Make & break wont run

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Mar 22, 2019
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I am a retired auto technician and have worked for 40 years in the auto industry, most recently as a Master Toyota Technician. I know engines and what makes them tick. That being said…..
I recently built a freelance 1 cyl. make and break engine. It is a 1” bore and 1” stroke. I purchased the TIM-6 ignition system. I decided to use this because it eliminated points and condenser and for size reasons, that made sense. I assembled the electronics and tested everything as per the instructions, and all is good. The system was installed onto the engine with the magnet on the cam gear and carefully aligned with the hall sensor which is mounted to a pivoting arm so as to be able to adjust the timing.
To make a long story short…. I can’t make this engine even pop. I’ve tried 3 different fuels, 2 different spark plugs, made 2 different versions of carburetors, and now has a carb off a model airplane engine. I tried priming through the spark plug hole and even tried starting fluid “ether” to no avail.
With the spark plug removed and grounded it shows a good spark. I mounted the LED timing indicator so as to be visible and the timing is perfect. Compression is good and its getting fuel. If I got even a hint of a “trying to fire” or a pop on ignition I would try to isolate a problem. BUT… I can’t get it to show any signs of ignition.
Is there a possibility of a bad coil? I tested the primary side to about 6 ohms and the secondary side is around 5K ohms.
Could it not be firing under compression? There’s no way to test that. The TIM-6 seems ok. I’m stumped.

I thought I’d write the forum to see if you could shed some light…. I need some help.
See the photo of my engine.

Pat Janson
[email protected]

Hi Pat Janson .
In the past, after the engine was running, I did some test...
With high voltage coil about 8 - 10 kv - using 1.5 and 3 volt batteries, the ability to ignite in the air with a distance of at least 8.5 mm is good enough for an engine with a compression ratio of about 7-1. and the gap for the spark plug is about 0.4 mm
You can try igniting at 8 or 10 mm - but only a few times, because too much ignition will damage the HV coil - that tells you if the HV coil is ok or not
I know you’ve got extensive knowledge in mechanics, and maybe this is a foolish question, but is your spark plug wet after your attempts? Carburetion, valve seating, compression testing, etc., etc., etc., are so important in these small displacement engines. I had a devil of a time with my Webster, trying every ignition scheme I could think of, and then took a look at my valve seating. First I found a small leak on the exhaust valve. Fixed that, but then it still wouldn’t run. Like your engine, I too had a passive “atmospheric” intake valve, and the spring was too stiff. I should’ve seen the dry plug early…

Hope I haven’t insulted you, just my 2 cents worth after having my own run of trouble in the past!
John W
“atmospheric” intake valve, and the spring was too stiff.
You are correct, atmospheric intake valve is a problem with this type of engine
When I make this type of engine, the spring only works to hold the vavle at the closed position with very very light force, valve and valve guide movement must be smooth.
With this type of engine, the spring or the force of the spring is something that I really hate
I'm going to ask a really dumb question - but only because I made this mistake myself.
Are you trying to start the engine in the right direction - wrt cam timing set up ?
The fact that it won't even pop bothers me. Is the cam set for clockwise or anti-clockwise rotation ?
Above comments on free running and bare minimum of spring force on the atmospheric valve absolutely spot on.
My apologies if it is just a dumb question.
Regards, Ken I
Thanks for your responses.
No, you are not insulting me. I am stumped and admit it. Your help is greatly appreciated. I admit that I am blind to something that I should see, but can't because I thought I built it right the first time.
I have looked for a wet plug but that is so very difficult to see on a new plug at such a small scale. I removed the head to inspect and found wetness in the cylinder.
I hear the "burp" on the intake stroke and believe that the intake valve is opening, but I could try a weaker spring. I will also double check the valve seating, though compression seems so good.
The engine turns clockwise when looking at the left wheel so the cam gear turns counter clockwise and timing is spot on. I have an LED set up right there to see the circuit closing snd opening. I tested the spark and found that it will jump about 3/8". Thats pretty good.
I am leaning at the atmospheric intake setup and the spring rate along with good valve seating and guide sealing. How do I make a valve seal for a 3/32" stem? LOL
Thanks for the ideas, I'll keep trying till I get it. I'll let you know my progress.
I am leaning at the atmospheric intake setup and the spring rate along with good valve seating and guide sealing. How do I make a valve seal for a 3/32" stem? LOL


Not necessary, making the valve move smoothly in the valve guide is enough
With the spring, turn the flywheel hard enough and fast and you will see the intake valve open and close

