Petrol/oil mixture

[John Wakefield]

I tried 30:1 and my 37A seized when it overheated so now I use 25:1 premix but should I be using 20:1?

I found this comment on the Villiers forum interesting.

Two-Stroke Oil Premix Ratios

The following is extracted from the Villiers forum, and is applicable to most twostrokes built before the mid-1960s.
As far as premix goes the 16:1 is still correct for running in a new engine and you can then cut down to 20:1 thereafter. Villiers began to recommend 20:1 in the early 1950's when self mixing two-stroke oil first became available. This is appropriate for both the engines you have . You will be told you can cut down the oil a lot if you use a modern synthetic oil. Do not do so. Synthetic oils are meant for modern two-strokes designed to modern standards. The older design of Villiers engines means they need a lot more oil. They are the last of the early design of two-stroke, for best results stick to 20:1. Because they are a slow revving engine compared to later two-strokes a two-stroke oil suitable for lawnmowers, chainsaws, etc, is fine for them. It will smoke when it is cold, it will smoke if you only travel short distances but it will stop smoking when it is hot and stop smoking if you ride it any distance. If a pre-mix two-stroke is smoky all the time its the riders fault not the bike. It is not being ridden far enough or long enough to keep clean. For years I rode two-strokes to work and they would get smoky in all the stop/start traffic. When it got too bad I would go for a fast ride on the local freeway which would clear the exhaust of the oily build up. The bike would then run sweetly for another month or so and I would then repeat the exercise.

If you had an old bike with an ordinary four-stroke engine and someone told you it would run better if you only half filled it with oil you'd think they were nuts. Cutting down on the oil in premix is exactly the same thing and just as foolish.

Do not bother with premium grade fuel. Again, because these engines were designed in the days of low octane fuel there is no point in using anything up market. Standard unleaded fuel of today is far better than anything available when they were new. Also, they are unable to take advantage of anything better so it is just a waste of money and you won't get any better performance. Always use unleaded. Leaded fuels can quickly foul up the spark plugs on Villiers engines and be a real nuisance. The introduction of unleaded fuel was a real bonus for two-stroke riders as it got rid of a lot of spark plug problems.

by 33d6

Very good advice, oil is cheaper than bearings. Keep to the engine manufacturers recommendation & you cant go wrong.

[Andy Z]

I would urge anyone who runs any 2-stroke at 50:1 to read this article by Gordon Jennings. Greeves knew what they were talking about when they specific 16:1 in their scrambles engines!

http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf

[Dogsbody]

Interesting article, but it's nearly 30 years old. In the 60s I raced a Silverstone and Norton on Castrol R because there was nothing better. Like Mike I now use Silkolene Pro KR2 as I don't run it often enough to use R as a/ it will separate after a few hours, an b/ it is hygroscopic. I have a crank that needs to have new mains ( Nametab conversion to needle rollers ) because it had been left standing after being run on R and had pitted badly.
On Pro KR2 the piston is much cleaner with no scuffing marks and rings don't suffer with sticking, although I admit not to running as hard as I used to!
Dogsbody

[John Wakefield]

Interesting article, but it's nearly 30 years old. In the 60s I raced a Silverstone and Norton on Castrol R because there was nothing better

I would agree regarding R, but it was the quantity of oil that was being tested rather than the type of oil. The writer did say that R was used in this particular test but concluded that similar results would probably have been obtained using other types of oil.

[Dick F]

Petrol/ oil Mixture

I think we still have rose tinted glasses for the old oils R was great in its day and the smell is second to none, but todays oils are brilliant, for trials and i mean long distance events also like Rob and myself have done ie the arbuthnut trial 75 miles , with the angliian on low gearing i have never had a seize up or plug trouble, the ratio has allways been 40 - 1, the new pogo stick bikes are i know water cooled and they are up to 95 - 1. I am not advocating going too stupid with mixtures for older bikes but most scramble classic riders are using the modern oils

[johnrunnacles]

The article may be more than 30 years old, but so is the engine technology we're talking about ........ or it should be?

Thanks for the reference, Dave.

[dave higgins]

Or it should be?...john! what are you saying!!!.... surely no one is running something they shouldn`t?

[Andy Z]

The article may be 30 years old, but so is the engine technology we're talking about ........ or it should be?

Thanks for the reference, Dave.

Absolutely right John, and anything with a plain bush for a small end will not do very on 50:1.

