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Engine Failure reason?
- Thread starter ialonso
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Thanks for the thoughts.
Additional details: Since It was rebuilt, It has been running it with 50-1 premix, in addition to the stock oil pump for break in. Carbs are brand new and set to stock jetting plus 1/4 turn open to run rich. While it ran it smoked like a mosquito sprayer.
Both rings were in pieces in that cylinder. If it's either lean or lack of lubrication, Has to be lean, since lubrication should be convered by the 50-1 mix alone.
Additional details: Since It was rebuilt, It has been running it with 50-1 premix, in addition to the stock oil pump for break in. Carbs are brand new and set to stock jetting plus 1/4 turn open to run rich. While it ran it smoked like a mosquito sprayer.
Both rings were in pieces in that cylinder. If it's either lean or lack of lubrication, Has to be lean, since lubrication should be convered by the 50-1 mix alone.
El Toro 33809
Well-Known Member
From my 2-stroke dirt bike days I was always under the impression that gasoline helped cool the engine. Would the premix and injection "aid" in overheating?
I paid for the rebuild, but I did not preform it. The other areas of the jug have almost a mirror finish on them. Not sure if the exhaust port was chamfered. It did run pretty well for 7 hours. Compression was 150-155 after the rebuild on all cylinders.
One other detail...The motor was running with the carb internal fuel pump, instead of a larger external pump. I have purchased external higher capacity pumps and plan to install them after the top end rebuild is completed.
I would look in to the fuel pump. Probably running the engine too lean with the internal pump. The external pump has a accelator pump in them that gives you a shot of gas when you push up the levers. I have the same boat so I am sure the external fuel pump pushes more than the internal one does.
I bought a head, cilinder and bucket online, and have replaced those parts.
I have also installed larger external fuel pumps, and I'm simplifying my filtering and fuel line routing to see how I do. I'm very close to being done with the fuel line re-routing. I'll update the board once I can run it again.
I ran it for about 1 hour after I installed all these parts, but picked up a piece of metal in the pump on the other mottor that locked it up. I had to remove the impeller to get the piece out, needed new wear ring too. It was o locked up I thought it was the engine seized. good thing it was the pump.
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So my problem I thought was the rotary valve turns out to be piston failure..
I've never dealt with this before. The head is somewhat pitted as well..
This piston had less than 7 hours on it.
Any ideas on reason for failure??
Thanks !!!
Easy! That piston was installed backwards, nothing more. Look at where the ring gap is. It got caught on the exhaust port.
Chester
That sucks, if someone built the eninge for you I would go back to them. Usually all the aftermarket pistons have an arrow on them telling you where to point them. If you built it you live and learn. Heck I forgot to adjust one carb on my Polaris SL750 and burned holr right in a new piston. I always double check the carb now after I installed them.:thumbsup:
If Chester is right the piston was installed the wrong direction and/or the rings were flipped and the rings broke they should start to smash on the head and cylinder wall. Usually if you don't have enough gas you burn up the piston by a hole or it breaks apart from heat. It does look like the rings were caught up in the pic and if the piston was flipepd around the ring gap would be protected. If you look real close at your good piston the ring gap is 180 degrees opposit of the bad one. The gap should be at the same place with both pistons.
bigJake
Well-Known Member
Chester is a man of few words, but my observation is he is NEVER wrong.
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