Yamaha 701 - Running Strange

[Ben Fredenburg]

Hi guys,

I'm looking for someone's expertise. I'm having issues with my Rickter FS2 that has a Yamaha 701 in it. It starts and idles just fine; however, when I give it full throttle, it only revs up to 1/4 - 1/3 throttle before it redlines. I've had the stock 38 carbs have been tuned back to factory settings except for the high speed/main jets - they're 1 size larger (135). The motor is a 701 - compression is just under 180 psi for both cylinders.

Below is a video of it running on the stand. I'm pulsing the throttle from 0 to full. As you can hear it's not revving up. The ski has a brand new MSD Enhancer and JM coil. Any ideas what could be causing this to run under power. Do you think it's a fuel issue?

Thanks,
Ben

 

[mxhead]

Wow that is one pissed off 701!

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[Freakie]

180 psi is way higher than stock....and you have A B pipe. .do you know what your pop off pressure is and pilot size jets.....does it bog down when its in the water ?

 

[Ben Fredenburg]

The pilot jets are set to 70. I'm not sure what the pop off pressure is set to - maybe factory. Yes, it does bog down when it's in the water.

 

[Freakie]

That suggests you way lean imo you need to drop the pop off from stock 55 psi to around 30 psi with that setup....will give more fuel to rev....might also go up to 75 pilot......

 

[JetManiac]

Stock dual 38 jetting is 70/130. Factory Pipe suggested is 70/135 but only as a starting point for an otherwise stock setup.

You have an a/m head with more compression and an msd with advanced timing and possibly other mods which all require more fuel. I would increase pilot to 75 to start as freakie recommended.

What are your adjusters set at now? Have you tired richening adjusters to see if it makes a difference? Also what about the temp sensor from stock head, was it disconnected at ebox?

 

[Ben Fredenburg]

Slow speed is 7/8s turn out, high speed front is 1/2 turn out, and high speed rear is 1/4 turn out. Yes the temp sensor is disconnected from the ebox.

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[JetManiac]

Slow speed is 7/8s turn out, high speed front is 1/2 turn out, and high speed rear is 1/4 turn out. Yes the temp sensor is disconnected from the ebox.
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Turn high speeds to 1 1/2 turns out and retest it.

 

[Ben Fredenburg]

Sorry, Chris. I gave you the wrong specs before on the high speeds. We have the high speed front 1 1/2 turns out and the rear 1 1/4 turns out. Would an extra 1/4 turn out on the rear make a difference?

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[jeremy chambon]

If you have a primer you can give it a couple squirts when it's doing that and see if the added fuel helped

 

[JetManiac]

Sorry, Chris. I gave you the wrong specs before on the high speeds. We have the high speed front 1 1/2 turns out and the rear 1 1/4 turns out. Would an extra 1/4 turn out on the rear make a difference?

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Probably not your problem then.

 

[jetx]

Is this a new msd install? Did you adjust the Rev limit ? Maybe turned it wrongway by mistake?

Rev limit is adjustable from 5500-9000rpm