Stihl MS660 big bore conversion.
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#202
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Lord Mounts revisited!
Please see the original post over on our Manilla Slope Fest thread:
http://www.rcgroups.com/forums/showp...postcount=1062
Please see the original post over on our Manilla Slope Fest thread:
http://www.rcgroups.com/forums/showp...postcount=1062
#203
[QUOTE=Jim.Thompson;12247263...
It is running the best it ever has now with both needles fully closed! ...
The elevators are vibrating at an alarming rate and at a large magnitude; I suspect that this is working the servos hard and draining the batteries....[/QUOTE]
IMHO, having to run any engine with both needles closed does not indicate the problem is fixed. Re the servos jittering seems to me to be either a radio issue or that the spark plug cap is not fully seated. Is it? Probably addressed before, but has this engine ever run correctly with the needles set to nominal positions? What have you done since then to make it not run right?
It is running the best it ever has now with both needles fully closed! ...
The elevators are vibrating at an alarming rate and at a large magnitude; I suspect that this is working the servos hard and draining the batteries....[/QUOTE]
IMHO, having to run any engine with both needles closed does not indicate the problem is fixed. Re the servos jittering seems to me to be either a radio issue or that the spark plug cap is not fully seated. Is it? Probably addressed before, but has this engine ever run correctly with the needles set to nominal positions? What have you done since then to make it not run right?
Last edited by spaceworm; 08-17-2016 at 03:31 PM. Reason: change "batteries" to "servos"
#204
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This all just isn't making sense my friend. Indeed, the servos moving that way is not ok, and indicates some sort of a problem with the ignition system, though I can't say that is the only problem you have. That problem may indeed be only the spark plug cap not on tight. You have to push them on very hard. You should also be running a resistor plug just to be safe.
It sure seems odd that you had it running perfectly on the test stand, and now on the plane it won't. That tells you something right there.
I think it is time to offer a case of XXXX Gold to someone familiar with small engines, and hopefully in aircraft applications, to come spend a couple of hours with you sorting it......
Sorry, but we are trying from here the best we can,
AV8TOR
It sure seems odd that you had it running perfectly on the test stand, and now on the plane it won't. That tells you something right there.
I think it is time to offer a case of XXXX Gold to someone familiar with small engines, and hopefully in aircraft applications, to come spend a couple of hours with you sorting it......
Sorry, but we are trying from here the best we can,
AV8TOR
#206
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There was a problem with some of the big bore piston and cylinder kits for the 660 having the piston skirt touch the counter weight and also some kits the cylinder flange extension would touch bottom of the seat in the crankcase and hold the cylinder mounting flange off the crankcase.
Maybe this is causing vibration?
Maybe this is causing vibration?
#207
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There have been SO many changes going on with this project it's difficult to determine what are the problems currently?. Any suggestions are at best a guess because of this, AV8TOR is right in my opinion.
My last suggestion is to obtain good local assistance even if payment is required!
My last suggestion is to obtain good local assistance even if payment is required!
#208
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This all just isn't making sense my friend. Indeed, the servos moving that way is not ok, and indicates some sort of a problem with the ignition system, though I can't say that is the only problem you have. That problem may indeed be only the spark plug cap not on tight. You have to push them on very hard. You should also be running a resistor plug just to be safe.
It sure seems odd that you had it running perfectly on the test stand, and now on the plane it won't. That tells you something right there.
I think it is time to offer a case of XXXX Gold to someone familiar with small engines, and hopefully in aircraft applications, to come spend a couple of hours with you sorting it......
Sorry, but we are trying from here the best we can,
AV8TOR
Sorry, but we are trying from here the best we can,
AV8TOR
Despite all that, every single small problem that has been found, I found myself just by perseverance, asking questions here and on the other thread and reading the answers here, such as yours etc.
I dearly wish it was just a case of "take it to an expert" and all will be quickly and easily solved.
Many thanks again for your comments though! I don't wish to appear unappreciative.
Jim.
Last edited by Jim.Thompson; 08-18-2016 at 08:06 PM.
#209
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I will defer any more answers to this thread until after our coming slope flying festival. This is my #1 flying event of my calendar and I want to have a clear head when preparing my fleet of gliders and sharing the company of the many fellow flying friends who will be there.
I should note that I will take the next month or two to review my options. These include looking a proper engine, short listed is a horizonally opposed twin cylinder 120 cc or thereabouts - DA120 or the like.
I am advised this so called boxer configuration is superior in terms of vibration.
Besides, I am aware that I am beginning to ask far too much from others including you respondents.
