Model hit or miss ignition fail
- Thread starter dkwflight
- Start date
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Don't go below 100: 1 if that's all the oil that bearings get. (50:1 is as lean as permissible for 2-strokes on Motorbikes to avoid crank failures!) - But should be OK for you if you are sure you need top-end oil??? Why are you using mix on a "4-stroke" engine? I suggest you simply lean the mixture a bit as the soot looks dry, not "oily". Don't worry about ethanol, unless you have elastomers anywhere on the fuel side, of soft-solder... Both can suffer badly with Ethanol. A regular spark-plug is a good as a "rim-fire" - according to my ex-colleagues in Engine Design and spark-plug suppliers. It's the central electrode that fails "flash-over) when enough soot covers it. All plugs have basically the same central electrode. Modern materials have special alloy earth electrodes that resist electrical erosion so much that the extra earths on a 3 side earth plug are a waste of your money. !00 years ago they were a great innovation to prolong the life of a plug: (3 gaps in parallel lasted 3 times as long) - when a plug only lasted a couple of thousand miles before re-setting. But today's plugs last >30,000 miles (subject to engine and load). And no-one needs a 100,000 mile lifetime plug! The real modern failure mode is the insulator surface degradation - NGK have the "best" clays (natural in their part of the world) but Champion have special clays within 1% of the NGK clays, so what the hell! (Bosch import clays as far as I understand? - Who knows?). Your plugs are suffering from TEMPERATURE - being so low in the hit and miss engine. You NEED a plug to run hotter (Not a plug for a hotter engine!) - like a plug for a 2-stroke engine, so the electrode and part of the insulator get hot enough to burn-off the carbon. But eliminate the carbon as much as possible by leaning the mixture. Just as much so it still runs well, but hopefully with almost no soot in the exhaust. You'll never have a hit and miss engine running clean because they run so cool (1 firing every 10 strokes or so? - LOTS of cooling and only 10% is heating...). But you can tune them to the "cleanest" condition to reduce de-coking frequency.
Hope this is some help?
K2
Hope this is some help?
K2
Sounds like you have naturally raised the compression by fixing the leak... so you can lean the mixture for the increase of actual compression as a result. (Higher compression takes a leaner mixture to ignite - because it is hotter as compressed - until you get to 14:1 = Stoichiometric air to fuel ratio... But you will know that I guess). Keep us informed of the results of further fettling and tuning... this is the interesting bit that people "learn hands-on" and there are no text books explaining this experience. Perhaps when you reach "Nirvana" with the tuning you can list all the little tweaks you employed to get there? A useful checklist for all and sundry... Just what this chat line is all about!
Regards,
K2
Regards,
K2
Hi
I bought some non ethanol 90 octane.
The engine runs better on this stuff. I was able to lean the mi several clicks.
It will be running along and the it quits firing, much like I shut the ignition off.
I do have a different spark plug coming to try,
I bought some non ethanol 90 octane.
The engine runs better on this stuff. I was able to lean the mi several clicks.
It will be running along and the it quits firing, much like I shut the ignition off.
I do have a different spark plug coming to try,
I think you should advance the ignition to just after TDC - or hopefully you can get it to run better with ignition at of before tdc. But it is TIME related - I.E. The speed of the crank at firing affects when the combustion develops max. pressure. This should be after TDC. Ignition too early before TDC will cause high stress on the con-rod and bearings. Early motorcycles that could idle at a few hundred rpm had manual ignition levers. These would be set advanced of TDC when running at rpm in the thousands, but just below 1000 rpm would need to be retarded to a setting from 5 degrees of advance before TDC, in some cases to some retard of 5 or 10 degrees after TDC. But my experience doesn't cover the ignition timing for your engine. I guess that as it fires when the revs drop down to 300 to 600 rpm (determined by when the governor allow it to fire), you may need 20 or 30 degrees of retard after TDC. But not more than 30 degrees after TDC.
Where is it set now? How easy to adjust - maybe in 10 degree intervals? As an experiment? I am sure you should find some settings for a similar engine from somebody with one, or on the interweb...
I am interested to hear how you progress.
Regards,
K2
Where is it set now? How easy to adjust - maybe in 10 degree intervals? As an experiment? I am sure you should find some settings for a similar engine from somebody with one, or on the interweb...
I am interested to hear how you progress.
Regards,
K2
Hi
I have not tried to set timing. I took a vid to shows timing. THe advance is only a couple degrees. I don't think I will try to change it. If I was doing the initial set up I might have gone for firing at TDC. In fooling with a weed wacker engine I set the timing for that RC lane conversion I set the initial start timing at 0 degrees TDC for hand starting. That conversion had an auto advance that , once running the timing advanced automatically.
This engine is set mechanicly
I have not tried to set timing. I took a vid to shows timing. THe advance is only a couple degrees. I don't think I will try to change it. If I was doing the initial set up I might have gone for firing at TDC. In fooling with a weed wacker engine I set the timing for that RC lane conversion I set the initial start timing at 0 degrees TDC for hand starting. That conversion had an auto advance that , once running the timing advanced automatically.
This engine is set mechanicly
More running showing my start drill adapter in action.
Hand starting can be done but I gave that up.
The engine is running on non ethanol gas I recently purchased just for this engine. At the end of the vid the engine stops on it own. This is what I am trying to cure.
Click on the link.
Dennis
Hand starting can be done but I gave that up.
The engine is running on non ethanol gas I recently purchased just for this engine. At the end of the vid the engine stops on it own. This is what I am trying to cure.
