1990 GT // Progress Thread

[nickandrisin]

Update:

The Sea-Doo is at the point where it will start right up and run whenever with no problems. I haven't gotten a chance to take the battery in for a load test yet, but it's next on my list.

I took the Sea-Doo to the lake yesterday to see how it performs on the water. I started it before heading to the lake, and I started it before dropping it into the water. Once I was in the water, it did not want to start as easily. It took about 30-45 minutes to get it started and to get it to stay started. I later learned this is because it does not want to idle in water. During a majority of the starts, occasionally I would hear a 'whirring' noise, kind of winding down, at the end of the Sea-Doo trying to start (starter?).

I was only able to get it running if I gave it plenty of throttle while cranking and immediately after. It will not idle in water, but it will idle on trailer fine. Do I need to adjust my idle speed screw? Once it's running and I'm feathering the throttle it performs fine. I can go full-throttle no problem and run it until I run out of room.

Anytime that it stalled out from too little throttle, it would take a few attempts to get it started again. Call me crazy, but it seemed like I could only get it started again if I switched which fuel line I was using between ON/RES. If I stalled out on ON, then I had to switch to RES, pump throttle 5 times, then start it up. If I stalled on RES, I had to switch to ON, pump 5 times, then it would start.

Ideas on where to move forward next? Does the starter need looked at? Do I need to adjust my idle speed? What's up with the fuel delivery?

Thanks!

 

[mikidymac]

It sounds like either your idle speed is too low or you have a issue with the pilot circuit in the carbs.

Make sure you follow the carb rebuild sticky about cleaning the 3 small pilot jet holes.

Idle RPM is 3000 out of the water which will give 1500 in the water. You need to set this with a tach, I use a TinyTach.

If you are still having hard starting it the water it is either low compression or too much rotary valve clearance.

 

[nickandrisin]

I restested my compression today and got 145 psi in both cylinders again. After running it on the lake yesterday I pulled the spark plugs today for the compression test and they had oil on them and the tips were black. Cranking the engine at full throttle with the plugs out results in no oil or anything coming out though.

I have ordered a tach and I will test to see what RPM my idle is currently set at. I will also look into pulling the carbs out to look at the pilot circuit. Am I able to just clean these pilot jet holes or should this be part of a full carb rebuild process?

 

[mikidymac]

I restested my compression today and got 145 psi in both cylinders again. After running it on the lake yesterday I pulled the spark plugs today for the compression test and they had oil on them and the tips were black. Cranking the engine at full throttle with the plugs out results in no oil or anything coming out though.

I have ordered a tach and I will test to see what RPM my idle is currently set at. I will also look into pulling the carbs out to look at the pilot circuit. Am I able to just clean these pilot jet holes or should this be part of a full carb rebuild process?

Full carb clean or not at all.
Someone did a really good job here The Seadoo Carb Rebuild Thread

Although I think you have the old round body style carb so it is quite a bit different.

 

[nickandrisin]

I have read through your carb rebuild posting quite a few times now. I do wonder where I can find the proper rebuild kit though.

This Mikuni listing on Amazon shows that it is compatible with all Sea-Doo 580 models, but it does not list the '90 GT in the specific compatible models section: Amazon.com

Do you know off-hand if Mikuni creates a rebuild kit for my style of carb?

I did find a listing from Mikuni for a 1991 GT carb rebuild kit; I wonder if it is the same carb?

Amazon.com

I did see another Amazon listing from Winderosa (I'm not buying from them, I'll buy from Mikuni if they have it), that shows a carb rebuild kit for a '90-'91 GT. So I would assume the kit for a '91 GT from Miknui would work on my '90, right?

 

[Spider4real]

OSD Sea Doo Complete 587 Round Body Single Carb Pkg (1988-1990) [OSD1100] - $44.99

 

[mikidymac]

OSD above is the kit you want.

 

[nickandrisin]

Update:

I purchased two of the OSD carb rebuild kits linked above and got to work. It would have been great if my model had the same instructions as the carb rebuild thread, but it can't always be that easy!

I started by consulting the service manual and saw that I needed to remove the entire RV cover to get the carbs off of this model. I disconnected all hoses leading to and from the carb, and got the RV cover off. I made sure to carefully keep the RV in place as I removed the cover.

I discovered a couple of things inside of the carbs that could be leading me to have hard starts and no idle.

First, my low speed mixture screw is supposed to be 1-1/2 turns out from seated; the screws on both of the carbs were locked in so tight that I had to use pliers just to unscrew them.

Second, the diaphragm plate gaskets were a slightly different shape and they were a different color than the diaphragm gaskets in the Mikuni kit. It may have been rebuilt in the past with incorrect parts.

