What is the oil for in the carbs?
 

OK,
I was wondering what the oil in the Hitachi SU carbs for a 72 240 was used for. It says to only use sae 20W oil. The problem is that I can't get 20W oil here. Nobody I have found carries any or can order it. The only thing I can get in just a straight weigh is 30W. Would it hurt anything to put the 30W in there and what is it used for.
Thatnks,
Charles

the oil is to lube the piston inside each carburetor. Its important for these pistons to move easily because all thats moving them is air velocity.

If you can't get 20W, use ATF but DONT mix 'em. Scott from ZTherapy says in his rebuild video to use Dextron ATF and thats what I put in mine and they work just fine. If you convert to ATF, take the piston out (VERY CAREFULLY), clean it and the area around where it was (VERY CAREFULLY) so its dry.. put it back and fill'er up.

Good luck!

ATF is a 10 weight oil with high detergent properties, I see no reason not to mix them, but I do not know SU carbs - I have heard of them being mixed with no problems stated however.

hmm--- mix what you like but I'm not gonna recommend it or include it in my advice :D

reading my latest issue of grassroots motorsports ...noticed an ad for "valvoline racing oil"--not street legal supposedly...may just give you 1-2hp or so (every bit counts)...it's a 20w...would that be better for your carbs or not? every bit counts they say...and if you gotta change it why not just go all out? just wondering what you thought on this one...comes in synthetic and regular versions--which one would you get for the carbs? thanks

Well 20W is what you should put in there... Just try it! You have nothing to loose but your labor and the $$$ to buy the oil. Maybe you'll find it to work great!

What about 30W? I have some of that. Would that be OK?