ululi1970

Hi all,
I made a stupid mistake reassembling the carb of a ST G-51, and ended up loosing the little O-ring on the HSN. For now, I just used a piece of fuel tubing over the brass knurled piece to minimize air leaks, but I would
rather have the thing fixed properly.

I would just buy the whole HSN replacement, but everybody seems to be out of stock. So I was wondering if anybody can tell me the dimensions of the o-ring, and I can order it from mcmaster-carr...
Thanks
Alberto

1QwkSport2.5r

My Italian made G51 doesn't have an O-ring on the main needle. There might be one on the low speed needle but if it's needed, take the carb to a mom and pop hardware store and use black rubber plumbing O-rings. The good shops have a big selection so you can stick one on, test fit, and try another if needed. It's ludicrous to buy O-rings any other way unless you can get them for $.05/ea. and free shipping. Even then it's still crazy.

ululi1970

I did stop by a hardware store which usually has a good selection of stuff but with no luck...

1QwkSport2.5r

You might need to look around more. But more importantly, are you sure there was an o-ring on the main needle? I've had several ST carbs in my hands and none of them had O-rings on the big needle and 3 of 4 don't have o-rings on the idle mixture needle. The 4th engine I haven't had apart yet to know for sure.

edit: any seal on the main needle is only going to seal the fuel from leaking out, not air leaking in.

ululi1970

Look at the description here
http://www.advantagehobby.com/79541/...%3DSUP12163145

under the include tab. There is a spring behind the O-ring that pushes it towards the spraybar, where there is a small recess to house it. Instead of installing first the spring, then the O-ring, I did the opposite. So now the O-ring is jammed inside the brass piece, where it does nothing.
I flew it yesterday, and the fuel tubing seems to work. However, it makes it more difficult to turn it (and tune it)...

1QwkSport2.5r

Two of my ST's have that exact needle and neither has an O-ring. If it were me, I'd pick the old O-ring out and forget about it. Unless it spews a ton of fuel out of the needle, I wouldn't mess with it. If it does leak, leave the fuel tubing on it. IMHO its not worth the time and money to find an O-ring. Just my opinion though.