1987 marathon bottom end tore up

[tierhog]

So my cart has been running rough. bogging on the bottom end. back firing. low power. Acted like it was flooding. It had 125 compression. I couldn't figure it out. rebuilt the carb. You name it i did it. Finally broke down and pulled the engine. I have never worked on one of these before. A lot of 2 strokes in cycles but never a Robin engine. Anyway. when I pulled the fan and balancer to check the seal. I saw twisted metal fragments under the balancer. I then noticed the crank seal had the copper or brass part in place but no rubber in it at all. I thought oh there is my problems (leaking out the crank). I pulled the seal to order new ones. Then I noticed where the twisted metal frags. came from. the bearing had all the balls on one side of the bearing and no spacers between the balls and the crank moved up and down about a eighth of an inch. My question is how did this thing run and how did it not throw that rod or seriously damage this engine. I am lucky i guess. Has anyone else saw this before on an 87 2pg. My other question is could I get away with just putting in new bearings and seals and leave the top end alone since i have 125 comp???? Or should I just rebuild the whole thing and be safe. Has anyone just reringed one and not put new jug and piston in. Trying to save some money on this as the wife is pissed about how much i spend on golf as is.. thanks for any comments or advice

[madoc1]

tier, if your crank is good, i would replace the three main bearings. these a very common size and you may be able to pick them up from a bearing house.
if not then the sponsors have them.

as for the jug and piston, if there is no scoring just measure the clearance between these. i believe 7thou is the max. rings are cheap ($16?), but the whole set up -piston and rings is just about $35 or so.

i would replace at least the rings as long as you are in there. just break the glaze with a hone and you should be good.

also replace both seals. if are still running the oil pump, dump it, as something had to cause this and it was probably the pump. just premix.

at the top of this forum you will a sticky. open and go to one with the stars. here you will find most all the instructions you will need.

[tierhog]

I didn't mention that the oil injection pump was shot (wouldn't pump). I have been premixing for about a month. I bet the damage was done during the time the pump was not working. I forgot about that until you mentioned it. I was under the assumption that if it still ran good it didn't burn nothing up. But I guess it did..Just progressively got worse as the metal shavings from the bearing tore more and more stuff up. Oh well lesson learned its premix forever now. That pump is going on EBAY. lol

[tierhog]

One more thing. Does anyone a scan of the service manual for the torque specs on the engine for this thing. 1987 marathon 244cc robin.

[tierhog]

Well i replaced bearings, seals and put in new rings. Cart runs great. Anyone know a way to quiet it down a little more.