Ignition Issue on a 1997 XP with a 787 Rotax

[Silentservice]

The engine turns over fine. Good spark coming from plugs. Gap set to .024". Sprayed fresh gas in each carb. Will not try to start. Plugs have wet fuel on them when removed. Checked compression of each cylinder (125 psi each). What is the probability of a sheared keyway on the flywheel? Is there anything else to check? Any help is greatly appreciated...Thanks!

 

[Dr Honda]

It's very unlikely that the flywheel has moved. It doesn't happen very often with seadoo. It's more likely that the gears in the rotary valve have given out. Also.. 125 PSI is too low on an 800 engine. That engine should be at 150 ~ 155 psi.


By any chance did you convert to premix?

 

[purple_people_eater]

check the coil in the rear e-box. make sure all conections are tight. use a test light to see if you have power to the white wire at the coil. if you do not have power there open up the mag housing on the front of your motor and inpect your pick-up coil.

 

[Silentservice]

I have not converted to premix yet. I do intend on doing this soon. You mentioned an 800 engine. Is this the same as the 787? I will pull the carbs and check the rotary valve. Do you know of a specific test I can do to verify?
I appreciate the quick response...

 

[Dr Honda]

Yep... the 787 = 800 in the seadoo world.

No real test... just crank the engine. You should see the valve rolling smooth.

 

[Silentservice]

I do have power on the coil primary. I also pulled the magneto cover and cleaned the trigger coil and stator. All looked good. I verified the resistance of the trigger coil as well. I have a good visible / audible spark at plugs. It did backfire once.

 

[Silentservice]

I pulled the carbs and cranked the engine. The rotary valve turns smoothly. I measured the gap and it is .010" like the book specified.

 

[Dr Honda]

Well... sounds like it should at least start.

I would hit it with some starter fluid, and see what happens. BUT... as I said above... 125 psi is too low... and even if it starts, it won't run well in the water.

 

[Silentservice]

It will turn over and will usually give one large backfire. I pulled the rotary valve cover to inspect timing. It rotates smoothly with no scarring or real signs of wear. Appears to be in good condition. I rechecked compression. I am getting 125 on the mag side cylinder, and 145 on the other.
Summary, new plugs B8ES, new fuel, verified trigger coil, ignition coil, rotary valve condition and timing. I also placed rods on both pistons, at no time during the cycle did the two move in the same direction. I feel very confused...I have fire, fuel, air, and timing appears to be correct. What am I missing??

Thank you all for your suggestions. I am learning more with every post...

 

[ski-d00]

you said you checked the rotary valve timing but did you check electrical timing with a dc timing light? simple to check.

if you have compression, fuel, and well timed spark, it will fire.

 

[6KJR]

Well... sounds like it should at least start.

I would hit it with some starter fluid, and see what happens. BUT... as I said above... 125 psi is too low... and even if it starts, it won't run well in the water.

Im shocked to hear you suggest that!

Check the plug that goes into the mag as well, Ive seen some of those posts get burned up before. Youll need a little mirror.

 

[Silentservice]

I believe I am getting closer to the problem. I have two questions though. First, how do I test the trigger coil other than resistance? It reads 245 ohms which is within the specs in the manual. What voltage should I be reading at the primary of the ignition coil? I am still not getting a consistent spark when reading with a timing light as ski-doo has suggested. Thanks again for the continued help! It is very appreciated...

 

[KyleB]

I'm interested to see what the problem winds up being because I am having the same problem with my 96 XP and I'm in the process of rebuilding the carbs. The responses that I got when I initially posed my question has be wildly different than some of these.

Kyle

 

[russianphil18]

questions

I have a 97' xp and im rebuilding the 787. at first it was just a piston problem (compression 90 and the other is 152) which i removed while the engine was still in but then i noticed the rod was moving up n down slightly so i pulled the engine and am in the process of taking the bottom end off. I have all the bolts out except for the one that the starter to flywheel housing is in the way of. So now i have to remove the flywheel and thats where im lost. the ignition cover is off but idk if i should remove the magneto flywheel cause isnt that the timing. From just looking at it i think the flywheel with the magneto flywheel just spin off. Also idk where to find the repair manual. iv been doing everything by just looking at it. Any help would greatly be appreciated. thanks

 

[Seadoobuddy]

RP18 - Welcome to the forum.
You should really start a new thread with your problem, it will get more replies that way.

If you become a premium member you can download the manuals for free and get faster response time to your questions from the experts here.

Rebuilding help I can't give.

 

[ocod]

Hello, and welcome.
Its better to start you own thread to get the best help.
If you google seadoo manual its the first one for free. Or join site for more personal attention to questions.

 

[ski-d00]

you need a special tool to remove the flywheel, it doesn't just spin off. it is pressed onto a tapered shaft with a keyway. don't try to spin it, you'll do major damage. you absolutely have to have the flywheel puller tool to remove the flywheel. the timing is set by they keyway so that is not a big deal. you do need a manual, you can get it here or a CD on ebay for $5, or other places online for free if you look hard enough.

 

[Bills86e]

The correct plugs are BR8ES gapped .021. Your CDI system needs resistor plugs.

Bills86e

 

[russianphil18]

thank you

you need a special tool to remove the flywheel, it doesn't just spin off. it is pressed onto a tapered shaft with a keyway. don't try to spin it, you'll do major damage. you absolutely have to have the flywheel puller tool to remove the flywheel. the timing is set by they keyway so that is not a big deal. you do need a manual, you can get it here or a CD on ebay for $5, or other places online for free if you look hard enough.

thank you. ill have to buy that. I will start a new thread if i have any more questions. thanks for the quick response everyone