250 1989 Yamaha YZ 250 For Dad

[SRAD97750]

Plenty of detonation happened in that cylinder Big Dan... Cut that bugger and find the cause... #1 cause according to my nikasil guy.... Piss poor gas the other being improper jetting.

I have no idea the conditions that this bike was placed under prior to my coming into possession.
The damage you see is quite old.

Luckily, for the YZ, it's in MY possession now.
The gas is fresh, new engine gaskets, new crank seals, replacement carburetor... I'm sure there is no detonation occurring now. -BIG DAN

 

[Mojavekid18]

Just ask BK about my packing job........................ No seriously though

 

[SRAD97750]

Cleaning. Measuring. Detective work.





Reeds look good.





Intake boot is surprisingly flexible and crack free.



Powervalve assembly out for fresh orings.



Measuring piston ring end gap. Still in spec. Need to check again after winter.







OK. So. DETONATION. This badboy has seen some hard times. Seriously hard times. At one point the engine chewed itself to bits. Evidence below.



In this photo you can see where the cylinder was just rat chewed away, and a fresh steel liner was installed.



Looks like the problem has been repaired properly and a new piston installed. (Which has totally different damage)

Tomorrow I assemble with some fresh oil, new carburetor, gaskets, and some fresh 91 octane.
-BIG DAN

 

[Mihylo33]

The cylinder looks they resleeved it. The head looks like it really needs to be cut though but it's hard to tell from the IPhone. Would I run it as is? You can bet your sweet sweet ass I would.

 

[cleonard]

Perhaps keep an eye on ebay for a cheap replacement head. That erosion will let combustion gases to where they are not supposed to go.

like this http://www.ebay.com/itm/02130-Yamah...Parts_Accessories&hash=item27cbbf40ef&vxp=mtr

 

[bobkyle2]

Do you got a steady hand

 

[SRAD97750]

Assembly. Using a good amount of clean 2T oil on everything.




















New seals and orings installed.








Got a new thrust plate









I've had a long week at work and I'm going to bed... Tomorrow, we'll clean the carburetor, finish assembly, and go for a test ride.
-BIG DAN

 

[SRAD97750]

BKs carburetor has green sludge in the bottom... Took a bit of brushing, scrubbing, and soaking. The current throttle cable fits perfect.
The slide is not as bad as you made it out to be, BK.






Assembled and ready to go!



Secured the thottle cable in place so there is no chance of breaking the clip and getting runaway throttle.


Cable secured here as well.



New exhaust O-ring, but there was nothing wrong with the old one.








Completed and ready to give her a test ride. -BIG DAN

 

[Mihylo33]

I wonder what's under the sheet behind the yz?

 

[SRAD97750]

http://www.youtube.com/watch?v=9vSmcyBCeDc&feature=youtu.be

-BIG DAN

 

[SRAD97750]

$770 including
Bike purchase
Registration
Top end gasket kit
Kill switch
Air cage
Crank seals
Front master cylinder rebuild kit
Air filter
Mud guard
PV thrust washer
Barkbusters/brushguards
Grips

Oh and about 15-20 hours of me tinkering with it.... Pretty good deal!
-BIG DAN

 

[jeremymach2015]

hell yeh dan get r done

 

[bobkyle2]

94ish carbbbbb

 

[carlosmotard]

I love you man, buy a yamaha yz 250cc 1989 damaged and could not find how or where parts were, thanks for all these pictures serve as a tremendous help .... I am from Venezuela

 

[SRAD97750]

Took my brother and dad for a ride, apparently to "Camp Stroke..."



The 1981 IT175 looking perfectly at home in the vast desert... Repaired and jetted out the ping. My brother was much happier riding the old beast.



The 1989 YZ250WR



Stopped at the end of some smooth singletrack. His first legitimate singletrack ever.







Did 24 miles around the fairview valley. Mostly quad track and sand.
At the end of the ride, pops mentioned he felt like he was much more comfortable with the sand after just a few short miles. We'll keep him riding as often as possible.
-BIG DAN