Bad news on the GT14

86turbodsl · Aug 30, 2004

Found out tonight that the front of the crankshaft is bent. I took the engine pulley off, and found that there's about 30 thousands runout or so. Enough to make the crank snout visibly move while cranking. Now, I've had lots of engines apart, but never a Yanmar diesel. Sooo...

1. Is this normal behavior?
2. If I leave it be, what will it damage?
3. If I have to fix it, does anyone have a used crank or know where
I can get one fairly inexpensively?
4. The engine is a 2T75U I think, is there commonality among 2 cyl
Yanmars?

This thing is starting to cost some real money, with all the bearings and parts I'm having to replace. I'd like to low-buck it, but not at the expense of reliability. Once I get it done, I don't want to mess with it for a while.

Opinions, anyone?

mark777 · Aug 30, 2004

86turbodsl,
IMHO It takes a big impact to bend a crankshaft (Yanmar) but not impossible. 30 thosuands is too much runout and running that excentric will ruin the engine and internals in a very short time. Wish I knew more, Good Luck, Mark

86turbodsl · Aug 30, 2004

Well, I just bought the thing, so I guess it could have had a big impact before I bought it. I didn't notice the problem before purchase.

So it sounds like I need to replace the crank. Or straighten it.
Hopefully someone will contact me with a used crank.

RodgerF · Aug 31, 2004

Check with some local machine shops, they may be able to straighten the crank. How bad do the bearings look? It's possible to crack the block in the main webbing area so be careful.

I'm not familiar with Yanmar engines but the principles are the same.

Rodger

86turbodsl · Aug 31, 2004

I dont' have the crank out of the engine yet. Based on what I've heard here, it's not normal, so I'll most likely be pulling the engine out this weekend. The engine runs so good I believe only the crank snout is bent, but the only way to be sure is pull it apart.

What makes sense here, bearings, rings, and gaskets, straighten crank?

normde2001 · Aug 31, 2004

I believe I would get more opinions on the problem. Depending on how you are measuring the runout, .030" could be only .015" off center, which ain't all that much for a low rpm engine. I was on a commercial turboprop airplane once that the prop hub appeared to have more runout than that. How did you first notice you had a problem? For all you know, it could have been running that way for years.

86turbodsl · Aug 31, 2004

It's the end of the threaded snout where the crank pulley mounts. Another engineer pointed out to me privately that the bearings would likely already be toast if the crank were bent internally, and suggested straightening the end, or living with it. The PTO has double u joints so I'm not worried about that. The trouble is, it's a tapered end, so I'll have to lathe a tool to attach to the end of the crank to use as a lever.

normde2001 · Aug 31, 2004

If it were mine, I wouldn't worry a minute about it unless it is causing an obvious problem. A possible (unneeded) repair could cost you more than you have in the tractor.

Jimbrown · Aug 31, 2004

I hate to say this but don't fix something that ain't broke. If it is not leaking oil and the belts stay on the pulleys it has probably been that way since new.

86turbodsl · Aug 31, 2004

They would send one out the door with that???
It's not tossing belts. In fact, it looks like it's the original
belt, pretty cracked. No oil leaks. I can't tell if it's got a
bent crank internally, I don't know how much vibration a
2 cylinder is supposed to have. It vibrates pretty bad when
idling, and the vibration goes pretty much away at higher revs.
I know a 2 cylinder is inherently unbalanced, but having never
experienced one, I don't know what to expect. Anyone else with a
2 cyl want to comment on vibration?