98 XP SEADOO 951 - not starting

[novaslow]

I have a fresh rebuilt SBT motor, I finished breaking it in and it ran great until a couple of days ago. The motor killed while riding it and would not restart. Compression is 125psi, has spark, fuel & carbs seems fine. When turning over the motor the engine seems to back-fire through the exhaust. We have replaced spark plugs, checked all battery connections and we are not sure what to try next. Any help would be appreciated.

Andy from Burnsville Minnesota

[frankey01]

Re: 98 XP SEADOO 951 - not starting

Something is not right you already have some engine damge that needs to be addressed with the compression I would use your warranty now and get it over with on the switch out.

[1fastski.com]

Re: 98 XP SEADOO 951 - not starting

if both clys are 125 its fine , it sounds like you need to pull the mag cover off and check your fly wheel . it prob came loose and spun the woodruff key

[frankey01]

Re: 98 XP SEADOO 951 - not starting

Chris
I know on the older motors if the compression is even and low it is okay but is it still okay on the newer 951 I thought they had to be much higher? Just asking not doubting at all.

[1fastski.com]

Re: 98 XP SEADOO 951 - not starting

i have built some very fast 951s with 125psi , numbers do not mean as much as being even , all guages are differnt , most important is to be even { now 70 /70 would be bad lol BUT if even i would bet the guage would be at foult :-)

[Bill O'Neal2]

Re: 98 XP SEADOO 951 - not starting

My first guess would be the flywheel magneto cup has come loose or, like Chris said, you forgot to torque the big nut on the flywheel and it has come loose.

Another possibility would be that a foriegn metal object is loose in the magneto housing causing havoc with the ignition pickup and magneto.

[novaslow]

Re: 98 XP SEADOO 951 - not starting

I have pulled the magneto cover and nothing is loose. can that sensor go bad and still send a signal to fire. should the mpem be reprogramed? my gauge is fine I have tested on my 96 xp and that is just fine. It had a little hestastion before it broke.

[Bill O'Neal2]

Re: 98 XP SEADOO 951 - not starting

Causes,
Backfiring through the carbs.
Broken reed petal(s).
Ignition problem, pickup, magneto, broken parts floating around in the mag housing.
Hole in piston. ( not with 125 compression)
Extremely lean condition due to clogged carb or massive air leak.

The above items are the things to consider when it backfires through the carbs.

The MPEM should not need to be reprogrammed. 125 psi is ok on an SBT motor.

[novaslow]

Re: 98 XP SEADOO 951 - not starting

I did replace the magneto on my last motor before i got this sbt motor. The motor ran fine up till that. I did find a very small piece of metal shaveing on that pick up. it is not back fireing threw the cards just the exhaust. should i exersize my warranty cause my motor is 7 months old or should?

[Technical Support]

Re: 98 XP SEADOO 951 - not starting

Your problems have nothing to do with the motor, you have a problem with your electronics as the other posters have stated. Any metal debris in the flywheel housing will cause problems.

[Bill O'Neal2]

Re: 98 XP SEADOO 951 - not starting

"I replaced my magneto". I'd start there.

[novaslow]

Re: 98 XP SEADOO 951 - not starting

I have replaced the magneto and cleaned the pick up. it still has the same problem. Any other suggestions. I have also replaced the coil 2 years ago. Will the reeds cause this or the carbs to backfire?

[1fastski.com]

Re: 98 XP SEADOO 951 - not starting

did you replace your sensor { pickup } that tells the engine when to fire ? have you checked to see how good { or bad } the spark is ? if you have good spark , pull one spark plug and gound out the wire to the post , see if it will start on one plug .

[novaslow]

Re: 98 XP SEADOO 951 - not starting

I haven't replaced the pick up. I had to order one it will be in next week. Please help I dont want to keep throwing parts at it and being wrong. I have check the spark with a spark tester it is fine.

[Bill O'Neal2]

Re: 98 XP SEADOO 951 - not starting

Many times when a magneto is replaced it is either mis-aligned when bolted to the flywheel or it is a 1999 or later magneto. which fires the sparkplugs at the wrong time and makes the motor backfire. Is it possible that this is what may be happening?

Is it possible the bolts that hold the magneto onto the flywheel have sheared off or are about ready to shear off?

Any of those things, along with the others I mentioned earlier, can cause backfiring out of the muffler.

When a motor backfires, it is almost always something to do with the magneto, the timing or the pickup.
The timing is fixed, so that leaves mechanical problems in the mag housing as the usual culprit.