93 SN ran great now poopty, carb rebuilt, then replaced new. Video included.

[750sx1992]

Gentlemen,

I need your help. I thought I had a carb issue. Paid a guy to rebuild it, convinced myself he didn’t do a good job, so just installed a brand new one from blowsion. Still running like poop. Disclaimer, I have not yet tried to tune the new one. When it immediately showed this rhythmic type of stutter on full throttle I gave up on even attempting to tune.

Is this a CDI issue? Spark plug gapping issue? Seems too consistent to be gapping. Anyway, I’m lost.

 

[750sx1992]

46mm mikuni
64u head
61x cylinders
Data plate on intake manifold says 650, so I’m guessing case in 650.
B-pipe
Compression is 175/175

Any other info needed.

 

[WFO Speedracer]

If you keep running it wide open unloaded on the trailer like that you won't have to worry about tuning it.

But I will give you a place to start replace the spark plug boots and see if your issue goes away.

 

[750sx1992]

If you keep running it wide open unloaded on the trailer like that you won't have to worry about tuning it.

But I will give you a place to start replace the spark plug boots and see if your issue goes away.

Any recommendations on boots?

 

[WFO Speedracer]

NGK resistor boots.

 

[750sx1992]

NGK resistor boots.

I’ve ordered the boots, but am rather surprised that was the only suggestion. Seems to rhythmic to be boots.

 

[WFO Speedracer]

I’ve ordered the boots, but am rather surprised that was the only suggestion. Seems to rhythmic to be boots.

It is a suggestion based on years of prior knowledge , it does not mean it will magically fix your ski.

 

[Quinc]

Check your compression, pull your plugs out and check those as well.

 

[750sx1992]

Check your compression, pull your plugs out and check those as well.

175/175

 

[750sx1992]

It is a suggestion based on years of prior knowledge , it does not mean it will magically fix your ski.

I appreciate the suggestion, I’ve ordered boots.

 

[bored&stroked]

Holy poop, you floored it out of the water? Stop hating your engine lol. That could just be the rev limiter cutting in. Out of water engine running tells you nothing.
There are many choices here. Boots is the easiest and cheapest to start with. Plug gap is almost literally never a problem, ever.
CDI's on the other hand, those can be problems.

 

[WFO Speedracer]

you never want to go full retard - Bing video

www.bing.com

 

[Myself]

Put a volt meter on the wires to the "charge" coil. Read the AC voltage at idle, then slowly increase throttle. What does the voltage do?

 

[WFO Speedracer]

I seeing you keep posting vids of running it wide open on the trailer, both here and on Facebook, what does the ski do when you are actually riding it, any ski ever made will hit the rev limiter with the pump unloaded , whether it's on the trailer or jumping a wave that's what the rev limiter is there for, if the rev limiter was not there the revs would go astronomical and when the impeller hit the water again all of the rotating mass of the engine and drivetrain would suddenly deaccelerate and things would start coming apart , posting these vids running it wide open on the trailer means nothing to me or anyone else here.

 

[750sx1992]

No change with boots. Will try and get video of how it reacts with pump loaded.

 

[750sx1992]

Put a volt meter on the wires to the "charge" coil. Read the AC voltage at idle, then slowly increase throttle. What does the voltage do?

I’m comfortable with electronics, but quite unfamiliar with the electrical system on the ski. How do I go about identifying the correct wires? Google search has so far been unhelpful.

 

[WFO Speedracer]

Do you still have the temp sensor hooked up, if so start by unplugging it , it should me a pink and a black wire inside of t and at the moment I would leave the electrical box open unless you like taking out and putting in 400 screws.

 

[750sx1992]

I seeing you keep posting vids of running it wide open on the trailer, both here and on Facebook, what does the ski do when you are actually riding it, any ski ever made will hit the rev limiter with the pump unloaded , whether it's on the trailer or jumping a wave that's what the rev limiter is there for, if the rev limiter was not there the revs would go astronomical and when the impeller hit the water again all of the rotating mass of the engine and drivetrain would suddenly deaccelerate and things would start coming apart , posting these vids running it wide open on the trailer means nothing to me or anyone else here.

I replaced the boots, attempted to tune carb. Here is a video of it in the water. Starts and idles nice. Transition from idle to mid is snappy. Once it gets above a certain RPM the stutter starts. Starting to think it’s some ignition component.

In this video, I started it, brapped sever times off idle, held mid range for a moment, then went to WOT.

 

[750sx1992]

Do you still have the temp sensor hooked up, if so start by unplugging it , it should me a pink and a black wire inside of t and at the moment I would leave the electrical box open unless you like taking out and putting in 400 screws.

Temp sensor is bouncing around in the bottom of the hull. I assume still connected..

 

[WFO Speedracer]

As stated earlier a bad heat sensor will cut spark like that , that is exactly how that circuit works, I noticed the Yellow spark plug wires, what kind of wires are they, are they resistor wires, carbon core or are they solid wires , if they are carbon core you have resistor wires, plugs and caps, resistor means resistance which means loss of spark intensity , resistors cut current or resist current flow, too much resistance and you have serious ignition issues.