Have just purchased a 750 Demon carb. I am needing to go up on my primary squirter size and noticed that there are 3 types....Center,Tube and Straight. Which type should I use? Also when stepping up in shooter size how many sizes do you normally step up to at a time?

Thanks
Randy
"Bad-Habit"

I always liked to use the tube-type. As far as stepping up you need to experiment with a combo of squirters, pump cams and possibly the size of the accelerator pump. Also make sure your carb is not drawing out of the squirter while underway. This is common if the ball check/plunger is stuck or missing and it will make you think you need a larger shot.

Roby

I have two 750 speed demons I Blower calibrated myself for use with
a supercharged intercooled application.

I had two increase the primary squirter from a 31 to a 37 Straight.
I beleave the 37 is the highest you can go with the 30cc pump.
The pink cam in pos 2 is the most agressive cam for the 30 cc.
When you whacked the throttles at idle I had a wicked flat spot.
the above increase helped but I ended up also adding the 50cc pumps
on the primarys. Big difference.
Before we did this we had someone push down on the accelerator pumps
using there thumbs at the same time someone whacking the throttles.
the flat spot diminished considerably. This is how we realized it needed
more fuel.
Oh yeah one more thing I beleave you have to go to the hollow squirter
screw to go bigger then 37.

Good Luck
Gerry

On a marine application you'll want to use the standard straight style squirters. You won't see a difference between them and the tube type. The tube type are designed for applications where you're looking for extreme throttle control when you're getting on and off the throttle very sensitively. Such as in a Road Race or Oval Track application. You won't notice the difference on a marine application, and there is the possibility of loosing one of the little tubes into the engine with the amount of vibration and pounding a boat goes through. A standard squirter screw will work up to a .042" squirter nozzle, over that you would need to install a hollow squirter screw to get the full benifit, and flow.

Thanks as always RumRunner....

BH

Reminder: If you use the 50cc pump be sure you switch to the funny looking brown cam.

Roby

Hi Doug, I dont know if you remeber me Its Gerry At Millennium motors. (Speed Demon B/C calibrating) did you guys make some Tunnel floats yet? I heard you were tooling up to make some I guess you were all out. I have been running without them. But would like them per your advice.
Call Me if you get some time I have a couple more ??,otherwise running pretty good.
508-399-6440
Thanks
Gerry

Gerry,

Yes, we've had them done for a few weeks now. Check with your supplier. Drop me an e-mail at [email protected]

Not an expert by any means but Ive learned about accelerator pumps the hard way, at least on my applications. I had to increase the size of my pump to 50 and REDUCE the size of my squirters so they would maintain a fuel stream long enough for the engine rpm's to increase enough so I had signal to the mains and they would start pulling fuel. This was with vacuum secondarys and single plane intakes. When I increased the squirter size I would get a big shot of fuel all at once and it wouldnt maintain long enough to get over the bog without hitting the throttle again once or twice.

You have a problem with jetting or perhaps an obstruction in the one of the venturis. This should never be a problem with a vac secondary carb unless you are using the white spring on a heavy craft.

Roby