Low compression on 90k motor

[user 213]

2 motors on Ebay right now, one a stripper, one loaded.
Better of the two

Thanks Rad. I already have a motor. The link to the '03 motor is a decent BIN price, depending on the mileage. No Throttle bodies or U-joint, but if someone is just doing what I am, swapping a worn motor out, it could be a good deal for them.

Just about have the motor swap done. Should be firing it up this week and getting back to Dark Side testing.

 

[user 213]

My concern if the ring seal is the culprit, which your wet compression test says is the case, would be that the ceramic composite cylinder coating would be compromised. Can't just re-bore like an old cast iron cylinder. This has certainly been bad for you OCfjr, but the good news is we don't hear about this all the time. The theory about leakage of unfiltered air makes a lot of sense.

Also worth noting is that I discovered the hose at the bottom of the airbox also off it's nipple.

I do wonder how bad the bores really are. I agree that you can't re-bore the ceramic composite bores, but you might not have to. It might be all ring and piston wear with the rings toast and the ring grooves wallowed out. I've seen some pretty decent bores on high mile motors, but with crap rings and pistons with double width ring grooves. A rebuild might be new rings, pistons and bearings with a little clean up and tweaking here and there.

 

[radman]

Still would be interesting to see what actually transpired. Could be that the valves and seats just got crusty enough to lose compression there, rather than a ring seal problem.

 

[Fred W]

Still would be interesting to see what actually transpired. Could be that the valves and seats just got crusty enough to lose compression there, rather than a ring seal problem.

Agree with it being interesting, but I thought that was the whole point of doing a wet and dry compression test. If the pressure goes up significantly when wet then it is the rings/bore. If it stays the same it is the valves. In this case it went up significantly.

 

[radman]

Still would be interesting to see what actually transpired. Could be that the valves and seats just got crusty enough to lose compression there, rather than a ring seal problem.

Agree with it being interesting, but I thought that was the whole point of doing a wet and dry compression test. If the pressure goes up significantly when wet then it is the rings/bore. If it stays the same it is the valves. In this case it went up significantly.

Missed that part. Agreed.

 

[ionbeam]

FWIW, when we tore my engine down last winter we found stuck rings in 3 cylinders. I've always run brand name gas and used oil that Yamaha would approve of. I have occasionally added Techron in the recommended doses. I don't believe that I've ever run my engine outside the range of 'normal use' (unlike a few that have revved the snot out of their engines while on the center stand, repeatedly whacking the throttle and reporting 'unnatural banging noises' coming from the engine :dribble: )

 

[Geezer]

FWIW, when we tore my engine down last winter we found stuck rings in 3 cylinders. I've always run brand name gas and used oil that Yamaha would approve of. I have occasionally added Techron in the recommended doses. I don't believe that I've ever run my engine outside the range of 'normal use' (unlike a few that have revved the snot out of their engines while on the center stand, repeatedly whacking the throttle and reporting 'unnatural banging noises' coming from the engine :dribble: )

There was a post by Jestal a while ago where he recommended that we wind the engine up under load in second gear and abruptly back off the throttle every once in a while. That would cause the rings to actually spin in their grooves and keep the grooves clean.

I haven't actually done it specifically for that reason, but that kind of riding is part of my normal squidly technique.

 

[charismaticmegafauna]

It's been my experience (after many decades hanging around the m/c scene) that fewer engine problems actually attend younger, more agressive, riders compared with the complicities that arise in motorcycles owned by older, more careful, riders. Seems counter-intuitive...? :blink:

Many motorcycles are designed to be ridden with verve and elan (hard) and can sometimes be "Killed with Kindness".

Often, IMO, riders need 'less motorcycle' so that they're able to ride the bike within its performance envelope more of the time.

Just sayin'.... (I'm sure none of this applies to anyone here)

 

[ionbeam]

Many motorcycles are designed to be ridden with Verve and Elan

Verve and Elan are my normal riding partners while Misfacio and Ruina are never permitted on any ride. If you own a hot blooded horse ya got to let it run.

 

[RadioHowie]

.....I've always run brand name gas and used oil.....

AHA!!! NOW we know the truth! It WASN'T the camchain tensioner...it was the USED OIL that fragged your Feej!!

Glad to see you finally fess up!

 

[ionbeam]

.....I've always run brand name gas and used oil.....

AHA!!! NOW we know the truth! It WASN'T the camchain tensioner...it was the USED OIL that fragged your Feej!!

Glad to see you finally fess up!

"...used oil that Yamaha would approve of." See, my used oil is still ok. Not using oil would probably void the warranty

 

[RadioHowie]

.....I've always run brand name gas and used oil.....

AHA!!! NOW we know the truth! It WASN'T the camchain tensioner...it was the USED OIL that fragged your Feej!!

Glad to see you finally fess up!

"...used oil that Yamaha would approve of." See, my used oil is still ok. Not using oil would probably void the warranty

Oh, trying to put things in context, I see....we're not buyin' it!

 

[user 213]

You gents are BAD. :dribble:

I agree it would be interesting to tear the motor down and see what is to be found. That may occur, by me or someone else on the list. FIRST however, I need to get the new motor up and running. Life is getting in the way at the moment, but hopefully it will happen shortly. Naturally, rain by the bucket full is forecast this weekend. <_<

 

[RadioHowie]

You gents are BAD. :dribble:
I agree it would be interesting to tear the motor down and see what is to be found. That may occur, by me or someone else on the list. FIRST however, I need to get the new motor up and running. Life is getting in the way at the moment, but hopefully it will happen shortly. Naturally, rain by the bucket full is forecast this weekend. <_<

"Real Life" DOES suck, doesn't it?!

 

[rogdeb]

Also worth noting is that I discovered the hose at the bottom of the airbox also off it's nipple.

And that little bugger is a ******* to re-install -- or is that the other way round?

Had to buy me a new long-long nose plier for it.

 

[user 213]

Update - I got the engine install finished about midnight on the 28th, went for a short test ride, came back and drained the oil, changed the filter and packed the bike for my trip to NV on the 29th.

Six days and 2300 miles later, I arrived home safe with zero problems or issues related to the bike. (that buffet at the Nugget did me in, but that's a different story.)

I went ahead and drained the oil as soon as I hit the garage and pulled the filter. The oil was nice and clean with nothing in the filter that I could determine. Looking good. Rotella Synth going in for a normal 5k cycle next.

If anyone else is considering an engine swap, you can do it yourself if you have a manual. It can take some time to do, but the real time issue is making sure you get the wires and hoses routed correctly. Take lots of notes on where the main harness goes under or over things like motor mounts and ditto for hoses/wires in the radiator area. The rest is actually pretty strait forward. The battery area is a real PITA too.

 

[chrisflock]

I too am quite interested in what is to be found with the motor tear-down. I've participated in a few auto-motor postmortems, I would wonder if there is significant wear on the cylinder walls of this ceramic-coat engine. Engineers might tell us that, because of the hardness of the ceramic, that the pistons and rings should show most of the wear.

Of course, they say the same thing about gasoline engines. And maybe they have a point, as readings on auto engines generally reveal that the cylinder has been 'stretched' out of round instead of a significant amount of material being removed, and in many cases the inside diameter taken parallel to the crankshaft is in spec, sometimes even SMALLER than spec.

I've even seen one engine with significant miles on a rebuild (+100k) that still had some evidence of honing grooves on the cylinder walls, but the cylinders were out of round to the tune of about triple the spec...

 

[03HiYoSilver]

OC,

Congratulations on your Success! Thanks for sharing your story.