1995 Seadoo Gtx project (need help with Carbs tuning).

[Malforces]

Hello guys.
I just completed an top end engine rebuild on a 1995 Seadoo Gtx I got for a very good price here in Washington state.
I verified that everything is working properly but I need some help tuning the carbs.
The Jet ski has brand new fuel lines, with new filter and new fuel selector valve and the carbs have been rebuild and pop off is within the recommended parameters ( pop off around 18 and 19 psi in both).
I set the low and high at the recommended 1 1/4 turns as indicated in the manual.
It starts right up I adjusted the idle rpms to the recommended 1500rpms.
I verified proper adjustment of the oil pump each time adjustment were made.
I ran the jet ski in the water (tied on the trailer) for few minutes in idle to see what is doing did some checking of throttle response and seems ok.
I did not want to do any thing pass a quarter of the throttle until I adjust carbs a little.
I stopped and checked the spark around 2 minutes and noticed that fuel and oil still present when I took the spark plugs out and they were cool to the touched and a little smoke coming out of combustion chambers.
I know I need to lean the carbs a little and just wondering if there are any recommendations on carbs settings for a new top end I might be missing.
Attached are pictures of the spark plugs and the dummy proof hand test ( too hot to handle too lean, wet and cool too rich)

 

[Malforces]

If there is carb guru here please let me know? Or if there is information about tuning a 1995 Seadoo gtx with a new top end and perhaps break in procedures I need to follow?

 

[Malforces]

Forgot to mentioned checks for leaks on the carbs and fuel system were performed and everything is OK (no leaks)

 

[MoDawg73]

I am not an expert, but I will chime in. I think the experts here would say that if the carbs were properly redone ( genuine Mikuni parts, proper pop off springs.), the fuel lines are replaced, the fuel selector switch is good, and there are no leaks in the fuel system, then the factory settings for the low and high speed needles should work fine.

There are also differing opinions about break ins, but what I did was 1/2 tank under 3000 rpms, running it for 15 minutes always varying the speed, then letting it fully cool. Cycling is supposed to be important. Then do the same for The next 1/2 tank at under 1/2 throttle (about 4200 rpms for me). 15 minutes at a time. Next 1/2 tank was same except 3/4 throttle. Last 1/2 tank you could go full throttle but not for more at Han a few seconds, and always varying the rpms.

It has worked out ok for me, but if you want, do a search for break ins and you will find a host of information.

Good luck!

Kem

 

[MoDawg73]

Also, I would be very careful to lean them out unless you know what you are doing. Lean will kill an engine quick.

Most guys I’ve read say that you set the low needle based on low end throttle response. You set the high speed needle based on a run at high speed and pulling the safety lanyard then inspecting the plugs. Also hear very knowledgeable people say it is stupid to run full throttle up for an extended period of time until you are sure it is not too lean.

 

[POPPS]

The book popoff is 19 to 35,,,it is recommended to run the highest popoff possible,,,your 18 to 19 is low...it will run richer,,,I like to split the difference for my start,,,so you should strive for 25ish,,,the low settings always work,,.if you used aftermarket carb parts, you are going to have troubles,,,I am continually rebuilding carbs that came in with issues and used aftermarket parts,,,they just will not run like the stock OEM setup.,,,your plugs should look like a light ale...light brown,,,not dark larger,,,or white ( dangerous) like milk.

 

[mikidymac]

MoDaeg is spot on with everything.

Also did you pressure test your new engine? I would never recommend skipping this step.

 

[Malforces]

Also, I would be very careful to lean them out unless you know what you are doing. Lean will kill an engine quick.

Most guys I’ve read say that you set the low needle based on low end throttle response. You set the high speed needle based on a run at high speed and pulling the safety lanyard then inspecting the plugs. Also hear very knowledgeable people say it is stupid to run full throttle up for an extended period of time until you are sure it is not too lean.

Thanks for the information, I adjusted the low end needles based on throttle response. And it working really good

 

[Malforces]

The book popoff is 19 to 35,,,it is recommended to run the highest popoff possible,,,your 18 to 19 is low...it will run richer,,,I like to split the difference for my start,,,so you should strive for 25ish,,,the low settings always work,,.if you used aftermarket carb parts, you are going to have troubles,,,I am continually rebuilding carbs that came in with issues and used aftermarket parts,,,they just will not run like the stock OEM setup.,,,your plugs should look like a light ale...light brown,,,not dark larger,,,or white ( dangerous) like milk.

Thanks for the information; I got the Seadoo manual for the 95 GTX and in there indicates 16 to 21 psi for dual carbs if I remember right (I’ll double check that)
Wondering if there is a more reliable source for the settings información

 

[Malforces]

I am not an expert, but I will chime in. I think the experts here would say that if the carbs were properly redone ( genuine Mikuni parts, proper pop off springs.), the fuel lines are replaced, the fuel selector switch is good, and there are no leaks in the fuel system, then the factory settings for the low and high speed needles should work fine.

