Full Bore


Sea Doo Tech Tips

Always refer to the proper service manual when removing and reinstalling an engine or for most service work.

This page is only to help with the most commonly overlooked or missed issues. 

RAVE valve or power valves.

After boring the cylinders on a Sea Doo 787/800 947/951 or any other engine with a power valve, you must relieve the  exhaust power (RAVE) valve for clearance or you will snag your rings and destroy your new top end.  The old rule of standard bore and first over don't need the valves relieved doesn't always hold true. As things wear they tend to get closer and eventually they make contact even on std bore with high hours. 

power valve

Valve on the right has been trimmed.

This edge can be relieved with a hand file or dremel tool (die grinder with sand paper drum)

You are only removing enough for clearance between the valve and the piston rings.

We do offer doing this for you on our top end kits.

Never reuse the old spark plugs from a failed engine in your fresh rebuild.  Small pieces of contaminates may be lodged in the plug and drop out after they heat up.

When disassembling the top end of Sea Doo (2 cycle) engine watch for the notorious cageless upper rod bearings the needles will fall out everywhere.  Take precautions and cover the crankcase when removing the pistons. 

Full Bore top end rebuild kits come with caged needle bearings.

Removal of ignition flywheel

pulling fly wheel

When removing the flywheel be sure that you don't thread the puller bolts in too far, you can damage the ignition coils.  The holes for the puller go all the way through the flywheel and the stator coils are right behind them.

Pictured is a Sea Doo 720.  The 580 and 650 also remove in this manner. 

Note the Sea Doo 800 and 951 models use a different puller.

Sea Doo 580, 650 and 720 ignition timing.

sd timing mark

If you have your engine (Sea Doo 580,650 or 720) rebuilt by Full Bore you can simply align the line (nick) in the stator plate to the engine block.  This mark was made with your ignition, flywheel, crank, and engine cases at the factory when the engine timing was set.

Oil failure.

broken oil lin

The most common engine (besides water) failure on the mid 90's Sea Doo 580,650, and 720 is the small oil lines from the oil pump to the engine (rotary valve cover) break.  From the factory they were painted.  Over time they dry out and become brittle, then break.  Often times the oil pump is blamed: do yourself a favor and check the lines.

Note: Newer lines were also painted but they changed the thinner in the paint.

On a Sea Doo this little rubber bumper goes on the end of the drive shaft, one on each end.  Often you will find it stuck in the P.T.O. balancer after you remove the engine.   If you forget, it the drive shaft makes more noise (rattle) than normal.

rubber bumper

Don't use RTV silicone on any gaskets other than exhaust.  On exhaust use hi temp orange.  RTV will break down and dissolve when in contact with gasoline.  Read the tube!!!  Better yet, read the service manual and use the proper sealants.

Sea Doo cylinder alignment.

When rebuilding the top end of a Sea-D00 580,650,720 or 800 the cylinders need to be aligned properly.  After sliding the cylinders into place install the cylinder bolts finger tight.  Bolt on the exhaust manifold  this will properly align the cylinders then torque the cylinders.  Note be sure to put Loctite to the threads of the inner (cylinder) bolts on the rotary valve side of the engine.

When installing the rotary valve cover on a Sea Doo 720/717 be sure to use a thread locker such as Loctite on the bottom 2 bolts.  From the factory the holes are bored all the way through the cases.  The thread locker acts as a sealant to prevent air leaks.

Sea Doo 2 cycle engine Break-in

 non fuel injected

A break-in period is required before operating the engine at full throttle. Our recommendation is 1 operating hour for a fresh (Full Bore) engine or new top end. We can not speak for our competition this only applies to our engines and top end kits.

10 hour break in period is a thing of the past. Because our Premium HD and Platinum engines are kept to such tolerances and by design break in period is only 1 hour so you can get back to what you really want to do.

During this period, maximum throttle should not exceed 3/4, however, brief acceleration and speed variations contribute to a good break-in. Continued wide open throttle accelerations, prolonged cruising speeds and overloading the engine are detrimental during the break-in period.

To assure additional protection during the initial engine break-in oil (same oil as are using in injection tank) should be added in the fuel tank for the first full fuel tank filling only.

To add injection oil in the fuel tank, proceed as follows: 

Fill fuel tank with approximately 5 gallons of gasoline; then, add 2oz of injection oil for every gallon of gas.  Fill up fuel tank with gasoline. Do not overfill.  In simple terms if your tank holds 11 gallons of gas you would add 22oz of oil to the first tank.  This is in addition to the oil injection.

NOTE: It is important to proceed in this order to allow a proper mixing of the oil in the gasoline.

This is while also using the oil injection system as normal.

If you are running premix only on one of our engines we recommend 32:1 fuel oil ratio for break in and 40:1 after the initial engine break in. 

Read before installing.

When installing your top end rebuild kit always refer to a service manual for torque specs, and general how to specifics. No hammers required for assembly.

  Always wash cylinders before installation.

On WSM (and most 2 cycle engines) the arrow on top of the piston points to the exhaust port. The ring end gap never goes towards the exhaust, it will snag and break.

On power valved engines like the Rotax RAVE valved 787/800 or 947/951 you must verify clearance and trim the valve to avoid contact between the rings and valve. Failure to trim the valve will result in serious engine damage.

No thrust washers are used when installing WSM wrist pin bearings with WSM pistons.

When installing WSM rings if there is a polished edge, it is installed in the top ring groove.

On Sea Doo 947/951 the rings only go on one way, if they don't compress in the groove switch them. Small letters near end gap face up.

When installing circlips be sure it is fully seated in the groove. Failure to do this may result in serious engine damage.

*Note resleeved cylinders often get discolored from heat involved in replacing the sleeve.

Download Sea Doo service manuals for free online. 

This page isn't ours but it is a free resource.

Download Free SeaDoo Service Manuals

A word about compression.

A word about compression and compression testing a 2 stroke engine.

Contact us

Email us at info@fullboreonline.com

Phone 989-340-1321

9-5 Monday - Thursday

9-4 Friday Eastern time 

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Full Bore
486 S Ripley Blvd
PMB #228
Alpena, MI 49707