2-stroke mix ratio and kinds of oil

[darren]

Sadly I melted the piston on my 2004 MXC 300 because I overheated it badly. However, I got to thinking something was weird because my piston melted and my buddy's (who overheated his bike just as bad) bike was fine. His gas to oil ratio is around 32:1 (what most oil manufacturers suggest) and mine is way out at around 80:1. I kinda figure that that was the main reason for the ceased piston (which ends up costing me around $900 and two weeks of down time).

This last weekend at the Moose XC I talked to all the mechanics who have a ticket, and most of them run around 40:1 in the summer and 20:1 in the winter simply for the ease of doing your math. I also heard a great deal about different oils for mixing. It seems that most of the trade mechanics suggested full synthetic.

Out of this I learned: that once your bike starts steaming...stop it immediately and let it cool down. And to do my mix just a little richer.

Anyways, it was a greate race this weekend, and it was good to see so many people.

[darren]

Just a side note, I took my cyliner to Jim Titmus and he did a fast and fantastic job on it. Definately recomend his services to anyone.

[thumper-darryl]

Be very carefull about "fancy" oils and high mix ratios. The normal 30-40 to 1 ratios suggested by most of the established oil manufacturers works great, And for winter use remember motorcycle oils have a fairly high pour point, meaning they are not designed for cold weather. learn from the sled guys and use a sled oil which is designed to stay mixed in cold weather.

[darren]

Thanks for the insight Daryl. That's a good idea to run sled oil in the winter. What kind do you recomend and at what ratio?

I'm not blaming my melted piston on the oil, I am just a bit weary, that's all. I used to use Opti 2 for a long time, so I think I'm gonna switch back to that. I've also heard that Motul is pretty good. Any other suggestions would be greatly appreciated.

[thumper-darryl]

Both proven products with established track records for reliability. Motul sled oil has been a reliable one for sleds running 250-300 HP. Will have no problem in a 50-60 HP bike.

[dirtyboy]

thumper-darryl,

Would you recommend using the sled oil in these temperatures? +5 - -5 or just below -5 ?

[thumper-darryl]

Specs I got on Opti had it safe to -10 c So if colder than that I will switch to sled oil.

[dirtyboy]

Specs I got on Opti had it safe to -10 c So if colder than that I will switch to sled oil.

Thanks. That's good information.

[chucker]

I ran opti-2 in my YZ 250 for 3 seasons, never had a problem. I mixed it at 100:1 (20L gas:200ml oil)
Now before you call me crazy (which I kinda am ...) that is the ratio to mix it at as per the bottle. The guy I sold it to came to look at it with a boroscope, and he thought I had just rebuilt the motor. No scuffing of the piston or cylinder. Personaaly, I think it's all about jetting it properly. If your jetting is out, it does not matter what your mix ratio is.

Of course, I wised up and now I have a thumper...

[dirtyboy]

Good info Yamaha dude, um Chucker.

I use the Opti 2 in my Sherco at 80:1 as instructed by my dealer. It's only been 1 year but it seems good. I thought 100:1 would not be enough oil. Just goes to show you.

[DirtGirl]

I have used opt for 14 years and never had a problem with it! We mix it to what the bottle says.

[Dobi]

I use the Opti 2 in my Sherco at 80:1 as instructed by my dealer. It's only been 1 year but it seems good. I thought 100:1 would not be enough oil. Just goes to show you.

Don't those things run on kerosene?

[thumper-darryl]

Opti recommends the 80-1 mix, and if you buy their pump dispensor for the 4 L jug it gives you the exact amount. Cool

[darren]

I was talking with a Stihl rep and he told me that Opti cannot be run with anything magnesium in it...I wonder if that causes any concern for my KTM?

Also, now I have a 2005 KTM 300 MXC and I still overheat it a bunch. Most of the pros I've talked don't use rad guards and all strongly suggested that I put the fins back in place where the guards are. This never used to be a problem til I started riding Peaterson trails and doing some nasty bushwackin. I don't think the oil was the problem with my 04 as it was more likely the ratio, jetting, rad guards, and just plain overheating the damn think WAY too much. I guess common sense has to take over at some point!!!

Thanks guys

[dirtyboy]

darren,

You can get these rad guards from KTM that are way strong and still allow you to put in the stock louvers in front of the radiator.

The back of the radiator is facing up in this picture. Darryl has a set if you want to see them in person.