I should note that I will take the next month or two to review my options. These include looking a proper engine, short listed is a horizonally opposed twin cylinder 120 cc or thereabouts - DA120 or the like.
I am advised this so called boxer configuration is superior in terms of vibration.
Besides, I am aware that I am beginning to ask far too much from others including you respondents.
#211
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Vibration as severe as you describe is totally unacceptable and may be contributing to your running/tuning problems. Your prop hub may not be true, or your crank may be bent or twisted.
AV8TOR
AV8TOR
#212
Have you checked/double-checked the spark timing? Rough idle and hard starting can often be caused by the timing being off.
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#217
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Here we go Av8tor: http://www.rcgroups.com/forums/showp...postcount=1543
Some description here: http://www.rcgroups.com/forums/showp...&postcount=778
Some description here: http://www.rcgroups.com/forums/showp...&postcount=778
#218
Here we go Av8tor: http://www.rcgroups.com/forums/showp...postcount=1543
Some description here: http://www.rcgroups.com/forums/showp...&postcount=778
Some description here: http://www.rcgroups.com/forums/showp...&postcount=778
Sincerely, Richard
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Fortunately, the damage is minor and I have already started to repair it. Building and repairing is good therapy for me, as I am competent at that. Makes me move on psychologically from the crushing feeling following the crash and the feeling of incompetence that comes with it.
One of my buddies will fly the plane for towing next year, I am sure.
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The Stihl still has an intermittent miss-fire, mainly at high RPM. It can be heard in the flight video here: https://www.youtube.com/watch?v=wwYrNwiMv2I
I have already reduced the spark gap to .5 mm, as with the recommended .6 mm gap, the engine suffered from high RPM spark breakdown and would not take full throttle at all. There are a number of possibilities I can and will explore when I get the time. I will bench mount the engine again and test until I get it sorted. I am not as rushed now that the plane has been inspected, registered and test flown.
Options include:
1. increase the spark gap up to .55 mm.
2. Decrease the spark gap down from the already .5 mm.
3. Change the plug to a hotter/cooler rated one.
4. Change the CH brand CDI --I have a cheaper Pegasus one from HobbyKing.
Beyond that, I don't know what to do. The battery power supply is 6.6 volt LiFe.
Any other suggestions most welcome.
I have already reduced the spark gap to .5 mm, as with the recommended .6 mm gap, the engine suffered from high RPM spark breakdown and would not take full throttle at all. There are a number of possibilities I can and will explore when I get the time. I will bench mount the engine again and test until I get it sorted. I am not as rushed now that the plane has been inspected, registered and test flown.
Options include:
1. increase the spark gap up to .55 mm.
2. Decrease the spark gap down from the already .5 mm.
3. Change the plug to a hotter/cooler rated one.
4. Change the CH brand CDI --I have a cheaper Pegasus one from HobbyKing.
Beyond that, I don't know what to do. The battery power supply is 6.6 volt LiFe.
Any other suggestions most welcome.
Last edited by Jim.Thompson; 09-23-2016 at 12:13 AM.
#221
My Feedback: (11)
Jim,
Do you encounter miss fire on the stand when you on the ground on the stand?
Try to do the same test and go to 7.4v. This will put more power out of CDI.
It could be 3 things.
1- the High compression of the engine may kill the spark and the spark will jump to ground in the cap or inside. 7.4v should give more voltage.
2- the spark plug style . With exposed Portelan or NOT. Some times this makes a difference. Gap also need to be right. See if you can find the right gap that Sthill recommends for that engine.
3- Carb adjustment, May act different in flight than on the ground. If the metering diaphragm gets bothered by the air around the hole.
Some people solders a little brass tube on the Metering plate and runs a tygon tubing in to the fuselage .
It could get rich, then high compression will make it misfire.
Those will be my thoughts on this issue.
Adrian
Do you encounter miss fire on the stand when you on the ground on the stand?
Try to do the same test and go to 7.4v. This will put more power out of CDI.
It could be 3 things.
1- the High compression of the engine may kill the spark and the spark will jump to ground in the cap or inside. 7.4v should give more voltage.
2- the spark plug style . With exposed Portelan or NOT. Some times this makes a difference. Gap also need to be right. See if you can find the right gap that Sthill recommends for that engine.
3- Carb adjustment, May act different in flight than on the ground. If the metering diaphragm gets bothered by the air around the hole.
Some people solders a little brass tube on the Metering plate and runs a tygon tubing in to the fuselage .
It could get rich, then high compression will make it misfire.
Those will be my thoughts on this issue.
