Yamaha WR250R Mega Thread

[10Cup]

Originally Posted by skierd

Decided that before I really truly decide to keep her or not, I better see how the old girl's motor's doing. To that end, its time to do a compression check to see how well the last 43,000 miles have treated her.

Step 1 - start the motor and let everything warm up

step 2 - take the seat, side panels, front wing panels, and gas tank off

step 3 - remove spark plug

step 4 - realize that the compression tester you bought doesn't have a 10mm thread adapter, you know the one you need to do the test

step 5 - Run to every hardware store, auto parts store, and motorcycle dealership in town looking for an adapter, in vain

step 6 - Admit defeat, buy the gauge kit that's 2x as expensive as the one you first bought a few days ago, and return home

step 7 - put the old plug back in, coil back on, and gas tank back on. Start motor again to warm it up again.

step 8 - Pull it all apart again.

step 9 - Thread in the compression tester... and... and...




She's not quite dead, but she's hurting very badly. Best dry compression it could muster is 75psi. Added some oil down the bore, and it spiked to just over 100psi. Spec is 121psi, low of 105, high of 135.




Its not entirely unexpected, as before I put her up for winter she felt a little down on power and had been dirtying the oil faster than normal. I was hoping it was just clutch wear causing the oil to go bad, and that the power thing was just my imagination, but the reality is the motor's old and tired. Glad I found it out not, before I spent a bunch of money on the suspension, but still..

Not sure what to do at this point. Right now, I'm just sad.

If you decide to have the cylinder brought back up to spec. I have used Millennium technologies in the past they are very good and not too expensive. Send them your piston/cylinder and what you want for clearance and it will come back spot on like brand new.

[cablebandit]

Athena

[Buzzbomber]

Originally Posted by skierd

Because I'm not sure what to do with it at this point?

I don't know if I can just throw a new piston and rings in it, or if I have to have the cylinder cleaned up too, then have the valve seats (at least) cleaned up, and roll on, or if its going to require a lot more than that. This would be my first top end replacement on any motor I've ever done.

*edit* spent most of the night not relaxing, and researching. Seems you can get by just cleaning up the cylinder since its Nikasil to deglaze it, and go from there. New piston, rings, pins, gaskets, etc ordered, along with a bunch of other stuff. Looks like this minor winter refresh is going major...

I mis-read the original post somehow......serves me right for being up still at 1 am.

[KansasBob]

Originally Posted by skierd

Decided that before I really truly decide to keep her or not, I better see how the old girl's motor's doing. To that end, its time to do a compression check to see how well the last 43,000 miles have treated her.

Step 1 - start the motor and let everything warm up

step 2 - take the seat, side panels, front wing panels, and gas tank off

step 3 - remove spark plug

step 4 - realize that the compression tester you bought doesn't have a 10mm thread adapter, you know the one you need to do the test

step 5 - Run to every hardware store, auto parts store, and motorcycle dealership in town looking for an adapter, in vain

step 6 - Admit defeat, buy the gauge kit that's 2x as expensive as the one you first bought a few days ago, and return home

step 7 - put the old plug back in, coil back on, and gas tank back on. Start motor again to warm it up again.

step 8 - Pull it all apart again.

step 9 - Thread in the compression tester... and... and...




She's not quite dead, but she's hurting very badly. Best dry compression it could muster is 75psi. Added some oil down the bore, and it spiked to just over 100psi. Spec is 121psi, low of 105, high of 135.




Its not entirely unexpected, as before I put her up for winter she felt a little down on power and had been dirtying the oil faster than normal. I was hoping it was just clutch wear causing the oil to go bad, and that the power thing was just my imagination, but the reality is the motor's old and tired. Glad I found it out not, before I spent a bunch of money on the suspension, but still..

Not sure what to do at this point. Right now, I'm just sad.

I did some quick math.......... 40K miles at an average overall speed of 40 mph, with and average rpm of 8k........... works out to around a half a BILLION cycles of the piston. Amazing really. If you count each pass up and down the rings have followed the length of the bore a full Billion times.


Looking at it another way............. The stroke x 2 = .35170604 feet, so it only takes about 15012.5 revolutions of the crank for the piston to travel a mile in the bore......... so in 40,000 miles, on the bike, the piston travels approximately 33,300 miles down the bore.
.

[rickypanecatyl]

Originally Posted by skierd

Because I'm not sure what to do with it at this point?

.

Couldn't you just do a 290 big bore? I have no clue but that might be cheaper than stock?

Kansas Bob - That was really... interesting!

[Reposado1800]

Originally Posted by skierd

Decided that before I really truly decide to keep her or not, I better see how the old girl's motor's doing. To that end, its time to do a compression check to see how well the last 43,000 miles have treated her.

