'04 Yamaha 800 XLT

[sigma1014]

I have blown two engines in this machine. The first one a shop replaced shortly after I perchased the used pwc. Not knowing the history of the machine, I thought it might have been abused. I blew the new one. I thought I gave it enough break in time by taking it easy before I started revving and hot rodding it (after one tank full) the engine seized. I believe that was my fault. With a new engine replaced under warranty, I took it easy for two tank fulls even with oil added to the tank and babyed it mostly idling around going down canals last summer. Labor day I began riding it a little harder and it performed well. This season I took it to the river thinking it was ready (last month) it performed well and after four days one piston started slamming into the spark plug. This time I was on my own, so I perchased an engine from SBT and replaced it myself. This is the third one. I'm tool and mechanically savvy but obviously not engine savvy. Being parinoid I put 3 quarts of SBT break in oil in the tank (15 or 16 gallons) more than recommended. I idled it in the driveway with water hooked up to make sure it runs and check for leaks and so fourth. I haven't put it in the water yet. Can you tell me what I'm doing wrong and the proper way to break it in and for how long? Also, why don't two strokes come already broken in? I appreciate any advice you can give me.

[Pale Rider]

Re: '04 Yamaha 800 XLT

I have blown two engines in this machine. The first one a shop replaced shortly after I perchased the used pwc. Not knowing the history of the machine, I thought it might have been abused. I blew the new one. I thought I gave it enough break in time by taking it easy before I started revving and hot rodding it (after one tank full) the engine seized. I believe that was my fault. With a new engine replaced under warranty, I took it easy for two tank fulls even with oil added to the tank and babyed it mostly idling around going down canals last summer. Labor day I began riding it a little harder and it performed well. This season I took it to the river thinking it was ready (last month) it performed well and after four days one piston started slamming into the spark plug. This time I was on my own, so I perchased an engine from SBT and replaced it myself. This is the third one. I'm tool and mechanically savvy but obviously not engine savvy. Being parinoid I put 3 quarts of SBT break in oil in the tank (15 or 16 gallons) more than recommended. I idled it in the driveway with water hooked up to make sure it runs and check for leaks and so fourth. I haven't put it in the water yet. Can you tell me what I'm doing wrong and the proper way to break it in and for how long? Also, why don't two strokes come already broken in? I appreciate any advice you can give me.

There are other issues going on for you to go thru several engines. When was the last time the carb`s have been gone thru?
I have known 2 stroke engines that run hard from the minute the button is pushed and the ski is started with no issues. babying a 2 stroke is also not good. You need the pressure behind the rings for the rings to properly seat. 3 quarts of break in oil is tooooo much... you could be making the situation worse by causing a leaner fuel ratio by adding so much oil to the fuel. 1 oz. of oil per gallon extra would be fine for 1 tank...
start the ski up and don`t go over 5k rpm for the first 20 minutes. shut off and let cool down. after sitting for 20 minutes or so, start the ski up and ride bringing the rpm`s up to 6k with slightly hard pulls and varying your rpm`s while cruising, do not stay steady with engine speed. shut down and let cool again. Refire the ski up, ride varying throttle and do harder pulls and hold the throttle wot for a few seconds only. Continue to ride the ski doing all these varying speeds with no steady engine rpms for any extended length of time. There are many ways and opinions on breaking in a 2 stroke, this is one way you`ll be fine...
Do that until the first tank is depleted. One the second tank do not add any additional oil, just gasoline. Ride the ski, going thru all of the rpm range with quick full throttle pulls for a little longer than before, let the ski wind up and slowly release, you really don`t want to chop the throttle on any machine...

Im going to assume you still have oil injection!? did you go thru all the oil lines, how about cleaning the oil tank and checking for contamination? is the oil pump functioning and set up correctly? what oil are you using in the oil tank?

when you have multiple failures, its either poor rebuilds, poor quality parts that fail, something was overlooked, the engines were not pressure tested, and/or there is an underlying issues that needs to be found and resolved first...

Hope this was helpful... diagnosing an issue on the internet is often difficult as more information is needed and the ski is not in front of the members helping out.
Loosing a rod bearing could be from lack of oil, but the piston skirt would also suffer and show damage. 2 stroke engines are finicky and need to be 100% in order to survive... good luck...