A couple of other points to consider:

1) Several Greeves models have pistons which have much greater surface areas than modern 2-strokes. This will generate more friction and therefore heat.

2) Motocross, road, trials and racing have very different requirements.

3) The absolute best, modern 2-stroke oils still are castor-based. You only have to look what the karting boys use.

What the Jennings articles was clearing up was the old myth of running very lean oil mixtures gives you more power. Maico once sold oil which they claimed could be used at 100:1. It didn't last long as the engines wore out in no time. Didn't smoke much though......

[merlin]

oil mixture

This thread reminds me of the farmer who got his cow down to one strand of hay per day then it died,are there any medals to be won for the least amount of oil used?

[Kim275]

I would urge anyone who runs any 2-stroke at 50:1 to read this article by Gordon Jennings. Greeves knew what they were talking about when they specific 16:1 in their scrambles engines!

http://www.bridgestonemotorcycle.com...oilpremix6.pdf

Andy - great article ..
IS LESS MORE?
IS MORE LESS?
IS MORE MORE?
IS LESS LESS?
....................MORE than LESS I would say

As other input here - for MX - protection and power - more @ say 20:1 is about right.....

Trials - is all bottom end - and you just need lubrication so I would guess you could run leaner - but why bother and I wouldn't go higher than 25;1 with a bronze bush small end....

The only painful example of More not being better than less for me was on my Cappra VF414 - I destroyed a piston running 20:1 R40......Reason - it has two Dykes rings in a MAhle piston - produces about 50bhp.....and they stuck in the exhaust port (hot) end - overheated the piston and the bottom front skirt destroyed itself.......Notably the small end roller bearing was also gummed up ............. so after the rebuild - I will probably go with the Chairman's Mix ... Silkalene Pro 2 KArt with a dash of Castrol R

On my QUB and 250 griffon's with Simon's forged racing piston with Wiseco rings - no issues at all with R40 in 20:1 ratio......

[Dogsbody]

With Pro KR2 you don't need a dash of R

http://www.fuchslubricants.com/pro-kr2

I run the lawnmower on fuel I haven't used on a weekend, 50/50 Blue Gas/ super unleaded and 25:1 Pro KR2- goes like hell and smells nice. And yes it is a 4 stroke but it doesn't seem to mind. Dogsbody

[John Wakefield]

The thing to remember is that stick to the manufacturers recommended ratio & you wont have trouble, reduce it and you could wreck the engine or at least shorten the life of it before a rebuild is needed. Over oiling wont damage the engine, under oiling may. I have always used standard mineral 2 stroke oil in my 4T engined roadster at 24:1 & its still running sweet after the 20000 miles that I have owned the bike, it had 38000 on the clock when I bought it, & its the original engine. Not saying the engine had not been rebuilt during that time but it appears not to have been, I did fit new pistons at 40000 not that it needed them but at the time I managed to buy a new pair c/w rings & gudgeon pins for about the same as a set of rings.
Just one other thing, back in the 60's/70's Castrol did a Self Mixing 2 Stroke oil, which was recommend to be used at a ratio of 16:1 as against 20:1 owing to the mixing agent content.

[dave higgins]

When i was running my bsa`s, i always used r-40 & always stuck a capfull in with the methanol to give the top end something to suck on.
Kim, had a mains conversion on the griff, ran it for a hour on r40 & found the mains had excess lift, after simon redoing it, i am now using putoline mx5, it seems fine now, could have been crap maching or the r40.....?
I guess all these modern race oils are pretty much the same spec & quality, so i`m sticking at the reco mix ratio on the bottle...

[aa will]

this is great on my recently built scottish outfit i was reconmended to use 40.1 mix with sikolene synthetic oil , runs ok and seems fine in the sections , but seizing about four times when running in ,i thought was my fault , so kept stripping the top half filing off the high spots then running until all seemed well then on the beamish trial it only seized five times on the road between sections, the plug reading looks good and the power is all there, i now am thinking that maybe 40.1 on a hard ridden trials outfit is not enough ,has anybody got any other suggestions on what mix and oil i should use , i have only been riding bikes for45 years but this has me confused. will.

[dave higgins]

Whats your piston to bore clearance will, any tighter than 4 thou could give you problems.
Oil wise i would try it at 25.1, also how hot is the barrel when it siezes? check your timing is not to advanced! case of suck it & see really, as has been said over oiling is not gonna cause any damage, start on a rich mix & work back from there...