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John_RI

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John_RI
I put a new-old model 19 in service in my 725 a few weeks back and had a problem of it not wanting to run at high speed under load. I assumed it was a carb/fuel problem. I found some debris in the tank so I flushed & cleaned the strainer - no change in operation. Swapped the carb with another one and that seemed to help for a while but the problem came back after 10 -15 minutes. I was still thinking fuel so I went through both carbs and supply from tank and have made no improvement in the engine's performance. It starts easy, idles fine. When trying to mow, from a cold start, I can begin at a high speed but after a few minutes it starts to miss, lowering the throttle setting corrects the problem but a few minutes later I have to drop the throttle again. Pretty soon I'm at an idle! Am I looking in the wrong place? Could it be electrical, points, cap, plug or the something with the ‘manga-matic' ignition system? Thanks, John(ri)

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PatRarick
Sounds like a magneto problem. Just went through that with an old model 23. It ran great when cold, but only had to warm up a little before it started to cut out when the governer opened the throttle. When the engine reached operating temperature, it would cut out and run almost like it was choked. Drop it back to idle, slowly bring the engine up to operating speed and it again ran fine until the governer opened up. Used an in-line spark tester and it was easy to see the spark cutting out when the engine started to miss. This engine has the "magnavac" ignition system with the magnets mounted in a rotor behind the flywheel and the armature surrounding the rotor. I believe the model 19 also has this system. Pat

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Roy
Al Eden properly diagnosed a similar problem on my Model 19. In my case the cam end clearance is excessive. The cam would shift axially causing the points to malfunction. I detected it because it only happen when the tractor jerked (as in starting up or going up hill). I solved the problem with an electronic ignition module that eliminated the points. Based on the above, I agree with Pat. Check the points and ignition system. Could also be the coil beneath the flywheel. The "magnamatic" as described by Pat on my engine works good. Good luck,

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John_RI
PatRarick, Your description of acting like it's choked when the governor opens the throttle is exactly the same in my case. What did you do to solve your problem? I might consider the auto type ignition but I would have to add a battery & charging system. Thanks for the info!

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John_RI
Roy, Do you recall how Al eliminated the magneto to identify the cam/points? I do have the problem at a ‘stand-still' so I think my problem is not quite the same as yours, but I will need to chose points or mag as the culprit because the solution will require having the other operational! Thanks!

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PatRarick
John, I switched to a battery ignition system. Last I checked, all of the ignition parts were still available from Briggs, but were very expensive. Your magneto may be OK. The older style had a pointed set screw that fit into a tapered hole in the crankshaft to hold the magnetic rotor to the flywheel. I have seen these come loose, wearing the bolt and the hole. The magnets do not pass the armature at the proper time, providing the same symptoms described. I have gotten past this problem by drilling the hole in the crankshaft a little deeper (about 1/4" deeper), and using a long allen screw. If I remember correctly the set screw is 1/4" coarse thread. Pat Pat

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Roy
John(RI), You will have to ask Al how he knew what the problem was. I spent years trying everything possible, including a new coil, so from my prospective the cam clearance was the only thing left. The electronic module was less than $15 so I tried it and it worked. Excess cam end clearance had to be the problem in my case.

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ReedS
I have a couple of those rotors, I'll take some pics tonight. Yes the 19's have a float. I think a sticky needle valve would have s ome other symptoms as well.

As you can see the one on the left is ready for the scrap pile. Believe or not the engine still ran with that rotor of course it was real tired at that point. Also obvious is that these are not the same as the one that John has and as evidenced by Pat's post are probably later production units.

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BillC
John, After replacing the 7-1/4 HP B&S with a 10 HP B&S in my 725, I had the same problem until I moved the condenser outside of the points cover. In my case, the condenser was overheating while mounted under the points cover, due to lack of air flow through the front grill open area. To move the condenser, add a short piece of wire to the condenser and mount it outside the ponts cover using the top mounting screw.

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BLT
quote:
Originally posted by PatRarick
Sounds like a magneto problem. Just went through that with an old model 23. It ran great when cold, but only had to warm up a little before it started to cut out when the governer opened the throttle. When the engine reached operating temperature, it would cut out and run almost like it was choked. Drop it back to idle, slowly bring the engine up to operating speed and it again ran fine until the governer opened up. Used an in-line spark tester and it was easy to see the spark cutting out when the engine started to miss. This engine has the "magnavac" ignition system with the magnets mounted in a rotor behind the flywheel and the armature surrounding the rotor. I believe the model 19 also has this system. Pat
This is what Pat was talking about I think. The coil is under the armature. From an old Model 19 parts book I have. [img]http://www.simpletractors.com/club2/attach/blt/mod19mag.jpg[/img]

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PatRarick
That's the one I am talking about, Bob. The set screw that I spoke of as wearing out, taking the hole in the flywheel with it, is part #92661 in the diagram. Pat

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John_RI
Thanks guys for all the help. I think I'll try the auto ignition and see if it solve the problem - at least that will tell me if the problem is the magneto. PatRarick, based on your reply about a lose screw holding the magneto, should I be concerned about something comming ‘undone' under the flywheel and lunching the engine?

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PatRarick
I would probably be more concerned about it if you go with the battery (auto) ignition. If it were to go while still running on the magneto, the engine would quit if it got too worn. With the battery ignition, it could trash the engine if it lets go. Pat

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Al
John, All of the above are good info, one other thing you might check is the vent on the fuel tank. Just loosen the cap, if it is plugged, it will run until the tank pulls a vacuum and as it increases the fuel flow will continue to decline. It will be a quick check. I believe some of the aftermarket conversions will convert the ignition. I will do some checking I belive they are under 20.00 and you just remove the points and cond and put the unit from the point lead to ground.. Good luck, AL Eden

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bhenry
I had a similar problem when the engine was getting powered up or when I was on rough surfaces. The solution was a defective key switch. Apparently the excessive vibration cause the keyswitch contacts to destablize and cause weak connection therefor causing my ignition system to fail or produce very weak spark. I bypassed the keyswitch for a test and it ran great. I couldn't fine a new keyswitch so I installed a heavy duty SPST toggle switch and ran a separate ground wire to the switch. It took my 3 year old son to solve the problem. He was riding on my lap and his foot was resting on the keyswitch in just the right way that it operated great. I took him off and was back to my orignal problem. :-) Ah then I knew were to look.... Good luck. Bob

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PatRarick
John, I can't answer your question. Have never seen or heard of a 200431. Assuming you mean a 240431 or a 300431, I would have to say that it will not fit. The crankshaft of the model 19 is not keyed for the flywheel, and there are no provisions for mounting the coil mount to the block. Pat

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John_RI
Thanks Pat, If there's no keyway that takes care of that idea. The 200431 was a cast iron 8hp that I think was only produced for a short time. I think the one I have is dated 1974. Thanks again everyone for all the help!

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