I am trying to dial in a VP30 perry pump on an O.S. 1.08 and I am having troubles down low. I have the pump leaned out all the way and the low speed on the carb leaned out all the way, but it will load up and die if I let it idle.

The O.S. 1.08 does not seem to have a very wide range for the low speed--that I think is the problem.

Has anyone had luck with this set up?

I was wondering if a Cline or Iron bay regulator would solve this problem?

--just had another thought--I think I will try removing the Venturi Insert. This should make the carb draw less down low---well I don't know if that will stop the pump from pumping more in there???

the Venturi insert works primarily at high speed.... is it the 7D carb? If so, you should lean the mid range adjustment.....

Yes it is the 7D carb with remote needle valve. Is there any way to lean the low speed out more than what the cam arrangement allows? Does not seem to have near the range of adjustment as the carb on the 1.6FX.

The mid range adjustment??? are you talking about the low speed & idle screw...cam with + And -? I am all the way lean or -.

Thanks for your reply. Again look at my original post....I have leaned out the low speed all the way and the pump as well.

I think one reason why the Venturi is in there in the first place is to help the carb draw enough fuel during lower throttle settings...the opposite is the problem for me so I might pull it and give it a try.

CARBURETTOR INSERT (for Type 7D only)
Two different sizes of carburettor insert are used with the Type
7D carburettor. A large I.D. insert is installed in the carburettor
fitted to the MAX-90FSR. A smaller I.D. one is installed in the
carburettor of the MAX-61 engine.
In the case of the MAX-90FSR, ordinary suction feed is sufficient
to use this carburettor with the large insert. If, however,
higher power output is required for aerobatic flying, it is permissible
to remove the insert. In this case, a muffler pressurised fuel
system should be used.
In the case of the MAX-61, a muffler pressurised fuel system
should be used on this carburettor with the smaller I.D. insert.
If higher output is required, it is permissible to replace this with
the larger insert, or to remove the insert completely, but, in
these instances, a pumped fuel supply, such as the Perry

After a lot of investigation I think I will install a Y between the fuel pump and the needle valve that returns to the tank. This bypass idea is usually implemented just before the carb, but I am thinking that my low speed will still be too sensitive with it that close.

I am thinking that this high draw on idle that this 7D carb offers is what makes it work so well with a typical fuel tank location.

I also think that removing the restriction in the venturi will slow the draw some.....thinking that is why they put the restriction there in the first place on the 7D--not to restrict the high but to help draw down low.

I will pull the venturi and try it then if that does not work I will try the remote bypass.

JIm....where is the mid range adjustment on the 7D carb ?

Dave.

I removed venturi--no change. Added a "Y" before needle valve and . This looks very promising. I screwed the pump back in to where it was when I got it. I have the idle still set at full lean and it has to sit for 15 seconds before it starts to load up at all. If I let it idle for 1 min and then go to full it stumbles just for a moment and then clears right away. Have to put the cowl back on and try it again. Might try to lean the pump out a bit again....my high speed is 1-1/2 to 1-3/4 out.

"JIm....where is the mid range adjustment on the 7D carb ?"

don't have mine anymore, and after 4 years, I can't remember.... if you have any heli-friends, they might know...

I remember using it on a ST2500 and it worked great....

[:-]

It looks like my pump problems are totally resolved. I leaned out the pump another 1.5 turns and my low end improved even more. The "Y" return into my fuel line just in front of the remote needle valve is the solution for me. I left the venturi restriction removed. Spool up is very good and it does not load up. Got the plane in the air today and the motor did not miss a beat. Very happy with it!!!