ckerley

2001 XLT 1200 with 72 hours

I took my wave runner out a couple of weeks ago and after running strong for about an hour it stalled on me. I was able to get it running again but had to constantly feather the throttle to get it back to shore. Got it back home, pulled the plugs to performed a compression check and noticed the middle cylinder had been detonated. I am looking for the root cause of this issue since I do not want to perform a rebuild only for it to happen again.

Performed a compression check on the three cylinders 105 / 0 / 105.
Performed a pressure test on the crank case and noticed I have a leak in the rear main seal with no other leaks.
Inspected the reed valves and noticed that three of the eight for the middle cylinder where way out of the .010 gap tolerance.
I am getting ready to rebuild the carbs.

My question is what do your think could be the cause of the lean cylinder causing the detonation.

Ernest T

Most common reasons for failures on that model:
1. Oil line coming off (just zip tied on many models)
2. Power valve dropping into a cylinder. Yamaha didn't fix that problem until 03
3. Lean run from a carb. problem.

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2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100

ckerley

Thanks for the hit list. The first two have been taken care of since I disconnected the oil pump, premix and installed the wave eater clips.

I tore the carbs down and discovered the pulse pump on the #2 cylinder was leaking and the pop off pressure was reading 92 psi. I am thinking the combination of these two things might have been the root cause of my lean condition.

I am in the process of rebuilding all of the carbs and will lower the pop pressure back down to the 60 - 75 psi range.

ckerley

So I pressure tested the crankcase and discovered I had a leak in the rear oil seals. That lead me to open the crankcase up and replace the seals. In doing so I found the smoking gun to my problem...one of the main bearing on cylinder #2 has come apart and was spitting pieces into the cylinder to be destroyed by the piston.

So now I need to replace the crankshaft....Does anyone have any recommendations on rebuilt versus new? And if so where to go.
Thanks...