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Thread: YZ/WR cam timing and in between
01-18-2005, 09:27 PM #1
YZ/WR cam timing and in between
what I am working with;
2004 WR 450,yz cam,throttle stop,GYT silencer with GYT 96 decibel end cap.
what I notice& what I want;
As the usual feel /mindset the WR cam just doesn't pull very well, the YZ cam pulls very nice but a little beyond what I need ,also believe the 96 decibel endcap is holding it back a bit at the upper revs. The bike is a do it all play bike for my novice(?) skills. have been riding for about 20 years not fast by any standard but ready to try and ride anything,MX,Hare scrambles,Enduros,Dual Sports,trail riding , and the most important ,racing to the beer meister when the day is done.
I was wondering if it is feasible take a yz cam apart and repress the gear on say 5 degrees advanced? Trying to get camshaft timing and exhaust configuration more in tune with each other and hoping that the 5 degrees won't mess with auto decompresion at cranking /kicking speeds.
Before I try has anyone ever tried this succesfully?
Are Hotcams available for a low/midrange boost compared to the yz?Also would advancing the intake cam a couple of degrees be beneficial to my ideal by lessening valve overlap?
01-18-2005, 09:56 PM #2
You might consider using the YZ flywheel with the WR cams. It would give you quicker reving without the overall YZ grunt. I like the YZ450 power but really need some flywheel weight but have just never done the mod. I'm installing an autoclutch and hope to solve my stalling issues(heavy on the back brake).
01-19-2005, 08:26 AM #3
I believe you can also do the Grey Wire mod and automatically change your WR Cam timing to YZ timing by simply unplugging the grey wire.
m y s i g n a t u r e:
I used to have it handle on life but it broke
01-19-2005, 09:00 AM #4
hmm interesting approach,but I am not sure if it will satisfy what I am looking for. Although the WR cam timing will rev out it just doesn't have the pull I am looking for.If I had my druthers I would prefer an engine like a klx/drz 400 type of power.Something in me just thinks I would rather stretch out the throttle cables on the rare occasion I open it up,then to ride a massively corked up, ill timed, racing engine at 1/2 throttle.I love how the YZ feels but realistically it is more than I can handle properly and trying to get that 12000 rpm 100 decibel monster more human
Working at a Yamaha dealer kind of limits my choices on bike purchases,besides the fact that I think the WR has a much better chassis/feel for me. Thats the reason why I am thinking of screwing around with the cam timing, to try and get its compromises more in tune with me.
I have the WR camshaft I can sacrifice, so dropping it off at a machine shop with the possibility of it coming back junk not really bothering me.Maybe I will retard that one and see if I can start the bike afterwards. Just hoping someone has tried this before and looking for experienced views/ideas
PS yes on the grey wire mod thanks and sorry
01-19-2005, 10:16 AM #5
I hope you find what your looking for, it doesnt hurt to try the gray wire mod anyway.
The gray wire changes the WR "mapping" to YZ specs by advancing the ignition timing curve. You can do this by removing the seat and gas tank. On the right side front of the motorcycle there's a black box (CDI unit). Follow the wires down to the junction connection and cut/unplug the gray wire. Be sure and use electrical tape to cover any exposed wires.
This improvement makes the WR450 behave more like the YZ450 power wise. If you want pure YZF like power you'll need to change the exhaust cam. Rotating the cam to YZ specs.
If it dosent help so be it but I did it to mine and it made a world of difference.
01-19-2005, 10:41 AM #6
It's important to keep in mind that the intake cam timing (specifically intake close and it's balance with compression ratio) has a far greater influence on the "personality" of an engine than the exhaust timing does. Small changes in the exhaust cam centerline have little or no effect on the engine. The only reason the WR has that bizarre exhaust cam timing in the first place is to eliminate some of the pumping losses associated with the super restrictive stock exhaust setup. They had to make a nearly 23 degree crank angle change to accomplish it. Like I said small changes in exhaust timing don't mean JACK.
All they are doing with the stock WR timing is starting the blowdown portion of the cycle super early (which kills torque) to work around the exhaust restriction. The smoother power people think they have with a WR is just a lack of torque. The restriction and the shortened overlap tends to limit some of the TDC pump through that comes with high rpm engines but it's a bandaid fix that works better when removed. Yamaha knew people would remove the exhaust restriction which is why they made it so easy to convert the bike to the proper timing.
Eliminating that compromise is the first step towards a more useful power spread. You can do it with a an OEM YZF cam or one of the good billet aftermarket cams like Hot Cams. Depending on the type of power you are looking for you can add an aftermarket intake cam and fill in the midrange and upper rpm power spread as well.
My advice would be to put in a YZF exhaust cam and leave it alone. You won't find powerband nirvana diddling with exhaust timing. A Hot Cams intake has an adjustable cam sprocket standard and tuning the intake close timing will give you far better results in trying to reach your performance goals.
m y s i g n a t u r e:
"another beautiful theory beaten to death by a gang of ruthless facts..."
- Tom Hanna (Master Metalshaper/Nitrogeezer)
01-19-2005, 05:11 PM #7Originally Posted by Rich Rohrich
01-19-2005, 09:14 PM #8
Hotcams has a nice little camshaft installation kit for $130. Dial indicator, base, studs, and degree wheel. Makes life easier if you don't have the required toolmakers toys.
m y s i g n a t u r e:
The Universe is my way, Love is my law. Peace is my shelter, Experience is my school.
Obstacle is my lesson, Difficulty is my stimulant. Pain is my warning, Work is my blessing. Balance is my attitude, Perfection is my Destiny. -Guillermo Tolentino
01-20-2005, 08:30 AM #9
Yes it looks like I am having to do some scrimping so I can get some new things to play with,(adj,intake cam). The ins. setup kit sounds pretty sweet, I do have a dial indicator, but the degree wheel I will need, and the mounting setup sounds a lot easier then having to figure out/fabricate one.
01-20-2005, 09:26 AM #10
The early Hot Cams install kit didn't come with a mount for the flywheel, but it's really easy to make one that will work with a K&N style flywheel puller. If you guys want to see an example I'll post some some pictures of the one I made tonight.
Here's some not so detailed pics :