WR-250 Cam Timing

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#1
All knowing and powerfull DRN Oz members.....

going to give it a shot and see what the difference is.....
where can I find the specifics on the exhaust cam timing (one tooth but which way) "How To" to change from WR to YZ specs for my ride.
Wanted to give it a shot this weekend and let you all know the difference........so......where can I find out how to do it exactly
Thanks all........and I did a search for the entire forum on cam and timing etc.....and no specifics came up
thanks!!!
HR
(yep dont ask, its 79 degrees, 15 MPH breeze coming off the ocean, ahhhhhhhhhhh:confused: )
 

z4me

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#2
If you get Dirt Bike - the May issue shows the operation pretty clearly.
 
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#3
It's important to know that you should to run a less restrictive silencer if you are going to retard the exhaust cam timing to match the YZF. The stock exhaust restriction is the reason why the cam timing is advanced in the first place on the WR.
 
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#4
Rich......Less Restrictive. . . as in

Silencer is still stock but I have pulled the pencil sized hole "baffle/restrictor" and replaced it with a down turn snorkle........breathes real well now, revs to the moooon and back....and the snorkle keeps the noise thrown in the dirt not up in your ears. (throttle limiter is history too......Mr. Hacksaw took care of that)
Is this enough "opening it up" IOT feel the difference?
or
do I have to replace the whole shooting match and purchase new....(if that is the case.......forget it!)
Thanks!
HR:cool:
 
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#5
Re: Rich......Less Restrictive. . . as in

Originally posted by Hawaii-Rider
Silencer is still stock but I have pulled the pencil sized hole "baffle/restrictor" and replaced it with a down turn snorkle........breathes real well now, revs to the moooon and back....and the snorkle keeps the noise thrown in the dirt not up in your ears. (throttle limiter is history too......Mr. Hacksaw took care of that)
Is this enough "opening it up" IOT feel the difference?
YEP, that should cover it.
 
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#6
HR
I have the same set up, and noticed a significant difference. There is a little more info in the Thumpertalk board, but still not very detailed. I read the feed back at 7 PM and was going to get the mag the next day to make the change. At 10 PM I got anxious and tore into it with no instructions. As a result it may have taken me a little longer, but it was pretty simple (done by 12:15 with a trip to get a C CLIP retriever from Home Depot). It is a good idea to have one of those little magnetic grabbers on hand, as there is a good chance of dropping the retaining clip in the engine.

A summary of the procedure is as follows;
1. Romove valve cover
2. Remove tensioner
3. Romove cam retaining bracket (the one towards front of the bike) WATCH the C CLIP
4. Rotate left cam clockwise one tooth (from 13 chain pins to twelve between timing marks on the two cams) Do this by lifting the end of the cam opposite the chain enough to drop the sprocket out of the chain so it can be turned.
5. Put it all back together (WATCH the C CLIP!) per the manual.

It is all pretty clear once you get the cover off.
 

z4me

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#7
Originally posted by Rich Rohrich
The stock exhaust restriction is the reason why the cam timing is advanced in the first place on the WR.
So is there anything to the claim that it gives the WR more torque down low?

Hawii-Rider - look in your email...
 
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#8
Originally posted by z4me
So is there anything to the claim that it gives the WR more torque down low?


Probably. With the stock WR cam timing the reduced valve overlap due to the advanced exhaust cam timing could in theory have a positive effect on low rpm torque, but the trade off of the early exh blowdown cutting into the expansion cycle (power stroke) would probably be a wash in practice. Engine braking is likely to be effected more than power. Having gotten a few rides on a YZF250 and seeing how it performs, my GUESS would be that in an engine this small the compromised stock WR cam timing would have a detrimental effect on torque across the board.

Unfortunately I haven't had the opportunity to get my hands on a WR250F so all I can do is speculate, sorry.
 
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#9
I don't think it increased the botton end, but increased the feel. It revs a little quicker and smoother so it gives the perception of better bottom since you get to the mid a little quicker and smoother. With the WR timing I could distinctly feel the transition from bottom to mid to top, now it blend together like it should.

I raced with the YZ timing yesterday and also noticed that the bike was a little more forgiving if I ended up a gear lower than I should have been.
 
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#10
Hawaii-Rider,
It really is a simple modification. As z4me stated, the May issue of Dirt Bike has a how-to on the change and believe it or not has it spelled out pretty simply for us knuckle-heads. Don't worry about removing the left radiator, it's not neccessary. Just remove the tank(leave the rad shrouds on the tank) and then proceed to (1) of bentbarz's directions. Make sure you have a telescopic magnet handy when you remove the cam caps. That little SOB c-clip will fall somewhere out of sight and will ruin your day. I knew in advance about the little c-clip so I was being extremely careful and the little SOB still fell in the motor:scream: I, like bentbarz, had to make a trip to get a c-clip retriever (magnet). If I had to do it again, I would slip the magnet under the front edge of the cam cap as I lifted it, so it would automatically grab the c-clip as the cam cap comes off. Lessons learned :confused:
What difference did the timing change make? It made my WR more responsive and livelier. It gives you the feeling that it pulls stronger off the bottom because it revs quicker. It actually made my bike more fun to ride, which I initially thought was an impossibility. I highly recommend making this modification.
Good luck,
Coop
 
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#11
WOOO HOOOO!

I knew there was a reason I thought dirt bikers were kewl..........

z4me..........cant thank you enough.......thanks for the email it was great....photo came out super!!!!!

You folks are the best! wow what a response surge, and you dont hate me for having great weather all the time either.....well except Longtime in california.........:confused:
I have the magnet already......(CR-500 circlip chase a few years back thank you :D )
now if the week would just end today....
.but I have a 1/2 day off on Friday so will get it wired for Sats run......and will let you all know what this old guy felt in the seat of the pants!
Thanks again all!!!!!
.........anyone need any coffee......Pineapple...mangos . . . ..free place to stay if you visit!?!?!?!?..I got 3 bikes........15 minutes from the riding area.......hmmmmmm
HR :cool:
 

RakO

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#12
Originally posted by Rich Rohrich
It's important to know that you should to run a less restrictive silencer if you are going to retard the exhaust cam timing to match the YZF. The stock exhaust restriction is the reason why the cam timing is advanced in the first place on the WR.
Hello Rich ,
Do you think that run a less restrictive silencer on my 250 WR would help for the "middle bogging effect" or I have to go for the YZ timing ?
I would like to keep the "technical trail" handling of the WR engine.
RakO
 

z4me

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#13
Originally posted by RakO

Do you think that run a less restrictive silencer on my 250 WR would help for the "middle bogging effect" or I have to go for the YZ timing ?
I would like to keep the "technical trail" handling of the WR engine.
Hey - I made the timing change yesterday and rode today. The trails here are tight, muddy New England style. The change took less than an hour, and would take me about 20 minutes to change it back - but I won't. The low end was not noticably different but the mid was all there. It was easy to loft the tire at any reasonable RPM on the trail - it was a big improvement in my eyes.

Originally posted by BCooper

If I had to do it again, I would slip the magnet under the front edge of the cam cap as I lifted it, so it would automatically grab the c-clip as the cam cap comes off.
You are the man for that tip! Thanks that is exactly whet it did and wouldn't you know it - the clip was attached to the magnet after I popped the cap off.

Originally posted by Hawaii-Rider

free place to stay if you visit!?!?!?!?..I got 3 bikes........15 minutes from the riding area.......hmmmmmm
That's it... I don't care if you have perfect weather. It's that you are only 15 minutes from your riding area that gets me :D ...well, what did you think of the change?

- Sean