1995 speedster

[Kanto92]

Hey guys hopefully the gurus see my cry for help.
New to working on Seadoo’s but very familiar with 2 stroke and 4 stroke bikes/ atvs and cars.

I bought a seadoo speedster twin 657x with zero compression in one cylinder. After opening up the top end I saw the cylinder walls were scratched up and the piston chipped. I rebuilt the top end and broke in the engine. Once I started to bring rpms up i noticed the same cylinder was hotter to the touch then the rest. Than it started stalling out, I immediately returned to shore and saw my compression was cut in half. I opened the engine back up and the same cylinder was damaged in the same way as before. The other cylinder was fine. I’m unsure if there is a tell tale sign here that I’m missing. If anyone is interested in giving me their two cents I have pictures I could post

Thanks in advance
Kyle

 

[Kanto92]

Pictures how I got the boat

 

[Kanto92]

After I rebuilt and broke in the new top end. Spark plugs are from the same engine to show difference between cylinders

 

[GGuillot]

You fixed the result, but still don't know the cause, I'd turn attention towards the carbs issues and take a close look at fuel delivery.

 

[Kanto92]

My first guess was running lean over heating and causing my issues. seems I should be replacing all grey fuel lines and will likely send the carbs out for a professional rebuild

 

[Kanto92]

I believe this is the correct kit for 657x in a 95 speedster , anyone want to chime in ?

 

[mikidymac]

Yes, but you will need two kits if it is a twin carb and also new needle and seats as they are not in the kits.

 

[Kanto92]

Yes, but you will need two kits if it is a twin carb and also new needle and seats as they are not in the kits.

Awesome thanks for the quick reply , did you read my issue further up the thread , looking for all the knowledge I can get from people who have been elbow deep in these boats.

Thanks in advance

 

[mikidymac]

Yes, never rebuild an engine until you find out what caused the issue. 9 times out of 10 on these it's dirty carbs/fuel system that causes the engines to fail.

Replace the small 3/32" oil lines, oil filter, fuel filter and rebuild the carbs using only genuine mikuni parts.

As an added FYI you should always leak check any old engine or one that has been apart since air leaks on a 2-stroke will run lean and melt down just like yours too.

 

[Kanto92]

Thanks now I just need to wait for the snow to start melting to get the boat back in the garage !!

 

[jason myers]

Lessons I have learned, I not a seadoo guru but have learned a lot of lessons the hard way:
*genuine mikuni kit*
If you replace the seat and needle valve buy the right size and the right spring to get correct pop off pressure mikuni has charts for spring to seat size. NEVER chop the spring. Perform every check on the carb you can with a pump and vacuum tester. Replace the carb housing screws with internal hex machine screws the original screw heads round off easly
If you take the engine out fork out the money for the engine alignment tool. I built the homemade tool that is floating around the forums because i had access to a machine shop, it doesnt get even remotely close to the sbt tool. When you shim the engines you might need to remove factory shims under the motor mounts. They have probably corroded away.
check your rubber bellow that holds your carbon seal in place. it should be very very stiff. if you disconnect oil feed lines foam ear plugs work great to plug the lines . Then make sure you bleed the air out going to your oil pump.
If you ever start having slow cranking problem on one engine check the ground before you start buying new starters. If you do buy a starter dont buy the cheap ones on ebay.
Keep extra exhaust gaskets on hand, seem like i find a lot of reasons to take my exhaust off and suck to wait 2 days to get a new one.
If you replace bolts make sure they are 304 stainless bolts just labeled stainless dont cut it
also related to your rebuild, if your piston ring got stuck and broke up check the bottom end for pieces of it.
Sorry to flood you with so much info but i wish i would have had all this info from the start.
I had to replace both of my engines within days of buying my boats because i didnt know the condition the previous owner left it in.

 

[Kanto92]

Hey guys so Iv finally found abit of time to start tearing into this project. I have done some research but thought id ask. I think I can slide my engine forward and remove it with the pump in , but is there any way I can align it properly after or do I really need to take the pump out. It adds a lot of work that I’m not extremely familiar with.

Thanks in advance

 

[mikidymac]

Yes, the pump has to come out to align it.

 

[Kanto92]

One more question so I’m clear , I can only find Manuel’s for the actuall Seadoo’s not for the boats. Am I safe to assume a speedster is pretty much the same procedure

 

[Kanto92]

So if anyone is interested I finally found out what’s causing my melting cylinder, the genius that worked on the boat before me forgot to hook up the small oil line that goes from the oil pump to the carb/cylinder. My fault for not checking but It was pretty hard to see until I pulled the motor.