90hp 2stroke seized

[tony351c]

How do you check crankshaft bleed lines

[walleye1]

It will be in the service manual.

[zenoahphobic]

I would suspect exhaust jacket....may have pin hole and letting water into cylinder. Usually one plug will have moisture/rust.

I'm probably thinking on the same track as you, but more guessing it's the lower crank seal.
My guess the water is rusting the bore and rings together gradually seizing the engine.
Sure way to test this, BUT NOT RECOMMEND, is to leave the engine for a long time if it is then impossible to turn over.
If you can't immediately get to fix this, and you have found water in the cylinders, at least squirt some oil through each spark plug hole (like winterising) after you have run it. Of course it is likely your bearings are gradually also corroding and you will also need to squirt oil down the carby throats cranking, but not starting the engine, many times to disperse this oil to all surfaces.

[tony351c]

It's been 4days since I last started her. Today she fired up no issues. I did spray corrosion stop into each cylinder and changed the plugs. These are the old plugs

[tony351c]

The engine was slightly tilted, but is this much oil in the carbs normal?

[zenoahphobic]

Yes those three plugs are different from each other. The left looks a bit sus, but I worry more about the middle one, it seems too dry and clean. Clean could mean water is getting in. Rod bolt has claimed he can read plugs very well.
Yes the oil in the bottom two is excessive. That looks like a single oil tank with no remote tank (I think all were). So the tank can't overflow. So too much oil is getting there by gravity, if your pump is incorrectly adjusted, it does not appear as excessive oiling by looking at the plugs (from here).
Unlikely, but you may have still have two issues with your oiling system, if there is no water getting into cylinder (s).
Which cylinders relate to which plug?

[holmen78]

I have just rebuilt my 2002 90TLRA and this is what I found faulty on it:

1. One of the 2 lower crank seals was totally busted.
2. None of the check valves to crank bearing bleed lines were working properly (they let pressure both ways).

Have you checked your reed valves? Small pieces missing makes oil come backwards into intake, I have seen it on bigger mercs. Bigger missing pieces makes the engine run rough like it’s backfiring through intake. Of course you can have a problem in the oil pump letting oil throug while not running, but Yamaha oiling system is known good quality and seldom fail so I would start with taking of carbs and check the reeds. You also have check valves on your oil lines, they make it hard for the oil to pour into the engine by just gravity. I had my oil lines taken of, laying on the flor for several months with check valves attached and the oil didn’t come out. Yesterday when I renew the check valves oil came out from all the oil hoses, both ways.

You can wipe the carbs dry and tilt it up and check for oil the next day. That way you know how the oil gets there.

This is just my experience and point of view.

[tony351c]

Those plugs are still new, maybe 10hrs or less. Left plug is top cyl, right plug bottom. More thorough troubleshooting today

[99yam40]

Those plugs are still new, maybe 10hrs or less. Left plug is top cyl, right plug bottom. More thorough troubleshooting today

well we can post up a bigger pic of the plugs and hope Rodbolt will drop in and give his expert opinion on what these 10 hour run plugs tell him.

[tony351c]

Restarted today no issues after a week of sitting. ?? Maybe the corrosion stop worked.