Need Engine Gurus

You haven't told us what you tried already. Is the engine running lean or hot?

In order I would try:

1. Replace glow plug.
2. Check for carbon build up.
3. Change to 5-10% nitro sport fuel.
4. Clean out needle and carb.
5. Check for leaking crankcase.

Good luck.

I'd say gas flow is being restricted somehow. Either in the intake, or by a partially blocked exhaust. Or indeed valves.

11x6 prop on a 61?? I'm running an 11x6 on a GMS 47.

Try a new glow plug (for kicks). New fuel? Replace the o-ring on the needle valve. Make sure you are getting muffler pressure to the tank.

John VB

Out of curiosity, has it ever been disassembled?

Mike D.

On 5/26/2004 11:03 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

First, I would not suggest running an 11 x anything on a 61. Stay with a 12 or MAYBE even a 13.

Replace the glo plug (an OS #8 or similar 'HOT" plug should help) and try some fresh fuel from a different jug.

Check for air leaks, especially around the backplate and carb also check the head gasket to make sure it isn't leaking.

Replace ALL the fuel lines including what is in the tank. Sometimes "older" fuel lines can partially collapse when the engine is under a load.

What's wrong with running 11 inch props on a .61?

Dave

An old R/C engine repair specialist (since retired) once told me that the majority of his poor running repairs were caused by the idle adjust screw being too lean. Try backing the screw out a 1/8th turn and see if thats an improvement or not.

Harry

We can make a box of wood.....FLY!!

In addition to all of the above, check the head bolts and sleeve alignment. (I don't know if the FX has a pinned sleeve) I had an engine was running great right up to the point where it died in the air. Found that the head bolts were lose, tightened them but couldn't get the engine started. Pulled the muffler and looked in the port. The sleeve had rotated and shut off most of the ports. Good Luck Bill

Might try the engine with the muffler off, I've seen plugged exhausts kill 2 strokes all sizes.

On 5/27/2004 11:20 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

IMHO, an 11 inch prop is too small for a 61 engine. The 12 inch does the job just as well without the risk of over revving the engine. If you have to have an 11 inch prop for clearance purposes, use a 3 blade prop.

Actually - an 11x7 is THE recommended prop for a .61 2 stroke engine... at least from my past 20 years of experience and the prop charts I have or have seen. I have used 12 and 13 inch props as well, but the 11x7 is the old standby.

Your actual mileage may vary...

FRedD

11-6 won't hurt a .61, although it may not be the most sensible prop for many applications. It will just run a little faster (and likely cooler..) than say an 11-7 or 12-6. As you say, 11-7 or 11-7.5 is/was a standard prop for them, until noise abatement issues pushed pattern fliers to larger props and higher pitch and the resulting lower rpm, making this somewhat of a new standard. I've run 11-6 on smaller models many times esp. with older 10cc motors, they tach out in the region of 13k which certainly isn't excessive. Whatever his problem is (I asked about disassembly wondering if the sleeve had been rotated, not knowing whether it has an alignment pin or not) the 11-6 won't exaggerate it nor be a part of the cause.

Mike D.

Ted,

All engines and airframes are not created equal, or for the same purpose. A low-end, plain bearing .61 might be perfectly happy running a 12 x 5 or 12 x 6 on a draggy, light weight Big Stick-type aircraft, but a high-end, highly tuned ball bearing .61 in a clean pattern ship with retracts and a relatively high wing loading is quite different matter.

I've been flying a Bridi Super Kaos for over 20 years and I used 11 x 7 to 11 x 7.5's on the first engine (a Super Tigre G.60 Bluehead) and currently, I'm using an 11 x 8 on a fairly strong Super Tigre G.61. I've tried other props and always come back to the 11 x 8 for this particular combin- ation. If I recall correctly from the owner's manual, Super Tigre actually recommended 11 x 7's or there abouts for both of these 60-size engines.

My current G.61 sports a Perry carb and Perry Pump plus a tuned muffler and it swings the 11 x 8 at about 12,400 RPM static on 15% sport fuel. I seriously doubt that as the engine unloads in the air that it even gets close to the RPM Super Tigre rates maximum horsepower at, which is stated as 16,000 RPM. My Super Tigres have survived many years and hundreds and hundreds of flights and are still in good shape. I like my Kaos to go fast... and it does! (straight up, too). :-)

Dave

Ted Campanelli wrote:

Ted,

All engines and airframes are not created equal, or for the same purpose. A low-end, plain bearing .61 might be perfectly happy running a 12 x 5 or 12 x 6 on a draggy, light weight Big Stick-type aircraft, but a high-end, highly tuned ball bearing .61 in a clean pattern ship with retracts and a relatively high wing loading is quite different matter.

I've been flying a Bridi Super Kaos for over 20 years and I used 11 x 7 to 11 x 7.5's on the first engine (a Super Tigre G.60 Bluehead) and currently, I'm using an 11 x 8 on a fairly strong Super Tigre G.61. I've tried other props and always come back to the 11 x 8 for this particular combin- ation. If I recall correctly from the owner's manual, Super Tigre actually recommended 11 x 7's or there abouts for both of these 60-size engines.

My current G.61 sports a Perry carb and Perry Pump plus a tuned muffler and it swings the 11 x 8 at about 12,400 RPM static on 15% sport fuel. I seriously doubt that as the engine unloads in the air that it even gets close to the RPM Super Tigre rates maximum horsepower at, which is stated as 16,000 RPM. My Super Tigres have survived many years and hundreds and hundreds of flights and are still in good shape. I like my Kaos to go fast... and it does! (straight up, too). :-)

Dave

Was taught WAY long ago Heli fuel has a higher oil content and protects engines better. I'm thinking the most probable suggestion of all the good advice and answers I've gotten is in the fuel. Thinking about it I have two engines that just aren't running right and the last run on a new Jett 50 BSE engine also didn't come up to it's RPM's. The engine hasn't ever had a rapid deceleration landing, compression feels about the same and the glow plug holds it's RPM's when I take the heat off, & I may have already changed it, just don't remember. Run this engine on OS-8 plug & my 4 strokes on OS-F's. Thanks to all, I'll let you know what it turns out to be- or if it turns out to be a new engine & plane...lol. Thanks again to all, Andy

We can make a box of wood.....FLY!!

Yep, they sure can. I once spent ages trying to help a friend get her 2 stroke motor scooter going after she had let it stand in the shed for a few weeks - changed the plug, cleaned out the carby, sat scratching my head in bewilderment

- it was getting fuel and spark, but wouldn't go.

Eventually, in desperation took it to a bike mechanic. Bloody wasps had plugged up the muffler with their mud nest.

David

BCarney147 wrote:

I worked on a friend of mine's weedeater and he told me the same thing. Just put it in the shed and week later it wouldn't run. Not even pop. I finally found the dirty dirt dobbers nest in the exhaust and removed it. Couldn't get the fuel in cause it didn't have anywhere to go. Eddie Fulmer