I'm not really a beginner, but this is perhaps an elementary question, so here it is. How far from the carburator can you mount the fuel tank on a 2 stroke (.45-.75 range) without the need for a pump? Or is there even an issue with the distance?

There IS an issue with distance, but it varies with each engine / muffler / installation setup

I doubt that there could be a definitive answer to the question; besides the Minnflier thoughts I could include that the attitude of the plane when it flies is also something to count. Some one have posted that he had successfully put the tank away several inches and the engine had performed well, even so, that does not determine the performance when the plane is flying because its constant change of attitude.
On some tank setups the benefit comes when they are almost sealed. Like the third line one pressurized with the muffler and a check valve (uniflow), but it will be a mess if the tank is in an upper position than the HSNV line. (You will find that the engine/carburetor is always flooded).
Like many things that we do ("when everything fails, then read the manual") testing is a choice but getting close with the manufacturers recommendations is always the right choice (no more than 3").
If there is a problem with your setup and the tank should be away from the engine, buy a pump and forget the problem.

I don't currently have any issues with tank setup. The reason for my question is for design ideas I'm toying with in my mind. I'll be converting a Sig Kadet Senior to a tail dragger along with some other mods and was considering moving the tank to the CG location and using a larger tank for duration. I figured by moving the tank to the CG location, all that extra weight would have less effect on CG shift as it's burned off. The area normally occupied by the standard tank could house the battery and receiver if necessary. I could use a pump if it were needed, but I'd rather not if I don't have to.

For something like a Kadet, where you won't be spending a lot of time doing verticals, putting the tank on the CG might not be any problem. And as you said, if it is a $30 Perry Pump should solve it.

Perry pumps work great for doing just that. $30 investment to avoid running lean and killing your engine sounds good to me

For a 75 mile non stop cross country flight I made successfully (on the second attempt) seven maybe eight years ago, I used stacked plumbing with three conventional tanks. A twelve ounce in the nose, a fourteen in the radio compartment near the CG and a twenty four ounce rubber banded on top of the wing on the CG. The power was a K&B .45 with a Perry, Varsane, Conley VP-20 ossilating pump mounted to the back plate. Not the VP-40 regulating pump.

Above wing tank fed the radio compartment tank and this tank fed the nose tank which fed the inlet to the pump and then to the carb. Muffler pressure was routed to the above wing tank.


This setup worked well and made the flight along old Route 66 possible.


John