premix question

[jts32]

I was talking to a guy on the river today about premix, and got both of us scratching our heads. One of the skis I have was converted to premix by the previous owner, and I was told by him to mix 40:1. I run Amsoil, and the bottle says to mix 50:1. I figured running 40:1 is added protection using a little more oil. After talking with this guy today, the question came up, does running 40:1 versus 50:1 cause more of a lean condition. My brain wants to think using more oil makes it run more rich, but by adding more oil, does it mean less fuel being burned in the cylinder, actually creating more of a lean condition? The stupid things you can wonder about after many beers in the hot sun.:drool5:

 

[LouDoo]

I don't recommend running pre-mix, but if you do run pre-mix the recommended ratio is 40:1. Be sure to use API-TC rated oil. And if you use Amsoil be sure not to use the dual rated.

Lou

 

[jts32]

I am running the Interceptor Amsoil, which I believe is the correct oil to use. It is not their TCW3 rated oil. Previous owner had a pair of SLX 1200s and had an injection failure on one, so converted the other to premix for peace of mind.

 

[Dr Honda]

Yamaha was notorious for loosing it's oil injection. Rotax on the other hand is Rock solid. There is NO reason to remove it on our Seadoo's. Not to mention, going pre-mix will just cost you more $$$... and have to deal with more smoke, and stank when running easy.

Also... the oil manufacture doesn't know what engine it's going into... so they can't spec a ratio. So totally ignore whatever the bottle says. Seadoo/Rotax specs 40:1 on our engines.


As far as the question of "lean or rich"... it depends on what you are talking about. Oil or fuel?


If you are talking about fuel, and the burn mixture... it's irrelevant. Yes, the oil will slightly displace fuel volume... but it's such a small amount that it won't change the air fuel mix. If you were pushing up to 25:1 or even 16:1... then yes, you may need to tweak the carbs a little.




Now... back in the day... when guys would pre-mix more... we would talk about "Rich Oil" or "Lean Oil" but it had nothing to do with the air/fuel mix. This was mostly with the dirt-bike guys.


And finally, the reason we would talk about things like rich/lean oil... is because people screw up, and occasionally double dose, or forget the oil. So... for all the guys who say... "The injection sucks, and I won't ever forget".... BULL $HIT !!! I can't tell you how many dirt bikes I've seen burn up because guys forget to mix in oil. (or miss measure) And that's just with a 5 gal jug. Do you really think it will be easier on a big tank?


So... service the oil injection... and leave it on. (PERIOD)


That's my story, and i'm sticking to it.

 

[Sportster-2001-951C-Stock]

Judgement call, depends on how it runs.

 

[donkey]

i can tell you that i USED TO HAVE 4 skis running premix.i spent a few hundred bucks to put the oil injection systems back on all of them.
i saved that much in oil in the first month of use. and i havent had a single problem with any of them.
i have 2 skis that belong to customers in my garage,right now,that were premixed,they both burned up due to ,,,," dude,i forgot to add oil".

 

[Sportster-2001-951C-Stock]

I just realized I didn't answer your question. Yes, the oil displaces fuel and the carburetor only delivers the pre-mix so there's less fuel thus leaner air:fuel mixture. If engine exhibits signs of being too lean the carburetor calibration should be compensated richer, accordingly.