Made the WR-250 Timing Change and. . . .

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Feb 24, 2001
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#1
Okay first off......
:cool:
Okay that out of the way....
real simple change, I stuffed a rag below the cam sprockets to catch the clip....but it popped onto the patio......clink...cling.......but I found it......anywhoooooo I digress....
real easy, didnt take off the radiator.....1 hour max, and like the others on the site, could do it less than 30 easy now that I have done it.

Starting: ...well now that I have been trained by the WR, it starts one kick, hot or cold...so no difference there.

Power: Same power, didnt really feel any gain or loss, but I did notice two things:
1. pulls harder, sooner.
2. Pulls very very smooth with the old WR timing "hit/surge" that came on at about 4 or 5 grand gone. It just pulls very evenly, from the very start. ;)
This is the way the motor (IMHO) should have been delivered. I feel the power is the way it should be now. I thought the motor was awesome before the timing change, and now....goodness.......incredible.
It is still a tractor in the slow stuff, roots etc no problem, and now no surprises when you crack the grip real fast if the conditions arent perfect (unlike here :confused: ) , cause it is so smooth....the mid range rush is gone..........so over all......a must do mod, and only enhances the performance of the machine.
Was at the local track yesterday, and went to the concrete starting gate where a bunch of 2-smokes were practicing their starts and gate runs to the 1st turn. 125s and 250s.
First one I choked....they all left me wondering "now what"
:eek:
after that, and got the roll off the pad down, I left everyone of the 125s behind each time (and I out weighed these guys by at least 40 pounds each (no comments please) and only one guy beat me about 1/3 of the time, and only to find out later he was the only one on a YZ 250 (not F) Dry and hard pack and junk dirt and the WR just hooked up, and coming out of the first turn...well......enough said.....
The motor is awesome and I refuse to change it back you cant make me!!!!!:p
Got the Universal Hi bend protapers on....with the tall mounts from TAG.....and now have room!
SWEEEEEEEEEET!
Well......I kind of (yeah right, kind of ....ha ha) recommend if you have the WR to make the change.....
Do it NOW! ! ! ! go out to the bike and pull the cover and change it, tell the Chief of House you will do the dishes later!
:confused:
okay I am done.....guess the pinapple was in the sun too long....I will calm down...
thanks to all that helped out on this ol guy making the Mod....especially Sean.....thanks loads.......
be good.......
oh.....another day...its only supposed to be a high of 81 all week.........:(
HR
I know......so catch me!
 

z4me

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May 4, 2000
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#2
HR -

I think you summed up my experience with the new timing very well. The main thing I noticed on the trail was that I could loft the front wheel over obsticles no matter where I was in the RPMs. Where I really noticed a major difference was in deep sand. Stick it in third and hold the throttle WFO - the bike screamed. Before the timing change it was much more of a challenge to keep the RPMs up and not loose traction in the sand. Like you said - it is a must do for WR250f owners.

- Sean
 
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Apr 4, 2001
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#3
HR -

I am just on the back side of the break-in process and I am seriously considering doing the WR to YZ timing change myself. :think I will be riding in some deep sand this weekend and by reading the posts on this mod, I may do it earlier than I thought. You mentioned that Sean sent you something that was very helpful. Can you pass it along to guide this WR newbie?

Sorry to hear about the bad weather ;)
 

Humai

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Feb 6, 2000
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#4
Guys, while you are in there doing the cam timing change, any analysis of the relationship between the timing "punch mark" on the cam sprocket and the actual exhaust cam lobe centre would be really handy. I am trying to establish whether the Euro model WR250F has the same cam timing as the US version.

Has anyone put a degree wheel on the flywheel and worked out the absolute cam timing of this engine?

Thanks,
Grant
 
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Aug 9, 2000
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#5
Humai,
Why can't you just count the timing chain links between the "I" mark on the rear cam sprocket (intake) and the "E" mark on the front cam sprocket (exhaust). If it YZ timed there will be 12 links, and 13 links if it is WR timed.
I would bet that Euro models are WR timed because they come with a very restrictive exhaust system that cannot be easily uncorked like the US models. According to Rich, this restrictive exhaust was the reason Yamaha had to change the WRs from the YZ timing. If you want me to post a picture of what it looks like, let me know.
Coop
 

Humai

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#6
Coop, I haven't yet been inside the WR to verify this, but my assumption is that all WR and YZ250Fs will have 13 links between marks when timed as per factory settings, regardless of absolute cam timing, as their setup instructions are going to be the same. The difference between the WR and YZ will be the position of the punchmark on the exhaust cam sprocket relative to the lobe centre.

Several factors regarding the Euro WR have got me wondering whether the Euro WR actually is YZ-timed. They are:

- Performance: My Euro WR250, in side by side lineups, performs as you would expect a YZ250F to perform. It beats piped KDXs and XR400s and can nearly keep up to an RMX250.
- Throttle response: The Euro WR seems a little soft down low and has good boost in the mid and top, just like the YZ-timed US WR owners are reporting.
- Jetting: The Euro WR likes leaner jetting (170 main), just like the YZ-timed US WRs do.
- Euro exhaust is much less restrictive than the US version with the plug in. Yamaha did not need to compromise cam timing on the Euro WR to manage the higher attendant backpressure the US plugged pipe would produce.

Of course all these assumptions could be total crap, but I'd like to compare actual cam timing between the US and Euro models somehow. If I get into the top end at some stage, I'll measure the timing with a degree wheel and let you know.
 
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#7
:think Hmmm
Humai
If you haven't already found out by then, I'm going to check my valve clearances the week after next and will check the exhaust cam lobe position for you. Of course, it will be YZ timing but it will tell you what you need to know.
Coop
 
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#8
The wr to yz cam timing change adds about 4hp to the 4,000 to 8,000 rpm range -- without taking anything away from lower down or up top.

Pretty cool!

Oh, BTW, in case you're wondering, if you put the YZ pipe on the WR, it makes the bike stumbly on low end, barks a little better at 1/4 throttle, and doesn't give it any more on top (compared to a WR with the snuffer out).