craciunaero
Cadet
- Joined
- Aug 9, 2016
- Messages
- 8
Re: Selva/Yamaha 400 cc 25hp 2stroke 70's rebuild Advise needed. Pics Included
Hello Friends,
This is my first post here so I want in first place to say Hello and thanks for taking the time to read this.
I bought last year a small boat that got under water from an accident. I fixed the boat and drayned the engine cleaned it real good without taking apart the Head or Crankcase. I took it to the lake last year and I ran nice but was making a very loud metalic noise so after a spin I took it out of water. I was able to adjust the iddle screw at that point so engine was fully functional but making noise. I suspected the crank bearings.
This year I took the motor apart to rebuilt it. As thought Crank bearing were totaly rusted and distroied so I replaced them and ordered new gaskets. Compression was 90 PSI on both cylinders wich I assumed is OK for the age of engine. New impeller and waterpump gasket, replaced O rings where waterpump pipe connects to engine basicly every possible O ring or gasket except Head and waterjackets.
After putting everything together with sealant I did what I think is a leak test. I pluged the exhaust with a piece of flat aluminum that was tight to the exhaust gasket. I then moved one piston to BTC and aplyed pressure through the spark hole. I was not escaping. I then moved to the other piston again not escaping. (Reed valve was also check with this test as I did not allow air to escape back to intake manifold).
So finally started the engine and put boat on water. It would die instantly when engaging gear. Iddle(air) screw could not be adjusted to overcome this. I then tried to set idle to 1700 and slam into gear to see if idle circuit was faulty but to my surprise it died again. I took boat back and disassemble to motor and I saw water in both cylinders, more in the bottom one. Also inside there was a mucky liquid, something that looked like grease mixed with water. You can see that in the pics.
So I opened the crankcase to check again and I noticed the FEY ring on the crank bearing was blocking what looks like a hole that goes from crank to the carb intake. In the pics is noted with nr 1.
Please shine some light on me and explain what does that air passage do and how I should arrange the ring and it has only one hole and on crank there are two, on opposite sides.
If someone knows please tell me how the fuel travels on this carburetor and how air adjustment screw works. The needle (tube) has a hole that connect the float chamber with the idle(air) passage.
Sorry for the long story. Apreciate any thoughts.
Attached is a PDF that has the schematic for this engine. Altought PDF is 2003 engine and parts are identical.
Hello Friends,
This is my first post here so I want in first place to say Hello and thanks for taking the time to read this.
I bought last year a small boat that got under water from an accident. I fixed the boat and drayned the engine cleaned it real good without taking apart the Head or Crankcase. I took it to the lake last year and I ran nice but was making a very loud metalic noise so after a spin I took it out of water. I was able to adjust the iddle screw at that point so engine was fully functional but making noise. I suspected the crank bearings.
This year I took the motor apart to rebuilt it. As thought Crank bearing were totaly rusted and distroied so I replaced them and ordered new gaskets. Compression was 90 PSI on both cylinders wich I assumed is OK for the age of engine. New impeller and waterpump gasket, replaced O rings where waterpump pipe connects to engine basicly every possible O ring or gasket except Head and waterjackets.
After putting everything together with sealant I did what I think is a leak test. I pluged the exhaust with a piece of flat aluminum that was tight to the exhaust gasket. I then moved one piston to BTC and aplyed pressure through the spark hole. I was not escaping. I then moved to the other piston again not escaping. (Reed valve was also check with this test as I did not allow air to escape back to intake manifold).
So finally started the engine and put boat on water. It would die instantly when engaging gear. Iddle(air) screw could not be adjusted to overcome this. I then tried to set idle to 1700 and slam into gear to see if idle circuit was faulty but to my surprise it died again. I took boat back and disassemble to motor and I saw water in both cylinders, more in the bottom one. Also inside there was a mucky liquid, something that looked like grease mixed with water. You can see that in the pics.
So I opened the crankcase to check again and I noticed the FEY ring on the crank bearing was blocking what looks like a hole that goes from crank to the carb intake. In the pics is noted with nr 1.
Please shine some light on me and explain what does that air passage do and how I should arrange the ring and it has only one hole and on crank there are two, on opposite sides.
If someone knows please tell me how the fuel travels on this carburetor and how air adjustment screw works. The needle (tube) has a hole that connect the float chamber with the idle(air) passage.
Sorry for the long story. Apreciate any thoughts.
Attached is a PDF that has the schematic for this engine. Altought PDF is 2003 engine and parts are identical.
Attachments
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