Why Won't it Run?
It's always good to see a story come full circle, and this one began at the end of July with a stationary engine mailing list member's e-mail for help and advice. As ever, the following comments reflect a variety of opinions that surfaced during this discussion on the ATIS Stationary Engine Mailing List.
I am working on a 7 HP Economy for a friend. It wouldn't run when he brought it over. I had to replace the rings (all of them were broken) and get the mag and igniter working. Someone else had started restoring the engine but sold it before they finished.
My problem is the engine will not run unless the choke is almost fully closed. The check-valve seems to be working, but the needle valve/adjusting screw is very loose. Could it be sucking air? I added a couple of washers to tighten up the intake spring, but that did not help either. Could I be off on timing?
There were several prompt suggestions for things to check and possible fixes, the first from GEM's own Hercules/Economy expert, Glenn Karch.
To check if it is sucking in air, try letting some propane from an unlit torch around the needle valve while the engine is running. If it's sucking air, you should see some difference. Timing shouldn't make much difference with the choke.
I will try the propane trick tomorrow if I have a chance. The reason I mentioned timing is because I am not sure where to set it. The flywheel is stamped 'spark,' and I have the mag set to fire when that mark is parallel with the pushrod and the mag is on full advance. Is that correct?
What color is the exhaust?
The exhaust is grayish black. If you open the choke more than a little the engine has to intake twice to fire. I have the needle valve open about three revolutions. Any more and the engine will not run, even opening the choke more.
I have a 7 HP Hercules that runs quite well with the needle valve opened less than a turn and with the choke open until I try to slow it way down. I made a new needle valve and it fits snuggly in the threaded hole. It has a rebored and sleeved cylinder and the piston is fitted with new rings and spacers. It also has new valve springs. It's often a combination of worn parts, things out of adjustment or weak ignition.
My 9 HP only runs with the needle valve almost entirely closed, too. I've been told if you run them loaded and faster you can open the choke up, but not if you're idling unloaded.
If you have high-tension ignition, set the timing at three degrees of advance for each 100 revolutions of engine speed. For low-tension use five degrees for each 100 rpm.
My 5 HP Economy needs to have the choke completely closed when running at a very slow speed - I even have to plug up the hole in the choke plate. I think your needle adjustment should be open 1/2 to 1-1/2 turn.
I agree the timing is probably all right. If it was too advanced, you wouldn't be able to start the engine and it would probably run fine at working speed. If the timing was way retarded, you would have a very loud bark at the exhaust and probably would be seeing red flame coming out of the exhaust pipe (if the pipe's short).
There's also the possibility you have an ignition problem. A very weak spark or bad plug can cause something like this to happen. The plug will only fire when compression is weak. If it gets a healthy charge of fuel and compresses it properly, the plug doesn't fire. Too small a plug gap will cause odd things to happen. If you can't get the spark to jump over at least a 0.025-inch gap (under compression), change the plug or give the mag another whack.
When I first got my ZC-52 I couldn't get it to run evenly at slow speeds and adjusting the needle didn't have a lot of effect. I tried fiddling with the intake valve tension (I just pulled and pushed gently on the valve stem when the engine was running), but that didn't have much effect.
What I did find, however, was if I held back a little on the exhaust valve it ran a lot better. Looking carefully, I could see the valve moving on the intake stroke, making the engine inhale some of its exhaust. I had put in the best of the old valve springs I had with the box of parts I made my engine out of, so I took it off and stretched it out, then reassembled it. The engine ran better for a while until the spring relaxed again. Everything was peachy after renewing both springs.
I'm not familiar with the Economy, but the mag will usually trip when the 'spark' mark passes the push rod - or at least close to that point. I would say your timing isn't that far off.
The needle valve should only need to be open one turn or less. It just seems to me that if you have to open the needle valve that much and still have the choke half closed, you have to be sucking air somewhere.
How's the gasket between the mixer and the head? My F&J tends to get loose there. My Witte was also loose, but the mixer threads into the head so I used plumbers tape to snug it. What's the condition of the intake valve guide? Try the propane trick - it usually will tell you where the air is coming in. When the engine sucks in the raw propane it will tend to run better.
Both my 5 HP and 7 HP Economy's run with the choke closed 75 percent or better, especially at slower speeds. I see most of these engines at the shows running with the choke partially closed.
Given a host of things to try, it was time to go out to the shop!
Thanks for all of the suggestions, guys. I am going to re-inspect the check-valve and check the valve timing. I will let you know what I find. I tried the propane trick as well as making sure the carb was tight to the head. Everything seemed okay.
Almost a month after the original query had been posted, we were given a full rundown on exactly what had be done.
Okay gang, I think I have it running okay okay now. To refresh everyone's memory, 1 have been working on a 7 HP Economy a friend bought at a show. Someone else had began working on it and, for whatever reason, bailed out. After some mag work I got it running, but it was running very lousy. The only way to get it to run was to flood it. Of course I couldn't get any speed or power.
There were several problems, and the biggest was valve timing. Talking on the phone with Ted Brook over about possible mag problems and telling him what I had found, he suggested the valve timing might be off. Ted sent me info on approximate settings. I changed the cam by one tooth and the engine ran much better. I then spoke with Glenn Karch, who gave me the specific timing for this engine. Turns out 1 needed to move the cam one more tooth. Needless to say, the engine ran better yet.
Once I was making some headway I looked for other issues. To start with, I noticed the spark timing kept moving. At some point in its life the push rod roller had frozen up and it had a huge flat spot. Someone freed it up, but they didn't machine the flat off. This was, of course, causing the timing to vary.
I also found the roller on the advance/retard shaft and the shaft itself to have 0.025-inch wear - as well as being out of round. I repaired the shaft, made a new roller and replaced the spring that holds the push rod down on the roller with a heavier one. The trip finger on the mag was worn very one-sided, so I welded it up and ground and filed it back down. That took care of the timing varying.
I also re-checked the check-valve. It was homemade and with no provision for a seat for the ball as well as no relief cut in the topside to keep from blocking fuel flow during intake. I made alterations that fixed these two problems. The gas tank also did not have a vent so I drilled a hole in the side of the cap.
Next, came new intake and exhaust springs, as well as a new needle valve. I also replaced the two trip springs on the end of the mag as they looked very weathered and weak. Everything got better as I went along, but I still couldn't get any speed out of the engine.
My friend wants to use the engine and not make a 'loafer' out of it, so I started working on the governor. After talking with Glenn Karch and getting pages from the manual from Keith Kinney's Web page at www.herculesengines.com, I knew what I had to do. The governor spindle pin was badly worn and the spring was homemade and weak. I don't know if the previous owner was trying to make a slow running engine, or what.
Anyway, I kept fooling around with different spring combinations until I started to get some speed. It's still not up to its rated 375 rpm, more like 275 rpm. I may try to get a little more out of it, but I may not push it - just in case something was to try and self-destruct! Yesterday evening the engine would run with two turns of the needle valve, no choke and no black smoke.
I belted it to Dad's DC Case tractor to put it under load. We shut the tractor down and let the Economy turn the tractor engine over. It would hit about four times and then coast for about four seconds. Needless to say, this has been a real education for me. Thanks to everyone who offered ideas and suggestions.
This thread proved to be very interesting to mailing list members since it covered so many of the basic elements that make an engine run - or not. Getting a detailed summary of the troubleshooting exercise was a big plus for list readers - and we hope it will benefit GEM readers, too.
Engine enthusiast Helen French lives in Leicester, England.
Contact her via e-mail at: Helen@insulate.co.uk
You can join the Stationary Engine List on the Internet at: www.atis.net