Step 1 - start the motor and let everything warm up

step 2 - take the seat, side panels, front wing panels, and gas tank off

step 3 - remove spark plug

step 4 - realize that the compression tester you bought doesn't have a 10mm thread adapter, you know the one you need to do the test

step 5 - Run to every hardware store, auto parts store, and motorcycle dealership in town looking for an adapter, in vain

step 6 - Admit defeat, buy the gauge kit that's 2x as expensive as the one you first bought a few days ago, and return home

step 7 - put the old plug back in, coil back on, and gas tank back on. Start motor again to warm it up again.

step 8 - Pull it all apart again.

step 9 - Thread in the compression tester... and... and...




She's not quite dead, but she's hurting very badly. Best dry compression it could muster is 75psi. Added some oil down the bore, and it spiked to just over 100psi. Spec is 121psi, low of 105, high of 135.

[click to show pic]




Its not entirely unexpected, as before I put her up for winter she felt a little down on power and had been dirtying the oil faster than normal. I was hoping it was just clutch wear causing the oil to go bad, and that the power thing was just my imagination, but the reality is the motor's old and tired. Glad I found it out not, before I spent a bunch of money on the suspension, but still..

Not sure what to do at this point. Right now, I'm just sad. [click to show pic]

Just re-ring it and solvent test the valves to make sure they are sealing.

[ba_]

Originally Posted by TwilightZone

>"I'm sensing that "

Heh... I put mine together the wrong way too... the first time.

Now I'm confused

Here is what it looks like if the short spacers go in the front:



Which makes the rack look like this - the front of the rack hits the fender



Here is what it looks like if the short spacers go in the back (my first attempt) - nice and balanced looking



Which makes the rack look like this:



The latter is correct, right?

[skierd]

Originally Posted by rickypanecatyl

Couldn't you just do a 290 big bore? I have no clue but that might be cheaper than stock?

Kansas Bob - That was really... interesting!

A new piston, ring set, wrist pin and circlips, base gasket, head gasket, valve cover gasket, and new bolts for the head and cam cover ran about $160. Best price I've seen on the Athena is $750. Even if I end up needing a new cylinder (crossing my fingers that I won't) its another $350 or so for the factory piece. More than likely I'd try to return or resell the piston set and send my cylinder to Thumper Racing, and send them the head too to clean it up as well.

I ordered:
New piston, rings, gaskets, pin, clips, and bolts, plus a timing chain just in case (it was only $18)
New clutch and throttle cables
New thermostat (motor's coming apart, why not)
New factory tool kit (I love the crappy little thing, it actually works well trailside in my experience with a few small supplements)
A couple drain plugs and gaskets
A couple oil filters
R kickstand and spring for the eventual set of dirt wheels
Oil seal and o-ring for front sprocket (pretty sure mine's leaking)
some misc blind (GYTR timing plug covers and 1-1/8" handlebar mounts)
and a whole host of misc bolts and hardware that I know are either corroded, somewhat rounded, or been used a lot and should be replaced.


But first I have to get the $(&#ing swingarm off. Here's a hint kids... TAKE THE DAMN SWINGARM OFF AT LEAST EVERY 6 MONTHS! I let mine ride for close to a year and a half, and its frozen solid. I fortunately found a used swingarm on ebay complete with a new pivot bolt and bearings for less than the price of a new bearing set from Yamaha, so if worst comes to fun I'll end up cutting the bastard out.

[KansasBob]

Originally Posted by skierd

plus a timing chain just in case (it was only $18)

Best 18 bucks you ever spent.

[TwilightZone]

Are the bolts the same length?



The latter is correct, right?

[ba_]

Originally Posted by TwilightZone

Are the bolts the same length?

They are. All 70mm

[Llamaha]

Originally Posted by skierd

But first I have to get the $(&#ing swingarm off. Here's a hint kids... TAKE THE DAMN SWINGARM OFF AT LEAST EVERY 6 MONTHS! I let mine ride for close to a year and a half, and its frozen solid. I fortunately found a used swingarm on ebay complete with a new pivot bolt and bearings for less than the price of a new bearing set from Yamaha, so if worst comes to fun I'll end up cutting the bastard out.

I would first try using a pneumatic drill before cutting out the swingarm. I know we used to use them to remove truck wheels from semi trailers and I don't think any swingarm nut in the world would be stuck harder than some of those are. Any local tire fitter should have one.

[KansasBob]

Only $15 at Harborfreight! Pneumatic Hammer.



http://www.harborfreight.com/catalog...t?q=air+hammer

I used one just the other day to drive the swing arm bolt out of a 35 year old Bultaco that had been out in the weather. I used heat from a propane torch too. Once I got it to budge I started working it back and forth.

[TwilightZone]

>"They are. All 70mm "

Hmmm... I'll need to go out and take a look at mine.

[ba_]

Originally Posted by TwilightZone

>"They are. All 70mm "

Hmmm... I'll need to go out and take a look at mine.

That would be awesome, thanks