '05 makes it feel softer and much less aggressive ("sluggish" is a term often used).  Timing mapping is a very big part of how the bike responds, whatever the valve timing.  The '08 and '09 models also differ in the same way.  The '08 was soft in the mid range, but no one ever complained about that with the otherwise identical '09.

 

The weight of the gas cap sized flywheel on the YZ's feeds into it as well. 

 

The 08-09 intake cam is supposedly advanced the most.  That should make it the least top end biased YZ intake cam all else being equal. 

The 08-09 intake cam is supposedly advanced the most.  That should make it the least top end biased YZ intake cam all else being equal. 

What information source claims the lobe angle of 450 intake cams have changed? link?

I tried this with a Wiseco cam.  It didn't work all that well.  Still spins a little too fast.  I have to kick it when it's cold.  If it's warm I can restart it with the button but I have to hold the throttle open a little.  Besides that the cams are nice.  There's much more top end.  The hit comes on a little higher in the rpms but not too bad.  I was hoping I could get it on the first try but I'm gonna have to go back in and grind a little more off. 

 

Next day it e-started cold on the second try with the throttle open a little.  I'd like to grind a little more off but I'm not in the mood for pulling it back out.  One of these days I'll get it.

Edited by chu

I pulled the cam again and ground it some more.  I rotated the pin both ways and ground where it would touch in those positions too.  It cold starts with the knob pulled or the throttle open a few degrees.  It starts good when it's warmed up.  Probably should have took just a little more off but that won't be happening any time soon.  Thanks OP for the how to.

Old but relevant thread, so I thought I'd ask->

Is there any hardened layer on these decompression pins?  I know there is one on the cam lobes.  Has anyone who grinded down some of their decomp pin found extra wear on the bucket when they checked their valve clearances next?

and for me to know..

would this work on a 2016/ 17 machine (WR with YZ cams)???

1 hour ago, patrick2wd said:

and for me to know..

would this work on a 2016/ 17 machine (WR with YZ cams)???

Completely different motor.   From what i understand there is no difference between WR and YZ cams ( or their timing ) on the new bikes.   Power difference is completely timing ( spark ) and fuel.

1 hour ago, patrick2wd said:

and for me to know..

would this work on a 2016/ 17 machine (WR with YZ cams)???

They have the same cams already

hmmm...

:huh:

why different part nbrs??

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