weakest safe mix

[Jerry In Maine]

have a '62 century plus. of course with it being a bushed motor it'll be wanting a 10:1 fuel mix.
curious though; anyone know the max ratio that's been safely used while still getting a good seal of the crankcase?

could i safely go to say, 13:1 or better w/o starting problems, performance issues or bushing damage?

[Horsley-Anarak]

I just mix 16 to 1 for all my seagulls now, I found that I had too many cans of different mix.

I got confused, so now it is just 300ml of oil to 5 litres of petrol.

H-A

[Charles uk]

Jerry you haven't given us the most important information, the condition of your Century, how much compression do you have?

[Rex NZ]

Jerry

I'd go with 16:1 & just basic motor oil

Rex NZ

[Niander101]

basic motor oil?

[Charles uk]

I don't think you'll find 2 stroke oil was commonly available in 62, so they all ran on basic 30 weight motor oil.

[Collector Inspector]

16:1 is all I have for 90% of my old Dears. One Jerry can on demand.

I find that perfect for general use with no damage through limited use.

Use modern oils.

B

[Charles uk]

Many of the Kiwi racers claim a performance increase through using 30 weight motor oil & many of them have done a lot of measured research on this subject.
I belive they use hotter plugs to prevent furring up when not running at full chat as 30 grade burns more readly than modern 2 stroke.

[Jerry In Maine]

thanks!
i wondered if the original 10:1 was for engine durability and longetivity as much as it was for perforance and wear protection. each of my gulls might get a couple hours running time each season, so its not like i'm going to wear them down in my lifetime, and a thinner mix causes less of a sheen trailing behind me for the local warden to follow.

with the 30w oil...do you guys use detergent or non-detergent types?

here's a follow up:
i'm in a local chapter of a nat'l antique outboard club . some of the guys run lithium grease in the lower units (which originally used gear oil) of motors until they can locate new shaft seaks to replace their old worn/leaky ones. the old seals leak the oil, but this isn't an issue with the grease. gearboxes seem to turn happily. any reason this would be dangerous to a gull?

[charlesp]

The oil/petrol mixt isn't so much about wear on the bearings - it's more about the rich or lean mixture at the carburettor. Too little oil for the carburettor means the motor runs too rich. Hence the conversion kits being jet or needle changes.

Running at 16:1 risks running too rich.

[Rex NZ]

Jerry

Here's my current opinion, which no doubt will be fiercely contested & as such I don't recommend it

As for fuel, I'd add 10% Avgas, as it's got lots of volatile component. Makes the motor easy to start, especially in cold weather

As for oil in the fuel, I'd use whatever is cheap. The specific output (output per unit of displacement) of the engine is extremely low. Given the relatively large bearing areas, the interface pressures are very low thus placing a low demand on the oil. Makes a durable motor. Conversely, a modern performance 125cc 2-stroke produces well over 10x the specific output of a seagull, Honda RS125-GP or CR125 MXer

As for Grease in the gearbox, Don't use grease. It can’t suspend leakage water & is extremely viscous. The biggest gearbox problem by far is internal corrosion. The manufacturer recommends heavy gear lube oils like EP-140 or SAE-140. These oils or grease have 2x major issues;
1. they don’t address the corrosion problem faced in the real world, &
2. they create alot of internal viscous lossess that reduce useful power to the propeller
The manufacturers reccomendations were made with the best knowledge & materials of the day, but, that era that has long been surpassed, (along with whale oil, acetylene welding & egg beater drills). Oil technology has advanced hugely including, the use of dispersants & friction modifiers. Unlike gear oils, modern engine lube oils contain dispersants & emulsifiers. These give the oil better ability to suspend leakage water as a relatively harmless homogenized solution. Without dispersants the water has more tendency over time to separate out from the emulsion. So given all this, I use a thinner oil such as ordinary modern engine lube oil SAE 10w40. Note that thin oil also tends to leak out faster & leak water in faster, this is especially the case in worn gearcases. Important you change it after every outing. Here's in NZ we've experimented with EP90, ATF, motor oils, chain oil, vegetable oils, & even diesel fuel. Water corrosion is always the ultimate problem. Wear is a non event.

Again, This is my current opinion, which no doubt will be fiercely contested & as such I don't recommend it

Rex NZ

[Jerry In Maine]

well stated and smartly supported rex...thank you.

i love my flock of 'gulls, just wish they wouldn't 'poop' gearbox oil on my garage floor when the drip pan gets kicked out from under them. too bad there's not a better shaft seal available to help control the leaks.

[Taspiper]

I have often thought along the same lines as you Rex.
I would of thought that a modern 90 outboard gearbox oil would be fine as long as the level is kept in check.
I note with interest though that websites like Castrol will still specify a straight heavy gear oil. Why if modern oils are better don't they suggest an alternative? Maybe it's the lack of modern sealing?

I don't think it would be very hard to adapt seats to a gull box and have looked at doing it but at the end of the day draining and replacing a little oil seems easier for the amount of time the engine is used.
If I were using my seagull every day I would probably make some mods for convenience.

[Taspiper]

As for mixture, I'm running 10:1 in my Century 100. It was designed for it and I don't mind the slight extra expense of the oil. I love the sight and smell of blue smoke and make sure to breath it in deeply as it removes congestion from the lungs from pipe smoking of strong navy tobacco
Oh and I guess we all have a little green in us but sorry...Stuff the greenies

[The Tinker]

You need to remember that seagulls have no crank seals. 10 to 1 give you the best seal in the crankcase. As well as lubing the bearings. If your engine is tuned right you have hardly any smoke to annoy the greenys. A hotter plug helps also tuning the propeller to allow the engine to rev a little higher also helps to burn the fuel and oil better. If you run engine leaner on oil the engine can be a lot more smokey as it is not burning fuel right. Because the Crankcase pressure is to low.