95 GTS Carb backfiring after rebuild

tkarvelis

Cadet
Joined
Jul 26, 2014
Messages
20
I rebuilt my GTS carb per service manual and Mikuni website. Poppet is set at 18psi. New Poppet valve with rebuild kit. High speed needle set to close per manual. Low speed is set to 1 - 1/4.

The ski starts and idles smooth out of the water. I can rev it to full throttle with no issues, but going from full to idle, it backfires through the carb.

I had to adjust the timing on the rotary valve only because it stuck to the cover when I removed the carb. I set it to the specs per the manual using a timing wheel.

I am hoping to take it out this weekend... Not looking good :(
 

Jeff Walkowiak

Lieutenant Commander
Joined
Jun 23, 2004
Messages
1,944
Could be running lean, it is called a lean cough, so better check the carb again
 

Jeff Walkowiak

Lieutenant Commander
Joined
Jun 23, 2004
Messages
1,944
no I don't know what you did to the carb but my experience has taught me not to mess with the pop off pressures , it could be air in the fuel line a restricted fuel supply a vacuum issue or even the rotary valve timing messed up when you accelerate and a 2 stroke coughs through the carb it is caused by a lean fuel situation what is causing the lean issue is another story.in itself. If I recall correctly the high speed jet on a sea doo is all the way in so I doubt it's the jet. My guess is the spring you changed for the pop off pressure, go put back the original one and see if it fixes the issue.

If it is backfiring when you let off the throttle not when you accelerate then you may need to revisit the rotary valve timing be sure to use a timing wheel that is made for your valve.
 
Last edited:

tkarvelis

Cadet
Joined
Jul 26, 2014
Messages
20
The pop off pressure is at 18. I never changed the spring. I did change the needle and seat. I did bend the arm a bit because it was sitting about 1/64 high on the spring end compared to the body. I will look at the rotary valve again. I don't have a wheel, but I used Autocad to create the angles I needed. per the manual, (130/65). The plate lined up perfect, so I don't think I am off a degree or two, I will redo it most likely Monday as my weekend is booked.
 

tkarvelis

Cadet
Joined
Jul 26, 2014
Messages
20
Well I had some free time, and opened the high speed needle about 1/4 turn. This did not help. I pulled the rotary valve, and I was off one tooth, but that did not fix the issue.

While I was playing, I noticed air bubbles in the fuel supply, and return. The return had more bubbles then the supply. I don't have a lot of fuel in the tank, it is maybe 2 -3 inches from the bottom.
 

tkarvelis

Cadet
Joined
Jul 26, 2014
Messages
20
It is now running. I found a pinhole in the fuel supply line between the filter and carb. I replaced the line and she screams on a hose.
 
Top