1990 SP backfiring and generally running like garbage

[hvguy]

1990 SP running poorly SOLVED broken flywheel key

Hi all, new here.

HISTORY:
I have a 1990 sea doo SP with a yellow Rotax 587, I picked it up off craigslist (with and extra 1991 for parts) and managed to get it running with a simple carb, fuel tank, hull and oil tank cleaning. Turns out the small black box inside the electronics case on top of the battery is probably bad, so I bypassed it to get it running. After about 4 hours of fun on the river i decided to replace the carb with a known good one from ebay. This fixed my idle issue and top end power problem.

Problem:
Yesterday at the lake, my buddy was out riding it around and managed to get to full speed, spin out, fall off and get back on without any problems. However once he started it, it was smoking and wouldnt run past 25% throttle because it would backfire through the intake and exhaust and die.

I tried cleaning the spark plugs, swapped the new carb for the old one that mostly works and it still does the same thing. Compression is 135 back 137 front. One thing I did notice is when it does sputter to life, run it for 10 seconds or so, ill pull the plugs and they are kind of wet.... however the ignition coil is in perfect shape.... judging by the compression numbers this engine has nearly no time on it. but the busted grate on the pump housing says otherwise.

Any ideas? I also pulled the carb apart and everything behind the diaphram looks good, all is moving. The fuel pump is pumping at a rate it usually does and when its running, looking into the carb, the jet seems to be supplying the right amount of fuel.

another test I did was pull the front boot off the spark plug while its running and it seems to loose a LOT of power, however when I do it to the back it looses only half...

all input is greatly appreciated as I am absolutely stumped.

-Orlando

 

[LouDoo]

Sorry, I'm not too familiar with this model ski, but generally if it's backfiring it's a timing issue, I would check the rotary valve timing.

http://www.youtube.com/watch?v=ULL5gfQs_UA

Lou

 

[Mekanix]

Replace plugs ?

 

[Coastiejoe]

I don't see where you mentioned changing out fuel lines. Do you still have Grey Tempo Lines?

If so, his aggressive riding may have broke free some if the green goo that forms in the grey lines.

I do agree with Lou in that back firing is normally a timing issue...


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[Dr Honda]

The 1990 woudn't have had Tempo hoses.


BUT.... I'm going to assume the "Little black box" you bypassed was the "Speed Limiter". Is this right? This box keeps the engine from over reving... and if it's gone, and you are riding it that aggressively... you may have damaged the engine.

Check the compression.

 

[Coastiejoe]

The 1990 woudn't have had Tempo hoses.


BUT.... I'm going to assume the "Little black box" you bypassed was the "Speed Limiter". Is this right? This box keeps the engine from over reving... and if it's gone, and you are riding it that aggressively... you may have damaged the engine.

Check the compression.

I knew the older skis didn't have them but wasn't sure of the cut off,,,,


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[Dr Honda]

I knew the older skis didn't have them but wasn't sure of the cut off,,,,


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Yep... depending on the model... they started in 92. By 95, they all had tempo hoses.

 

[Seadoobuddy]

Yep... depending on the model... they started in 92. By 95, they all had tempo hoses.

So the early ski didn't have the gray lines then they went to the gray and now back to black......sounds like an expensive experiment.

 

[Coastiejoe]

So the early ski didn't have the gray lines then they went to the gray and now back to black......sounds like an expensive experiment.

Our government works the same way,,,,


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[hvguy]

The 1990 woudn't have had Tempo hoses.


BUT.... I'm going to assume the "Little black box" you bypassed was the "Speed Limiter". Is this right? This box keeps the engine from over reving... and if it's gone, and you are riding it that aggressively... you may have damaged the engine.

Check the compression.

speed limiter? mpem? black box that records all my date? nobody knows lol, ill post pics when i get it apart. and the compression is 135 back 137 front

I don't see where you mentioned changing out fuel lines. Do you still have Grey Tempo Lines?

If so, his aggressive riding may have broke free some if the green goo that forms in the grey lines.

I do agree with Lou in that back firing is normally a timing issue...


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the fuel lines are canadian black fuel hose, and the insides looked good, the oil lines are a brownish transparent color, but all is well, and its pumping fuel. as for backfiring, I though it was like a mower magneto where the only way the timing can be off is if the crank was pulled and rotated a few degrees which is usually impossible because the shaft is tapered and keyed.

Replace plugs ?

will do that today even though I know they are good from visually cranking the engine and seeing them fire, however they are original

Sorry, I'm not too familiar with this model ski, but generally if it's backfiring it's a timing issue, I would check the rotary valve timing.

http://www.youtube.com/watch?v=ULL5gfQs_UA

Lou

the valve is mechanically coupled to the engine, it cant be moved without disassembly right?

