OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Millers Falls 13hp

Hi Grumpy, have checked out my vernias with a new battery. Measured the same drill as the other day, 1mm came up 097mm again, so i checked the 1.5 came up spot on, 2mm came up 2mm, checked the 2.5mm came up 2.48mm, so i am thiking it may the drills themselves. They arent dear ones so it anybodys guess now.
Did get my hands on a 1.2mm drill bit, got told if i break it dont come back, hoping it wasnt going to be to big. Carefully drilled out the spare jet and gave the motor a run. It seemed to smooth out just a little bit more. Would it be worth going just a tiny bit bigger and see what happens.
The motor had been sitting in a box since bieng bought, not sure how long ago that was, so my guess is the carby has never been apart till i got to it. The only reason i took it apart was incase there was dust and such in it. Have some photos of the emulsifier. Cannot see any damage or scraps on it.

The emulsifier looks good, Paul.

As for the jet, I'll tell one of my interminable stories to set the scene for the next step. About 15 years ago I had the job of working on a couple of very old high performance cars. One had been rebuilt and ran badly, the other was in pieces. Neither had the original carburetor, which could not even be described, the cars were so old. The previous tenant had tried to get the engine running by modifying a completely different carburetor (from a Tiger Moth engine). My approach to making it run was check that the ignition, compression and valve timing were right, and then blame the mixture strength. It was misfiring too much for things like spark plug colour to make any sense. So, I drilled out the main jet in steps, finding it ran better with each enlargement. Finally, with the jet 0.120", it ran properly (it was originally 0.080"). The trouble was with that huge jet diameter, it wasn't vaporising the fuel, it was just spraying liquid like a fire hose, so in cold weather it went back to running badly. A colleague pointed out that when you need a huge jet, that means there isn't enough "venturi vacuum" generated in the carburetor, so we needed to try a smaller venturi in the same carburetor. The colleague turned up a smaller venturi, and I soldered up the jet and started again, with the result that it ended up running properly with the jet at 0.080". At that point it was vaporising the fuel properly too, so it ran in hot or cold weather. A bit of research revealed that the previous tenant had thrown out the Tiger Moth venturi and made his own, much larger one.

The moral of this story is that there is no great difficulty in enlarging the jet step by step, and observing whether it runs better. The modification is easily reversed by soldering up the jet and drilling a new hole through the solder. Furthermore even your enlarged 1.2 mm jet is only 0.047", which is not a large jet, so you aren't coming to the end of the road with drilling it out in steps. The issue is, unless there is something wrong somewhere, the right sized jet should be somewhere near the original size, and it obviously isn't going to come out that way.

What I would do, is enlarge that spare jet further, until it stops running better each time you enlarge it. Then we can see how well it is running, and whether we can find an explanation of why it needed the bigger jet.

Hi Grumpy, sorry but am going to have to pause here until further investigating, have explained on other thread, RE: Tecumseh one. Thanks Paul

Hi Grumpy, have also done here as suggested re: tecumseh motor, have removed kill wire from ignition mudule, with the ignition off the tester showed 0.00, with ignition on it showed 0.44.. Quick question, if it is the ignition module, re: tecumseh thread, how could it have died so quick knowing it is a new motor, or is it a case of when they feel like it they just go.

We have no strong reason to believe it is an ignition problem caused by putting 12 Volts on the kill wire Paul. The question needs to be cleared up by you checking for voltage on the kill wire of the second, or "Miller Falls mower" until you tell us what it actually is. What I think we have so far, is a mower that runs erratically. You have reported that the fault comes and goes with changes in the air cleaner, but I think more recently you have found that it is erratic all the time. If I heard it, I could probably tell you what is wrong. Erratic ignition is normally characterised by two features. First, the engine cuts in and out sharply: each shot is either fired or not fired. Second, there is usually some popping in the muffler under at least some conditions, due to the fuel that doesn't burn on the missed shots.

The way to find out for sure if it is an ignition fault that is gradually getting worse, is to put an in-line spark tester into the high tension wire. We discussed how and why, and how to make one, in a previous thread of yours:

https://www.outdoorking-forum.com.au/forum/u...amp;Main=9879&Number=59818#Post59818

I think what should be done now, is to try that test on both your engines. Afterwards, keep the tester close to hand when dealing with engine faults. What I hope we've both learned from this thread, is that your descriptions of fault symptoms are so different from what I am used to, that we are at risk of going in completely wrong directions if we don't start with some basic hard data.

Applying 12 Volts to the kill wire is a serious abuse of the module, since it applies a potentially high, continuous current to a circuit not remotely intended for such treatment. I don't recall enough cases of it being done to have much idea how long it takes to destroy a module. It may vary widely.

Hi Grumpy, have done test with the in-line tester, did have good constant strong spark. One little thing, hope i'm not getting off topic, but the motor ran beautifully while idling, on full revs it seemed to surge/hunt just the tiniest of bit. Am wondering if i was to put original jet back into carby it might be right.
The way it was running with no wires connected it has me pionting back to bad wiring on the mower base, but that is something i will look into very shortly.

I recommend that you put the carburetor back to standard condition in every way that it has been changed, Paul.

The objective with diagnostic processes is to find the cause, which is usually a single cause. That implies that everything that has been changed, should be restored to original condition immediately after the test that was made with that single item changed. If you don't do that you can develop new problems due to the changes that have been made, and it can become impossible to isolate the original problem.

It sounds as if we now have evidence that the Millers Falls engine has a good ignition system. We don't know at this point what the problem was, so we want to get the engine into its original condition, except with the electricals disconnected from the mower. If we can get it running like a new one under those conditions, we can start to examine the electrical connections in detail.

Hi Grumpy have changed everything back to original.
Do you want some photos of electrical connections that are on motor and on mower base, or is there something else we do before going to them.

I think we should get the engine running properly before changing topic, Paul. My preference would be to get the engine right, close this thread, and open another on the mower frame. Hopefully we'll be able to find a wiring diagram for it, and check whether the machine is different from the diagram.

Hi Grumpy, have given motor another run while on base, no wiring connected , and it ran like a dream. Other then opening up the mixture screw to just below 2 1/2 turn, didnt touch anything else. If i had of tried this motor without the wiring connected from the start i wouldnt of had to stuff you around and waste your time.
Now on to tackling a wiring problem.
Thanks heaps for your help Grumpy,, special thanks for your patience.

It's the outcome that counts Paul, not how long it takes. Besides, I just don't like to see a Honda or Honda-copy not running properly. And this hasn't really been a long thread.

Please open a new thread in the ride-on mowers section so we can take a look at your wiring issues. Include as much detail as you have on the mower, to maximise our chances of getting hold of a wiring diagram.