b pipe ski vibration

[jetskidude1113]

I've notice this a way back but never brought it up. Anyone experience more vibration 1/4 throttle with a b pipe compare to stock exhaust on their superjet? I notice it on my SN and RN. good alignment and everything. once it pass 1/4 throttle it's fine and smooth, just when I let off the throttle setting up a turn I experience the vibration.

 

[X2Kid]

The different mass (lighter) and structure of the aftermarket pipe might be inducing a resonance that the heavier stock pipe avoids/absorbs. All theory, of course!

My response to such conundrums is to just nail that sucker wide open. Braaap!

 

[jetskidude1113]

I was thinking the same where as the heavier OEM is pretty solidly mounted against the motor and the lighters B pipe chamber is held together only on both ends with couplers. just wondering what others experienced. Hell ya.. just pin it!!!.

 

[john zigler]

Did you grind the ribs off your hull? Are you sure it is not hitting the engine mount?

We build many SJ's here, with B pipes, and have no vibrations.

 

[jetskidude1113]

It’s on my 2011 so there is plenty of room to the hull, not like my SN which I did have to grind the ribs. It is not sitting on the mounts as there are plenty of clearance between it. I will check my alignment and mounts see if any are bad. Thanks for the responses.

 

[wmazz]

just when I let off the throttle setting up a turn I experience the vibration.

Engines vibrate when they are rich. What is your current jetting? and
screw settings.

Other possibilities are cavitation, did you silicone seal the ride plate?


Bill M.

It is possible the pilot circuit is rich and when you close the throttle
the engine's manifold vacuum suddenly increases and causes the next
acceleration to be rich.

Check your spark plugs!

 

[jetskidude1113]

Engines vibrate when they are rich. What is your current jetting? and
screw settings.

Other possibilities are cavitation, did you silicone seal the ride plate?


Bill M.

It is possible the pilot circuit is rich and when you close the throttle
the engine's manifold vacuum suddenly increases and causes the next
acceleration to be rich.

Check your spark plugs!

Was thinking about that also, my jettings are 70/135, pop off pressure is stock as I can remember, adj are 3/4L, 5/8H great throttle response and plugs looks good. BTW, it's a Raider 62T motor and the recommendation for low jets are 67.5 (stock) but not sure if I want to try that. also think I might be loading up the waterbox due to the Flow Control Valve opening too soon, it is more noticeable on a small tight practice buoy course compare to a bigger course that the ski is able to open up longer to blow the water out. Lots to look at.. Thank again

 

[wmazz]

Your specs wouldn't indicate a rich low speed or pilot circuit, but do
you remember what spring and seat was in the carbs?

I was also wondering if you have a low idle, fast idle, or no idle?



Bill M.

 

[joelake]

I recently removed a cast protec Mach 2 pipe from my sj and put a b pipe on. No hull rubbing etc for either pipes....... B pipe has definitely let some more vibration be felt....

 

[kevbo]

All my two cyl skis have a noticeable vibration zone around 1/4 throttle. The engine doesnt shake any more but the hull resonates at this frequency. The weight of the stock pipe prevents the engine from moving as much so it feels smoother. Engines really shake with a dry pipe/manifold since they're lighter than even a B-pipe. Any rattling is something that is attached to the engine hitting the hull. Chaffing is the main long term maintenance issues.

 

[jetskidude1113]

Your specs wouldn't indicate a rich low speed or pilot circuit, but do
you remember what spring and seat was in the carbs?

I was also wondering if you have a low idle, fast idle, or no idle?



Bill M.

if I have to guess, stock spring. idle is about 1200-1500 in water

 

[jetskidude1113]

I recently removed a cast protec Mach 2 pipe from my sj and put a b pipe on. No hull rubbing etc for either pipes....... B pipe has definitely let some more vibration be felt....

I had a ProTec black cast pipe on my SN 650 and much less vibration compare to my B pipe on my 62T 701. But it's not really a fair comparison for me from a 650 to 701

 

[jetskidude1113]

Is the Waterbox strapped down tight?

yes, super tight, with added 1/4" rubber paddings to move the box higher to prevent pipe hitting the engine mount.

 

[jetskidude1113]

All my two cyl skis have a noticeable vibration zone around 1/4 throttle. The engine doesnt shake any more but the hull resonates at this frequency. The weight of the stock pipe prevents the engine from moving as much so it feels smoother. Engines really shake with a dry pipe/manifold since they're lighter than even a B-pipe. Any rattling is something that is attached to the engine hitting the hull. Chaffing is the main long term maintenance issues.

good point, I'm gonna make sure the alignment and all mounts are good. I feel its just the characteristic of the pipe. just gonna send it. Thank again.

 

[jetskidude1113]

Problem fixed, guess was really not a problem. The vibration was just rattling from the nose cover, fire extinguisher holder and other loose stuff that rattles at the same resinence. I added some weather strips to dampen everything I can find rattling and now it’s pretty smooth. Kevbo called it. Thanks

 

[john zigler]

Good, thanks for the update.