YZ exhaust cam/ACV question


8 replies to this topic
  • shaun_heb

Posted March 21, 2009 - 06:15 PM

#1

I have an 06WR450. This is my first bike and I've only had it for a couple months. I'm mechanically inclined but at the beginner levels of dirt bike knowledge. So I was told that an 05 YZ exhaust cam would be nice upgrade for my bike along with disabling the ACV valve. The problem is I'm not quite sure I understand the benefits. I was wondering if some of the more knowledgeable members could help fill me in.

The bike has ECV removed , YZ throttle stop , JD jet kit , stock exhaust mod. On the way is FMF Powercore4 slip on and powerbomb header , Powershot Ap cover and Powernow.

Last I'm also going to try the RedBeard mod.

  • Fullbore4

Posted March 21, 2009 - 11:12 PM

#2

I have an 06WR450. This is my first bike and I've only had it for a couple months. I'm mechanically inclined but at the beginner levels of dirt bike knowledge. So I was told that an 05 YZ exhaust cam would be nice upgrade for my bike along with disabling the ACV valve. The problem is I'm not quite sure I understand the benefits. I was wondering if some of the more knowledgeable members could help fill me in.

The bike has ECV removed , YZ throttle stop , JD jet kit , stock exhaust mod. On the way is FMF Powercore4 slip on and powerbomb header , Powershot Ap cover and Powernow.

Last I'm also going to try the RedBeard mod.


YZ exhaust cam will give it a lot more power.
ACV valve was a Yamaha addon to take the pop out on decel.....YZ's don't have it......by disabling it, you can actually read the plug color, meaningfully. Throttle response is a bit better and you can use a much smaller pilot jet. Also you will be able to set the fuel screw much easier by idling the bike like Eddy Scisneros talks about. The best needle is the 05 YZ OEM needle (NFLR), not the JD red and definitely not the blue one. The Powershot AP cover works better than the Boyesen covers. FMF Powercore 4 is awesome for the 06. Powerbomb moves the power a bit lower. The Powernow noticably helps low end and smaller jets are used because air flow through the carb is enhanced and pulls more gas. The redbeard mod is the best AP mod because O-rings break but the leak jet must be sized LARGER (I recommend a #75-90 (stock is 55 I think)).

Others may not agree with me but I've followed the advice of pros on this site through heavy research and I have found my results through tedious trial and error. Seasoned riders with Hondas, KTM's, Kawis and other Yamys have verified my results. Let us know what your results are and have fun wrenching.

  • shaun_heb

Posted March 21, 2009 - 11:34 PM

#3

Exactly the kind of answer I was looking for. I will post my results as soon as I can. Taking the bike out for a three day no mod trip on the 27th. After that I will begin the build up with a nice base line to work with.

  • William1

Posted March 22, 2009 - 05:06 AM

#4

Unless you run race fuel, you cannot read a plug, the additives in pump fuel make it impossible.

The ACV (coast enricher) adds a little fule under high vacuum situations like when you close the throttle from high rpm. The down side to a ACV is it can make getting the fuel screw just right though I have never had a problem. The other issue with it can be if the spring or diaphragm go bad, though this would be obvius by a sudden richening and subsquent poor rideability. I leave them intact, just inspect once a year. If you must do the ACV diabling, depending on the method used will define whether the pilot jet (or slow air jet) must be changed.

Redbeards mods are intended for the slant FCR, not the MX version now in use. True the oring used in the oring mod break, but they can be replaced in a couple of minutes on bike quite easily. Or, you can replace the stock AP spring with a stiffer one like from Merge Racing and be done with it.

If it were my bike, the Powernow would go in the trash, all it does is mask poor jetting (if it is poorly jetted) and reduce top end. Regarding the AP cover, unless you are a good 'B' class or better rider (and even then,,,), the AP cover change will be unnoticed.

The YZ cam will add a bit more kick to your bike but your single track riding will be more difficult as you will loose a bit of power on the low end of the rpm scale. If you ride desert or other wide open places, it is a good thing to do.

What are you calling ECV???? Did you mean AIS?

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  • Fullbore4

Posted March 22, 2009 - 08:32 AM

#5

If you disable the ACV replace the MAJ (main air jet-stock 80) with a 100 to lean out the circuit a bit.

As for the AP, I've tried em all and had the best results with the Red Beard mod. But again, its the results that count, not what others say. Happy wrenching.:thumbsup:

I never check the spark plug color myself on this bike. I go strictly on how it runs.

  • Fullbore4

Posted March 22, 2009 - 08:53 AM

#6

By red beard mod, I mean safety wire the linkage, grind off the diaphram stud and drill out the leak jet to an equivalent 75 or so.

  • grayracer513

Posted March 22, 2009 - 09:28 AM

#7

IMO, the redbeard mod is a caveman approach to a "problem" that you may not even have.

Once the accelerator pump is timed correctly, it may not need further tuning. If it is decided that it doesn't deliver enough fuel because the linkage spring isn't stiff enough, Merge Racing makes a heavier spring to replace the original that won't break the way O-rings eventually do. Furthermore, using the spring instead of wire eliminates the need to grind off the diaphragm button, which causes the fuel output duration of the pump to be extended well beyond reason.

Read:

http://www.thumperta...330#post4415330
http://www.thumperta...966#post6081966
http://www.thumperta...344#post6091344

  • William1

Posted March 22, 2009 - 01:38 PM

#8

Also, the ACV has nothing to do with the main fuel circuit (main air jwt and main jet).
Some that disable it change the Slow Air Jet to be able to retain a reasonable sized pilot. The ACV is interconnected to the pilot circuit.

  • Fullbore4

Posted March 22, 2009 - 09:14 PM

#9

Also, the ACV has nothing to do with the main fuel circuit (main air jwt and main jet).
Some that disable it change the Slow Air Jet to be able to retain a reasonable sized pilot. The ACV is interconnected to the pilot circuit.


Right......I meant the Pilot Air Jet should be changed from a #80 to a #100. My bad.....LOL.




 
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