Functioning Oil Injection System...run premix as a precaution?

[Mikes1200STXR]

Hey Everyone! I have my 1200 STX R up and running...I replaced all the oiling lines while I had the engine out. Since the lines took time to prime, the first few gallons I put in I ran at 50:1 premix as a precaution. The oil pump system is now primed and working fine...does it make sense to also run some level of premix as a precaution? 50:1? 75:1? All I can see as a side effect would be dirtier plugs and maybe some slightly decreased performance.

[Hurricane1000]

You should be fine...

When I ran the STX-R I never ran any extra oil in the fuel.
It will actually cause a lean condition in the system. More oil, less fuel....

[Mikes1200STXR]

Thats a good point. I was going to add 5 more gallons of fuel which would bring the ratio closer to 100:1. Need to clean up the carbs still, it wants to surge up and die when idling, like fuel pools and then it starves. The ski sat for 2 years and the carbs have never been opened so I am sure there is some gunk in there.

Any other advice for the 1200 STX R? I'm keeping mine stock, its just another toy to play around with once in awhile. I fixed all the little issues on it that I saw (resealed the driveshaft tube with 5200, replaced the impeller and wear ring, new plugs, carbs, new gauge display). I've never owned a jetski before, just boats, and for what it is, its pretty simple.

[Hurricane1000]

That is a super nice ski......I loved mine and the Ultra 150's I owned.
Same engine....different hull of course.

[steve45]

Yes, you should run pre-mix for the first 5-10 hours. You just did a top end overhaul, correct? The manufacturer recommends running pre-mix during break-in, so you should also do that when breaking in a rebuilt engine.

I don't buy the idea of the engine running excessively lean with pre-mix. If you run 50:1, that's a 2% change. I've never seen anybody that can adjust a carb that accurately.

Also, keep in mind that oil burns. It is a fuel, although it burns slower than gasoline.

When you break in an engine, you're really trying to create wear in a controlled manner. The rough surfaces of the rings & cylinders wear on each other, creating microscopic hot spots. You need extra oil to prevent overheating of these hot spots, which could lead to seizure.

[Mikes1200STXR]

Did not do the top end yet, had decent compression (117+) across all cylinders. My question is more aimed at running premix as a failsafe if the oil pump fails.

[steve45]

Oh, I thought you said in your first post (8/30) that you were going to do a top overhaul, but I re-read it and it says that you're going to do it over the winter. Sorry 'bout that.

I've run oil injection only, oil injection + 2 ounces per gallon, and oil injection + 1 ounce per gallon. I currently run 1 ounce per gallon. I think it was faster with 2. I run my 150 hard, I'll often run it at full throttle for half an hour or more, so I like lots of oil. The oil pump isn't likely to fail, but oil lines can fall off and carbs get plugged up, so a little pre-mix won't hurt.

[Mikes1200STXR]

Thanks Steve! I think I will just go with the premix for peace of mind. Worse case is I go through plugs quicker, but from the sound of it I will not be doing a significant amount of riding every year (<50 hours).