Hey guys I was hoping to get some urgent help here so thanks for reading this. I have a 2002 Kawasaki Mojave 250 4 stroke and just finished some repairs on it and it is idling badly, and backfiring/popping when you let off the throttle.

It started when I noticed a leak from the weep hole at the bottom of the water pump. I made a 2 hour drive specifically to ride the four-wheeler after it sat for a long time, so I ignored the leak, filled the radiator up with water and rode it for a bit. The engine was getting pretty hot and I noticed my cooling fan on the radiator never came on, so the engine may have over-heated but I'm not sure. The engine was really jerky and sputtery, and was back-firing when I let off the throttle so I figured the carb needed to be cleaned or something.

After I investigated the water pump leak and ordered a full gasket kit, I tore the right-side engine cover off to replace the oil seal and the mechanical seal for the water pump. The oil was completely contaminated with water, and I found the water pump seals to be completely deteriorated. I figure the contaminated oil was simply due to the bad seals on the water pump, so I cleaned the engine some, installed the new water pump seals, and re-installed the engine cover. I filled the radiator back up, and put fresh oil (and filter) in the engine. I replaced all of the carb jets and gaskets (had a clogged starter jet) and it fired right up and seemed to run fine at idle. It was no longer jerking around but was back-firing still when I left off the throttle. After the engine cooled down I re-checked my oil level and it looked clean.

I loaded the quad up onto my trailer and drove it 2 hours to my parents' home. I had started the quad up since the last time I saw that the oil level was good and the oil looked clean, and now all of the sudden, after the trip on the trailer, the oil level was higher than it last was and visibly contaminated with oil. The water level in the radiator didn't seem to be noticeably lower (though it may have been) so I thought maybe it was some residual contaminated oil from the rest of the engine that I couldn't get to.

Before I changed the oil again to get rid of the contaminated oil I changed the spark plug with the correct NGK plug and correct gapping per the repair manual and it was still popping some. I let a friend take it for a ride and he claims that the thing started idling badly, he feels hot air blowing out the right side of the engine somewhere (that may just be the exhaust pipe), and it's popping and back firing really badly. The air filter and intake system is clean, I just cleaned and replaced the jets on the carb.... so now I'm wondering if something may have gotten damaged when I took it out and possibly over-heated it that one day.

I'm really not sure what may be wrong so any suggestions would be REALLY appreciated. I really need some help ASAP please. Thanks so much!!!

-Andrew

 

Correction: I meant to say that the quad had NOT been started up since the last time that the oil level was fine and free of water, placed on the trailer, and hauled 2 hours away. Before I went to even start it up after the drive, the oil was contaminated with water again.