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VFRCaptBob

Bob's 2002 YZ250F build

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12 pins stick in my mind. I did a total rebuild about thirteen  years ago on my boys 02. Every bearing etc. etc.  Athena 290 kit. I'm getting ready to do the suspension on it for me. He lives in Fla. now and hasnt been on it in 7 years. Did you have the head redone yet ?

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I did miss the opportunity to re do the head but I am waiting on a flywheel puller tool to change out the cam chain. I have to have four running bikes for out family trip to OcotilloWells over Xmass New Years so I am abbreviating this project to finish another 2001 WR250f project for my wife and daughter to share rides on. Plan to revisit the head valve rework for next year. 

And I have to reconfigure a 3 rail trailer to accomodate 4 bikes but that's for another post. 

Edited by VFRCaptBob

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Changed the cam chain and water pump seals as I found a mystery puddle of water under the bike. 

Here's the problem. Intake cam had 1 slightly tight valve originally. Assembled tried to start it and then found another slightly tight intake valve. Adjusted it and reassembled and now the final valve was slightly tight. Wierd. Turned engine over and re checked. All are now in spec. Bike still won't fire up on the kick starter. 

Since I have an 04 wr or yz ex cam i adj cam timing with 12 pins between 12 oclock marks instead of 13 when I originally tried to start it. 

It sputters and pops but won't fire up. To my eye the ex lobe looks slightly advanced w 12 pins setting. 

I am considering pulling the head and taking it in for a rebuild. Photo shows 13 pin setting. 

Was considering push starting it to see if I can adjust the carb and get it to start and idle.

Any thoughts appreciated. At this point I am considering taking it in to a shop.

20181014_083608.jpg

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On 12/7/2018 at 2:04 PM, YAMAHA NICK said:

Check your woodruff key and make sure the flywheel is lined up perfectly.

Ok. Thought I was pretty spot on. But I am so far out in the weeds right now i appreciate anyone's best advice. Still could use confirmation on cam timing with auto decomp cam mod. All the original threads are lacking specific information and picture have been deleted.

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I had a similar experience with the valves seeming to be off like you mentioned. It ended up being the woodruff key had sheered when I reinstalled the flywheel. First time for everything I guess.

If your timing is right. Then it’s fuel. Have you checked the squirt duration of the accelerator pump? Is the bowl getting correct fuel level? Is the spark strong?
I’m having flashbacks from a few months ago. I had a similar experience

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Gave it my all Sunday.  Re checked valve lash and flywheel and woodruff key aligment. Pulled and re installed.

Tried 2 different timing settings.

1. Intake cam '02 stock setting at TDC '04 decomp ex cam 12 pins and 13 pin on cam chain between 12 oclock marks.

Checked spark it looked good to me.

Decided to pull the carb and do a more thorough cleaning and service.

Tried injecting a little fluid directly into carb. No change.

Acts like no spark, no fuel poor compression.

Edited by VFRCaptBob

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Sounds like cam timing may be off, I debated on the factory cam for my 426 but ended up going hot cams. I’ve looked at picks of my valve timing and it’s way different looking BUT I HAVE 426 AND HOTCAMS. What does the other side of the cams look like? Here is mine for reference, I know the 250 and 426 share a lot of parts they are two different machines. IMG_2538.JPG
Do your cams point the same general direction?

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I have actual FSM for the 2001 WR250F . PDF FSM for the YZ426F  and the 02 YZ250F.

Don't have the leak down test tools.

There's a good picture on page 1 of this post of how my cams are timed presently. Lobes look correct. 

I am considering hot cams for the YZ250F and installing the 04 wr ex cam in my 01 wr since it still has stock cams.

For now I just need them running for my upcoming trip.

Any good shops or mechanic recommendations would be welcome too.

Thanks

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Took bike in to Nathan at Factory Wrench in Redondo. So far he found all 3 intake valves are leaking. Compression is below 80. So he is going to go through the head. Said he found black powder residue on top of the new piston but rings piston and cylinder are all good. More to follow.

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21 hours ago, YAMAHA NICK said:

Good to hear some resolution but sorry about the repair bill forthcoming.

I was already into it for around a thousand already with suspension and bigbore kit and misc. Thinking of coping out and having him finish the WR for me too. Work is starting to pick up right before vacation. 

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And she runs. $490 parts and labor. Tore it down to the piston, gone through the head. New seals and rejetted the carb to perfection. I pick it up on tuesday. More after I pick it up. 

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And she runs. $490 parts and labor. Tore it down to the piston, gone through the head. New seals and rejetted the carb to perfection. I pick it up on tuesday. More after I pick it up. 

Did he recut the seats and replace the valves or just replace the seals? I’m debating pulling mine back apart and sending the head off.

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