Yamaha g9 backfire through carb

[Bryans200583]

I’ll just break a couple blades off 180 from the ones that I broke. Haha. Nah I’ll run it and see what happens. I hope this is my problem. I’m gonna get on it when I get off work so I’ll let you all know. Crazy thing is, the other day when I took the motor out to take a picture of the timing marks I thought about the flywheel and how I changed it. I was thinking that it couldn’t be the problem cause you would think they were the same I case someone broke one. I find out in a couple hours. Thanks again fellas

[CP241]

Originally Posted by cgtech

Please tell me you have not recently changed the flywheel (iron thing with fan blades) for another! (I broke mine, so I swapped another in) If so, this case is solved. I once did this, it made timing & spark so "whacky" it wouldn't be anywhere close to "driveable", only spit & fart at best. (If so, see the engine swap sticky below to figure out "what to do next").

I have a feeling....that may be it.

https://www.buggiesgonewild.com/showthread.php?t=20101

Good catch!

Hopefully that's it, I feel for the guy.

[J-ROB]

Wow, that's some good troubleshooting there CG, it's gotta run after he swaps them back..... I mean he has all the things needed for the engine to run, except for the correct timing for the spark.

[Bryans200583]

Sorry it’s been a while since posting but had life going on. Well, I changed the flywheel and it still won’t crank. Would using the crankshaft from the other engine cause the same problem? Just wondering if it’s not keyed in the same spot than it would throw the timing off also. Appreciate it.

[cgtech]

The "other flywheel" didnt whack the sensor, did it? Are you using the sensor that matched its original flywheel?

[Bryans200583]

I’m using all the parts that were originally together now other than the crankshaft. This one just looked a little better shape. And the sensor didn’t get hit or messed up

[slonomo]

Originally Posted by Bryans200583

Well, I changed the flywheel and it still won’t crank.

Now it won't crank?

[Bryans200583]

Nope. Nothing. Turns over all day, getting gas, spark and won’t start.

[slonomo]

Ok, so it cranks....but won't start. I'm thinking you have a problem with your primary ignition somewhere. If you have spark and it won't run, it's not timed right. Either wrong flywheel/magnet position, or pulsar coil issue.

I think you have done everything you can to your ability. Maybe it's time to take it to a mechanic that can put eyeballs and hands on it. It's really tough for us not being able to see it and touch it etc.

Sometimes when I work on engines it's not just a "procedure" think but also a "feel" thing. Every engine has its quirks and they all want something different to run, it seems. An experienced engine mechanic will know what it needs. I'm just out of options for you.