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96 GTX Carburetor Rebuild

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Titaniumboy

Titaniumboy

Active Member
All I was planning on doing to my 1996 GTX was to replace the gray fuel lines (see “96 GTX Gray Fuel Line Replacement” thread) But then Mikidymac gently persuaded me to rebuild the Mikuni carbs since they had not been touched since 2010.

And it was strongly recommended to stick to genuine Mikuni rebuild kits

So I found a couple of Mikuni rebuild kits on OSD Marine (osdparts.com) that appear to be a decent price. These kits appear to have more parts than the standard rebuild kits.

OSD 1223 $108.99

OSD 1270 “Back to OEM” $128.99

But then he has a bunch of add and delete options on both of these rebuilds? I’m really confused as to what I need or don’t need.

Second Question: Would it be preferable not to bump or run the engine at all until the carbs are rebuilt and the fuel lines replaced? Or would it be useful to run the ski for a couple of minutes on the hose to get a baseline for comparison?
 
Rebuild carbs replace fuel lines first. Only thing I would do before hand is check the compression.
 
You can get one for free to borrow from Autozone or other auto parts stores.

I would avoid the one that Harbor Freight has in the store as it has been known to read low.
 
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mikidymac said:
You can get one for free to borrow from Autozone or other auto parts stores.

Do not buy a Harbor Freight one, ever.
Click to expand...

Geez, you've got to be the most close minded person on this forum. As I've seen in the past, your word isn't gospel, you can be wrong.. Harbor Freight sells a wide range of compression gauges, from $30 to $120 that read up to 300 psi. They sell thousands and thousands, have hundreds of reviews, mostly positive. Do you really think none of them are accurate? "Ever"....????
 
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GGuillot said:
Geez, you've got to be the most close minded person on this forum. As I've seen in the past, your word isn't gospel, you can be wrong.. Harbor Freight sells a wide range of compression gauges, from $30 to $120 that read up to 300 psi. They sell thousands and thousands, have hundreds of reviews, mostly positive. Do you really think that none of them are accurate? "Ever"....????
Click to expand...
I have been wrong and I am sure I will be again. Maybe don't take things so literally?

The one that they sell in the store is well known to be inaccurate and a lot of people have thought they had low compression due to the way it is designed. I fixed my post above as to not offend the great GGuillot.
 
mikidymac said:
I have been wrong and I am sure I will be again.

The one that they sell in the store is well known to be inaccurate and a lot of people have thought they had low compression. I fixed my post above as to not offend the great GGuillot.
Click to expand...

They sell a lot more than just one model in the store... People on the FB forum are buying them all the time from there, they 'work'.
 
GGuillot said:
They sell a lot more than just one model in the store... People on the FB forum are buying them all the time from there, they 'work'.
Click to expand...
Then by all means buy one, nobody is stopping anyone.
People are free to buy and use whatever they like. The OP asked and I gave him my opinion just as you are free to.
 
[sarc]
Settle down boys. Don’t make me pull out my belt.
[/sarc]

On my way to borrow a compression tester.

Is there anything I should put into the cylinders before doing the compression cranking? Remember the ski has not been started since 2015.
 
Lol,I know @GGuillot is a good guy, we both have the Seadoo sickness and passion.

For compression test.
Fully charged battery.
Spark plugs out and plug caps grounded
Hold throttle wide open and crank until gauge stops climbing.
Repeat with other cylinder.

Don’t add anything to the cylinders like oil.

Perfect compression is 150 psi, at 120 it’s pretty much done and ready for a rebuild. And the cylinders should be even or within a few psi of each other.
 
So leave one plug in, take out the other plug, and install the compression tester in that spark plug hole.

Any easy way to ground the spark plug wire?
 
Nope nope nope.

Apparently I DO need to take out both of the spark plugs. And apparently there are plug cap studs meant to ground out the plug cap.

compression test


I hate it when I don’t know what I don’t know.

I could not find any info on doing compression test in the Seadoo 1996 Shop Manual. Weird.
 
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Titaniumboy said:
Nope nope nope.

Apparently I DO need to take out both of the spark plugs. And apparently there are plug cap studs meant to ground out the plug cap.

compression test


I hate it when I don’t know what I don’t know.

I could not find any info on doing compression test in the Seadoo 1996 Shop Manual. Weird.
Click to expand...

Either one or both plugs out can go either way depending on what you believe so no wrong answer.

Yes, you must ground the plug wires on the provided grounding studs.
 
So I borrowed a compression tester from O’Reilly Auto. I removed the cap plugs and put them on the grounding studs. We shall not discuss how long it took me to find those grounding studs; I kept looking for the grounding studs to be near the engine head, not right next to the friggin battery.

It took longer than I thought it would to get to the maximum pressure reading, probably a good 5-10 seconds. My GTX sounded damn fine for not having turned over for so long.

I got readings of 155 to160 psi on both cylinders, with both readings being closer to 160 than 155.
 
I would say you are in really good shape with almost perfect compression.

If it was me I would put a little premix down the carbs and see if it will fire. I don’t run them really but it’s a nice confidence boost and reassurance it runs before tearing it apart.
 
I was quite pleased with the compression readings. In another thread I had guessed that the ski had about 110 hours. The info center says 86.3 hours.

Since I am going to replace the fuel lines and rebuild the carbs anyway, what would be the harm in trying to start the ski the normal way? This old gal has been super reliable over the years and I’m 95% confident she would fire right up.

If the premix really is the way to go then I have some dumb questions since I have never started my ski that way before. I haven’t even had the carb covers off while owning it (and I am the original owner).

1. Premix ratio? I have some 50:1 available that I use for a small generator, but of course it is not using Seadoo oil.

2. Amount of premix into the carbs?

3. How to get the fuel into the carbs?

Sorry for all the dumb questions. Thank you for all your help.
 
So I found a couple of Mikuni rebuild kits on OSD Marine (osdparts.com) that appear to be a decent price. These kits appear to have more parts than the standard rebuild kits.

OSD 1223 $108.99

OSD 1270 “Back to OEM” $128.99

But then he has a bunch of add and delete options on both of these rebuilds?

I’m really confused as to what I need or don’t need.
 
Any premix will be fine just t see if it will fire.
The reason for not running it long is if the carbs are dirty it will run lean which isn't great for the engine even on the trailer.
 
Like I said it could be lean and mess up the pistons and cylinders and possible run away on you. The only reason to run it is to make sure it runs before dumping more money into it and that can be done with just a little premix.
 
Thank you. I will do a trial run on some premix.

Off to place an order from OSD Parts for their “Back to OEM” Mikuni carb rebuild kit.
 
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