high revs

[Rogue]

Just after some ideas from you guys, I have an issue with my Aqua Jet at high revs and speed.

It seems to be fine whilst holding it in my hands in the water once its off and going full pelt the engine dies off then comes back suddenly, then dies off and so on.

I have replaced the glow plug, checked the mixtures and made sure of good fuel.

All I can think is that maybe it is the tuned pipe not giving out enough pressure for the tank.

Any ideas as to how to check?

I have guages for the car but I dont think they would be that accurate at this low reading.

Just a little lost atm I'm in the process of dealing with my hobby store too.

Any help and ideas guys thanks.

 

[Tim_Duggan]

Also - what prop are you using? Have you flushed out the needle valve at all? Tried to richen it up a tad, does that make any difference?

 

[Rogue]

Ummm the prop I am using is still the standard one, been waiting for my octura x637 for over a month now and I have no idea what the needle valve is lol....carbie? Guess I should read my manual on that one!

After just talking to the hobby store they said it could be the bottom end mixture too lean, I wouldnt have thought that would affect it at high rpm, but they say it does :blink:

I put the high end mixture back to standard so that is richened out.

I also plan to put on the old exhaust and put the tube in a glass of water to check the pressure difference between the pipes.

 

[Krusty 181]

I would have to agree with tim that it sounds like it needs more fuel (richer)

has this problem only just started happeneing?

if so i would be checking the whole fuel circuit for dirt /blockage

Andrew

 

[Ron Olson]

It sounds lean to me. Try giving the throttle blips and richen the high-speed needle until you start to get a slight lag when you give it a blip. Once the carb is set this one usually doesn't need much adjustment you just have to set it up for where you live at.

 

[Tim_Duggan]

Needle valve = high end mixture

Unscrew it completely, put some fuel in the tank, remove the pressure line off the muffler / pipe and blow hard into it for about 2 seconds. fuel should come out the carb along with any crud that may have lodged in it. refit needle at the reccomended setting and re-fit the pressure line. Take the plug out and crank it over with the fuel line pinched to get out any excess fuel. Wind the low end screw out anti-clockwise by 1/2 a turn.

It shouldn't sound snappy when you free rev it from idle, a slight hesitation from idle is what you want to prevent the low end influencing the high end. Adjust the low end screw accordingly.

The high end will need to be adjusted on the water. If it sags like you said in your initial post, it's too lean or starving for fuel for some reason. If it just putts around blowing a lot of smoke and not really revving much - the high end is too rich. wind it a few clicks clockwise to lean it and then re-test.

On small engines - mixture can change dramatically thru the day due to air conditions. Learning how to tune them is handy!

 

[Rogue]

Ecexllent!

Thankyou heaps for the info I'll give that a shot tomorrow.