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Top end rebuild

4x15mph

Jetboaters Lieutenant
Messages
1,428
Ratings
738 9
Points
173
Location
Downingtown, PA
Boat Make
Yamaha
Year
2001
Boat Model
LS
Boat Length
19
#1
I started on my rebuild and I thought I would document what I could. This is my STBD engine and I am doing the rebuild while the engine is in the boat.

- For the breakdown, I just pulled off what I needed to in order to pull off the cylinder (air intake, exhaust, exhaust bracket, etc. I also moved the engine forward since I wanted to replace the entire immediate bearing assembly to eliminate a slow leak that I had. The hardest part for me was removing the circlips that hold the piston on but I had a sharp pick tool that was able to fit in the groove and pry out the clip. I had to use a scope camera that I bought off amazon and it was so helpful to see the clips and understand how they work.
- For the rebuild, I sent the cylinder out to fullboreonline and ordered their premium top end kit. They bored and cleaned my cylinders, fit the right size pistons, rings, bearings, circlips, and included the necessary gaskets. I am very happy with the quality of this kit and fullboreonline answers the phone when I call and have so much expertise to share. Everything I had hoped for
- I cleaned up the cylinder head with brake cleaner and cleaned up all areas from where the cyljnder was removed. Fortunately this was the oem top end and there weren’t any sealants used on gaskets leaving the surfaces pretty clean.
- I installed one of the circlips on each piston (outside of the boat). Be sure to install the opening of the clip at the top for WSM pistons as noted in the instructions. (Note - my kit was WSM so my notes here are for that brand specifically. Follow any instructions you get with any other kit). I found it easy to install the clips if you put the open end into the hole at 90 degrees and then press on the end that is sticking out of the hole and rotate it into the hole. Then press on the ring with a flathead to make sure it is fully seated into the groove. Critical step!
- I then sprayed my head gasket and exhaust gaskets with permatex copper gasket spray. They are multi- ply, metal gaskets and riveted together. I will not use any sealant on the cyljnder gasket which is a material gasket and is installed dry at the factory as well. Some use sealant here but you shouldn’t have to if you have clean surfaces. Thanks fullboreonline
- I installed each piston, arrow on piston facing the exhaust, including the new bearing, wrist pin, and circlips. Note that for this WSM piston kit they specifically state NOT to use the bearing washers. Tip: I used one of the original wrist pins to press the clip into the grooves and this worked perfectly. (see picture)
- Once all pistons were on the cranks, I put the rings (2) on each piston. There is a long edge on the ring opening and that faces down and seats around a “nub” in the ring groove to keep the ring from spinning. Note that the ring openings should be on the opposite side of the exhaust.

I’ll edit this and add more tomorrow when hopefully I finish up putting it all back together. Sunday may be the break in and it should be 80 degrees
 

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Last edited:

4x15mph

Jetboaters Lieutenant
Messages
1,428
Ratings
738 9
Points
173
Location
Downingtown, PA
Boat Make
Yamaha
Year
2001
Boat Model
LS
Boat Length
19
#2
Rebuild went great and engine started out of water. Biggest tip I have is to pay attention to the service manual when installing heads and cylinder since almost everything requires Loctite thread sealant (PST). I went through 2 tubes. I am very happy with this fullbore kit in terms of ease of putting it together.

Now for the bad news - I have a leak on the carbs for the other engine which I rebuilt and then rebuilt again (1 carb) when it was leaking. Sending out for a full rebuild/remanufacture to make them better than new.

Cleaned up the boat today and will cover with a new cover tomorrow.... next spring, I will bolt on the new carbs and we should be almost better than new. Great weekend working on the boat!
 

4x15mph

Jetboaters Lieutenant
Messages
1,428
Ratings
738 9
Points
173
Location
Downingtown, PA
Boat Make
Yamaha
Year
2001
Boat Model
LS
Boat Length
19
#3
9EF180E6-6350-4232-BCA0-DA578C796350.jpeg Carbs are done and look brand new thanks to Jetski Solutions. Unreal! I am not installing until the next season and I may get the other rack done as well over the winter.

Not a great pic but it is secured to wood which is glued to the box and I want to keep this in tact.
 
Last edited:

Beachbummer

Jet Boat Junkie
Messages
1,307
Ratings
790 10
Points
148
Location
Houston TX
Boat Make
Yamaha
Year
2008
Boat Model
SX
Boat Length
23
#4
Very nice!!! To lengthen the life of the carbs on an older boat I had, I installed 2 fuel filter/water separators in series...it may seem like overkill but frequently the second filter was dirty too..this would make them last 3-5 years instead of 1-2. (It was a SeaDoo though)

Best of luck. Those carbs look brand spanking new!!!
 
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