F9.9 won't run

[Ghenster]

i've got a 2012 FT9.9 LEPL.

In the morning it started as easily as it always has done, ran smoothly with no issues.

In the afternoon, literally the same day, it wouldn't run. Doesn't catch at all.

Motor cranks fine, pulled one of the spark plugs, held against the block and saw sparks, so get to thinking its a fuel issue.
Pulled the fuel pump and pumped the fuel primer, no leak from the diaphragm.
Tried cranking while pumping the primer bulb, nothing.
Even tried some engine start into the air intake, and it still doesn't catch at all.

So I'm back to thinking its an electrical issue, but I'm at a loss as to what to check next.

With it running absolutely fine in the morning, then not at all in the afternoon makes me think it should be something obvious, like a loose connection, but I can't see anything.

Any suggestions on where to look next gratefully received

Thanks

[99yam40]

If it has spark and putting fuel into the cylinder does not make the cylinders fire then you are left with too much fuel to ignite , timing of spark is way off, or no compression

[TownsendsFJR1300]

Are you in the US? I can't find that model # in the parts list..

For S&G's, drain the carb(s) and catch what comes out. Look for any debris. Is the under the hood fuel filter clean, free of water, etc?

I take it the fuel tank vent is CLEAR..

Your red safety clip (if equipped) is indeed inserted fully?


It would help if you could confirm if you have spark or not. Simply pull the plugs (make sure they work-not fouled), then plug them in, ground to metal and crank the motor over.

Please up date what you find..

[cleddau1]

Longshot especially on such a young engine but check cambelt has not snapped otherwise follow a logical troubleshoot as advised; GOOD spark, fuel in the carb, good compression.......

[Ghenster]

I'm in New Zealand, could explain the different model codes..

Fuel vent on tote tank is defiantly open, although forgetting to open it in the past hasn't ever caused an issue.
Safety clip is fully in, didn't think I would get any spark without it. Its on the remote so very sure its correctly fitted.

When I drained the carb, only fuel came out.

As for spark, when I checked one of the plugs I got a good spark earthed against the block, I'll double check the other.

With the plug out, I'll check the gross compression by turning the fly wheel by hand and plugging the hole with my finger, don't have the gear to check anything more than that.

I'll check the timing belt is still there, hadn't even considered that one. Anyone know if the 9.9 has interference between the valves and pistons? Didn't hear any nasty noises when cranking it though.

Thanks for the suggestions, will update with what I find

[Ghenster]

Spark was good (but changed plugs just in case),
Compression was fine,
Carb was stripped and cleaned, no issues there
Then it ran. Then it wouldn't again.
Went through the electrical side, but everything working.

Timing looked a little off, but nothing major. Then the timing was way out

Turns out the key in the keyway between the flywheel and the shaft had sheared.

Hence when try to start, only the flywheel was turning, not the crank, most of the time, occasional the remains would catch enough for it to turn over and start and run.

Yamaha tech said it was only the second time he had ever seen anything like it

[cleddau1]

Thanks for feedback; surprised compression was OK though.

[TownsendsFJR1300]

Thanks for the update.

Kinda odd that sheared unless the flywheel wasn't tightened down fully.

Cheap fix thou!!!!