OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines alternator issues ???? maybe

I scored a greenfield mk2a eIII 8.5-30 ride on that was supposed to be blown up, anyway after 4 mows it did, conrod thru block, swapped motor off an older 8-30 and shorted starter lead in the process, during change out also swapped alternator off blown to older motor, as it was working, but now it seems to run ok except for surging, rev up down up down, but it seems to now not be charging, is it possible one of those diode things near ignition are gone or something with the solenoid, no increase in voltage at battery when running, also near ignition is both a red and black plug with those diodes on it and there seems to be a spare wedge connector on ignition, it has a block of 5 with one separate, does one of those red or black go on here, I cant recall taking it off. if using jumper leads, key start works great, but no increase of voltage at battery, thanks.

Hi theppy2760, welcome to Outdoorking.

I am concerned that you mowed 4 times, then the engine blew. Did you check the oil level and clean the engine cooling fins when you acquired the mower? It would be unusual for an engine with prior damage to take that long to blow, if the problem (nearly always either no oil or clogged up cooling fins) had been corrected.

To look into your problems we need to know the Model, Type and Code of both the original and replacement engines. This will be stamped on the cooling cowl.

Ok the blown motor is 196707 0170-01 9908071A
the older replacement is 193707 0315-01 89060512

And on inspection removing blown, the cooling fins did have a bit of clogging.
Just for the record, I bought this from a mower shop, he told me motor was blown, took it home started changing motors, then thought, what the hell lets just try it, motor started by key, ran fine, mowed, again again again, then after 4th mow being careful not to get motor wet, with engine running and cutters engaged, while hosing under cutter deck, heard a TINK, everything stopped, found hole behind starter, and starter itself once opened had been smashed internally, outer magnet that is, from the force of the rod hitting it.
the replacement now has the flywheel and alternator from blown on it as it was working before, problem as earlier described.

Thanks for explaining, theppy2760. The mower shop guy probably had some reason to expect it to blow - like, when it came in it had no oil, for example. Please make sure the replacement has clean fins and clean oil. An ounce of prevention is worth a ton of cure, and all that.

Here is the Illustrated Parts List for the blown engine:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6hovIVJ1DajI.pdf

Here is the Operator's manual for the same engine:
http://bsintek.basco.com/BriggsDocumentDisplay/mssAIQ-K_ny7tH217FzoPu.pdf

Here is the Illustrated Parts List for the replacement engine:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6opwCVJ1DajI.pdf

Here is the Operator's manual for the same engine:
http://bsintek.basco.com/BriggsDocumentDisplay/mssAIQ-K_ny7tH217FzoPu.pdf

Now, getting to the actual issues. First, you reported that the replacement engine was hunting (cycling in speed, with the speed control set and not changed). This is nearly always caused by lean mixture. (The rest of the time it's caused by a mechanical problem, most likely a bent and jamming linkage.) You have had a stroke of luck here - that engine, being older, has a large one-piece Flo-Jet carburetor, which is practically bomb-proof, and has adjustable mixture, both in the idle and main systems:


To adjust the idle mixture, set the engine at idle speed, and adjust the screw marked "Idle Valve" as follows. Turn it slowly clockwise until the engine begins to slow down (lean limit). Note the position of the screwdriver slot. Turn the screw anticlockwise until the engine begins to run roughly and slow down (rich limit). Note the position of the screwdriver slot. Set the screw halfway between those two positions.

To adjust the main mixture, set the engine at maximum speed and turn the high speed needle valve anti-clockwise viewed from above, or clockwise if you have crawled underneath it for some strange reason, until it either hunts (cycles in speed) or slows down slightly (lean limit), then note the adjuster position. Turn it the opposite way (clockwise viewed from above) until it starts to slow down (rich limit). Note the adjustment position. Set the needle valve halfway between the rich and lean limits.

Turning to the alternator issue, do you have the low output or high output alternator? Here are the two of them for the blown engine:


Here are the two of them for the replacement engine:


In each case there is a part-circle alternator (877A), which only produces about an Amp, and a full-circle alternator (474B), which produces about 10 Amps. Did you install the alternator from the blown engine in the replacement engine, because the replacement engine had an 877A, and you wanted a 474B to get the extra charging current?

