I have an early os-25 rc and would like to turn a new venturi for c/l use. About what size ID wil I need for it to work well..

Lou;   I'm guessing probably about 15 yrs probably a bit more. I have a 20 and a 25. The 25 has what appears to be a casting # on the case  2001 It also has AS stamped into one of the mounting flanges. The 20 is stamped as well but RN. I'm sure I can buy the venturis but that wouldn't be like I did it myself. I like to tinker anyway. rog

I will do that. Delrin Ok or must I use aluminun.  thanks rog

You are right Delrin is neat stuff. One last question. Is there anyway to use th r/c NVA?   rog

You are right Delrin is s havve shown that a post just may be the bneat stuff. One last question. Is there anyway to use th r/c NVA?   rog

 y1Yes there is, I've used them to make a post type assembly. Some studies have shown that a post is the most effecient form of NVA we can use. Using the modified RC assembly also puts the needle vavle on the same side as the tank outlet, and better yet, allows a straight shot with the fuel tubing.

You'll need to recompute the opening size considering that the post only extends half way into the opening. You also may need to shorten the post with a dremel tool so that it only extends half way into the opening. Mine setup like this, have worked perfectly for me.