Heartland

My Feedback: (9)

So yes, I bought an AP .061, and yes I got what I paid for.... and I will likely find a Norvel to put on the plane but would still like to narrow down the issue with the Wasp. By the way it's going on a Ziroli Mini Sukhoi.

Here's what happens. I can get the thing started, and it runs for about 5-10 seconds, then dies. Don't prime it, just flip-flip-flip-.... then it starts again, dies after 5-10 seconds. I could do this all day long. Now... when it is running, there's a good drip coming out of the front of the crankcase behind the prop hub. There is a lot of endplay in the crank (forward and backward slop). In fact, there's .011" endplay as measured with a feeler gauge between crankcase and back of prop hub. Also, the head gasket looks like a first grader cut it out of aluminum with some scissors. I don't get quite the satisfying "pop" when flipping through compression that I seem to remember with my little Cox motors.

I've taken apart the motor and flushed all parts with fuel. I believe there are two problems here, the lack of a good seal around the glowplug, and the crankshaft endplay. There's obviously a vacuum leak behind the prop hub since it's leaking so much.

So the crappy head gasket might make it hard to start and sacrifice lots of power. But my hypothesis is that the leaking crankcase is causing a vacuum leak so that I flip until enough fuel pools in the crankcase to get it started then that fuel burns off, and as it does gets sucked out of the crankcase eliminating any seal that the pooled fuel provided around the crankcase/crankshaft leaving a vacuum leak that prevents more fuel getting sucked into the motor to keep it running. Thoughts?

Like I said before, I'm going to find a quality motor to put on the front of the Sukhoi. Just want to see if I can figure out a solution for the AP, otherwise it's going back to the hobby shop for a refund. I bought the AP Hornet .09 a while back and the darn thing runs like a champ. I just don't want to put that on the Sukhoi since it's so dang heavy. It'll go on a trainer for the kids or some such thing.

combatpigg

My Feedback: (3)

The pumping efficiency can escape out the front of the engine. End play isn't as big a deal as axial play. When the engine is running, the prop is trying to pull the engine out the front. This is good, so the crank pin doesn't rub the backplate. .011" is quite a lot, though.
The good news is the AP cylinder / piston set is pretty good usually and a direct swap with Norvel.

Andrew

Welcome to the world of Chinese QC. Buying a WASP is a crap shoot. The good ones run OK; the poor ones run, well poorly. Although the crankcase is bushed, every one I've seen had a shoddy bushing/crank fit with quite a bit of side play. About the only thing you can do is use a high castor content fuel to get as much sealing as possible.

You're being kind describing the head gasket - replace it with a third party gasket (COX .049 gaskets are a dropin). You can get gaskets from [link=http://coxengines.ca/]COX International[/link] or Larry Driskill at [link=http://www.kittingittogether.com]Kitting It Together[/link]. That COORS can gasket probably contributes more to a poorly running engine than any other part. Be sure the gasket sits flush on the shoulder in the cylinder and that there are no chips stuck to the shoulder or bottom of the plug. You can also buff the bottom of the plug using 400 to 600 grit sandpaper with oil on a piece of glass.

The needle valve/throttle body thread fit is very loose and can suck air - add a piece of large fuel tubing that slips over the throttle arm retaining nut and over the end of the NV body. Make sure all screws are tight and that the backplate is tight. I have also replaced the carb O-ring seal with a thin donut cut from silicone fuel tubing. Sometimes the OEM O-rings are either hard, fit poorly or have taken set and fail to seal.

Use at least 20% nitro with 18 to 20% castor in your fuel. There's an old saying in my part of the country: "You can't make a silk purse from a sow's ear." Sounds like you didn't get a WASP, you got a PIG.

andrew

Heartland

My Feedback: (9)

There doesn't seem to be a lot of sideplay in the crank, at least not that i can easily see or feel. I know that when the motor is running the crank is pulled forward, so I wouldn't think the endplay would hurt vacuum that much, but it seems to be (leaking around front of crank), and I have no idea what kind of thrust bearing surface there is inside the crank. Any good ideas for popping the drive washer/hub off the crank so I can remove it from the case and check things out? The crank is the only part I didn't remove when I disassembled and flushed the motor.

I looked at the bottom of the plug and can see obvious machining marks, so I'll polish it. think I've got some 600 and 1000 grit. And thanks for the tip on the Cox gasket and sealing the needle valve body, I'll give those a try. BTW I'm running fresh Sig 1/2A fuel. Thanks for all the tips guys.

combatpigg

My Feedback: (3)

To feel for side play, grab the prop with force and try to rock it lengthwise with the crankshaft bore. It might be OK at 3 O'clock, but at 6 O'clock [for example] you might find slop. Even the slightest amount of "rocking" means it is junk.
A "dunk test" will quickly reveal leaks like this. You run an air line into the intake [make sure the intake port is open], pack clay around the air line. Make sure the piston is sealing off the exhaust port with at least a fresh prime. If there is SPI, you will have to plug up the exhaust port.
Now dunk the engine in a glass of water and blow into it with low pressure. If there is a leak out the front, back, carb or head, you will see a stream of air bubbles. This test can be rigged in less than 10 minutes and will eliminate a lot of "tire kickin'" and "hemmin' & hawwin'".

Mr Cox

To get the crank out just insert the prop screw all the way in and give it a gently tap or two, with the backside and piston already off.
A bit of heating can help too.

Sounds to me like it is not getting enough fuel while it is running, try unscrewing the nneedle some more and also check your tank height. If it is too high it may slowly sip in to start it but not able to draw enough while running. The muffler pressure is not very reliable either, given the poor seal of the muffler.

The sloppy crank in a new engine is a pain, but it is usually affecting the idle more than top end. Full castor fuel can help to seal a bit but there should be stuff coming out in the front, that is what lubricates the plain bearing.

Edit; Ooops there is no prop screw, just tap the crank from the front then...

Andrew

The WASP uses a tapered split collet, so it should tap out faily easily.

Secondly, the point CP made about sideplay not being uniform is important. The bushing in the engine I pulled down last night appeared to be bored offcenter. Sideplay 90 degrees to the cylinder was almost non-existant, but was significant along the axis of the cylinder, so you must check thru 180 degrees of rotation.