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04 Yamaha WR250 - No compression

MBRider

New member
Joined
Jun 30, 2022
Location
Santa Cruz
Moto(s)
Dual Sport - WR250
Adventure - V-Strom 650
Name
Kevin
Well it sure didn't sound good....shifted into third on the road coming back from a trail ride....heard a very distinct metallic 'snap', the engine lost all power and heard metallic sounds before I pulled in the clutch and coasted to a stop. When I kick it, I find no compression in the cycle...nothing, but it does kick and I don't have any metallic sounds when I kick it.

It sure seems like I've broken a timing chain, cam, ring, etc based on that sound and no compression.

It feels like it has become a 'parts' bike - is it worth it to drain the oil and look for metal or pull the tank and scope the cylinder? If I'm not gonna repair it, likely better for who buys it to examine the oil etc.

With no compression I just don't see any repair of the top end coming in under $1K. I just serviced most of the bike, new tires, etc. Go figure.

I'd love any input or advice on what to do next....I'm bummed
 
I think just starting by checking (if possible as long as no hole in piston or connecting rod hasn’t failed) and visually seeing the piston move up and down would be a good start. Then open up the cover to see valve movement and timing chain. Hopefully it will be a relativlely cheap/easy repair.
 
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No harm in draining the oil, just take pics and/or save the oil if you'd like to pass the info to a new owner should you sell it. I'd start by washing it really well and then pull the valve cover, that'll tell you if the cam chain is still there. And again, take pics if it's info you want to include in a listing. You could also pull the stator/cover and see if the cam chain is all bunched up down there. If you pull the valve cover and the chain is gone, you'd probably want to pull the stator/cover anyway to see if the case survived.
 
I think just starting by checking (if possible as long as no hole in piston or connecting rod hasn’t failed) and visually seeing the piston move up and down would be a good start. Then open up the cover to see valve movement and timing chain. Hopefully it will be a relativlely cheap/easy repair.


THIS ...great advice

Mad
 
Thanks Guys! Really appreciate the ideas...I've got a little bit of hope. I'll start pulling stuff apart and see what I can find. Fingers crossed !
 
Well, I scoped the engine and discovered a snapped off valve head. Looks like this engine is pretty much destroyed. It's interesting as I just had the valves adjusted within the last year. Oh well, I'm thinking this is now a parts bike.
 
Completely fixable but it depends on how much you want to spend And it's not too hard of a job

Mad
 
I've picked up a WR450 in the meantime and thinking I may just sell this as a parts bike or maybe someone wants a project bike. I had just put new tires/brakes, fluids, plastics and new forks seals on it too!

What do you think the shop cost would be to rebuild the upper? I'm concerned the lower is damaged as well from all the pieces of the valve head falling down into the lower.
 
You’ll need to know more about how that valve broke off. Pretty rare for them to just do that. Any sign of impact on the piston crown? If so, this may have started as a timing chain failure.
 
You’ll need to know more about how that valve broke off. Pretty rare for them to just do that. Any sign of impact on the piston crown? If so, this may have started as a timing chain failure.
Yes, I was able to see damage on the piston crown...spark plug was clearly damaged as well from the impact. Yes, most likely a timing chain failure kicked off the damage.
 
I've picked up a WR450 in the meantime and thinking I may just sell this as a parts bike or maybe someone wants a project bike. I had just put new tires/brakes, fluids, plastics and new forks seals on it too!

What do you think the shop cost would be to rebuild the upper? I'm concerned the lower is damaged as well from all the pieces of the valve head falling down into the lower.
Unless the piston came apart, the pieces should have stayed in the top end or went out of the exhaust. I'd at least pull the head and take a look

Mad
 
Dropping a valve usually results in the cylinder head looking like it took a shotgun blast. Usually requiring welding, re-machining, valve guide and seat replacement. There are some places that will do this if you google for motorcycle cylinder head repair.
https://millennium-technologies.com/ is one. Another option is a used head and cylinder. Try Ebay.
 
Dropping a valve usually results in the cylinder head looking like it took a shotgun blast. Usually requiring welding, re-machining, valve guide and seat replacement. There are some places that will do this if you google for motorcycle cylinder head repair.
https://millennium-technologies.com/ is one. Another option is a used head and cylinder. Try Ebay.
Yup, that's exactly what the head looked like...uggggly :) Thanks!
 
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