Here is the wiring diagram for your mower:



Please clarify your questions about the wiring, by referring to the diagram. Essentially the blue wire is the ignition kill wire, and the orange wire is the battery charging wire. There should be a diode on the engine side of the plug connecting to the orange wire. If you have the 10 Amp alternator, you should see a slight increase in battery voltage when the engine is running at maximum speed - probably a few tenths of a Volt, if the battery is fairly flat. If you have the 1 Amp alternator, you would not see a measurable increase in battery voltage.

mine on both engines is the dc only, half crescent type, 877a.
im guessing those two other WIRES NEAR IGNITION SWITCH I ASKED ABOUT ARE FOR THE HOUR METER THAT MINE DOESNT HAVE. but there is still a spare wedge on switch, possibly unused then

I think the switches are usually general purpose, with provision for some extra functions. Your machine has the most basic wiring arrangement that I have seen on any decent machine - and I see that as a good thing generally. (I'd have more safety switches, but that is a personal view.)

If the two unused wires are bound together, and if your machine is missing the hour meter, I'd guess that is the explanation.

Your feeble little alternator probably does charge the battery slightly, they don't often fail. You can check by putting a 10 Amp ammeter between the engine's output wire (red) and the mower's battery charging wire (orange). You should see a current into the battery when the engine is running at maximum speed, and zero current when the engine is stopped. If you get less than a third of an Amp of current, most likely the diode in the red (engine side) lead will have failed, but it doesn't happen all that often.

ok great, thanks for all the assistance grumpy, will do checks and report back, going off something else I read elsewhere in the forum, I HOPE I haven't wasted your time, if im not mistaken, it seems these charging capabilities are only to just maintain a battery to start mower and not so much as able to charge a run down battery, unless run for quite a while, I have only run for about 10 mins max thru this so far, maybe leave it running for half hour on high revs and see where battery voltage is then, but will still do tests suggested, right now in fact.

Yes, the little alternator is just supposed to maintain the charge in a healthy battery, not recharge it. You need the 10 Amp one to charge a battery. However once you have everything running properly, and the battery charged, the system you have should maintain your battery, and allow it a long life. It is best to use a battery charger to deal with a flat battery - the number of hours your alternator would take to recharge it would be ridiculous.

I look forward to hearing from you when you've gone through the carburetor tuning procedure, and also checked that there is at least a little current going into your battery. Please be sure your engine is full of clean oil - the Synchrobalance system it has in its crankcase is very unforgiving of poor lubrication.

your advice was very good, I followed all instructions and although not purring like a kitten, it is definitely running better, under load sounds better than no load, and I cant seem to get idle as slow as it probably should be, might just have to invest in a service and/or tune up.
I figure rebuilding the dead motor and getting the hole welded may not be a complete waste of time, may need it one day, but im in need of a conrod for the following motor, can anyone help me out, thanks.
196707 0170-01 9908071A

Hi theppy2760,

If you post your make, model number of the engine and part number of the conrod you are chasing in the "Wanted" forum topic HERE you may get better exposure and one of our members may have the part you are looking for.

If it is now running well under load and you are just a bit dissatisfied with the idle, there are some simple procedures you can go through that might improve it. Before doing this though, are you sure that you adjusted the idle mixture, and assessed the idle quality, with the air cleaner fitted, and the choke wide open? Have you set the idle speed for 1,750 rpm? Did you bear in mind that side valve engines normally miss some shots at idle, but should nevertheless run steadily at constant speed? (The idle quality needs to be compared with other single cylinder side valve engines, not with OHV, OHC, or multi-cylinder engines.)

First, check that the carburetor is not flooding. Turn on the fuel but do not start the engine, and see if, after five minutes, fuel is dripping from the top of the float bowl, or coming out of the jet in the venturi. If it is flooding, mixture will gradually become overly rich at idle and tuning the idle jet accurately will be impossible until you fix the problem by servicing the needle and seat.

Second, check the idle mixture screw setting you ended up with after adjustment. To do this, turn the screw gently clockwise until it bottoms very lightly, counting the turns and the final fraction of a turn. It should have been open approximately one and a half turns. If it was very far away from this, go through the idle mixture adjustment process again. If you consistently find it needs to be open substantially more than one and a half turns, you will need to clean the carburetor, paying particular attention to the idle system.

Third, bear in mind that you did not tune the engine, it is as received except for having adjusted the mixture. Whenever you acquire a second-hand engine in unknown condition, you should clean or replace the air cleaner element, clean the cooling fins, ensure that the choke is opening and closing fully and correctly, clean the spark plug properly and gap it (or replace it), check the tappet clearances, and test the compression. After doing that, and mowing the lawn so that it settles into its improved state of tune, adjust the idle mixture again using the same procedure as before. If the idle quality is still poor, we will need to discuss it further.