Advice please fellas.

Just converted one of my engines , an OS 46LA to C/L.

The only NVA/Spray Bar assembies I have place the hole in the venturi slightly off centre.

So , does this make any significant difference please ? If it does , which NVA do you recommend please ?

Much obliged ,

Robin.

Geoff , very much obliged for the info.

Many thanks from S.W.France ,

Robin.

If your engine is upright or inverted, it will make no difference.  Side mounted, it does make a difference.  Move the tank up or down a little as needs be.  I have swapped out NVA's on a profile when the tank was hard to move. 

I've used nylon washers, but don't any more.  They over time give a little and loosen up, leads to the NVA rotating and air leaks.  I now use alum spacers when I need to center a NVA.  I put a little silicone goo on if worried about leaks.  For ST type (4mm dia) I use K&S heavy wall 1/4" alum tubing, ream it out to 5/32 then part off to the right thickness in a mini lathe.

Dalton,

The old Perfect brand after-market spraybar+needle setup is also usually smaller diameter than most modern NVAs. That may - no, will - make a difference in needling and general usefulness. Muffler pressure may reduce the effect and allow a bit more power from a less-restricted intake. ASIR, most threads and needle ratchets were fairly coarse, and threads a bit loose in clearances... Tendency to leak air?

Dead-centering the spraybar jet is not essential - close to centered seems plenty good. And you can punch holes in thin aluminum, such as the tops of pull-tab cans, with a pliers-type squeeze punch for, like, 1/4" holes. Those punches come in several diameters, often found at craft sections in big box stores. E.g., I use 5/16, 1/4, 3/16 and 1/8 punches. For spraybar diameters, I usually drill the appropriate diameter first, then center the drilled hole by eye in the appropriate hand punch. ...Let's you work in a fineness of a few thousandths of an inch, and with metal that doesn't keep crushing down like nylon or other plastic or gasket stock.