OS 25FX Set Up Help Needed (Photo Added)

LAST EDITED ON Nov-16-04 AT 07:16 PM (CST)
 
I need some help with set up for an OS 25 FX. I’ve recently acquired two of these motors but know nothing about them. Currently they are set up for RC. Can they be used for CL? They have a remote needle, I’ve never used a remote needle. Do they work as well as a front mount through the venturi?

Has anyone used them for CL? Where and what parts would I need? How do they run? What size model can they pull around? Lots and lots of questions.

Can it be make to run like a 25FP?

Anything you guys can share will be greatly appreciated.

LAST EDITED ON Nov-18-04 AT 05:38 PM (CST)
 
I would think the run would be very similar to the way most people run the 25FP. Run it in a slightly wet 2 stroke, let it rev and use a lower pitch prop. Probably a 9-4 or 9-5. A .250 or slightly smaller venturi would probably be a good start. You can put a Bru-line air flter on it if a .250 turns out to be a bit too big. It should be able to pull a 400-500 square in model just fine.

When I converted my 40LA to control line, I kept the remote needle valve. It was OK, but not that good. I got the cl needle valve assembly from Tower Hobbies, installed it, and have a nicer run. IMHO the more plumbing you can do away with, the better off you are. The only reason for the remote is to keep careless fingers out of the prop. If we follow proper procedures, that shouldn't happen.
Glen

This is a complete guess, but to make it run like an 25FP, you would really have to do something bad to the engine!
Seriously, this is purported to be a more powerful engine than the FP--at least in RC circles. Some of this might be due to the small rc carbs OS typically puts on the FP series (at least on the 40 FP). You might start with a 10-4 prop and trim the diameter until the engine is happy.
I think the only downside of this engine is that it is probably heavier than the 25FP. With the same venturi size, it might perform like a slightly heavier version of the 25FP.

In R/C form this engine has a huge amount more power than a FP25.I would agree with Alan and start with a 10-4 and a .250 venturi with OS needle.Then see if the RPM is resonable.In R/C form these little motors turn a 9-6 at about 14,500-15,000 RPM.Very nice R/C engine .As far as Stunt goes ,we will wait to see what you find?

LAST EDITED ON Nov-19-04 AT 10:31 AM (CST)
 
I’ve received plenty of input from many of you on how to go about this one. It seems clear by the responses both on the board and private E-mail that this is motor is a current “Hot Rod” for RC use but not widely used in CL. The power that it’s supposed to have is very attractive to me, along with the fact that I got two of them thrown in with another engine deal.

I’ve decided to first try with standard front placement NVA and ditch the rear needle. This is simply due to not having the rear needle experience. I have not had any luck finding a replacement back-plate that doesn’t’ have the remote needle bracketry on it. I’d rather not butcher the factory plate because I may learn to use and like the remote needle. I notice that a FP 20-25 back plate has the same bold pattern but it’s not as deep. If any one knows of another back-plate that will fit, please let me know.

The venturi insert needs to be .511” outside diameter. I’m going to try to use a smaller OS 40 insert that has the correct O.D. with an inside diameter similar to a stock FP 20-25 of 6.5 - 7mm. I will also be using a stock OS 20-25 FP NVA.

I like the idea that this motor may be able to swing a bigger prop. I’ll start with 10-4 (APC?) and also experiment with 9-4 and 10-3.

The one thing I’m unsure of is a test plane. I was thinking of an ARF. It’ may be too much for a Flite Streak. I don’t know. Maybe a Cardinal? Any thoughts or suggestions on this?

It may be a while until I can get out and give it all a try. The weather is getting pretty crummy up here, but I will let you all know how it works out.

Just learning about all this myself, so again, I want to thank all of you for the helpful responses.

KIWI is using those dual BB OS engines in speed limit combat, he does not use a venturi just a needle valve in that large opening. His engines run real well. I think he is using 8-4 props.

KIWI jump in here, we missed you at our Sept. contest!!!!

Not using a Venturi, very interesting. I’ve often wondered if that could be done.

Kiwi sent me an informative E-mail about his Combat use of them. Never having flown Combat, I’m not familiar with how they are set to run. It’s my understanding that they are set to go “nuts out” screaming for full speed during the entire flight. Is that correct? I’m hoping I can tame it down for Stunt.

>The venturi insert needs to be .511” outside diameter. I’m
>going to try to use a smaller OS 40 insert that has the
>correct O.D. with an inside diameter similar to a stock FP
>20-25 of 6.5 - 7mm. I will also be using a stock OS 20-25
>FP NVA.

Chris:

I converted an OS 25 SF to C/L with good results. The SF is the predecessor to your FX. I used a standard OS 25 FP venturi with outer diameter of 0.392 inches. Looks like your venturi will need something much larger. I will be interested in your final solution for this as some SF motors have the 0.392 inch dimension and newer ones have the 0.510 inch like your FX.

I don't think that you will be able to use the stock OS 20-25 FP NVA unless you plan to mill the sides of the crankcase. On my SF motor, the width of the crankcase where the NVA mounts is 0.665 inch. The FP NVA is designed for 0.581 inch.

I opted for an ST medium NVA. I found that the fine thread of the needle provides fine adjustment of the mixture. You can buy the ST NVA from Leonard, RSM, or Virginia Hobbysport.

I run the motor in a fat 2-stroke with very consistent runs on a Skyray.

Let us know your solution for the venturi.

Regards,

>I don't think that you will be able to use the stock OS
>20-25 FP NVA unless you plan to mill the sides of the
>crankcase. On my SF motor, the width of the crankcase where
>the NVA mounts is 0.665 inch. The FP NVA is designed for
>0.581 inch.
>
>I opted for an ST medium NVA. I found that the fine thread
>of the needle provides fine adjustment of the mixture. You
>can buy the ST NVA from Leonard, RSM, or Virginia
>Hobbysport.

>Regards,
>
>Lawrence Williams
>Yorba Linda, CA

Lawrence,

Thanks for the info on the NVA. I’ll try the ST medium that you suggest; I’d rather not mill the case.