97 Sportster MPEM ?

[Umbrella]

Rebuilt engine, runs great for short time, then cuts back to low speed. Throttle has no effect, except to kill engine when pulled back to idle. Neutral switch OK.

How can I test the MPEM, or replace it. SeaDoo has discontinued the part (204 470 035,) but the price was $900, so I wouldnt buy it anyhow.

 

[kustomkarl]

Welcome to the seadoo forum umbrella. Just because the part number has been discontinued doesn't mean it isn't available anymore...it must have a new part number now that's all. It sounds like fuel problem than an electrical problem. If the MPEM was bad it would keep blowing fuses or have no electrical power at all.

It sounds like you need to remove the carburetors and clean them. If you're careful and don't tear or damage the diaphragms you won't need to buy a rebuild kit. Pay attention to the internal filters too. If you have gray fuel lines you need to replace them with black fuel lines available from auto parts stores like Auto Zone. Measure the length you need and bring a sample with you so you get the correct size. Replace one at a time so you don’t get them mixed up. If you need clamps replace them too. Use small stainless steel clamps also from the auto parts store.
I hope this helps out.

Karl

 

[Umbrella]

97 Sportster MPEM ??

I bypassed all fuel lines with one 1/4 inch ID hose with bulb from outboard. Same problem. Also removed muffler, thinking back pressure could be the problem.

Is there a way to bypass the MPEM?

Thanks for any help.

 

[kustomkarl]

Did you clean the carburetors? Running clean fuel through dirty carbs will not change anything.

Karl

 

[Umbrella]

The carbs were rebuilt when 2nd engine put in. I will try re-terminating the spark plug wires tomorrow morning.

 

[kustomkarl]

Keep us posted on your progress.

Karl

 

[Umbrella]

Continuation of problem 97 Sportster

I finally got back to this hole in the water. I re-terminated the plug wires. No help.

Bypassed fuel filter and reserve switch, put in-line filter in place. Filter is clear plastic, so I can see the problem is insuficient fuel flow.

It will run at half throttle arround the lake, and seems like it will continue until I drop it back to idle, then it won't go again for several minutes. This is when I look at the filter, and it has no gas. So I idle back to the dock, looking for a hand gernade. The gas tank is 3/4 full, hose and dip tube look good, so I don't know how it picks up the air. Seems like it should siphon without a pump.

I have an external pump from a PWC, is there a way to modify the carbs to use it, removing the internal carb pump?

Replaced the pulser tube today, no help. I want to check the internal carb filter, but am afraid of losing springs while standing on my head.

 

[Umbrella]

97 Sportster continued......

Removed carbs, put in double thickness of anti-siphon valves as recomended in Mikuni documents. Also checked filter, all ports are clean, new 1.2 seats and valves. Pop-off at 42 psi on both carbs. New diaphrams, o-rings. I thnk fuel flow is ok, there was an air bubble in the in-line filter.

Problem continues - ready for gernade!

Re-statement of problem - Starts, idle rough, accelerates at dock in water, sputters some at half to 3/4 throttle, then cleans up. Pull back to idle, then push up again, and no power, sounds loaded (rich). If I can make it away from dock, it will sometimes run great (seems like it will go forever) until I drop back to idle, then it will not go again. Idle back to dock. Try something else.

Boat for sale if anyone wants a project!

 

[vilord]

have you checked that the low and high speed screws are properly set on both carbs? Try the factory settings.

If that doesn't work, you can try this: http://seadoosource.com/carbadjust.html and see if you get anywhere... the guide is for a single carb machine, and yours is dual carb, so it might take some finagling to get things right.

 

[timmyboy76]

Umbrella....man, I thought I was the only one, with this problem. I replaced EVERYTHING, wires, electrical componants..blah,blah,blah. Set it at 1-1/4 on low, high at 0,. Come to find out, my carbs were not pop'n off consistant, why, dont know, but, ended up get'n carbs, set at those specs, and using "black" float spring, get'n mid 50's for pop-off, with 1.2n/s.(factory oem # for spring, is the black spring in kit).
...until figured this out with carbs, the meantime, when mine acted up,.. just pop the choke, and, WHAM, boat spooled back up again. but yah, worked great first time launch'n, get passed bouys, no problem to WOT, burn a full tank, as long I didnt bring to idle, then damn thing fart out, not goin past 4k at 15-20mph...

 

[timmyboy76]

hey...come to think of it, only cost souple buks if you dont have one, but check out the o-ring for the inline filter, if dried or missing, get one. Have read threads/post, that replace'n this, fixed the problem, cuz its caus'n/pull'n air in system...keep posted, curious to fix problem.

 

[Umbrella]

Sugusted solutions - tried

Thanks for the sympathy, I will try the choke trick this PM.

I have removed the factory fuel filter, because it may have been clogged, and used an in-line unit. Still have same problem, even when using outboard gas can. (To eliminate fuel line possibility.)

I would like to put known good carbs on to see if problem is fixed before paying another $400 for new ones. For what I have spent on this so far, I could have bought a good boat!

 

[96 sportster]

how much you want for it??? e-mail me at jandlpropertymaintenance@yahoo.com

 

[Umbrella]

97 Sportster

The choke pull when in problem did not work, killed the engine. Seems to prove carbs are running too rich.

I found some carbs for a reasonable price, and will try them before I sell it.

 

[timmyboy76]

darn...last shot b-4 the carbs, chief...disconnect the red wire from rectifier...see what happens..:banghead: