Main jet setting on Simplicity 725 Model 19 engine

[TomF 0]

Can anyone tell us where to start with the main jet setting on a Simp. 725? We're trying to start with the needle 1.5 turns out and it doesn't seem even close for some reason. The needle is grooved so I'm sure that's affecting things. We have successfully run very grooved main jet needles, so we're wondering what effect this may be having in this case. What's the theory on grooved needles anyway? Al? ;-) Tom and Peter Feldpausch

[dlcentral 1]

if its grooved new needlde and perc. tube[iside carb] is required it's prob. damaged.

[Sandy_Lake_Imp 2]

1 1/2 turns is the proper starting point. Make sure the jet inside the carb that the needle is controlling has not backed out. It should screw in 'til tight.

[Al 6]

Tom, Affirmative to all above. If the needle is groved, probably the jet in the nozzle is swaged out from the needle being forced into it. The groove in the needle makes it extremely sensitive because instead of it being tapered and making the inside of the jet progressively smaller, it remains straight and the shoulder is like the head of a nail over the jet and fine adjustment is almost impossible. I would replace the needle for sure and if you still have problems replace the nozzle next. A word of caution, when you go to set the new one use your fingers and watch for the "feel" of when it touches the seat. Stop there and backup 1 1/2 turns for a starting point. If you turn it in very hard OR use a screwdriver, it will be same show second performance. Also if you pull the whole needle assy out, back the needle out a couple of turns before you reinstall it. That way if you should lose the fiber washer and not notice it until later, or tighten it too tight when you reinstall it you won't force the needle into the nozzle and damage it. You can always reset it. Good luck, Al

[TomF 0]

Thanks for your input! It makes very good sense. We continue to learn on each post we make. Tom and Peter

[KenW 0]

It is just as easy to rebuild. It doesn't take long and not too expensive. I just rebuilt my 725 but I believe I started at 3/4 turn. Als check the govenor link to be sure it is moving freely. There is a little flat spot in the link rod that has a tendency to break so the throttle cable does not work. I also start mine at 1/3 throttle and just about 1/3 choke (Chicago winter). It is easy to flood out the Mod 19 if it doesn't start right away. Good Luck...Ken Williams