I have a Moki .61 long-stroke rear exhaust that I'm preparing to break-in. The question I have is do I break it in using the un-cut header and pipe? I'm planning on using 5% and am prepared to put at least a gallon through it prior to any header adjustments. I'm familiar with pipe tuning, but only on an engine already broken-in. It was suggested to me that I use only the header during the break-in, so I really need your help/ideas here. Thanks, Mark

K, I have the side exhaust version, when I got it I couldn't keep fuel at the carb, it turned out that the banjo shaped fitting that's bolted to the carb and serves as the fuel inlet was too large and air was getting in around it. I'd just run it with the pipe and header the way it is because you can't set the header length until it's broken in. It won't take much breaking in. I broke mine in on Fox 5% nitro fuel with 20% 50/50 lube.

I'd go ahead and join the header and muffler the way they are....too long.
The reason ? It's a low RPM, long stroke motor, and doesn't have to be
wound up real tight on the RPM's for break-in.

After you get a few tanks run through it, check the RPM and see if anything
needs to be done. See the head-pipe on this OS RF long stroke engine ?
I never cut the header because the engine was turning exactly what it was
supposed to turn....11,400, with a 12-8 Zinger, on 15% nitro.

See what the engine is doing before you break out the tubing cutter.

FBD.

Thanks Hobbsy and Dave, Do you know what I should be looking for as far as rpm's after break-in on the Moki and 5%?....Mark (ps how about a propeller recommendation as well)

My best guess is it would run right along side the OS pattern motor....

....mid elevens with a 12-8 Zinger. The Zinger turned out to be "Best Prop"
for my engine. Did you notice the plane is a an old Kaos ?

FBD.

How could I not? I especially like the the scorched fin! I'll be looking for the numbers soon. My first Moki. They way it's built looks like it could be a stump-puller. Thanks again...Mark

KAOS, the MOKI .61 has the same bore and stroke as the MVVS .61, 23mm bore x24mm stroke, the standard MOKI .61 was 24x22.5

Thanks again hobbsy. The weather here's so chilly, and work schedule so heinous I don't know when I'll get around to this, but now I have a place to start....Mark