84 EZ Mara Robin runs fine> falls flat> backfires> takes off

[letitbe]

I have a 84 EZ Mara Robin engine EC25-2PG it runs great then starts stalling, dies, backfires then sometimes takes off fine but then falls flat again. I have changed filter. Any thoughts? Also can anyone tell me something about this engine? hp and such. Follow up, Replaced plug, runs fine> falls flat> backfires> takes off> runs fine. Repeats this. I'm thinking electrical as it is seeming to load up causing the backfire. (thoughts?) Does anyone know what the primary and secondary coils are to test at for resistance? Mine--Pri= 4.9 Sec - 12,000 which I'm thinking are both a little high. (thoughts?)

[Larry1950]

First of all your dealing with an old 2 stroke. Most likely the main seals are bad and or worn cylinder piston and rings. Also that old probably has point/condenser ignition.. What your are describing sounds like the condenser could be failing. Or a carburetor problem. Anyway I would start with a compression test, should be more than 100 psi. Anything less than 100 psi its rebuild time.

[wthompson]

Great old carts and tough as a hell. Compression is the first thing to check, the oil injection systems on these carts fails and you don't realize it until you have no compression. Best thing to do is premix the gas and oil 50:1. You know it has oil this way. Also, the carburetor could need cleaning and adjustment or fuel pump, pulse line or fuel filters clogged. Attached is a service manual, it's for an 1985 with 2PG is all the same. Let us know what you find.

[letitbe]

Thanks wthompson, I had already found the manual on this site, TG and who ever put it there. You know this all came about in the middle of a restore. I've added turn&tail lights, horn, built a new seat, 4 new tires, new custom steering wheel, decals removed and 3/4 the way sanded and ready for primer. The wiring was a mess, so now that this has happened I decided to redo the wiring. After starting I noticed that there was 6-12 inches to much wire in most of the wires, and there were broken and eroded connections. I've redone all of it and just need to put on a new end on one of the S/G motor wires and a new battery cable, and check compression. I don't quite understand the purpose of the micro switch on the back of the F/R plate, and it was disconnected so I did away with it. What I saw in the diagram it appears to create a dead short when shifted into reverse for some reason, also were the manual shows the ground wire on the F/R plate on mine there is what appears to be a fuse socket and nothing on the connector in back. I was finally able to get the carb off, the nuts were in such a tight place I could only get about a 1/6 of a turn with a open end wrench. I drilled the stud holes in the intake out and put spacers(because the heads of the bolts hit the sides of the intake gooseneck) and bolts in from the back side. Carb had some dirt in the breather adaptor plate, so I have purchased an aftermarket breather/filter for it and should be here today. The carb has been cleaned and is back on, all parts seemed ok, so good in fact it has had a kit put in it at some time I would think. Though I thought the float adjustment in the manual was a bit high, I went by the book. The pulser coil specs called for a 120-180 ohms and showed 77. Can anyone explain to me why a lesser resistance would be a problem as long as it is not a dead short as I would think that it would only make the spark hotter if anything? Timing should still be as flywheel passes. The coil read a 3 ohms on prim. and a 12k on sec. in specs. I'll find out today if all the effort has fixed the cart. Does anyone have any idea what the Hp is of the Robin EC25-2pg, 244cc engine? And can anyone tell me what the item is in line from the oil tank to the oil injector pump? A filter or check valve?

[wthompson]

when checking the pulser move the flywheel and see if resistence changes. it should change.

9 HP.?

[letitbe]

Thought I had it fixed but died on way home. I put a timing light on it while running jacked up and after awhile lost fire. I' ve had this happen before, coil test ok cold, but fails after engine warms up. and thus I have ordered a new coil for it. Thanks for all help

[dan the lake man]

try the ign switch itself it could have dirty contacts and only making contact intermittently . if the contacts are not making good contact it would be like turning the key off while driving.... just a thought.

[letitbe]

I have replaced ign. switch and cleaned, shortened, or replaced every contact point on the cart, the compression showed to be 107, but it really runs hard when running so I don't think that is the problem, but do agree that it is about due for an overhaul. I feel that the timing may be a little off but again, that is not the big problem, but will check later. The new coil should be here Wed. , we'll see if that is the problem, if not, then it must be the pulser coil as per low ohms. Thz for all help