battery disconnected stops running

[Sportster-2001-951C-Stock]

We are talking 951 motor, right?

I'm looking at this chart man, and the largest jet affixed in the 947 was a #80, so I'm kinda wondering how you wound up with a #82.5 pilot, was that factory and this chart is wrong?

http://www.seadoosource.com/carbreference.html

But if you don't have a 2.0 seat then that needs to be changed too, IMO, straight away. It's pretty much agreed upon by everyone the 951 needs a minimum 2.0 seat orifice.

 

[number5]

Ya seat is 2.0 and 165 main. When I get back home the jets should be there and I'll change coil first since that will be easiest.

 

[68ragtop]

Do these skis have accelerator pumps? My old 97XP, (while not a 951) had very lean low speed jetting. it's lean'ness was masked by the accelerator pump. I was able to eventually compensate by bringing the LS screws over a full turn further than spec'd. But it only worked for me because my issue was at low RPM's. I should have increased a jet size or two on that ski, but I never did.

 

[number5]

It's after that. Off throttle it's great then bogs

 

[68ragtop]

Just was pointing out that if you have an accelerator pump, they can mask a lean condition.
Wasn't sure if your ski has one or not.

 

[Sportster-2001-951C-Stock]

Yep, I think all the 951 carb's have a-pumps but I bet he already made sure it's working. The pump shot gets consumed pretty quickly and if the transitions aren't flowing enuff it will fall flat on it's face a good while before the main venturis begin flowing.

 

[Sportster-2001-951C-Stock]

Ya seat is 2.0 and 165 main. When I get back home the jets should be there and I'll change coil first since that will be easiest.

That SHOULD be plenty fat, with the 82.5 pilot it's fatter than mine is but hey if it's too lean it's gonna fall on it's face. Maybe your carbs are a little different from mine so I dunno for sure what the subtle differences might be, if any.

My carbs are the later vertical shaft revision SBN-46i., are those the horizontal butterfly shaft carbs on yours?

Only other thing I can think of is maybe the reeds are tired. Who knows, maybe the iggy coil, could be I guess, or even the CDI in the MPEM but if it was that then you shouldn't have a good WOT either, WOT is pretty much the hardest condition to fire a plug.

Mine has two separate coils on it so that seems different too.

 

[number5]

Ya its strange. Older I get trouble shooting recreational vehicles is not fun for me anymore. I don’t mind preventive maintenance work. Grew up wanting to work on jet and rocket engines. You know if its not done then we can’t ride them. If it was easy to troubleshoot I would be proud to own this particular two stroke. I would like to remove the epem and find a cdi with a close rev limit and curve this engine needs. I don’t look at the gauges anyway. A rectifier and aftermarket start button with kill lanyard. 2 to 1 intake quad venting lectron carb. No oil injection. I have a trx250r I have been racing in hare scrambles since 99. Since the 450 came out in 2001 they have taken over. Now I get a lot of people walking around and looking at my bike as if it was a museum piece.

 

[Sportster-2001-951C-Stock]

Yeah, MPEM's with everything inside were a bad idea IMO. Assuming there is a problem with the CDI, might be able to find a solvent that can dissolve the MPEM potting? Not sure what that solvent might be, but I'm sure the capacitors in the firing circuit will eventually break down at some point? A pocket oscilloscope on the coil primary might reveal some clues.

In the case of some 787 motors the CDI is external to the MPEM:

"DC-CDI Module
The DC-CDI module receives the input from the
trigger coil and signals the ignition coil when to
fire. It also has the rev limiter function built into its
circuitry, as well as the ignition timing curve. The
DC-CDI module is mounted in the cover of the
conventional electrical box."

 

[number5]

So the 787 cdi can be used on the 951? Its just rev limit and curve that matters. The static trigger is what determines firing timing should work. 787 also have a seperate rectifier?

 

[Sportster-2001-951C-Stock]

Yes, the 787 has a separate rectifier and I guess if you could work out the timing issue about any CDI could be used, even the programmable ones that allow you to determine your own timing curve.

The 951 carb motor is the only MPEM that has the internal rr as far as I know, but that's easy enough to disable and jump around with an external rr. Your ski probably has the external rr, is my guess, mine has internal.

For me, the show stopper is the internal CDI, not sure how to work out an advance curve or what ours looks like.

 

[number5]

One day after a few top ends sand blasting transfers and porting then ill do it.

 

[Sportster-2001-951C-Stock]

Right, meanwhile you might consider leak checking your crank seals b/c if they're leaking that would cause a lean air/fuel mix as well.

 

[number5]

tried a few different jets and no change. Runs exactly the same. New coil. Crank seals are good.

 

[Sportster-2001-951C-Stock]

Are you sure your fuel lines are leak tight and unrestricted? I think you're saying it's running out of fuel......(didn't read back through entire thread)

 

[number5]

I took it out Sunday. The carbs are worn out. I believe the casting internally is not within spec from corrosion. Im buying a new set. The fuel lines are all new. I also changed the fuel filter with a different style.

 

[number5]

Put a new set of carbs in.
Runs great now

 

[Seadoobuddy]

That's great that you found the solution.

 

[Sportster-2001-951C-Stock]

There ya go, aluminum carbs were corroded sounds like.

 

[number5]

It was a learning process.