Oil myth or truth?
 

No, not another oil thread. Everyone has a brand he prefers and we don't need to discuss what is better or who uses which oil why. My question is concerning flash points and engines.

I wonder why all 300 Gasser's I know (and I know quite some) have a tendency to spooge. When I compare it to all my former KTM 300's and those of friends it is very obvious that the Gasssers spooge a lot(!) more. I dare say it is not the carb/jetting nor does changing from 50:1 to 60:1 make any difference. So why is this?
Lower compression? Lower combustion temperatures? (colder plug vs KTM)

Second question is, is it true that an oil with very high flash point (e.g. Motul 800) produces much more spooge than an oil with a low flash point (e.g. Motul 710)?

The statement that spooge is solely a jetting problem has been proven to be wrong at least 100 times.

I crosspost my questions on TT.

I expect it's a combination of things. I know when I run an oil with a lower flashpoint I get less spooge in my 2018. Lower flashpoint means more oil is burning off.
In my 2012 with a house of horse power exhaust and pipe I got zero spooge..

Kelsey from RK Tek said its a combination of silencer type, misfire and oil flash point. That confirms what you say!

Many thanks, I get a clearer picture now...

Higher flashpoint definitely means more spooge. I use Motul 800 and the silencer is always oily when I do a repack. I only have to wipe it off and reassemble. No carbon on the screen at all. In the old days it was common to remove a 2T baffle and heat it with a torch to remove all the deposits. A Krizman type spark arrestor definitely makes more spooge as oil vapour condenses on the swirl bullet.

I had less spooge with 710 than 800, but if i spent more time on the limit i probably would have rather used 800.
I also believe that if you jetted properly with 800 you would be able to get almost no spooge

Something that has been shown by the TPI is that you will always get some spooge with a premix bike, the tpi mix changes quite considerably, this shows that 2t oil is required at different amounts at different engine demands, a premix bike is not able to change the mix (but you may be able to prevent it getting all the way to your tailpipe with good jetting)

Flashpoint is important - Motol 800 won't burn untill it gets over 400 degrees farenheight. Amsoil Dominator will burn at about 200 degrees. Both are great oils and have their place. Smaller 2strokes race bikes run very hot because they are run wide open all the time so the 800 works for them. I ride an ec 300 gasser that may never see 400 degrees in a riding day because I ride mostly tight, technical, singletrack. I have tried to run 800 and it forces me to have to clear the engine out (clutch in rev it) on a regular basis. Plugs don't foul out but they get oily and would be more prone to fouling. Who wants that?
Oil that goes into your gas has only two places to go - it gets burned in combustion or it goes unburned into the exhaust. It is easy to think that the least amount of oil that gets burned off is the best for your engine but that is only true up to a point. Beyond that point the excess oil gums up your exhaust valve and saturates your exhaust packing - both can adversly affect how your bike runs.
I have mostly run Amsoil Dominator & Amsoil Intercepter the last 20 years and I go 200-250 hours on a 300 topend. The lack of wear on the cylinder and lack of carbon on the head and piston is proof that the oil is doing its job very well. I have also ran Amsoil Saber (roughly 350f degree flashpoint) and had the same isues I have with Motul 800 (if I ran it mixed less than 75/1). The more oil you run (lower mix ratio) the cooler your motor will be and thusly more need for a lower flashpoint. The Saber is however a great oil (my choice for trials bikes) and made to protect your engine mixed 100/1.

I have had several 250 gassers and several 300 gassers. My speed and riding stile is the same on both. The 300s are obviously stronger on the bottom so they are ridden at less rpm and that is why they stay cooler than 250s and do better with a lower flashpoint oil. More rpm means more heat - bigger engine means less rpm to make power.

I have a HOP exhaust on my 2011 gasser - no spooge most of the time but the opening in the silencer is huge (and loud). I suspect the larger opening is responsible for the lack of spooge - less restriction means less spooge getting traped in the muffler packing it just gets blown out the back.

I'm near certain the exhaust silencer is the problem on these bikes.

I've ran Amsoil dominator on all 3 of my gassers over the last 10 years. All have had head machined, been jetted myself, and used on the same trails.

My fuel economy has always been comparable between bikes.

My 2010 had the smaller FMF turbine core. No spooge. I don't think I ever even bothered to repack the silencer in 300hrs. I'm bad.

The 2013 used to dribble everywhere.. right up until the point that I cut the bastard back to the rear mount. After that it only every had an oily mist at its ring bit. No dribble.

My 2018 has been lubricating the swingarm as it makes it's way out the exhaust, down the seam and then drips from there.

Riding more aggressively helps.. Lugging in singles creates more.

All 3 bikes always had evidence of spooge at the join between the silencer and pipe.

Therefore, it is, in my opinon.. Mostly caused by the silencer/exhaust running far too cold. Oils with higher flash points only make the problem even more evident.

Agree with what you say Jakobi. I run Amsoil Saber Pro and it fouled plugs even with 80:1.
The Motul 800 produced lots of spooge and it is way better with Motul 710 for the said reasons. Since a year I run 710 successfully.

However, it plays a role that I ride slower and not a lot of WOT. Sometimes in technical stuff I ride the first two gears for an hour and that was where the two oils were a lot different. The 710 still produces too much spooge and I will try two things. First measure the squish on OEM head, then on OEM GP head. I will see where the differences are. The head change will hopefully improve fuel consumption. The 40 pj may help also as I ride a lot on the pilot jet with small throttle openings.

After the head change I will change the pilot jet to a 40. I want to keep the NECW in #3 as it gets warmer every day now and I felt the NECW being very nice, except it sounds too rich down low. I also run a small main jet (172) and I think that fits perfectly to my riding style.