I am building an OMP Yak, with a Saito 72 for power. My other Saito 72 didn't come with a velocity stack, but this one (a Golden Knight) does.

I will mount the engine last, to try to get the CG right, but if I mount it all the way back, the velocity stack is right against the fuse. I am nearly certain that the engine won't run correctly like this. If I remove the stack (second pic), I am still concerned about the airflow. Suggestions anybody?

I ran into the same problem in my EF 540T, I wanted the velocity stack so I could mount an air cleaner or at least put some pantyhose over the stack...trouble is my motor sets so close I can't even mount the velocity stack... I have about 1/4 inch between the fuse and carb.. anyway after 30 or so flights it's not been a problem, airflow is fine. the only thing I could come up with was to drill a 1/2 inch or so hole through the fuse where the carb set's... since I've not had any running issues I just killed the air cleaner idea... my FA-72 the only motor I run without one... I'd mount the motor to set CG and fly it


John

Mine has the same clearance, less than 1/4", runs fine. I think there is plenty of room w/o the stack.

Thanks.

I will run it without the stack.

Leonard

Isn't the velocity stack mostly for fuel economy anyway? (it just stops fuel from exiting the carb when the flow is less than ideal between intake strokes).

I have a Saito .72 GK in my TufFlight 4D:

www.tufflight.com/4d.html

The stack is about 1/4" from the mounting beams and partially obscurred for direct airflow. It runs fine this way and is the most reliable engine I own.

The only time it ever quits on me in a hover is when I run out of fuel.

Were can I get a velocity stack like that for my Saito .72? TIA

Nogyro,

How does your engine run without the stack? I didn't think it made much difference.

Here's where you can get one though: $7 from horizon:

http://horizon.hobbyshopnow.com/serv...=ALL&tag=qsrch

wind junkie,

Thanks for the info. Next time I order from Horizon I may get one. My Saito .72 runs fine. About the only problem I've had is if you do a lot of hovering, it tends to lean out quite a bit. I had a Cline regulator laying around and put it on. Now it's like a YS with the pressureized system. No leaning what so ever. I saw your video on the 4D! Those are some bad a## planes! You guys are great pilots, sure make it look easy. I had my Saito on a spa3d. Much better than listening to those 2 strokes screaming in close. I may try one of the 4D's sometime. The spa3d is kind of limited............

I've got another .72 without a stack waiting for a Jeff Williams Sledge. I will remember your cline regulator results in case I have similar problems.

We're not such great pilots. It's just practice. You know the drill. If you've got a Spad3D, you're most of the way home by now I bet. Our 4Ds just speed up the learning curves cause they're so durable-- a lot like the spads, only lighter.

I like the airfoil wing on the 4D. They look like they actually fly. The spa3d's tend to get a little"squirrely" sometimes. Like dropping out of the air when you turn downwind.