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anyone worked on a Cushman OMC 2 cyl engine,,,? |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
![]() ![]() ![]() ![]() ![]() Posted: 27 Jul 2024 at 10:04pm |
I been working on a horizontal 2 cylinder OMC engine for a friend,,, the PO had cut wires and made a mess of things trying to start engine,,,,??? Starter is out and new one ordered,,SO,,I am trying to shade tree it to start. First tried my 1/2" Hi Torque NAPA impact but engine rolled to the compression spot and would not go past that point ,,,,? I then dug out "Brutus" ,,my 1/2'Craftsman Hi Torque low RPM drill and ,,,,same reaction as the impact,,,! I removed BOTH spark plugs for funs and the frigging thing would still stop at the compression spot,,,? I can roll the engine past the compression spot with one hand and is not binding but acts as if the spark plugs are still in engine,and bucking compression,,,,?? Anyone got any kind words of wisdom, what to look for,,,??
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5715 |
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I would put a borescope in the plug holes and see if there's debris in the chambers... or carbon soot on the pistons
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Hey Dave Kamp,,,it sure good to visit with you, my Friend,,,,This is sure an ODD thing, Dave, as when you roll the flywheel back and forth at the place where it stops,,it feels EXACTLY LIKE when you are pushing against compression in the cylinders on the ignition stroke,,,,? Very puzzling to say the least. Taking the spark plugs out did not make any difference when rolling the engine back and forth,,that "spot" would be there at every revolution, but I do not think it is an internal piston obstruction,,rather it is just like when you reach the compression/ignition spot on the flywheel,,,,???
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DMiller ![]() Orange Level Access ![]() Joined: 14 Sep 2009 Location: Hermann, Mo Points: 30510 |
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Ring ridge in cylinder loaded with carbon.
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Hubert (Ga)engine7 ![]() Orange Level ![]() ![]() Joined: 12 Sep 2009 Location: Jackson Cnty,GA Points: 6217 |
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Since it’s a 2 stroke you may have to look further. Check for solid carbon buildup in the piston ports or a stuck reed valve. Just some random thoughts, it has been many years since I worked on a 2 stroke engine.
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Just an old country boy saved by the grace of God.
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im4racin ![]() Orange Level ![]() Joined: 12 Jun 2017 Location: Garrison ND Points: 907 |
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If it’s a 2 cyl the compression you are feeling is the back side of the piston. They use that pressure to blow the new fuel charge into the cyl to help evacuate the spent gases out of the cylinder. That’s why the Detroit 2 cyl has the blower.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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if it won't turn a 360 by hand 'somethings' bad... maybe pour a 'decarbonizing liquid' in it over night or longer. do NOT use anything but HAND power to spin it BAD things ($$$$$) can happen !!!! FYI Early 2 strokes (without tranny ) spin engine 'backwards' for reverse.
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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Thad in AR. ![]() Orange Level Access ![]() ![]() Joined: 12 Sep 2009 Location: Arkansas Points: 9386 |
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Lots of good advice here. I’d also be checking magnet clearance on the flywheel.
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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WHOOPS,,,I might of mislead ya'll,,,it is a 4 stroke 2 cylinder engine with the 2 cylinders in an oppossed horizontal position kinda like them volkswagons and the older Corvairs. Whatever is in one or BOTH cylinders is what is pushing back on the flywheel from turning freely. I can roll the flywheel easy enough past the spot it trys to push back,,,,?? When engine is rolled right to the push back spot, I can roll it just a few degrees past the spot in either direction and engine will roll away from this "spot" of it's own doing. Since I do not have a bore scope,,I'm gonna remove the head and take a look see, as it prolly is some build up of carbon and needs cleaning up and removed,,,, Many Thanks for all the suggestions and help Guys,,,,
![]() Edited by desertjoe - 28 Jul 2024 at 9:19am |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Hey Thad,,That right there sure might be a consideration as what is happening happens at SAME spot in the engine rotation and sure could be the culprit,, This engine uses what Cushman calls a "TiMER" with single contact points and condenser inside it. Power from a 12 volt battery goes thru a "Resister" then goes thru TWO ignition coils, (one for each cylinder,) wired in series and on to the "Timer" or distributor with contact points and a condensor inside it. That wiring path kinda don't make sense to me as the "TIMER" only has the one wire on it's single connector,,,,?? Am I missing something here,,,??
Edited by desertjoe - 28 Jul 2024 at 9:50am |
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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one con rod could be busted......