 

[hvguy]

here is a video
http://www.youtube.com/watch?v=zmtvZBGyC9s&feature=c4-overview&list=UU-DoedaIDDTTmlKtfqtE6aQ

 

[Mekanix]

Next theory would be the flywheel coming loose or the ignition plate coming loose.

 

[Dr Honda]

Next theory would be the flywheel coming loose or the ignition plate coming loose.

Yep. An over-rev could have loosened something behind the MAG flywheel.

 

[hvguy]

Yep. An over-rev could have loosened something behind the MAG flywheel.

im no expert in seadoo world but could this really happen? i guess it could have over revved when the pump lost prime in the spin out but... hmm, ill take it apart this evening after work and take a look-see

ill update my findings then.

thanks again!

 

[Mekanix]

im no expert in seadoo world but could this really happen? i guess it could have over revved when the pump lost prime in the spin out but... hmm, ill take it apart this evening after work and take a look-see

ill update my findings then.

thanks again!

High rev's unloaded and then suddenly under load again could have shocked the flywheel and sheared the woodruff key or possibly twisted the crank in the center.

 

[hvguy]

High rev's unloaded and then suddenly under load again could have shocked the flywheel and sheared the woodruff key or possibly twisted the crank in the center.

its official, pigs ARE flying... after work ( 1am eastern) i decided to tackle the flywheel. And then it occurred to me that I dont have a flywheel puller AKA a steering wheel puller... thankfully I work at a machine shop; so I cut one out of .375 6061 aluminum.

after cranking and cranking and hammering; the flywheel flew off ( and this is where I am absolutely baffled ) the key was sheared off and the timing was i believe retarded quite a bit; thus the pre ignition and running like garbage.

SO the big question here is.... how in THE HELL did this happen..... its a tapered shaft, the key is a bit small I must say, however the flywheel was literally rusted on there with a GARGANTUAN nut WITH loctite AND a lock washer torqued to stupid ft lbs.

pics for your viewing pleasure... (im hosting these on google's tiny pic so that they will hopefully last forever so that if any other poor soul has these symptoms this will surely identify the problem)

I also added a little drawing of the puller I made if anyone has some spare aluminum, a jig saw and a drill. The center hole I made 1/2-13 out of convenience and taking into consideration the size of breaker bar I was going to have on it lol. oh, USE OIL ON ALL CONTACT POINTS. the 3 bolts the flywheel takes are M8 mine were probably 2" long; be careful not to crank them into the coils behind the flywheel.

 

[Dr Honda]

I had one shear the hot rivets between the hub, and the outer flywheel. There's a LOT of force when that happens. You should feel lucky that you didn't break the crank. BUT... there is still the real possibility that you pushed it out of index.


Get a rev limiter on that engine !!

 

[Coastiejoe]

Glad you found the issue at least,,,,

And that you have the ability to work in the engine.


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[hvguy]

I had one shear the hot rivets between the hub, and the outer flywheel. There's a LOT of force when that happens. You should feel lucky that you didn't break the crank. BUT... there is still the real possibility that you pushed it out of index.


Get a rev limiter on that engine !!

where might one find a rev limiter? I tried swapping out the black box with my parts ski and its still didnt work.

Oh and if its worth anything, I paid 250$ on craigslist for both of them. lucky me

 

[hvguy]

well, i attempted to retro fit a honda 3mm key and it came pretty close, except the half moon part that goes into the crankshaft was too large of diameter; so I resorted to popping the flywheel off of my parts engine and robbing its key.

ring ding ding ding

back to running as good as it ever did.... although it seems better; almost as if its been broken this whole time and my buddy only made it worse. food for though

still looking for some info on that rev box. According to some above posts this year and engine didnt come with a rev limiter.

thanks again for everyone's help

 

[Mekanix]

Got a pic of that box and the wires coming out of it ?

 

[hvguy]

Got a pic of that box and the wires coming out of it ?

nope. but I went outside to take one just for you.

theres also a box inside the front engine cover but im about 75% sure thats for the ignitor or what have you ( pictured in background )

the one I disabled was in the grey electronics box above the battery and has rotax written on it not denso... so who knows

dont panic btw, the parts in the box are from the salvage doo

 

[Mekanix]

What parts were the wires atached to ?

 

[hvguy]

What parts were the wires atached to ?

good question, i believe they went to the buzzer maybe? or perhaps to the handle kill switch, either way, those are both gone, and it has no safety kill switch lanyard, your guess is as good as mine.

However when I unplugged the red wire going to the (i believe) yellow wire headed to the ignitor it runs, so I rewired the stop switch next to the start switch to connect those 2 so that I can kill the engine.

 

[Mekanix]

Does it still charge the battery?
There's only a few things it could be.
RevLimiter
Regulator/rectifier
Relay

That engine only has a single phase charging system by the looks of it.