Other 1993 Yamaha WR500 Top End Inspection

SRAD97750

SRAD97750

Moderator
Staff member
Well, 60 hours on the clock since the overhaul.
https://www.dirtbikeaddicts.com/content/threads/1993-yamaha-wr500-teardown-overhaul.5621/
Time for an inspection! :prof:
Look at the filth onto her... I rinse the bike as often as I remember to... I guess not nearly enough...:picard:

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Missing Fwd Mount Bolt and Cylinder Nut. Look at the mess from the leaking base gasket...
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Missing Head Mount Bolt.
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Greasy...
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RTV from my clutch cover gasket blow out due to a plugged vent tube.
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Lost the tip of a fin at some point. Must be the exhaust clearance...
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Some damage to the stator cover... It's a dry bay, so a little JB Weld and black rattle can.
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-BIG DAN:thumb:
 
SRAD97750

SRAD97750

Moderator
Staff member
Overall, I think it look amazing for having over 260 hours since this Wiseco piston was installed on this stock bore. This 60Hr inspection was run 32:1 KalGard w/91 octane, Jetted for little/no smoke ever, ridden in hard trails and wide open desert. Has a 3 Hr GP Race on it as well.

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Some Build up, but not concerning.
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Even Richness, I need to dial it in a bit...
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Cylinder has some blowby stains but still perfect.
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This was a new pin 60 HRs ago... Mostly oil/fuel staining from my overly rich condition.
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Blow-by to the pin on both sides... These rings were new and in spec 60 Hrs ago. We'll see how far they've gone.
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I am wondering if the cylinder is going to spec this time... Lots of blow-by, hoping it was just the rings wearing.
-BIG DAN:thumb:
 
Mihylo33

Mihylo33

SRAD97750:
Overall, I think it look amazing for having over 260 hours since this Wiseco piston was installed on this stock bore. This 60Hr inspection was run 32:1 KalGard w/91 octane, Jetted for little/no smoke ever, ridden in hard trails and wide open desert. Has a 3 Hr GP Race on it as well.

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Some Build up, but not concerning.
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Even Richness, I need to dial it in a bit...
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Cylinder has some blowby stains but still perfect.
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This was a new pin 60 HRs ago... Mostly oil/fuel staining from my overly rich condition.
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Blow-by to the pin on both sides... These rings were new and in spec 60 Hrs ago. We'll see how far they've gone.
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I am wondering if the cylinder is going to spec this time... Lots of blow-by, hoping it was just the rings wearing.
-BIG DAN:thumb:
Click to expand...


Not horrible Danno....
I don't like how that piston skirt looks Danno. See the ripples in the color? That's an indication of wobble or slap ideally at the bottom of the stroke. I also an a little concerned with that wrist pin looks a little concerning. Can I get a pic of the wrist pin bearing inside and out?
 
SRAD97750

SRAD97750

Moderator
Staff member
2strokesteve89:
Is that cylinder sleeved? It looks like it but I thought they started plating those cylinders around that time.
Click to expand...
These carry-over yz490 motors have always been steel. I think the 250cc of 93 was definitely nikasil coated.
This one has hundreds of hours, still stock bore.
I have decided that to really hold this thing at 100% takes a superhuman effort, so they seems to last forever with my mediocre riding skills. :smirk:-BIG DAN
 
SRAD97750

SRAD97750

Moderator
Staff member
OK. Looks amazing...
Piston average 86.70-73mm
Cylinder average 86.78-82mm
Ring lands 0.046"
Piston Ring Thickness 0.045"
Ring End Gap 0.025"

SRAD97750:
End gap .016" top ring .018 bottom ring.
View attachment 16483
Click to expand...

Ring End Gap change over 60Hrs = 0.006-8" or 44% growth. (Personal Service Limit is 0.036"):thumb:
Piston/Cylinder Clearance = 0.08-0.085mm (Service limit 0.105mm):thumb:
Ring/Land Clearance =0.001":thumb:

I will sleep on it, but the A+P mechanic in me says I should run it to 100Hrs and check again.
New pin, Clips, and Bearing of course. The pin has a blue line... me no likey...

Fit, Form, Function. -BIG DAN:thumb:

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Faint Blue Line on the left. The right end is not brown, just a weird photo.
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Mihylo33

Mihylo33

Unfortunately I can not find my notes and other wrist pins. The bearing looks great and unstressed. The wrist pin really concerns me and is causing me to loose sleep. It isn't sitting right in front of me but for $100+ I would freshen up that topend and wrist pin. It's cheap insurance and you can do another inspection in 60hrs. If the wrist pin looks the same in 60 hrs have a look at the rod for twisting. I think the older 490's had that issue back in the day. Your jetting appears to be right on for what you are doing maybe even slightly lean. That carbon is normal for that oil and makes me happy. No lean marks on the bottom of the dome.
:cheers:
 
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