1996 Sea-Doo newly rebuilt 787 having carb problems

[Big Fish]

You never mentioned whether or not you replaced The original gray tempo fuel lines.

Jimmyluke, yes I changed out the Tempo lines years ago. I forgot to mention that.

 

[racerxxx]

If I read this correctly, you did not remove the high and low needles during the rebuild? If not you could very possibly have crap in the low side.

Or, go back to the water, open the grey electrical box find the voltage regulator (3 yellow wires and 1 red wire) and disconnect the red wire and run the ski. If the regulator has gone bad it will make the ski run down on power and come and go with spurts of power. It's a free test, but remember with that disconnected you WILL NOT be charging your battery. So, make it a quick 5 minute ride and stay close to the shoreline.

Image completely stolen for reference only

 

[Big Fish]

You shouldn’t have to adjust the screws at all. You have either an air leak somewhere in the fuel system, or you have some plugged up passages in the carb still. To rule out the air leak, take the fuel line off of the reserve nipple on the sending unit and run it directly to the carb inlet bypassing the filter and separator. If it runs better like this, you know you’ve got a leak somewhere in that system. If not, I think you’re going to have to dig back into the carbs and make sure they’re absolutely clean.

Hey Jeremey I want to clean up the fuel lines today. First just to be sure what size fuel lines do you use? I’m going to replace the feed from the tank to the carbs which is the one I have the filter on. I’m going to eliminate that potential leak. When you say bypass the reserve line and run directly to the carb how would I do that if the line from the tank runs directly to the carbs already(meaning the one I’m going to replace)?

 

[mikidymac]

Standard 1/4” automotive fuel lines.

 

[JeremyD615]

Just run line from the carb inlet directly to the reserve nipple on the fuel tank. Of course you only want to do this temporarily to rule out leaks in the feed system. If you leave it this way you will not have a filter or a selectable fuel reserve.

 

[Ckrawiec]

Oh, Happy Day.....I pulled the '96 out of the water and went into the carbs on Sunday morning (6:00am, nice time to work while everybody is asleep). Took everything apart, carbs out of the ski back on the bench. Clean, clean, clean....I put back ALL the original MIKUNI parts (removed the 757 rebuild kit parts). Put the carbs back in the ski....NO JOY....could not get the ski started. A little gas down the throats of the carbs and they would fire but not for long....what the heck is wrong now???? - DOH, dummy. In my exuberance, I didn't connect the PULSE line back to the carb.....connected it......JOY JOY JOY! Started immediately, maintained herself at 2800 rpm.

Fixed my 12V low problem too.....stator resistance checked out, rechecked all the fuses, traced continuity from front of ski to the rear box connection...all good. Noticed a "little" corrosion inside the connection plug to the rear electrical box, carefully cleaned/ scrapped that out. Made sure all wiring was where it was supposed to be, tightened all grounds, etc. JOY JOY JOY..... started ski and battery voltage was running at 13V+ (rectifier/regulator is obviously working), no more 12V low message on guage , no maintenance light.

Put back on the water....she starts right up, checked RPM's on trailer in water, idling at 1500 +/-, throttle response was good. Told SON to go easy for a minute or two to get her warmed up and burn through any stale residual gas.....then BAM away he went.....full throttle, no hesitation, no bogging down....SHE GOES! Oh, Happy Day! Now, running even better than the day I bought it.

Moral of the story....stick with OEM Mikuni kits.....save time and aggravation (I testify!)

 

[JeremyD615]

Lol... I’m glad you’ve decided to join the brotherhood of genuine Mikuni advocates! Now that you’re a member, you’ll never be able to leave though.

 

[Big Fish]

I will eliminate the inline filter to hopefullly eliminate that as a potential issue. Hope it’s as easy as that.

Update guys. I eliminated the inline filter and replaced that fuel line and still have the problem. I knew it couldn’t be as easy as that. I will pull them off today and see if I can make some progress over the weekend. Thanks again for all the advice. I know I have a stripped screw on the valve body assembly on one carb so I’ve never taken that out. Maybe my issue is underneath that. Any idea best way to remove one of these stripped screws. I assume carefully tapping it out but that could get scary with such a small part.

