Take a Look At My Crank

[ConnerVT]

I never would have thought I'd ever start a thread with that title.

Spent this afternoon splitting the engine case of my '71 T500. I knew going in that while the rest of the bike enjoyed its 15 year sleep very peacefully, that the engine may be a different story.

My first indication was the oil that dripped from the tail end of the exhaust when the bike was delivered. Obvious that a lot of top oil was pumped into the spark plug holes, to try and free the motor so it would turn. Fighting the cylinders off, as well as the piston wrist pins, was a chore, and more top oil was freed to the garage floor. As you can see from the picture from my bench, it wasn't pretty.

TOP_002.jpg

I now have the crankshaft out of the case, and was hoping for some input. The left bearing is very stiff, compared to the center and right. The left side is definitely filthy, compared to the other side. Both rods seem not to have play up/down, but the left does have a bit of side/side play.

the plan is to send this one off to Bill Bune for rebuild. But is this a viable candidate to be rebuilt? This is my first time this deep into a motorcycle engine, so I don't have any experiences to compare from. I was hoping some of you folks who have seen much more than me would give some input.

Thanks in advance for the help!

CRANK_003.jpg

CRANK_004.jpg

[ConnerVT]

Of the case:

CRANK_001.jpg

CRANK_002.jpg

[tz375]

Several things come to mind. Too much oil is never enough to prevent rust - unfortunately.

The left side of teh crank is rusty on the webs which isn't good, but can be cleaned off with a wire brush. The left big end appears to be rusty or at least dirty. The rollers look encrusted with something.

usually when a crank looks like that on the outside, the big end pin and big end of the rod also tend to be rusty as well. If a bearing is tight, in this case it's probably rusty. Flush the whole thing through with wd40 or kerosene and see how it sounds. If it sounds and feels as smooth as baby's bum, you might have gotten lucky but don't bet the farm on that outcome.

The good news is that the crank can be split and cleaned and rebuilt. The bad news is that a couple of the bearings are not available from your local dealer but there are aftermarket suppliers. PEDRO in the UK and others have replacements and can do the work. Bill Bune in MN is great for crank splitting and rebuilding.

Eric (Zookie) is a T/Gt500 expert and is in the US. He'll know what's available here and where to get it from.

There's also a lot of debris in that left lower crankcase. It may be from a prior blow up, not cleaned out or may be rust related. It's the side that gets dry and tends to fail. RD Yamahas have problems on that side too. Common to see a standard size original right piston and a left that 4 or 6 oversizes larger on those bikes.

Nothing that's not repairable though.