Third, one of the carbs had the needle/seat corroded so bad that I had to use pliers to remove the needle out of the seat.


And fourth, there was a buildup of some brown powdery substance in both of the carbs.


I removed everything from each carb and began the cleaning process with carb cleaner. I made sure to spray it through each port and verified that it was spraying out of all of the tiny holes inside of the carb body.

As I begin to put the carbs back together, I am running into a few questions.

Question #1 - My replacement needle does not look the same as my previous needle. The new needle does not have the little metal piece on top that allows it to connect it to the arm/lever, the needle looks to be a different size, and the old needle has a rubber tip, while the new one has a metal tip. Did my kit contain the wrong needle?


Question #2 - When holding each carb body up to the light, it looks like they are both adjusted slightly differently in terms of how far they stay open at idle. Do I need to adjust one or the other to make them match? Pictured below, the first carb is the MAG and the second is the PTO.


Question #3 - My carb does not have a high speed adjustment. The kit comes with a new high speed adjustment o-ring. I do have a "main jet" screw though with an o-ring. The o-rings do not seem to be the same size though. Am I able to use the replacement o-ring with this main jet or do I need to keep the old one in there?


Question #4 - When reinstalling my gasket that goes between the carb body and the intake manifold, is there a specific direction the gasket needs to go? It is slightly different on each side.

Question #5 - Do the carbs need repainted? They both have plenty of flakey paint coming off on them.


Thank you everyone for your help so far. I'm excited to get this thing up and running properly. I am using the time that I have the RV cover off of the Sea-Doo to drain the oil from the system and replace it with the proper oil.

 

[mikidymac]

1. New Needle and seat should be fine.
2. The idle is set on one carb and the connecting arm should make them the same.
3. Not sure on the HS screw.
4. No need to repaint.

 

[nickandrisin]

Thanks for the response. What is the process for installing the new needle? Don’t I need that little metal piece on top for the lever to hook onto? The the little piece that sticks out of new needle pushes in, kind of spring loaded.

 

[mikidymac]

Correct, the clip isn't needed.
The one you pulled out is either not a Genuine Mikuni part or someone installed the newer and incorrect needle.
The new one that came in your kit is correct for your Round Body carb.

 

[nickandrisin]

Update:

The carbs have been rebuilt and I pressure tested them and they are at the correct spec currently.

While I had the RV cover off and the carbs out, I figured that was the best time to drain all of the oil out of the engine and lines and get the correct oil in. I removed all oil lines and completely drained them before adding in the new oil.

I am having an issue with one of the oil line connections. It is the connection right under the RV cover/carb area, I believe it goes to the lower end of the engine. The line there was pretty rough on the end, so I trimmed off about half an inch and then put the line back on with a metal clamp. There seems to be a very slow leak from this connection. I put a clean paper towel under it to verify that this is where the oil leak is coming from. Are there any suggestions on the best way to secure this connection?

 

[Spider4real]

That oil line feeds the rotary valve cavity. It's possible the clamp on that old oil line might have cracked it. I personally would change the line. New line and clamp should solve the problem. But it will mean draining the oil tank one more time.

 

[nickandrisin]

Update:

I changed out that leaking oil line and the leak was fixed.

I put everything back together and took it out on the lake yesterday. Everything seems to be running exactly as it should, but the idle is set a bit too low I think. I had to keep the throttle slightly depressed while on the water or else it would die.

So my next step is to adjust my idle speed. I know where the idle adjustment screw is, but I have a question on my target RPM. I know I have seen on these forums that we should be aiming for 3000 RPM out of water, and I think 1400 RPM in water. My service manual states: "Turn screw so that engine idles as 1200 RPM in water or 1500 RPM out of water." That seems low, no? It may be different because it is the 587 motor?

I do have a digital tach installed and I also read on this forum that these Seadoos are 2 sparks per revolution, is that still the case for the 1990 GT? I'm not sure how to look that up.

 

[Spider4real]

I would set it to 1200-1400 in the water and see how it does. As long as you don't need to hold the throttle it will be fine. And i would be very curious what it does when it's out of the water.

I don't see why the yellow engine should be much different than the white one. My 92 587 idles 1400 in the water and about 3200 out of the water. When under no load the RPMs should go up more than 300.

I believe you are right with the 2 sparks per revolution. I think all seadoo 2 stroke engines will be the same. But I'm not 100% certain. Hopefully someone that knows can chime in.

 

[DougtheSlug]

I'm very impressed by the writeup and photos you provided, nickandrisin! With your attention to detail I'm sure the old GT will be a ski to be proud of...Bravo!!