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Post by banditbob » Mon Jun 25, 2012 7:21 pm

Hi chaps just some info on fuel, At the moment its running on premix ,Its running on avgas 5ltrs to 200m of Castrl R is this allowed in racing and should i be using a full synthetic? any advise from you racers will be helpfull.cheers bob

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Post by Luders » Mon Jun 25, 2012 7:24 pm

Depending on the level of tune, but at the high end, a 50/50 avgas/pump piss mix is used with an oil ratio of around 35/1.

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Post by dave32 » Fri Jul 06, 2012 2:10 pm

You would be better off using castrol A747 (synthetic based with castor),run it at 30.1.
Castrol R is ok but it will leave alot of deposits(plugs/pipes/combustion chamber/piston crown) in a short time,also it will attract moisture when left andwill seperate from the needs to be used straight away then dumped.
There are lots of good oils out there though,Motul 800 (roadrace not mx),silkolene pro 2,morris race 2 are some of the ones ive used that i would recommend.
Im still confused about the 50/50 mix,i believe it has carried over from the days when 4 star leaded was available at the roadside pump and racers on a budget mixed this with Avgas.
i cant see what the benefit of mixing super unleaded is,no matter who runs it at club level.Both fuels require different setups to get the best of them.
Benefit of leaded is not so crucial on jetting and parts last longer (piston/crank etc).
Benefit of unleaded is its available at the pump and race circuits.
You would be better off sticking to 1 or the other (100% Avgas or All super unleaded) in my oppinion.If you have a readily available supply for avgas the go for that as the price difference is not great between that and pump fuel.
ive run full Avgas in my KR and tried super unleaded,there was no noticeable difference in performace between the 2,the only thing that needed doing when running the AV was to drop the needle (lean it out) 1 position.
bear in mind im only trackdaying it so am not after max perfromance,if i was racing then i would get the heads machined for Av and probably run more ignition Advance.
only reason i use Av is i run a 93 TZ250 and 93 h***a RS125 so have to get the fuel for them anyway.
When you think about the above 2 machines,they are either Leaded or unleaded setups,im not sure why the kR or any high performance 2 stroke should be any different and need the 2 mixing.
on another plus,Avgas and 747 smell better than anything :D

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Post by Rocket » Fri Jul 06, 2012 5:29 pm

ACU handbook states leaded petrol mixtures up to 102 RON,
Avgas I believe is 105 RON,
super pump gas is 97/98 RON,
50/50 mix gives 101 or 101.5 RON (legal for racing),
although I have been told in the past neat Avgas would be ok in
2 strokes due to the lead content.

I run Silkolene pro 2 (33:1) 50% Avgas/50% super plus,
partly for costs, availability of Avgas but also to get some lead content in the fuel.

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