 

[racerxxx]

I usually drill the head out on those when I find them stripped. Head to Lowes get an M5 x 16? flat head. I think that's the length, take your good one to match up. I want to say 14mm is the correct length but you're not going to find that. They will require an Allen key so I don't think you'll find a Philips in a metric flat head at Lowe's.

 

[Big Fish]

I usually drill the head out on those when I find them stripped. Head to Lowes get an M5 x 16? flat head. I think that's the length, take your good one to match up. I want to say 14mm is the correct length but you're not going to find that. They will require an Allen key so I don't think you'll find a Philips in a metric flat head at Lowe's.

Racerxxx and all, I was able to tap out the screw and thoroughly clean both carbs and the cleaner is flowing very strong through the 3 small holes and the large one. No issues there but still can’t get over 3500 rpms! This thing is killing me. It starts and idles great but if you try to go beyond 1/4 throttle or so it just sits and bounces between 3000 and 3500 RPMs. You snap the choke and it launches to 7000 rpms and takes off for a 1 second then back down to 3000-3500 RPMs. This has to be a tuning issue but I’m following instructions on idle set screw and low speed jets and can’t make any progress. I can’t believe the dealer will pay a kid 10 bucks an hour to tune this in 20 minutes and I can’t figure it out. I’m beyond disappointed. I’m going to have to either bite the bullet and pay a dealer to tune or just move on from this thing which I’d hate to do. Brand new engine and I can’t even see what it will do. Any ideas let me know. I think I’ll go have a beer

 

[racerxxx]

Without going back and reading everything, have you disconnected the voltage regulator red wire?

 

[Big Fish]

Without going back and reading everything, have you disconnected the voltage regulator red wire?

 

[Big Fish]

Racerxxx,
Sorry forgot to try that but i’ll Do that first thing tomorrow. When I disconnect the red wire what should happen? Meaning if the ski runs fine the volt regulator is bad? Just looking to understand what I’m looking to see and what that would mean I have to do. Thanks as always for the help

 

[mikidymac]

Yes very common on the 96’.

 

[racerxxx]

As mik said, yes, the ski should run like it should. Free easy test

 

[Big Fish]

As mik said, yes, the ski should run like it should. Free easy test

Ok guys disconnected the red wire on the voltage regulator and no change in condition. I’m at a loss. The only thing I have not done is that fuel line bypass someone suggested earlier to eliminate a fuel line air leak. I’m not sure what line to disconnect and run to the carbs so I didn’t do that. Is the gas line air leak the most likely issue or do I just need to find someone who can tune these carbs? Not many Sea-Doo places want to bother with these things anymore and will likely cost me as much as the ski is worth to get tuned.

 

[mikidymac]

It’s marked RES on the side of the fuel sending unit and the fuel selector. Just run a piece of hose from the RES nipple on the sending unit to the inlet on the carb. The fitting on the carb you want is the one on the front carb that is connected to the fuel strainer.

 

[Big Fish]

It’s marked RES on the side of the fuel sending unit and the fuel selector. Just run a piece of hose from the RES nipple on the sending unit to the inlet on the carb. The fitting on the carb you want is the one on the front carb that is connected to the fuel strainer.

Sorry I’m being dense here but I get the Res port on the selector but on the MAG carb there are 2 gas line inputs I believe one is the pulse so I assume you mean the other one is that correct? I would have thought I had to go directly to the fuel line that branches in back of the PTO carb and sends a line to the PTO and MAG carb.

 

[mikidymac]

No. There is one on the front of the MAG carb that goes to the strainer and that’s the inlet.

The pulse line is on the fuel pump cover to the engine cases.

On the side of the carb there’s a line that feeds the PTO carb from the MAG, remember only the MAG carb has the fuel pump.

Finally each carb has a return fitting that connects with a plastic “Y” then goes to the tank RET fitting.

 

[Big Fish]

Mikidymac,

Thanks again. Got it now. I will try to replace the line to the input on the Mag carb to see if that changes things.