Fuel:oil mixture for RM 125 B

[SON]

Political correctness or blatant snipe....you think what you want

Ted last weekend at Easter Creek there were 3 kids on Yamaha R15s that I assisted massively,
Current AMA Youth rider of the year Tommy Edwards, Hunter  and Zane Ford.
Those 3 plus Current Australian Junior Speedway/Roadrace/Dirttrack Champion Max Croker will all ride the Juniors at the World Superbikes at the end of the month,
Over the last 30 years I have assisted a few other young champions,
I think I know a little on hired guns!
By the way Have you ever used an 85 plug before?

[Paul552]

Am I reading this correctly?? SON I use BR8ES so would that be BR85ES???

Does that make sense??

[SON]

The 85 or 8.5 that I stock is a NGK Racing plug not the standard type

[80-85 husky]

Wish I new about these years ago. every year in my Gemini Boss 80, the bloody 8 plug would whisker on the first hot day of spring and I would use a 9 until the autumn cooled and it would pooh that so back to an 8.

I was using BP zooooooom phut as fuel.....this was 73 - 76

[SON]

Plug is B85EGV

[Lozza]

Too much oil can result in seizure as well. The unburnt oil glazes up the ring landings and piston walls, causing premature wear. Personally, I have all my 2 smokers (including whipper snipper) on Motul 800 at 40:1 for years,  and I have never had a seizure. I ran my 74 Elsinore at 40:1 and the piston and rings lasted 2 entire seasons without any signs of scuffing. Shite, my whipper snipper is at least 10 years old and it revs to the moon and back without any dramas so I don't see why a 125 would require more oil than any other 2 stroke.

Unburnt oil is from improper jetting and ignition, if your Elsinore had 50hp at the wheel you would have an entirely different story to tell. Whippersnippers have no load to speak of on the engine. Go to a local kart track and listen to a ICGP kart hitting 18,000 rpm and you will understand why some engine need more oil 

Plug is B85EGV

That's not a race plug 

[SON]

NGK have Racing on the box
They are a dearer plug, not from the standard range

[Branchy]

http://www.ebay.com.au/itm/261384134756?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

go karts are probably the most hammered engines around tuned to an inch of the life check out their plugs oils etc

[djr]

Bring back the 2 stroke  AUTOLUBE system , that's what I think .
 then you only need to argue over what brand of oil to buy , not premix ratios.
I once read a Yamaha technical article which said with there autolube system the equivalent oil / fuel ratio at idle was something like 200:1 but at full throttle it was 15:1 .
 this would seem to back up the theory that higher revving engines need more oil, but I don't know what the extra oil is doing ,maybe it is giving the bearings & piston rings more lubrication or maybe the oil is just absorbing heat and then going out of the exhaust ?
 I would think  a 125 single cylinder bike would be getting revved harder than a 500 single cylinder bike by most riders , so if the theory is correct then  the smaller engine may need more oil.
also its easy to forget to check your air/fuel ratio {jetting} when you try different premix ratios as one affects the other {I am sure you already know this }
anyway good luck ,dave

[80-85 husky]

its all about the film of oil on the working surface... high quality synthetic oils have a much stronger base than cheap oils and as such maintain a good film over working surfaces even at lean ratios. cheaper oils have lighter base and need more oil to maintain a lubricating film.

[Digga]

That is good to know.
I definitely want my spares kit to have some in amongst the eights and nines.
I will be around to get a few tomorrow.

At the Mr VMX Dean Burt fouled his plug at the pit gate,
I pulled an 85 from Beetles or Gilesys tool box,
I didn't ask Dean if he noticed a difference in his RM400, but it did run sweet,
It just makes sense,
8's range between 7 & 9
9's range between 8 & 10
85's range between 7.5 &  9.5
Just where Air cooled VMXers live

Interesting thread on tuning. I have little or no idea how to tune a bike so trying to take in all of this from you guys but some of it is going over my head. I have a YZ125G that I have just finished & about to take it for its first run this weekend.

The book says run at 20:1 which I did when I first started it up. Blew a bit of smoke & oil so thinking of going up incrementally to 25:1 & then stop at 30:1 The plug recomended in the Clymer manaul & the original owners servcie manual is a Champion N-59G but the plug in the bike is a NGK R BR8ES. So question is would I be wise to get an 85 so I have some roon to tweek with this all?

PS - the original Yamaha Genuine Parts catalogue calls up an NGK B10EV plug?

[Ted]

Maxima 927 at 30:1. BR8ES IS FINE

If you are a lightning fast teenager go to a BR9ES

All my bikes run the same brand oil , same oil ratio and same plugs. They range from 125cc to 500cc in size

Whatever oil you choose stick with it....that is the secret

[pmc57]

I'm surprised there hasn't been more input into this thread from others given it's done the rounds more than once on this forum, but anyway, here's my two bobs worth.

How I understand two stroke tuning and fuel:oil ratios is they are two seperate issues but have distinct links.

We often hear the comments about backing off oil / fuel ratios with underlying belief from the authors this leans the fuel mix and helps to stop plug fouling. This is exactly the opposite of reality, by decreasing the amount of oil in the fuel mix it actually allows more fuel molecules to air molecules during the carby atomisation stage which richens the fuel mix. This richer fuel mix decreases combustion performance which increases the event of unburnt fuel (spooge) occuring and poorer peformance.

Think about it... less oil in the fuel increases the amount of fuel within the air/fuel mix after the carby has done it's bit.... give it time it will come to you.

In my opinion if the "book" says run 20:1, stay with it and concentrate on your jetting as a means of solving any plug fouling and spooging issues. The oil in your mix is there to lube the bearings and cylinder/ piston walls as well as a cooling element only. Don't think that by reducing the amount of oil in your fuel mix it will solve your tuning problems, all it will do is cause you to chase your tail.

I say stay with the book recommended fuel mix ratios regardless of oil brand or oil type and adjust your jetting and plug to ensure correct and best performance. Best performance is obtained by optimal sealing around the piston rings by the oil (good compression) and by clean and efficient combustion (good jetting).

[SON]

And the quality of base oils in 1977 was
Leaded Petrol v Unleaded ??
Back then there was only a few oils that you ran at 40:1 or 50:1
Now so many more,
I have been asked about the 85 plug, as previously explained they are perfect for an aircooled 250/500 MXer 125s should have 9 if it is ridden correctly, but if you are older, heavier, slower, run the 85.
Motul 800 is far more available than the Maxima in most Oz cities.

[Ted]

Maxima 927 oil available from

Teknik Racing NSW 0247322626

Daley Crockets shop QLD

Or ring the importer, OHLINS 0395809465  Victoria   They will let you know who stocks it in your town