Allotment Gardening Advice Help Chat

Chatting => Equipment Shed => Topic started by: mushroom on July 20, 2007, 05:13

Title: A question about fuel with older 4-stroke rotovators
Post by: mushroom on July 20, 2007, 05:13

hi,

Am i right in thinking that the older 4-stroke petrol rotovator would have normally required leaded fuel? Now that leaded is unavailable, is super unleaded sufficient? Or is a drop of 2-stroke added (is it a lubrication thing with lead or is octane (anti-knocking) related?

Title: A question about fuel with older 4-stroke rotovators
Post by: Gwiz on July 20, 2007, 06:01

the briggs and stratton engine fitted to most of the usual suspects and antique equipment that crop up on this forum, is made in the USA. they have been using unleaded petrol over there for much longer than us and so they were  desinged to run on unleaded from new.
although the briggs engine is made of alluminum, it has hardened valve seats which enable it to run on unleaded from new.
you can use the lowest grade unleaded that is sold over here, and should avoid using super unleaded because the octane rating is too high, and that WILL damage the engine.
you dont have to add any two stroke to the fuel unless you are fueling a two stroke machine.
BUT, the reason that there is some confusion about unleaded fuel is because when two star petrol was faised out over here, many people found that after a very short while of using unleaded fuel, their engines would not start. this was because the unleaded petrol softened the hard carbon deposits in the engine, these inturn often became loose and gummed up the valves so that they would not shut correctly, or kept gumming up the spark plug.
the only way to avoid this was to decoke the engine.
the additive that is sometimes put into unleaded petrol is there to stop it from going off. lead is a great preservative insofar as leaded petrol stays "fresh" for a long time. untreated unleaded can go off in a very short time as the butanes and whatnot that are put into it evaporate, leaving you with somthing that you can clean a paint brush with, but can't run a mower/ rotovator on.
other types of additive are available to put into the petrol to replace the lead. this is needed on our older cars with cast iron cylinder heads that have not been converted for unleaded use.
i hope that this helps :wink: