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91 Four Stroke Surpass

Old 11-15-2014, 02:35 PM
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Tony Iannucelli
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Default 91 Four Stroke Surpass

I've got three others of these engines running in warbirds, all running very well. I use 20-20, OSF plugs, 15-6 props and run all of them on the slightly rich side. Back flip starts, great transition, etc.

I got a new one from a friend's estate, never run, but it had been sitting for a few years. It felt and looked perfect when I got it. I installed it in a new plane using all the same stuff I use all the time. Clean new tank, new lines, etc. It started and ran for a few minutes and quit. Hasn't run since. I sent it to Hobby Services and got it back a few days ago. They replaced the main bearings - which looked fine to me, after all, they've never run, but whatever. They also told me the timing was wrong, and that "turning it over dry" probably caused that to happen. ??? I've got 43 years in the hobby, 40 of them with OS engines, and never heard that one before. Anyway, $100 later, I installed the engine and it won't run. It's getting fuel ... if I block the muffler, it drips on the ground when I choke it. Idle screw is out about 2.5 turns, main about 2.75. If I blow into the vent line, fuel comes out the carb line. The lines are new, and big enough. Tank elevation is correct. No restrictions I can see. The engine is mounted on a 45 degree angle. I have another inverted, and two others side mounted. No issues. Before I send it back again, what am I missing? By the way, new OSF, using three different glow igniters that work fine on everything else.

Thanks for your help. Even though this is an older Surpass, it was/is new, and it should run as well as the others I have. I hope the latest repair is warranted and covers the next one. --Tony
Old 11-17-2014, 08:39 AM
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Bax
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If you have a good plug, good compression. and good fuel, the engine should fire and run. the 45-degree down angle is the problem. That allows fuel to drown the glowplug. With an electric starter, you may be able to get it to run if you start out with it dry, but choking it will only add liquid fuel to the cylinder and drown the plug.

Your best bet is to put the engine on a test stand, mounted upright, and get it tuned so that you're confident it's running well. Then put it in the airplane and be very cautious about priming it.
Old 11-17-2014, 01:49 PM
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Tony Iannucelli
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Well, I've considered that the 45 degree angle is the issue, but I'm not convinced. As I mentioned above, I run another OS91 inverted, no issue ever. As you know, these engines love to be wet to start. Two others are side mounted, no issues. I pulled the engine from the plane, opened the back plate, and the engine was essentially dry inside. I pulled the plug, and it was also perfect. So I guess I was wrong. The engine is NOT getting fuel sufficient to start. Dripping from the muffler is not an indication the fuel is getting to the plug apparently. My #1 glow igniter is computer controlled and puts out 1.4 volts minimum-constant. It would let me know if the plug was drowned out. I blew on the vent line and the carb line flows perfectly. I'm starting to suspect the carb may be clogged in some way. I sent the engine to Hobby Services again, with details.

I've run many planes with the engines at a 45. Never an issue. I had an OS70 that ran perfectly mounted that way in a UCANDO which had a high tank level, as you know.

Meanwhile, I'm going to install another 91 that I know runs well but before I do I'm going to fly it again in the plane it is currently in. I'll let you know the results. Thanks for you help. It's difficult to diagnose something like this from 1,000 miles away, and I appreciate it. I hope Hobby Services runs the engine. I'll let you know.

I might have to put a trusty OS61SF pump in it, but I hate to cut up that cowl. Thanks again, Tony

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Old 11-18-2014, 05:22 AM
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microdon2
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Tony - I have a similar problem - my old OS 91 Surpass starts but then stops almost immediately. I've gapped the lifters, HS is a 2 turns, new F plug, good compression, bearings are fine, LS needle is at 2nd ridge perpendicular to the carb throat. Tank and tubing are fine. I'm going to open the LS a bit - but maybe there is a blockage in the carb, as you say. Any other thoughts on your end?
Old 11-18-2014, 05:51 AM
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Tony Iannucelli
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You have the advantage in that your engine was running ... mine is new except for running a few minutes initially and then never after. Air, fuel, heat.... that's all these engines need. We know the heat is there, new glow plugs. We know the carb barrel opens and closes, so it's getting air. Only other thing is fuel. Fuel pours out of the carb line when I puff on the vent line. So the fuel is there, at least to the carb nipple. Something is blocking the fuel in mine to the cylinder head / heat. Mine doesn't even run out the prime after I choke it. It doesn't get the prime. When I sent the engine to Hobby Services --who are generally great in their service-- I was disappointed to see they changed bearings in my engine to the tune of $50+ labor. The bearings didn't need changing. Even if they were bad which they weren't, that has nothing to do with the engine not starting which is why I sent the engine in to them. They said the timiing was off and it was because I "turned it over dry". Sounds like they think I'm either not awake or this is my first engine. It's actually about engine #50. I have now sent it in again. So far I'm out $120 with shipping and all, and so my point is simply don't send in the engine. I'm sure they didn't even run it.

