Oil for 50cc high revving 2 stroke?

[1 SX]

Good day!. This is a question regarding a better oil to use in this vintage scooter/moped/bike. 1970 50Cc 2 stroke 3 speed manual. mileage reads 389 miles, with 240 miles being put on in the last couple weeks.

As of right now, im using the FACTORY OEM 2 cycle OIL FROM 1970's. This bike has 2 tanks one for the gas, one for the oil. The oil tank is about 1.5 QTS. I also use 2OZ MMO/Per gal of 93. The engine is spotless. just removed the head yesterday, zero carbon on piston - with the arrow even visible, no carbon on the head, no piston play, no scoring, great comp @ 130.

Now the reason i ask this, is i was out on a midnight cruse, and about 30 miles in of mostly 3/4 throttle or more, right as i was pulling on to my 2 mile long dead end road, the engine started to sound really bad, like a mower running with out oil, i thought the piston was going to explode. power was still fine, i just drove it super easy and made it home thinking the engine just checked out. the next morning, i get up, disassemble the engine, and yes EVERYTHING is perfect? zero carbon on piston - with the arrow even visible, no carbon on the head, no piston play, no scoring, great comp @ 130. Starts right up first kick, and runs perfect with no engine sounds...

Now im thinking the engine got to hot, and the old oil could not "stick" to the metal parts, and it basically was over heating.. Or maybe the sparkplug is too hot, and the fuel was being burned before the spark could ignite it. Should i try a next cooler plug? The current spark plug reads a tan color.

What is a good 2 stoke oil to use? I usually just buy the 1 gallon 40:1 mixes at the gas station if i need any for the chainsaw or weedeater. But being this bike will be used ALOT more, and at or near WOT, and will also have engine braking going down hills, and running for extended periods of time, Whats a better choice for 2 stroke oil? Thanks!

 

[volk06]

I use the Stihl ultra 2 cycle oil for my equipment.

 

[expat]

Back in the Day, I would not trust the oil tank to deliver,
We would Pre-mix the oil and gas Just to be sure!

It could be the MMO saved your engine?

Personally, I'd rather see a little wet carbon than an engine Dry and clean.

 

[1 SX]

Im new to the 2 stroke game. Why would the oil tank not deliver? That makes me a little unconformable. Maybe thats what was happening? I even adjusted the oil delivery for a touch more.. .to note, the oil tank is going down at a decent rate. i estimate by the 800-900 mile mark i would have to fill it up with 1.5QTS if i left this old oil in. It also smokes for a minute or 2 when you start it up in the morning.

 

[mene]

I would use opti-2 injection or pre-mix, better pre-mix, like it was said, Would you trust an injection system 43 years old that hasn't been used much?

 

[expat]

Engine braking for more than a few seconds was also considered a No No.

 

[Slick17601]

If it's that old, I'm not sure I would still trust the oil injection system. I would block it off and go premix 40:1 with a good TC rated oil.

 

[Chris142]

Id lose the oil injector and mix torco gp-7 @40-1.

 

[Mackelroy]

MOst 2 stroke racing oils are not desined to be run in an injector pump, but they are the best protection wise. Yamalube R has always been about the best between protective and clean.

But if I was running an injector pump, and really riding the street you dont want to have to be manually mixing every tank. The Belray SI7 has been a good injector pump oil.

 

[Smoky14]

By putting MMO in the gas you are leaning it out. MMO doesn't burn so you are reducing the amount fuel reaching the engine since the jet size didn't change. If oil is going down in the tank the injection is working, most of these we set too rich from the factory for break in purposes and need to be reset to spec after about 500 miles.
Yama-lube injector oil was one of the best on the market.

YMMV Smoky

 

[Cujet]

Delete the oil injection if you want trouble free operation.

I run 32 to 1 in all my 2 strokes. It's the best combo of protection and power.

Also, ethanol in the gas, coupled with oil will effectively lean out the jetting. If you decide to premix, consider a larger main jet.

Castrol TT-S or other EGD rated oil will work perfectly. Motorcycle shops are a good place to get such oils. Cycle gear has a good selection of 2 stroke oils.

Stay away from redlline racing oil. It is not the product for your application. It will actively promote corrosion of steel and brass parts. Plus it's awful with moisture in the fuel and ethanol.

 

[Realtech214]

Originally Posted By: volk06
I use the Stihl ultra 2 cycle oil for my equipment.


^^ YES

 

[expat]

"
Also, ethanol in the gas, coupled with oil will effectively lean out the jetting. If you decide to premix, consider a larger main jet."

That depends if the oil is injected into the combustion chamber independently of the Gas.

If the oil is metered into the gas prior to the Gas/Oil mix entering the combustion chamber (as I suspect) the addition of the oil (per-mixed)won't make a difference.

Ethanol (in the Gas) may make a difference, but really, a machine of that vintage most likely has facility for mixture adjustment.
So you will just 'Tweak it' till it runs right!

 

[1 SX]

Very good points!, I will think about going to pre-mix! The oil line goes to the carb so should be easy to bypass. But in the mean time, i will head down to the local Suzuki dealer and pick up one of the listed oils for inject systems.. Should i back off on the MMO? I love this stuff, so to me, you can NEVER have too much MMO, but can you? Could this be my hard to get running when hot issue? hummm

 

[Cujet]

Originally Posted By: SL2
Should i back off on the MMO? I love this stuff, so to me, you can NEVER have too much MMO, but can you? Could this be my hard to get running when hot issue? hummm


I'm not sure that MMO is harmful. However, it does contribute to the leaner jetting issue, by diluting the gas. You might be better served by using more 2 stroke oil instead of MMO.

Just an FYI, 32 to 1 is a great mixture that will protect your engine under all conditions. It's also very easy to mix, at exactly 4 oz per gal.

I was involved in 2 stroke oil testing way back when. Not as the engineer, but as a tech. I got to disassemble and measure, then rebuild, install and occasionally test. What I learned is that wear rates increase as oil is reduced. And power increases as oil is increased, to about 8 to 1, at which point it was hard to maintain idle.

8/1 made the most power but idle was problematic
16/1 was the practical maximum and made more power than leaner mixes
32/1 protected as well as more oil
50/1 resulted in just slightly more wear on race engines
100/1 did not provide sufficient protection

We were using factory supplied TCW (outboard oils)

We tried Bel-Ray MC-1 and a few others briefly, without any difference in performance or wear.

So, the teams went racing with 150HP XS, inline 6 cylinder engines, with 16/1 fuel/oil mixtures and real world HP was North of 200. Needless to say, we won more than the other guys.

This is a long winded way of saying that 32/1 will work very well for you.

 

[RobertButler]

This noise you heard may well have been low octane knock also known as pre- ignition.
Could be oil carbon,fuel octane related or timing. If you have points no problem.
If not, more difficult to slightly retard ( 2-5 degree max)
This condition if allowed to continue could seriously damage your engine.
First thing for you is to use only premium fuel.
Consult old school aircraft tech for specifics.

 

[RobertButler]

Changing to cooler plug is always a good idea.
Try to use only synthetic oil designed for air cooled (hotter ) engines.
Chainsaw oil is ideal for you. Carry a small bottle with about 3.5 of oil to give you 40:1 to gal to get home
When you go to reserve out in the sticks.
I would love to see more scooters,motorcycles on the road
Oil is to valuable a resource to waste.
67 year cycle/scooter/outboard / auto tech