Ok stupid question Old 2 stroke fuel mix?

[megalodon]

Ok the stupid question for the day is. What do the old 2 strokes run on?
New ones are normal unleaded 50:1 and i know years back you couldn't run 2 strokes on unleaded it had to be leaded or lead replacement.
Just ive had nothing to do with 2 strokes since they stopped making lead replacement fuel. I didn't even know they stopped it :)

PS get the digs in quick on this one it will be one of the few times:)
Nothing better than making a Aussie feel like a idiot without having to help in any way.

Only reason i decided to pull my head in and ask here is. 7 servos couldn't tell me. Mechanic at a servo couldn't tell me and what is meant to be a outboard salesman couldn't tell me over the phone either. So ive given up.

[timddo]

Different 2 strokes use different amounts. 50:1 to 300:1. The best thing is Read your manual.

[megalodon]

Thanks. What im after is what do i mix up to run a old 15hp Johnson seahorse. Very old white thing

[Hot_Snappa]

Mate, I'd be going back tp the manufacturer and asking the question!

[megalodon]

Thought about that but i also thought surly there must be a few people here that run these engines on tinnies.

[Noelm]

that engine will be plain ordinary unleaded with a 50:1 TCW3 oil, and your done! I guess it IS a premix?? and not a VRO?

[Noelm]

as a general rule, stay away from all the E10 mixes and the like, it would appear that older Engine gaskets , fuel lines and O rings and so on do not like it too much!

[Noelm]

wooops, just read the HP, it IS a premix engine! so as mentioned 50:1 Unleaded, or I guess premium will not hurt it!

[Noelm]

just as an extra, extra thought, what year model is it?? or if you do not know, post the model number and we will see for you, being "OLD" can be a different thing to different people, to some a 2000 model is old, but to others a 1960 model is still just a "pup" so lets find out huh!

[megalodon]

Thanks for that.
Old meaning its around maybe a 85 model. It is a premix.
Where would i look for the model number anyway?

[thatp1g]

mate, I think you are right to wonder on the fuel for older motors. Mostly it's not the two stroke mix but the type of fuel that confuses people.

Each motor will have a reccomended premix ratio, most are 50:1. You need to find out the ratio for your motor.

However where it gets a little bit trickier is 'what fuel to mix the oil with?'


Standard petrol used to have an octane rating of around 91 - 91.

Super used to have an octane rating of around 98.


The octane rating (Research Octane Number) is the important thing with older two stroke motors. A higher RON indicates the fuel can be compressed further without pre-ignition occurring. The whole point of using a higher octane fuel is to retard the burn rate of the fuel to allow more advanced ignition timing and higher compression.

Manufacturers used to tune two-strokes (and other motors) to run predominantly on standard or super. Hence your low compression and high compression motors.

It didnt matter if you put super in a low compression motor by mistake.

It did matter if you put standard in a high compression motor by mistake because the fuel would pre-ignite causing 'pinging'.


The Lead Replacement Petrol you speak of was just high octane unleaded with a Valve Seat protecting substance pre-added to it.

You can still buy valve protector additives to put in your fuel yourself but you only need to do that if you are putting the fuel in a four stroke motor.

So - if you can find an owners manual for your motor and establish if it has a compression ratio below around 8:1 you are fine to run the lower octane unleaded fuels - if it is higher than that then you will need to run the high octane 'premium' unleaded.

And stay right away from the ethanol blends. Older gaskets and carberutor metals aren't designed for the highly corrosive stuff. Besides which it has a lower calorific energy equation despite it's higher octane rating which means that you will end up chewing through the juice (up to around 30% more fuel in some cases).


I'm not mechanically qualified (just as a disclaimer) so check my opinions out with a mechanic at a boat shop if you have any doubts still.

[Noelm]

geees and 85 model is just getting run in, 50:1 it is, and premium will be Ok, as will "normal" unleaded as mentioned, if it has not been used for ages, might be good to replace the water pump and gear oil, and give it a set of plugs as well, or as most people will do (me include) get some fresh fuel, hook it up to the muffs and give it a kick in the pants!

[Noelm]

the model number is usually on one of the transon brackets on a plate.

[tigermullet]

My 8hp Mariner (re-badged Yamaha) is an 85 model and uses 50:1 unleaded/tcw3.

I think that the premium fuel is a bit of a waste as the octane rating for normal unleaded is good enough. Never had a problem but it did need a full service last year. I guess that I should not complain but, at the time, was thinking,"You just can't buy quality any more".:)

[oldboot]

lead or not shouldnt bother a two stroke as there are no valves.

make sure you are using a good two stroke oil intended for 50:1 not standard mower oil.

I've run quite a few things on high octane ( not the top shelf stuff) and they all seem to run nicer on it...... old cars, mowers, chainsaws, brush cuttrers.

there are some that will argue that the higer grades have less rubish in them.

regardles of what you decide to run......get a full tamk thru it and get it tuned to that fuel and stay with it.

cheers

[megalodon]

The question was mainly to do with fuel type. Back in the good ole days when i was riding 2 stroke road bikes you only used normal leaded fuel not super and when un leaded fuel came on the market you were told to never put it in your bike and stick with the lead replacement fuel. Now they do not make any lead replacement fuel i was just wondering what everyone was using in the old engines since we were told not to do it back then. So bottom line i guess now is run the thing on whatever and make sure the mix dose not burn the plugs and does not oil them up to much and life should be sweet. I just wanted to check first because for all i knew they could have a additive out for un leaded fuel to make it suitable for the old 2 stokes. Best to check first.
Thanks

[dnej]

The lead only protected the valve seats and stems,and as mentioned above,two strokes dont have that issue,so unleaded is fine.
David

[dogsbody]

The question was mainly to do with fuel type. Back in the good ole days when i was riding 2 stroke road bikes you only used normal leaded fuel not super and when un leaded fuel came on the market you were told to never put it in your bike and stick with the lead replacement fuel. Now they do not make any lead replacement fuel i was just wondering what everyone was using in the old engines since we were told not to do it back then. So bottom line i guess now is run the thing on whatever and make sure the mix dose not burn the plugs and does not oil them up to much and life should be sweet. I just wanted to check first because for all i knew they could have a additive out for un leaded fuel to make it suitable for the old 2 stokes. Best to check first.
Thanks

Had an ole Holden and used to put in an additive they have at servos can also get it at supercheap and the like. Can't remember the name Valve something or other.


Dave.