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5715 |
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My Cushman uses a Kohler K-single, so I can't do a direct comparison, but I've worked on others with the OMC 4-stroke horizontally opposed twin. This was a very unique motor for Outboard Marine Corporation... we expect, from their Evinrude, Johnson, and Lawn-Boy, that it'd be a two-stroker, but it's not... it's truely a unique beast for OMC. The 'timer' is no different from any other ignition system, because of it's horizontally opposed arrangement, both cylinders are at TDC at same time, one is on exhaust stroke, the other is on compression stroke. Both spark plugs fire at same time, one on a viable charge, the other on exhaust, so it is what is referred to as 'wasted spark' operation. Simplifies ignition. The ONAN CCK in my detassling platform, and in my Miller Bobcat welder are same, but instead of two coils, it uses just one coil that is 'double ended'. There's good and bad to a double ended coil, benefits are that it's just one coil to mount, and services both plugs... the bad is that it's just one coil, and if it goes bad, you lose all spark... I suspect you've either got a ridge, or some debris in there. Horizontally opposed engines are susceptible to that sometimes, particularly if debris can fall into the carb and migrate down in there. Pulling the heads WILL help alleviate that. The alternator on these was frequently a stator coil beneath the flywheel. If you have debris in there fouling the rotation, it'll do that, but it also may just be tight clearance or strong magnet. IIRC they used a charging stator very similar to, perhaps same part as used on the SkiTwin/FasTwin/Industrial 40 two stroke outboard (it was an option on the ski/fast, and standard on the industrial 40hp, they all had electric start as an option, charging was an option on the Ski/Fastwin. The magnet on those was just a sector portion, not a full circle of magnets).
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5715 |
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Power from battery flows through ignition switch, through resistor, into one coil primary, out, then into to other coil primary, out, then through timer contacts to ground. There WAS (initially, but possibly eliminated sometime) a wire that went from the START solenoid to the first ignition coil, to bypass battery power AROUND the resistor during starting. The reasoning for this is frequently misunderstood: When the engine is running, and the generating system is recharging the battery, you're seeing about 14.2ish volts on the electrical system. To make the coils survive 14.2v, they must be wound to run well at 14.2. When the engine is CRANKING, however, system voltage gets pulled down, could be down around 9-10v. Coil won't work too well there. So they make the coil work well at 9v... but once the engine is RUNNING, it's getting pounded with 14.2. So... when engine iS RUNNING, coil current is limited by the resistor. When CRANKING, the resistor is bypassed.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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Thad in AR. ![]() Orange Level Access ![]() ![]() Joined: 12 Sep 2009 Location: Arkansas Points: 9386 |
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Being a 4 stroke makes me believe stuck valve With the valve spring bound up and pushing on the cam when it rolls past center. |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Hey Dave Kamp,,Many Thanks for taking the time to explain this for me. On the wiring diagram I downloaded,,it DOES show the start solenoid with two small connections in addition to the two BIG connections for the battery input and the outlet to starter. One of the small connections on solenoid does have a wire going to the positive side of first coil. The other small connection quite possibly was removed as the wiring diagram does show a wire on second solenoid terminal but this dwg is so fuzzy I cannot follow where it terminates,,,, got any ideas,,,?? OK, I "WAS" going to buy two new 12 volt coils but with your info will this design require special wound coils by Cushman,,,?? you know the word "special wound" means HIGH Dollars,,,,???
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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DJ, do me a favour, post the model number info.....please I do NOT want to go 'north 200 feet'... prefer to surf the web !!!!! ANYTHING but go to 'contractors BBQ ' !!!!!
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Sure thing, Jay,,,,it is a 1980 Cushman Three Wheeled Turf Truckster It has the 18 HP OMC 2 cylinder horizontal opposed cylinders with the 3 speed Transmission with reverse. Tag on dash reads : Model: 898515-8010. No other numbers anywhere. I was informed the first two numbers AFTER the dash designates the year produced,,,,All this other info I have gleaned from several Cushman forums. Hope you have better luck than I have as there appears to be a huge lack of documents left from Cushman with an even worse situation about parts availability AND pricing,,,,,
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Well,, I got a bit of an update on the OMC engine.I figured I was gonna have to pull the cylinders or pull whole engine out so I was removing the flywheel and LO AND BEHOLD when it came off,,,,there was the danged'est bunch of UGLIES stored in there by RATS,,,,maybe at least a 5 gallon bucket full for sure,,!!! ![]() AND,,,I still have a NO SPARK sitiation on the engine. I tested both coils , one at a time using the battery and a spark plug and they both tested good,,altho spark was not to big ,,it was a spark,,,?? Hooked both coils and the timer (distributor) as per Dave Kamp suggestions and still NO FIRE at either spark plugs or at the points,,!! For funs I installed the old condensor and still NO FIRE,,,!!! What the heck could be the problem,,,???? How do you "TEST" the timer,,(distributor),,?