Well, after much tinkering I finally got my engine to run. I replace the intake spring with a much weaker version. It still would not run, so I tried starting with a power drill. That turned it too fast and the governor kicked in and defeated the effort. So I tied the fly weights down and tried again. It fired after spinning it at full speed with the drill. I played with the carb needle valve setting and adjusted the timing slightly and it runs at about 1500 RPM (a guess).
It still will not start by hand, must be spun up with the starter... but it runs.
I'll keep tweaking and see how good I can get it.
Thanks, Pat
Hi Pat !
Thanks for the update
Congratulation !
With small engines especially with the "atmospheric intake valve" type, I usually make the parts very smooth together, friction or a little jam.. will affect its speed.
With spring atmospheric intake valve, it greatly affects the speed of the engine, when the force of the spring is greater than necessary, the negative pressure in the cylinder when the piston moves down the BDC at a slow speed is not enough to open the valve. so I usually adjust the spring to just keep the valve at the closed position and need very little force to open the valve.
Congratulations Pat! Nailing down issues like those can make a man pull his hair out. You didn’t say what kind of rings you used, but if they’re cast iron, as you’ve probably guessed, will take a bit of running to seat them and establish enough compression.

Tiny displacement engines are REALLY brittle and need everything balanced in perfect harmony to run properly, that’s why many folks use a viton ring in their engines. Hot and miss engines don’t coast well with a viton ring, that’s why cast iron is the best choice for rings in hit and miss applications. I’ve never built using a viton ring, but it sure has been tempting when I’m struggling with the kind of crap like you’re facing!

So, once again, congrats on getting anything going! Check your compression, if you’re running cast iron rings they may seat and take care of the slow speed issues, look over your mixer settings (needle valve, fuel tank position, venturi bore), and play with the timing. These little things are nothing like what you’ve been working on other than requiring fuel, air, and heat. I’ve been building and working on 2 and4 stroke motorcycle engines since 1965, and I continue to be puzzled by the incredible balancing act it takes to make my models run.

Keep us posted!

John W
I thought I'd post a video of my engine running. Many hours spent tuning and adjusting.
Thanks to all for the help and ideas to get me through the "it won't run" crisis.
Still some work to do, but I'm happy at this point......
Thanks, Pat
Question from the cheap seats--You asked in your first post about help with a "make and break" engine. A "make and break" engine is a different thing than a "hit and miss" engine. Are you aware that there is a difference?---Brian
Yes Patrick, I am. Most people are not aware that they are two different types of engine. The engine you are asking about appears to be a "hit and miss" style engine.
I may have used the wrong expression. A make and break uses the ignition system for speed control and a hit n miss uses aspiration as the speed control.
Where I live they're all the same.... no one cares about the difference. The engine does the work and a running engine is fun to watch.
I stand corrected... I built a hit n miss engine.
Don't feel bad Pat. Damn few people are aware that there is a difference, and information on make and break engines is quite hard to come by. You're right, Make and Break engines controlled the engine speed through Making and Breaking the ignition circuit of the engine. Hit and Miss engines controlled engine speed through the use of counterweights on a governor operating a linkage to hold the exhaust valve open during the "miss" cycles. I just did a search for "Make and Break" engines, and there isn't much information available-- and some of what is available describes hit and miss engines, not make and break engines. Here is a link to a make and break engine running a small boat, but very little in the way of technical information.---Brian
Oh, Brian, I don't feel badly at all. I enjoy working in my shop building whatever I want whenever I want. I decided to build this engine using nothing but my "junk drawer" and assorted bar stock and whatever I could find that would work.
The semantics of what it should be called is quite meaningless to me.
This is a Hit n Miss engine that I scratch built from bar stock and assorted scrap. It is a 1" bore and 1" stroke. It took me about 2 months of spare time work and then a lot of fussing around to get it to run satisfactorily.
Everything is made from bar and plate stock except for the crankshaft and connecting rod, the carburetor and the flywheels.
The crank and rod were retrieved from an old derelict sewing machine. Much machining was needed to adapt them for this engine. The flywheels are cast iron caster wheels for heavy equipment with much machining to bring the to where I needed them. The carburetor that I made did not work, so I made another one and it didn't work very well either so I opted to use a Fox model airplane engine carb. I made a manifold to make this work and it does a good job.
I'm here trying to have fun in my shop now that I'm retired.
Please enjoy my effort.... it's fun to share. Feel free to contact me.

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