Engine power problems

[RideFlyDive]

99 super jet only mod is factory B pipe. Idle to WOT lugs then instant snap and takes off. Will do same if easing into throttle. If I can make it hop from idle it clears and takes off. As soon as I let off throttle it starts all over again.
Any ideas of what is causing this?

 

[Chase Musetti]

Carb related. Sounds rich.


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[RideFlyDive]

Carb related. Sounds rich.


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Tried leaning the low no change. Leaned high to a 1/2 better top end but still lags. 70/135 jets stock spring and needle

 

[tomski]

Carb related. Sounds rich.

That's lean.

 

[Chase Musetti]

That's lean.

Could be. When it bogs then takes off it was usually rich for me. When it just stalls then it was lean.


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[Chase Musetti]

Tried leaning the low no change. Leaned high to a 1/2 better top end but still lags. 70/135 jets stock spring and needle

Did it run fine before then start doing this? Or did you add the pipe and then it started acting up. Need more history.


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[RideFlyDive]

Just bought the ski. Had a 760 in and guy pulled it out in 701 and put a FP on it and couldn't get it tuned right. I cleaned carbs and found out for some reason he had 70 low and a 60 high jet in there. I changed the high to 130 and that's where I'm at now.

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[RideFlyDive]

Update still having the same issue. I've changed needle and seat to 1.8 put 80 gram spring and can't tell any difference at all. Any ideas?

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[Chase Musetti]

Did you check the pop off pressure?


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[Freakie]

Agree. U need to check the actual pop off psi......with just a b pipe on stock motor.....40 psi is fine.....make sure the n/s is not leaking....that means pop off should be a big pop and not a slow fizzle

 

[Yami-Rider]

If you messed with tuning and there was no change in how it ran, you could possibly have something not right with carbs or fuel system.

 

[Sxi 1100]

Any time you do an upgrade like a factory pipe on a stock 701 you will need to upgrade the jetting.
@JetManiac has those parts


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[Bryan.wells]

sounds lean on the bottom end

 

[mbrick]

You mentioned you tried leaning the low, did you also try richening it?

As others mentioned, check pop off and that it's crisp. Also that it holds pressure.

Maybe it's starving, did you try bypassing the fuel selector or checking the tank vent is working? Will usually die if it isn't venting, but worth checking the simple things.

 

[ngerk]

I went through his carbs completely after he did so they have been cleaned twice. He pulled the carbs and tried different jetting just to see if it would change more times then I could count and the problem stayed. To clarify, its not a normal rich bog or lean hesitation. It will literally lug for several seconds then take off hard. Again, if you unload the pump it takes off with full power. It is a 62t/62t, twin 38s, carbon reeds, lightweight flywheel, b pipe, unknown impeller. Now this info is coming from the previous owner so I can't confirm all of this stuff quite yet. He just picked the ski up recently so we just jetted to factory pipe specs and took it to the lake. My ski runs perfect with these settings so figured his would do the same. There are now a lot of things we will have to go over and check.

Update to today: We eliminated the fuel selector and swapped my carbs on the ski to start ruling things out. It was running perfect for the first couple of minutes it hit the water then it suddenly went back to lugging around. At one point it was like a light switch turning off and on.....power, no power, power, no power. I am now pretty sure it is an electrical problem. Any idea? I'm thinking coil, stator, or cdi? It supposedly has a new stator from jetmaniac and a rebuilt coil from someone (owner didn't remember). Plan is to start ruling out electrical next.

 

[mbrick]

Good update.

The initial good run, then back to normal could indicate something is heating up and then failing, which is not uncommon for electrical components.

There was another member on here recently that had a bad pulser coil that solved his poor run condition. He had bought a stator assy from SBT. It was out of spec when checking resistance.

I am not an expert but it seems like the order of chances of failing from most likely would be the stator, coil and then cdi? But someone else may know from your symptoms which it is.

Here are the specs, they definitely need to fall within these numbers from the service manual. Screenshots in the next post.

Pulser coil
White/red to black: 12.6-15.4 ohms

Charge coil
Brown/white to black: 497.7 to 608.3 ohms

Ignition coil
Primary side (orange to black): 0.078 - 0.106 ohms
Secondary side, but hard to read well with caps attached: 3.5-4.7 kohms

 

[mbrick]

Here are screenshots of ignition component tests:

 

[Bryan.wells]

Triple check the spark plug boots, a few skis here in Washington have had the feeling that it is almost hitting a 2500rpm rev limit on and off. the boots got replaced and that fixed it. When the ski is lugging does it have the feeling of "extra vibration" or like "buzzing" feeling?

 

[mbrick]

Triple check the spark plug boots, a few skis here in Washington have had the feeling that it is almost hitting a 2500rpm rev limit on and off. the boots got replaced and that fixed it. When the ski is lugging does it have the feeling of "extra vibration" or like "buzzing" feeling?

Good idea. Also make sure the aluminum thread on nuts at the top of the plugs are not toast.

I've seen the aluminum nut's threads be totally gone and the nut is just sliding on and off. Not to mention now the entire cap is full of aluminum dust. Shot.

Better yet, just replace them now with solid top plugs to be sure.

 

[ngerk]

Good update.

The initial good run, then back to normal could indicate something is heating up and then failing, which is not uncommon for electrical components.

There was another member on here recently that had a bad pulser coil that solved his poor run condition. He had bought a stator assy from SBT. It was out of spec when checking resistance.

I am not an expert but it seems like the order of chances of failing from most likely would be the stator, coil and then cdi? But someone else may know from your symptoms which it is.

Here are the specs, they definitely need to fall within these numbers from the service manual. Screenshots in the next post.

Pulser coil
White/red to black: 12.6-15.4 ohms

Charge coil
Brown/white to black: 497.7 to 608.3 ohms

Ignition coil
Primary side (orange to black): 0.078 - 0.106 ohms
Secondary side, but hard to read well with caps attached: 3.5-4.7 kohms

Hey thanks for that. I have the service manual as well but it didn't occur to me to simply test the parts first. I have a spare stator, coil, and CDI but it would obviously be smarter to test his first. The electronics are sort of a mess. All of the stator wire connectors are outside the box. The starter solenoid is also mounted outside the box. Haven't been able to look through any of it yet.