Enigine stops running

[Early Riser]

Out on the lake today my 450 grizzly backfired on deceleration and died. I had to use full choke to start it again. The first time I was hauling a trailer and about 15 members of our daughter's cross country ski team. I let off the throtle slightly, the engine lightly backfired twice and then died. The second time it did it right in front of the landing, again on mild deceleration. It ran and idled fine after starting it again on full choke.

It is a 450 Yamaha with only about 70 total miles. So far I love this machine and it usually runs great in the cold. It really wasn't even too cold when this happened - probably 10 degrees.

Do I have to leave it on full choke while running in cold under a load? Any other thoughts or suggestions on why it lightly backfired before killing?

[jltimm]

I have had backfiring also when breaking in a new machine. After awhile it seems to go away as the engine slowly breaks in, at least it has for me on several machines. Once the machine is warmed up you should not have to use the choke at all.

[spearchucker]

Bad gas or the carb is dirty. If it runs on choke the engine is too lean, so check for a plugged jet or plugged fuel filter.

[Early Riser]

Thanks for the suggestions guys. The gas is from deer season so shouldn't be too bad should it? I have put only non-oxygenated high octane fuel into it. Like I said it only has 70 miles on so I havn't run too much fuel through it yet.

[KatoMike]

If it has sat for an extended period without being run (2+ weeks) the gas could start to gum the carb. I try to run mine at least twice a week.

[spearchucker]

The fuel shouldn't go bad in that amount of time if it was non-oxygenated (ethanol free), but you can still get bad gas. I use Seafoam pretty regular, especially in the winter, as a cleaner and gas stabilizer. This may help get the gas burned up and it may clear up with fresh gas. Seafoam will help keep the carb clean, but if it is clogged, you will have to take it apart and clean it (easy job).

[KatoMike]

Another option, after you get the carb cleaned, is to use some Stabil if you know you are not going to use the machine for a while. It is a little more forgiving than Seafoam if you add a little too much.

[Scott K]

I may be replying alittle late, but I will give you my 2 cents.

High octane gas is nice for most of these machines, but not needed though. The biggest problem with high octane fuel is how long has it been sitting in the gas stations tank. If you get it from a busy gas station that sells lots of fuel, then I would recommend it, but if your stopping to get fuel in a small town, chances are the high octane fuel doesnt get used very often! I would much rather use 89 octane that was pumped into the tank within the last few weeks then take some higher octane thats been in the tank for 4-6 months or more. Fuel stabilizers are a good idea if the fuel in your tank is going to be in there for more then a month.

As for the back firing on decel, most likely valves out of adjustment, or carb getting dirty, or just adjust carb a little richer. The machine shouldnt have to have the choke on after warm up, if it does its running lean, due to possibly one of the reasons I listed above.

[arctic_scrap1]

The gas is your problem. My friend had the same machine and it will not run on non oxy 93 octane. It will just die and backfire.

[Early Riser]

Thanks so much for the information. I will try some different gas for the next fill-up.