Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
The Regular Stuff: Chat, Buy, Sell, Off Topic, etc. => General Discussion - Scale Model Gas Engines - Hit & Miss - Throttle Governed - Non-Compression – etc => Topic started by: dsenechal57 on July 11, 2023, 01:17:25 pm
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Well done on finding and fixing an issue that would have baffled me for much longer!
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I believe I have found the issue. It appears that there is a defect in the Hall sensor that is causing a double-spark: one at TDC and the other about a third of the way to bottom. I removed the Hall sensor and positioned it higher (so only the bottom would be near the magnet on the rotor), adjusted the timing so the now-single spark would fire at TDC, and it seems to be running like a champ.
On a side note, the folks at stirlingkit had no interest in helping with this, or with providing a replacement ignition system. They only offered me a 15% discount on a future purchase. There are other companies that sell these little engines, so I'd encourage you to patronize them rather than stirlingkit.
I appreciate all of the suggestions and feedback that you folks provided.
Dave
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An update:
I believe the issue is in the wiring somewhere. On occasion, I can get the engine to run - sometimes continuously, and other times for 10-15 seconds. Other times, most often, it won't run at all.
I removed the spark plug wire from the spark plug. When turning over the engine by hand and holding the wire a short distance from the spark plug, most often, I do NOT see a spark at TDC. Sometimes I'll see a very faint spark, followed by a "faint-er" spark about a third of a revolution later. On rare occasions, I'll see a good spark.
Not sure what is causing this variation. It does seem to change as I move things around, but that may just be a coincidence.
I've contacted the seller. Hopefully, they'll be able to send me a replacement ignition system.
In spite of the difficulties, I still think this is a neat little engine, and looking forward to having it up and running again.
Appreciate all of the feedback!!
Dave
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Thank you.
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Bonjour Dave,
My engine had already the M3 threaded hole, this is why I tried an oiler, I would not have made a hole by myself to avoid any possible future guarantee issue.
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Thanks, Jan,
I'll give that a try.
Dave
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Years ago when i purchased my M90, i experienced the same sort of problem once...
The engine ran flawlessly, and then suddenly died, and was impossible to start again after.
It turned out to be some residue (maybe from manufacturing), that had placed itself on the exhaust valve, keeping it ever so slightly open at all times.
The fuel system is as simple as it gets on these, and the minute loss of vacuum from the non-sealing exhaust valve, was enough to prevent a proper intake of fuel.
As soon as the exhaust valve was re-seated (by merely flicking it a few times, and turning it around in its seat), the engine ran again...and has done so ever since.
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One more question, Raphael,
When you added your oiler, did you drill a hole in the sleeve? If so, any special trick to doing that, other than to make sure there are no burrs to score the piston?
Dave
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Merci!
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Bonjour David,
The different diameters are listed, I remember 3 or 4 mm but not 2,5 mm.
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Are they the M2.5?
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Bonjour David,
Here : http://www.microcosm-engine.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=brass%20oilers&inc_subcat=0&sort=20a&page=1
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Thanks again, Raphael,
Could you tell me the source for the oiler that you used on yours?
Dave
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Thank you Dave ;D
As I hope you know it, please note that this engine is made by Microcosm then sold by two or three resellers on eBay for example.
I don't know if they have stock of spare parts to send in case of customer request so I think you have been advised to buy one and I expect this will solve your problem, despite the fact other members of this forum didn't give yet an opinion.
If you wish following my (misa)dventures with my Hit & Miss engines, don't hesitate to have a glance to my "Hit and Miss et autres moteurs" YouTube Playlist https://www.youtube.com/@rhavrane/playlists and you will also learn French ;)
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Thank you, Raphael,
Yes, I thought that was a little strange, too. I have sent that information to the seller. I hope that they will recognize the issue and send a new ignition module. Rather than wait for their response, I did go ahead and order a new part. If the seller sends a replacement as well, then I'll have a spare.
I really appreciate your comments and input.
Dave
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Bonjour Dave,
What you describe is weird, I have never heard any of my engines having several sparks more ore less simultaneously, that doesn't sounds good to me as it doesn't make sense to have a spark when the first one has made the gas explode.
As I am not a specialist, I would just imagine that the electronic modules could possibly have an issue... Who would confirm or not ... ?
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Thanks for the replies thus far. Did a little more experimentation. The ground wire is securely attached to the engine, so that's not the problem. I checked the resistance on the electrode running through the spark plug, and it's around 14 kohms, which is reasonable, so I don't think it's the spark plug. Not sure what the gap is supposed to be, but it appears reasonable. When I turn the engine over, I hear a very faint spark at top dead center, but then another faint-er spark about 1/3 of a revolution later (slightly before it reaches bottom. Should there be two sparks, separated by a third of a stroke?
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Pull the plug, ground it to the head and spin the flywheel. You should see and hear a spark. If no joy….
— With these engines it is critical to maintain a tight ground wire connection. If I recall correctly with that engine, inside the wood base the wire can be seen secured by one of the motor mount screws. If that comes loose, it can cook the electronics. Tighten the ground, repeat the plug test and hope.
— If the ground was tight, it could be the Hall Sensor. In this forum there have been discussions about the sensor failing, ways to test and replace it, and sources of that individual part.
Otherwise, EngineDIY has a replacement ignition system https://tinyurl.com/bdekhf47
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Bonjour Dave and Welcome,
https://youtu.be/Q91Ju0Peu2Q
As you can see it (and I have made other videos on my tests), I also have this M92 and had a lot of difficulties to make it run. Gil ;) helped me to solve my problems.
At first, you have to check if you have a spark plug whose electrodes have a spacing slightly less than 1 mm and of course a spark almost at the compression point.
Of course, the gas should go to the carburator.
The plug should not be wet because too much of gas (I use Unleaded 98 + a drop of 2 stroke oil).
The needle valve is open about 1/2 turn and is awfully sensitive, especially when the engine warms up.
If it doesn't start at all, try a few more opening degrees if it starts and stop, close.
I hope this will help you, good luck and let us know your progress / success !
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First off, "Hello"! Glad to be a member of this forum.
I received my M92 last week, and it ran great right out of the box. Using lighter fluid as fuel, and oiling the moving parts occasionally with light oil applied with a blunt-tip syringe. It ran well for almost a week, but a couple of nights ago, as it was running smoothly, it just stopped. Hasn't run since. I've changed the batteries, drained and refilled the fuel, and verified no crud in the carburetor. Compression seems fine. Nothing made a difference. I'm thinking/guessing that it might be the ignition module?
Questions: 1. Any thoughts on what might be the cause, or other avenues I might explore? 2. Where's the best place to purchase replacement parts for this (I bought it from sterlingkit).
As an aside, I did send them an email, and received a reply to "please send photos showing the problem". Not wanting to be a smart*ss, I refrained from sending a picture of the engine not running.
Thanks!!
Dave