There are also differing opinions about break ins, but what I did was 1/2 tank under 3000 rpms, running it for 15 minutes always varying the speed, then letting it fully cool. Cycling is supposed to be important. Then do the same for The next 1/2 tank at under 1/2 throttle (about 4200 rpms for me). 15 minutes at a time. Next 1/2 tank was same except 3/4 throttle. Last 1/2 tank you could go full throttle but not for more at Han a few seconds, and always varying the rpms.

It has worked out ok for me, but if you want, do a search for break ins and you will find a host of information.

Good luck!

Kem

Ken,
Thanks for the information; I was planning to do something very similar but with shorter intervals 10 minutes

 

[Malforces]

The book popoff is 19 to 35,,,it is recommended to run the highest popoff possible,,,your 18 to 19 is low...it will run richer,,,I like to split the difference for my start,,,so you should strive for 25ish,,,the low settings always work,,.if you used aftermarket carb parts, you are going to have troubles,,,I am continually rebuilding carbs that came in with issues and used aftermarket parts,,,they just will not run like the stock OEM setup.,,,your plugs should look like a light ale...light brown,,,not dark larger,,,or white ( dangerous) like milk.

I just got home and double checked the Seadoo manual and the información there os 16 to 21 psi for dual carbs and 22 to 29 for single carb. Attached is a picture of the page in the doc.
Now I’m wondering if that doc is a real Seadoo manual

 

[POPPS]

Apologies,,,my info is from the mikuni site,,,I will double check,,its mikuni...not from your manual,,,
generally,,,stock setups have relatively high popoffs,,,maybe just give it try,,,to properly adjust the low speed screws,,,I will have the air box off so I can access the low speed screws,,,back the ski/trailor /secured,,,into the water, deep enough for the pump to draw in water,,,And usually I, turn the pilots in 1/8 of a turn till the motor wants to bog/lean out, Having the ski in the water and secured will keep it under load,,,to truly set the pilots out of water is a general area adjustment since there is no load on the prop/motor and thus the carbs,,,the stock /spec carb settings are spot on,,,unless you have a carb,,,that is partially blocked,,,and then the pilots need to be turned out from stock.
The pilots are VERY sensitive,,,and 1/8 of a turn can make the difference between a lean bog..,and perfect,

 

[Malforces]

Apologies,,,my info is from the mikuni site,,,I will double check,,its mikuni...not from your manual,,,
generally,,,stock setups have relatively high popoffs,,,maybe just give it try,,,to properly adjust the low speed screws,,,I will have the air box off so I can access the low speed screws,,,back the ski/trailor /secured,,,into the water, deep enough for the pump to draw in water,,,And usually I, turn the pilots in 1/8 of a turn till the motor wants to bog/lean out, Having the ski in the water and secured will keep it under load,,,to truly set the pilots out of water is a general area adjustment since there is no load on the prop/motor and thus the carbs,,,the stock /spec carb settings are spot on,,,unless you have a carb,,,that is partially blocked,,,and then the pilots need to be turned out from stock.
The pilots are VERY sensitive,,,and 1/8 of a turn can make the difference between a lean bog..,and perfect,

Popps I really appreciate all the information. I have been doing exactly what you described by pure coincidence; I removed the air box to have access to the pilots I kept the flame arrestor installed; I'm 'll always trying to error on the rich side and I will fine tune this more as the new top end gets broken in.
I'm tuning the jet ski in the water i hope soon I'll be checking 3/4 and full throttle but i'm being very cautious about that as I know 1/2 and 3/4 throttle position on a lean setting can be dangerous.

 

[POPPS]

After having studied many breakin methods,,,( breaking in a piston before a race),,,is to ride the boat at half throttle (be on plane),,for 15 minutes,,,and then let it come down to an idle,,to reduce the pressure on the rings,,,then I ride at 2/3 throttle for 15 minutes,,,and then let it come down to idle for a couple minutes,,,then I take it up to 3/4 throttle for 15 minutes and then down to idle to cool down the rings,,,and then finally I go WOT for short bursts,,,and back to idle,,5 or so times,,,and then WOT for as long as I want,,
The theory is to gradually put pressure on the rings with cool down periods,,,if you are not on premix,,,you could add a cup of oil to the tank...if it is a DI you cannot add oil to the tank.,,this has always worked for me.

 

[Malforces]

Popp

After having studied many breakin methods,,,( breaking in a piston before a race),,,is to ride the boat at half throttle (be on plane),,for 15 minutes,,,and then let it come down to an idle,,to reduce the pressure on the rings,,,then I ride at 2/3 throttle for 15 minutes,,,and then let it come down to idle for a couple minutes,,,then I take it up to 3/4 throttle for 15 minutes and then down to idle to cool down the rings,,,and then finally I go WOT for short bursts,,,and back to idle,,5 or so times,,,and then WOT for as long as I want,,
The theory is to gradually put pressure on the rings with cool down periods,,,if you are not on premix,,,you could add a cup of oil to the tank...if it is a DI you cannot add oil to the tank.,,this has always worked for me.

 

[Malforces]

Poops thanks for sharing this very valuable information.
I’ll make sure to follow up the steps described in your message.

 

[POPPS]

There are many theories,,,I studied many,,.and the philosophy behind this made sense to me,