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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welcome to 'my world of pain'.. wad a B&S motor in a rider,go both ways but NOT round and round. For SURE it has to be busted con rod(seen that ). Yank engine out of rider, drain oil, tear cover off, WTH ??? con rod IS good...OK, morning shot...WHAT stop crank from going round and round ??? Well for me it was 3/4s of the MAGNETS that are SUPPOSED to be glued to the flywheel !!! 6 decades of turning wrenches on small engines and that was the FIRST time I'd seen that.... sigh, I need a new hobby...
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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Well, Jay,,,at least you did not find a king sized Rats nest in your project like I did,,,,!!! That was amazing at the amount of garbage them rats had "RATHOLED" in the space behind the flywheel,,,!!!!
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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What could possibly be wrong at the timer, (distributor) the distributor sees 12 volts negative coming at it and goes thru the points and on to ground which makes the contact points go" fitzzze" when they are forced open (spark) so,,,why no spark on this OMC,,,??
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5715 |
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The 'timer' is nothing more than just contact points. Pull out the coils, install a double-ended coil for an Onan CCK-series, it'll work fine. To run two coils in series, they need to be 6v coils, not something you'll find in many environments nowdays.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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WELL, Dave Kamp,,,you're a Champ,,,but Ummmmm,,,you wouldn't ,,,,by chance,,,happen to know of a PN I could throw at one of them current style of parts persons,,,,that savey these things,,,,huh,,,? ![]() ![]() But,,,,I'll give it a go post haste this very morning,,,,,sigh,,,,, ![]() ![]() WAIT,,,,WAIT,,A Minute,,,let me run this Double ended coil for a Onan by Ms. Google,,,, ,,,,you know how these parts peoples are these days,,,,,,,
![]() ![]() Edited by desertjoe - 29 Jul 2024 at 5:09am |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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On the "No Spark" sitiation,,,it almost has to be the timer (distributor) that is not grounded properly as THAT is what provides the spark that goes back to the secondary windings on the coils which then provides the spark to the spark plugs,,,,right??? Fingers crossed,,,,,
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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dot,,dot dit,dotdit, dit, ddotdeeeeeeeeeee, that right there is morse code for,,,,,"I HAVE SPARK AT THE PLUG WIRES AND THE TIMER",,,,!!!!! YEA,,,YEA,,,YEA I am stoked, Guys,,,!! I used a hot wire to the terminal at the timer and jiggled, moved, pushed condensor and all wires around and finally seen where the main terminal at the side of the timer was going to ground and stopping everything right there! Made a fiber washer and repositioned the terminal where the points and condensor would not ground out on the timer case,,,WHEW,,,!! Now on to more interesting things,,,like putting a spark in the engine and hear it run,,,,?? MANY THANKS for all who worried on this thing with me,,,,
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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Ok...progress !!! Now, I wanna SEE a pickture of youe new beastie !!!!
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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desertjoe ![]() Orange Level Access ![]() ![]() Joined: 23 Sep 2013 Location: New mexico Points: 13510 |
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OK, Guys,,as I have repaired the 12 volts going to ground at the timer,,I am on to completing the wiring in engine compartment and now find one of the two resistors is possibly bad. The 12 volts will not go thru it,, from either direction. on one corner of the porcelin body it has the following : 60 followed by the OHM icon, 10%25 W,,,? What do I order??,,,Or does the engine even have to have it to run? There is a second resister that did not have any wires connected to its terminals,,,?? Hey Jay,,I ain't forgot you, I still am having issues with trying to post pics hoping ole Buckskin agrees to help me get all my pics in one place so I can find em,,,,,????
![]() Edited by desertjoe - 31 Jul 2024 at 7:53am |
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 22170 |
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that's a sixty ohm, 25 watt resistor though I suspect it might really be a SIX ohm ( get extra eye power and see IF it's says 6.0 ohms. Itty bitty decimal point between the 6 and the 0. |
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 79917 |
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Joe... i have no idea what your resistor is, but as Jay said "MOST COILS" for tractors / cars are in the 2-3 amps size... so yours might be a 6 ?? .......... 60 would be odd , unless i just dont understand your system..
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Like them all, but love the "B"s.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 79917 |
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and YES... there are 60 watt resistors (AMAZON) if that is what you need..
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Like them all, but love the "B"s.
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