#yamaproblems : a rebuild thread

[Gravy]

I seem to have a problem, a Yamaha problem.
I keep buying them.
I picked up a 2001 WR250F to rebuild for a 2nd bike.
I seem to always have someone visiting that wants to ride and this seemed like a good choice so we'll see if it hangs around for a bit or if I just sink a bunch of money into a bike for someone else to enjoy



Motor is out for inspection.

 

[Rot Box]

Nice. Were the 250's e-start back in 01? I loved my 02 WR426. Great bikes.

 

[Gravy]

Nice. Were the 250's e-start back in 01? I loved my 02 WR426. Great bikes.

Thanks, e-start began in 03, I've also got an 06 YZ auto decompression exhaust cam on it's way to get rid of the decompression lever. I believe it also improves the exhaust cam lift, and duration ever so slightly and begins opening the valve earlier perhaps.

Pictures to come.

 

[Gravy]

So the PO of this bike thought the bottom end was going out and it wouldn't start.
He paid Lindsay Machine check it out. They tore the whole top end down to individual pieces and they assured him it would need a new crank and piston and quoted him a repair to the tune of $1995 +tax.



WELL.
I pulled the engine apart and found this:
[video=youtube;qm3MJhAGo38]https://www.youtube.com/watch?v=qm3MJhAGo38[/video]

Bad rivets on the flywheel. Apparently a common problem on early WR's.
This took out the stator and caused the no start issue.



I had the crank mic'd and it is perfectly within spec.
I checked the head and piston: no issues what-so-ever. But I have new rings and a new timing chain going in just to freshen it up. It actually has a newer OEM piston by the part number.

 

[Gravy]

The left side radiator was pretty beat from a crash or two so I pulled it to straighten it out


While I'm pretty good at straightening up radiators....


I can't fix leaks or torn tanks... and apparently it had a torn tube bad enough that my local shop couldn't fix, so I've got a new one on order too!

 

[Gravy]

Parts are rolling in.
Auto-decompression exhaust cam specd for a 06 yz250f
Not only will this make the bike easier to start, and breath a little easier, it will make it much harder to stall.



Yamaha OEM rings




Maxima air filter.

 

[Greg]

I'm a sucker for a project bike! Thanks for sharing, should be a fun 2nd bike.

 

[benjy]

Hey, I like this thread!!! Speaking of, the girls have been asking when Leo is going to come visit again You might as well bring the spare bike when you come down

 

[glockman]

Looks good. I'm a little surprised Lindsay didn't catch that. They have always been really good to me.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[Rot Box]

Just curious.. Any idea on the weight difference between the WR250F and WR400-450's these years? Noticeably lighter or not much?

 

[Gravy]

I'd imagine it's similar. I had a 99 yzf400 at the same time the po had this bike and it "felt" lighter than my bike, but truthfully on the wr400 the stator and flywheel are the same as the 250, so I'd imagine lots of the bottom end is the same. Likely the "light feeling" was from less gyroscopic forces from the smaller stroke & bore. So draw your conclusions from there.

 

[Greg]

Just curious.. Any idea on the weight difference between the WR250F and WR400-450's these years? Noticeably lighter or not much?

I owned a WR250f for a short time and of course my WR450f, the WR250 is significantly smaller, easier to whip around, etc. The 450 feels quite a bit heavier than the 250, I'm not sure how much but just spitballing I'd say it FELT like around 30#s. The 250 was also a lot more buzzy, and rightfully so.

I did a few basic mods on my WR250, YZF exhaust, the grey wire mod (YZ ignition timing) and some carb work and that thing SCREAMED on the top end! It was a mini-monster at high RPM, pulled like a 250 2 stroke!

 

[Gravy]

Lindsay quote: $1995 + tax= $2131.66!!!


MOoore parts


I've already assembled the valves, but I'll tear it down and replace the stem seals because (as I was pleasantly surprised) this t0p end gasket kit came with new ones
I'm planning to make a video late next week to show you how I do valve stem seals fast without any special tools. Watch for it.

 

[rholbrook]

I have a radiator you are welcome to if it fits. I believe it's the right side with the cap. I would have to check for sure but it came off of my old WR450 It was an 06

 

[Gravy]

MOOooore parts. I think that's all I need for a bit. I hope.

 

[Gravy]

I assembled the valve train with the head on the bench to check clearances. Looks like the new YZ auto decompression cam fits perfect for me. All the valve shims took between 1.76mm and 1.84mm which means they've likely only been adjusted once on the exhaust and never on the intake.
I likely will not need to re shim at all.


The manual shows the valve clearance to be:
Intake --- 0.10 ~ 0.15 mm
Exhaust --- 0.17 ~ 0.22 mm

And I'm at:
Intake --- 0.127mm - 0.152mm
Exhaust --- 0.152-0.176

Well I went from 1.80mm on the exhaust to 1.75mm

So now the exhaust is at 0.202mm- 0.226mm. Perfect.

 

[Gravy]

Motor went together.


And then I tore it completely back down trying to figure out where these went...


Well. They don't go inside the motor at all. haha. This is for the gear position sensor


The other two go to exterior oil lines hahaha. Well I wasted about an hour, but that's what happens when you reassemble a couple weeks later.

Bam no more decompression lever


before


After: no more backfire screen

 

[Gravy]

WR timing has 13 pins between the 12 o'clock timing marks. With the YZ cam it's 12 pins between them.







Timing




Motor is in the bike and the new radiators is on and all the fluids are full.
New fuel line too.





New Grips




New air filter in. Airbox lid off.

 

[Gravy]

It lives!
[video=youtube;RAcvN1X5LxQ]

I need a little carb tuning to take advantage of the performance upgrades, but I rode it around the neighborhood for a bit.
Having rode this bike prior to the mods; it has much more power and starts very easily now.

I need to research "the grey wire mod." Greg any advise?

 

[Tonkaman]

I live it when she fires right up like that! Good job