OS .25 FSR venturi size

Hopefully one of you guys can help me out. I have a OS .25 FSR with a RC carb on it. I'am trying to get a venturi and nva for it, but Leonard needs to know the size. I don't have dial calipers, a micrometer, or even sized drill bits. If anybody has this engine could you please measure the barrel that fits into the case for me.

He says he has some for Thunder tiger pros in stock. Will these fit the OS?

Any information you might have to help me would be greatly appreciated.

>
> Hopefully one of you guys can help me out. I have a OS .25
>FSR with a RC carb on it. I'am trying to get a venturi and
>nva for it, but Leonard needs to know the size. I don't have
>dial calipers, a micrometer, or even sized drill bits. If
>anybody has this engine could you please measure the barrel
>that fits into the case for me.
>
> He says he has some for Thunder tiger pros in stock. Will
>these fit the OS?

Steve/Leonard;

On my two FSRs, I used the standard 25FP venturi, and it fit fine. No leaks.

However, I did have to go with the longer NVA Leonard sells, as there is more metal AROUND the hole where the venturi goes.

I have a couple of TT venturis, but have never tried one in the OS. I will try one tonight and let you know.

Hope this helps.

>Steve/Leonard;
>
>On my two FSRs, I used the standard 25FP venturi, and it fit
>fine. No leaks.
>
>However, I did have to go with the longer NVA Leonard sells,
>as there is more metal AROUND the hole where the venturi
>goes.
>
>I have a couple of TT venturis, but have never tried one in
>the OS. I will try one tonight and let you know.
>
>Hope this helps.
>
>Bob

That is all I need to know. I have these venturis in stock and that will solve the problem.

You da Man Bob,

Go ahead and send both of those out Leonard, venturi and NVA for the .46 and .25 if you would. I'll also E-mail you later tonight, in case you didn't get a chance to read this.

Thanks,

>On my two FSRs, I used the standard 25FP venturi, and it fit
>fine. No leaks.

Verrrrrry interesting! I just checked mine out and this is correct, at 10mm bore, both for the 25FSR and the 25F-ABC. However, in the larger sizes (same case) 28FSR and 32FSR, the carb bore hole is 13mm, as is the 25VF (and 40FSR).

Ya can't tell yer hole sizes by the crankcase (or the catalog). At least I couldn't find this info in any published OS material.

Then on to the bore size in that 25FP venturi! This means that the engine could use the 25FP or 35/40FP (small) venturi as options. The (in)famous Pat Johnston chart would indicate a .255 venturi with an ST type NVA and the 25FP is .257 (6.5 mm) and should be an excellent starting point.