What size and thread is an OS .35 muffler screw?

[RknRusty]

What size and thread is an OS .35 muffler screw? Are they the same for .25 through .40 engines?
Thanks,
Rusty

[Tim Wescott]

I have OS FP 20, OS LA 25, OS LA 40 and OS LA 46 engines.  They all use the same screw, which is a M3xmumble-mumble.  I'm almost certain that it's M3x0.5, and I'd be astonished if what fits the engines I have doesn't fit the FP 35.  I get them at the local farm store, which has a well-stocked hardware section.  If you're going to mail order I'll check the next time I'm downstairs and let you know for sure.

Get socket head screws, and make sure you have the right sized hex key -- cross-head screws are just asking for a stripped-out head.

It is M3x0.5.  30mm long is a bit much for the E2020 muffler on an FP20 or LA25, but works fine.  It's just right for the E2030 muffler on the bigger engines.

[Howard Rush]

How long are these screws?  I have some extras in a couple of sizes.

[RknRusty]

Thanks guys. I can probably get them at Grainger.

[Steve Helmick]

Ace Hardware should have what you need, but also don't overlook the R/C car shop down at the strip mall. If you go to the Ace place, also get a couple of 1/4-28 heat treated hex nuts. Nice to have them with SAE hex size instead of metric hex.   Steve