Stumped about 1100 backfiring

[waterfreak]

Unbelievable. I had never seen a twisted crank before. And as of tonight, I have two in a row.
A guy brought over a Polaris triple to have me replace a bendix. He just told me it needed to be replaced. His "other" mechanic had already taken off the flywheel cover. The old bendix had some teeth chewed up.
Okay, so I put a replacement bendix in it and it cranked fine.
Then I put some gas in it and tried starting it. It immediately backfired, reversed the engine and sheared the flywheel key.
So I called the guy up and told him about it. At that point he tells me that the engine suddenly stopped last time he had it out and would not restart. His buddy mechanic tried starting it several times before the bendix went out.
With this new information (I really wish people would tell me the whole story to begin with), I started thinking......it stopped, and when restarting was attempted, a bendix got chewed up.
I got it to crank fine as long as it wasn't actually firing. As soon as it fired, it kicked the engine hard enough to immediately break the woodruff key. :thinking:
So I indexed the crank. Wouldn't you know it, slightly out of phase.
I figure it slipped to where timing was over-advanced. When it fired, it kicked the engine into reverse.
The owner won't like that one.

those Polaris triples are notorious for twisting cranks , besides , the electronics in those things are a freaking nightmare!
On another note, I have never seen a Yamaha twist a crank before!

 

[WFO Speedracer]

When they bring me something and say tune it up , I tell them there is no tune up on a watercraft, replace the spark plugs yourself, if that doesn't fix it bring it to me and tell me what its doing and we will go from there.

 

[Matt_E]

Hah, I get that, too.
"I need a tune up".
"Um, ok. Is there something wrong with it?"

 

[Matt_E]

I pulled that crank out yesterday. The bearings and rods looked beautiful, not noisy at all. But something was very wrong with the web rotation.


Oh, and putting on a triple cylinder on the crank cases by yourself is teh suck.

 

[ryan]

try doing a kawe tripple.the yamahas are easy. lol

I pulled that crank out yesterday. The bearings and rods looked beautiful, not noisy at all. But something was very wrong with the web rotation.


Oh, and putting on a triple cylinder on the crank cases by yourself is teh suck.