Click on the link.
Dennis
I got to suspect the atmospheric valve.
I cut two coils off and now I can't get a mix that fires. Youare right, I shot myself in the foot on this.
Is there any place I can get a music wire diameter .0145 diameter
The coil is .247 diameter
about 1/2" long about 12 turns
I have wound springs but it is a PITA
Dennis
I cut two coils off and now I can't get a mix that fires. Youare right, I shot myself in the foot on this.
Is there any place I can get a music wire diameter .0145 diameter
The coil is .247 diameter
about 1/2" long about 12 turns
I have wound springs but it is a PITA
Dennis
Hi Dennis. I am sorry to hear of your intake spring problems... These things are finely tuned by the original designer.... I have one on and atmospheric gas engine that I cannot get to work. My experience is that the original design must be followed exactly, as "any old spring" won't work. I have a selection I made as I didn't have exactly the design on the drawings, and that is my downfall with that model.
Good luck fixing that one!
I was unable to open the vid on timing, post #30, and the attachment on post #32 fails as well. Possibly my software? - What format are both of these?
From the post #31 vid I estimate the engine firing speed to be maybe 200~300rpm... so if it wasn't running I would start with ignition at maybe 10degrees retarded, or at TDC and work around there - chasing the "best" condition - until I found the optimum. But as you have something good (when you fix the inlet valve spring) you can just hunt in 5 degree intervals around where you are and see where the optimum timing lies. Back in the 1980s, I worked with a guy who had an engine on a dynamometer, and at various speeds and loads he was recording the actual optimum timing for ignition for max power at each engine speed from Idle upwards (in 500 rpm intervals) by rotating the contact breaker plate (actually, rotating the whole distributor) and watching the power result from the dyno, then using an oscilloscope to record the optimum timing he had found. This data went back to the "advance-retard" engineer to fine-tune the advance-retard mapping. But you have not got a dyno, just an ear!
Enjoy!
k2
Good luck fixing that one!
I was unable to open the vid on timing, post #30, and the attachment on post #32 fails as well. Possibly my software? - What format are both of these?
From the post #31 vid I estimate the engine firing speed to be maybe 200~300rpm... so if it wasn't running I would start with ignition at maybe 10degrees retarded, or at TDC and work around there - chasing the "best" condition - until I found the optimum. But as you have something good (when you fix the inlet valve spring) you can just hunt in 5 degree intervals around where you are and see where the optimum timing lies. Back in the 1980s, I worked with a guy who had an engine on a dynamometer, and at various speeds and loads he was recording the actual optimum timing for ignition for max power at each engine speed from Idle upwards (in 500 rpm intervals) by rotating the contact breaker plate (actually, rotating the whole distributor) and watching the power result from the dyno, then using an oscilloscope to record the optimum timing he had found. This data went back to the "advance-retard" engineer to fine-tune the advance-retard mapping. But you have not got a dyno, just an ear!
Enjoy!
k2
Hi
Stretching the intake spring was a success. It was and does not now move during the idle strokes. Only when it should fire does the intake move.
Soot in the spark plug can prevent proper firing. I have proved this a number of time by blowing the soot out of the plug
Stretching the intake spring was a success. It was and does not now move during the idle strokes. Only when it should fire does the intake move.
Soot in the spark plug can prevent proper firing. I have proved this a number of time by blowing the soot out of the plug
You could try a spark plug grade for a 2-stroke engine. These are intended to run much hotter at the electrode end so to burn off oil and carbon deposits. As mentioned before, the hit and miss engine hardly generates enough heat to clean the plug. But the leanest practical mixture, with ignition timing tuned to the optimum, will help get the plug temperature up maybe enough to self-clean?
K2
K2
What is the make and manufacturer and grade marking of the spark plug? I guess it is an original - as planned by the model supplier? - Therefore should be good for the thermal selection. Which all points to the mixture being rich. Carbon is conductive and causes flash-over down the length of the insulator when too much carbon exists. This sometimes will keep the engine running, but often just a "dead" engine - like you have. Clean in an ultra-sonic bath if you have one, and/or spray with aerosol "Carb. Cleaner". Even use oven cleaner liquid (Caustic! - so wear gloves and eye protection!). Soak overnight then rinse well and dry thoroughly. A hard-wood cocktail stick will do to rub deposits off the surface. DON'T scrape the ceramic with any metal - ever!
But it is OLD" - spark plug ceramics do develop surface cracks which cause spark-failure, like you are experiencing. It is an ageing process of the temperature cycling and electrical flash-over that can "glaze" conducting deposits onto the ceramic surface. (In microscopic cracks). - Which is why you should replace the spark-plugs in the car at the manufacturer's service intervals. - Trust me, I worked with Champion on engine spark-plug tuning for an engine.... 2 grades of heat selection away from the manufacturer's selected grade of plug can cause ceramic failures, which tend to be catastrophic in an engine...
Enjoy...
K2
But it is OLD" - spark plug ceramics do develop surface cracks which cause spark-failure, like you are experiencing. It is an ageing process of the temperature cycling and electrical flash-over that can "glaze" conducting deposits onto the ceramic surface. (In microscopic cracks). - Which is why you should replace the spark-plugs in the car at the manufacturer's service intervals. - Trust me, I worked with Champion on engine spark-plug tuning for an engine.... 2 grades of heat selection away from the manufacturer's selected grade of plug can cause ceramic failures, which tend to be catastrophic in an engine...
Enjoy...
K2
