Working on a plane for a friend. The first 4-stroke I've dealt with and learning a few things....

It has a Reeves' carb mod according to the graphics on the plane. The tip of the nylon screw is distorted/melted, probably from running backwards. What shape should the tip be, or does it make any noticeable difference?

Since this is mounted inverted in a Legacy, it places the intake quite close to the cross-grain filler between the engine mounts. There is some charring and erosion. I was thinking about bonding in some type of heat shield to maybe make things less fire-prone. The first thought was a small piece of tin-plate material.  Anyone else doing something similar?

Thanks for the help,

Dave

Hi Bob,
can you please post an image with the inside side of the fuselage showing all the route of clean air to the intake.
And what effects can one expect in flight while flying without this fix?
I'm going to maiden my new ship with Saito 72 in a few days.

Regards,
Vitalis

Bob,
Thank you for your reply. It definitely helps.

This engine is set up as a OTIAS 62, and I didn't realize (I was the guy holding the plane) that the engine was being started "backwards" until I felt the air going the wrong way.... I also did not realize that they would run backwards continuously, or that the intake  becomes the exhaust and vice versa. With what I have heard since then, I would probably just stick my finger over the muffler to shut it down quickly, or maybe pinch the muffler pressure line to cut off the fuel?

We used a starter, but red to red doesn't work if the engine is set up for reverse rotation.... We will add that to the preflight prep list as well.

I will go ahead and just square up the end of the choke screw, since you are suggesting that a standard screw is preferred. I didn't know if it was supposed to have a taper on it or not. But now we will have to find the right position for the screw all over again. Is there a thread on how to do this?

I made a heat shield out of tin plated steel to screw down on the bearers that covers the wood around the inlet in case there is another mistake. No need to burn the plane up....

As far as the air scoop, I guess I am going to suggest to the owner that we try it out as is, with the air coming in via some really big cutouts in the Legacy cowling. I moved the bulkheads around, so there is now one right behind the intake, which should add a bit of cowl pressure. Rear intakes have worked well for me on racing planes, including B-TRs and F2C planes, so it is worth a go. It tended to stabilize the run and settings. Hopefully the big 4-stroker will do the same. If not, then a top-mounted air intake scoop lurks in the future....

I wanted to rebend the exhaust pipe per recommendations in a prior thread, but since it is not my engine, I didn't want to experiment with that process. I will rotate it so that a nose-over won't knock it off the plane--hopefully.

Thanks for the photos and the information,

Dave

Danish,

Can you be less cryptic about finger flipping methods for large 4-strokes? I'm beginning from zero here....

Do you mean that you slowly or gently flip backwards and expect it to kick forwards, knocking your finger out of the way, and starting? I know that works great on Mongo-compression engines like the Supertigre C35 if you get it wet before flipping. Safest method. On the other hand, I whack a K&B 40 pretty hard forwards (Dykes ring). Not much experience yet with 60's, but have an Enya CXL 61 Pro going into something soon and a rebuilt (sort of) K&B 61 that needs test running. Since these are 2-strokes, I'm pretty confident I can figure them out pretty quick. No such illusions about the Saito....

I use a glove anytime it is not a wood prop. I use a glove on a wood prop if I am unfamiliar with an engine's eating habits....

McDivot

Ok, I think I get your method for hand propping the beast. Thanks!

I just cut down the melted screw. It was plenty (too) long, so I knocked off a bit on the bandsaw then took it to the belt sander, and finally broke the edge with a file. Pretty much a flat tip.

If I can get the final trim colors on it, we can test out the engine again.

Dave

We got a chance to run the beast today. Stan brought it to the field and had everything ready. We used the electric starter exclusively. Started right up with a rich needle setting. Needed to turn in the choke screw from my guesstimated starting location. Did the published needle process but was still too lean to run when we tipped the nose up. Added a few more clicks until it would hold under all orientations. First flight was too much power--and then the pressure line came off the muffler and it became a strength contest.

Put a cable tie on the fitting and got ready to tune again. Reinforcements (Mike) arrived along with a tach to find the setting. Mike was able to set the choke and needle better, but we blew another hose connection in flight. These things must have ungowwa muffler pressure! By the last flight, had a decent setting (a bit rich) but it ran reliably and was getting usable lap times--somewhere around 5.1 seconds. Plenty of thrust everywhere. Need to get a time on the tank next. It's a 4 oz. Sullivan, but now there is room in the fuselage for a 6 oz. tank since we moved (replaced) the bulkhead.

So good progress but not quite dialed yet. Stan wants to take off a bit of the tail weight. Before the next session.