Rough idle?

[Randypape]

Hello, my 1996 gti idles rough without touching the throttle. If I move the throttle a little then it smooths right out.
Once I give it and it takes off past idle it runs great. I haven't done the plug test / adjustment procedure posted yet. I thought I saw somewhere that there were standard settings for the mixture/idle screws for these carbs? For an old unit I sure had a lot of fun with it this last weekend and even pulled single tubers with it. Any advice or suggestions are welcomed. Thanks Randy.

 

[jjsinaz]

Increase the idle speed. Should be 3000 rpm on the trailer/1500 in the water

 

[mikidymac]

Also these 720's aren't smooth at an idle like a car, they do shake and vibrate.

 

[Randypape]

Ok thanks for the replies. I do know if I go to restart it right after shutting it off , it'll start better if I opened the throttle a little . For a 26 year-old ski I'm still very happy with it. One other question should I switch to premix to prevent engine trouble down the road? Right now I see the oil injection is working .

 

[mikidymac]

The oil injection is very reliable but.....
1. Make sure you are only using APT-TC rated oil never TCW.
2. Change the oil filter every couple of years.
3. Replace the small 3/32" oil lines from the pump to the intake manifold every few years.
4. Make sure the oil pump is adjusted correctly.

 

[Randypape]

I'm using the full synethic seadoo oil along with non ethanol gas because the guy I bought it from did and I have 140psi on each cylinder so I don't mind spending a little extra on it. I've had this 3 years now without any issue's. Thanks

 

[Randypape]

I'll have to see where the filter is and how I'd adjust the oil pump. The previous owners buddy owned a shop and went over this for him when he bought it.

 

[mikidymac]

That oil is the best you can use although the 720 doesn't need the full synthetic. The white bottle mineral oil is fine.
The filter is the white plastic cylinder between the oil tank and oil pump.
The oil pump adjustment is on the pump on the intake manifold under the carb. It is much easier to see with the black air filter housing removed and a mirror.

 

[Randypape]

Thank you for responding and you expertise.

 

[Matt Braley]

You can also trim back the spark plug wires a 1/4". The plug boots have lags inside so when you give them a couple counter clockwise twists as you pull they will pop right off. Trim back to solid wire and screw back on till they stop. This will clean up the slight ignition miss at lower rpm that most older engines like that have.