Adrian
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Try to do the same test and go to 7.4v. This will put more power out of CDI.
..........................................
2- the spark plug style . With exposed Portelan or NOT. Some times this makes a difference. Gap also need to be right. See if you can find the right gap that Sthill recommends for that engine.
3- Carb adjustment, May act different in flight than on the ground. If the metering diaphragm gets bothered by the air around the hole.
Some people solders a little brass tube on the Metering plate and runs a tygon tubing in to the fuselage .
Some people solders a little brass tube on the Metering plate and runs a tygon tubing in to the fuselage .
..................................
Those will be my thoughts on this issue.
Adrian
Adrian
edit: The spark gap recommended for this engine is .5 mm. See attached screenshot of the service manual.
Last edited by Jim.Thompson; 09-23-2016 at 01:22 PM.
#223
My Feedback: (6)
Great job Jim. Very nice plane, and great flying. It's neat to see a low wing plane built as a sport plane/tug instead of a high wing. I like it!
In the first video, I thought I heard some occasional rich misfiring, and was going to suggest a one screwdriver width adjustment leaner on both needles and see how it did. However, if you have tuned back and forth and can't get rid of it, then it probably is the ignition. Shot gun it. Replace the ignition, the sensor, and the spark plug, and bypass the ignition switch and run straight from a known good battery. But please, use a new CH or RCEXL, (or RCEXP), and not the Chinese Pegasus.
Great quality ignitions at both of these places:
http://www.rcextremepower.net/rcxpignitions.html
https://www.ch-ignitions.com/product...ns/single-cdi/
Good luck, you'll get it there.
AV8TOR
In the first video, I thought I heard some occasional rich misfiring, and was going to suggest a one screwdriver width adjustment leaner on both needles and see how it did. However, if you have tuned back and forth and can't get rid of it, then it probably is the ignition. Shot gun it. Replace the ignition, the sensor, and the spark plug, and bypass the ignition switch and run straight from a known good battery. But please, use a new CH or RCEXL, (or RCEXP), and not the Chinese Pegasus.
Great quality ignitions at both of these places:
http://www.rcextremepower.net/rcxpignitions.html
https://www.ch-ignitions.com/product...ns/single-cdi/
Good luck, you'll get it there.
AV8TOR
#224
My Feedback: (6)
Just listened/watched the latest video you posted. It is definitely rich on the low end. The high speed miss is questionable. I would still try a new ignition. If it runs fine on the ground from idle to half throttle, but goes rich in the air, then it is pressurized air in the cowl as described by Adrian. You can plug that Stihl rectangular regulator cover vent with something like epoxy, (I use Seal All), then drill and tap it for a fitting and run a vent line into the fuselage. I do this on all my planes.
If you can't get it to run lean enough to not four stroke while flying at low to mid range power, but still give good throttle response, then try a larger prop. It sounds like your prop unloads quite a bite even in a mild dive, which makes me think you have plenty, if not too much pitch. Try going with a larger diameter. It will load the engine harder, possibly help with leaning the low end/mid range out, and give you a thrust boost as well.
AV8TOR
If you can't get it to run lean enough to not four stroke while flying at low to mid range power, but still give good throttle response, then try a larger prop. It sounds like your prop unloads quite a bite even in a mild dive, which makes me think you have plenty, if not too much pitch. Try going with a larger diameter. It will load the engine harder, possibly help with leaning the low end/mid range out, and give you a thrust boost as well.
AV8TOR
Last edited by av8tor1977; 09-24-2016 at 02:01 PM.
#225
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In the first video, I thought I heard some occasional rich misfiring, and was going to suggest a one screwdriver width adjustment leaner on both needles and see how it did. However, if you have tuned back and forth and can't get rid of it, then it probably is the ignition.
Shot gun it. Replace the ignition, the sensor, and the spark plug, and bypass the ignition switch and run straight from a known good battery. But please, use a new CH or RCEXL, (or RCEXP), and not the Chinese Pegasus.
Also, I am watching and reading about a string of Rxcell ignition problems/failures on the Bull BE124 engine thread with some concern.
Your shotgun method is what I will use.
Thanks again.
Great quality ignitions at both of these places:
http://www.rcextremepower.net/rcxpignitions.html
https://www.ch-ignitions.com/product...ns/single-cdi/
Good luck, you'll get it there.
AV8TOR
http://www.rcextremepower.net/rcxpignitions.html
https://www.ch-ignitions.com/product...ns/single-cdi/
Good luck, you'll get it there.
AV8TOR
Last edited by Jim.Thompson; 10-05-2016 at 11:56 PM.