OS 91 pumped vs not pumped

[n8sx]

In researching my choices for a 90 class machine, I am not finding what reasons a person would or wouldn't go for a pumped motor. Please let me know you thoughts on the benefits or downfalls either way. The heli is going to be a 3d heli, though my skills at this point won't allow it that much 3d, LOL.

[mewsikman]

Personally I have seen the trouble with a pumped engine..... You can't leave fuel in the pump otherwise it just won't turn over the next time it comes out to play.... There are other reasons but i can't think of them atm... Also its just one more thing to go wrong.....

Id rather buy the non pumped then just let the muffler pressurise the tank....... If I had to buy a pumped engine it would be a YS not an OS

[DavidH]

YS is not a pumped engine. YS uses a pressurized fuel system. The YS uses a regulator to control fuel flow from the tank.

I have the OS CSpec, it has the OMI Big Bore Carb and Cline Regulator. It is a pressurized fuel system also.
This CSpec use to be a pumped motor. I switched it from the pump to the pressurized fuel system setup. Personally I think the pressurized fuel system is more consistent. YS's are good motors, just difficult to obtain the engines and parts the majority of the time.

David

[stevehonn]

I've got an 'unpumped' 91SZH in my Fury but fitted with an OMI modified carb with Cline regulator, pressurised from a nipple on the backplate and a one-way valve. I had some problems with inconsistent runs with the standard motor but since switching to a pressurised system its ran sweet as a nut.

[electricsceadu]

i've had 3 os c spec pump engine where the pumps failed
i will never buy a pumped engine again, stick with the non-pump
i'm running a new non-pumped c spec in a t rex 700 and it runs fine (i got it at a very good price new)
go with the sz or hz non-pump

[hornet dave]

non-pumped OS SZ works good for me with a uniflow setup for my fuel lines. The motor does vibrate a bit, though.