Back to your issue. Your engine is running out the prime. It's not drawing fuel on its own from the tank. Could be an air leak somewhere. Could be dirt in the lines. Remove the main needle completely, and see if you can hear air coming through the carb when you blow into a line you connect to the fuel nipple. Open the idle screw a bit. Leave the igniter on the plug if it starts, and see if it keeps running. Increase the nitro in your fuel. Try fresh fuel. If the bearings are really sticky or gritty, replace them. In your case, new bearings might help. Boca Bearings here in Florida have a wide selection and I highly recommend them. Get good bearings, not the economy grade. Those are my only ideas, and please forgive me if some of my suggestions insult your knowledge. I know that hurts...
Old 11-18-2014, 06:58 AM
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Tony -

I agree - it seems like I'm running out the prime, and that it's not drawing fuel on it's own from the tank. I failed to mention that I just changed the lifter springs in this engine - one had broken, so I used two I had from another, wrecked OS 91 Surpass. (getting those spring retainer pieces into place is the hardest RC engine thing I've ever done - those guys MUST have a tool for this...). Could be that - when I reassebled - I didn't seat the manifold \ tube between the carb and the piston head totally - that could explain an air leak. (though it's bolted in now - you'd think it SHOULD be seated correctly). Will also test fuel flow into the carb, as you suggested.

For your engine issue, I'm really surprized they would change the bearings, as it's a new engine, and I don't get that "turned it over dry" comment at all. How would that affect timing? I don't think those engines can even skip gears. Did you check the valve lifter gaps? (though that should also be good, since it's new). Also, did you try mounting this engine vertically, just for this test?

Thanks for your input.

Mike D
Old 11-18-2014, 07:39 AM
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I sure don't understand what happened. I see the invoice comments about it, but nothing about timing. With gear-driven timing, you cannot have the engine change timing whether it's wet or dry. To change timing, the cam gear and/or crankshaft gear would have to be severely chewed up. I also don't see that the engine was run. If that engine continues to be a problem, PM me, and we'll get your engine straightened out.
Old 11-18-2014, 07:47 AM
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Tony Iannucelli
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Hi Mike. Regarding my engine, it's like they say, "new old stock". This engine did sit for several years mounted in a plane but never fueled in my buddy's shop. When he passed away last year, I bought it from his estate, which I also helped liquidate. It was installed in my Heritage Focke Wulf a couple of months ago, and I attempted to start it for the very first time and fly the plane just a few weeks back. The rest you know.

The connection on your engine from the intake tube to the cylinder head has a gasket. Did you remember to put that in and is it OK? Something I would forget, which is why I mention it. If it was nicked, that would be something I'd either replace or get some high temp silicone on it. My gap is about .05mm on the valves. I think that's about correct. I didn't adjust them, that's factory. Yours should be OK if you watch them work when you turn the engine over by hand. I have not mounted my engine vertically. I hope they do that at Hobby Services. I'd be happy to eat crow if it runs and that was the only reason. Keep in mind they suggest INVERTING these engines in their Top Flite 90 size warbirds. I can't remember when I've seen any four stroke engine mounted vertically in anything but a sport type or trainer plane at the field or in manuals. I currently have another Focke Wulf with an OS at 45 degrees, a Spitfire with one inverted, and two others with side mounted 91s. No issues. But like I said, crow would taste fine if the darn thing runs. I also have a YS in a Kyosho Stearman that's been flying for 15 years with no issues -- although lately I wore that engine out. I'd love to wear out this OS.... Some pics to prove my point..... At-6 side mounted, Spitfire, inverted, FW on the side, Stearman at a 45.

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Last edited by Tony Iannucelli; 11-19-2014 at 06:19 AM.
Old 11-19-2014, 06:18 AM
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Tony Iannucelli
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Hi again Bill. I sent you a PM. Please let me know if you received it. Thanks, Tony Iannucelli

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