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97 GTX. Normal engine noise?

AquaEye

AquaEye

Member
1st Seadoo owned. 1997 GTX with 40.3 hours. Previous owner had ski stored for 3+ years with full tanks of oil & gas. Inspected before purchase & I insisted that we do not start for demonstration purpose's. Motor turned by hand easily( no spark plugs). Previous owner showed dealership maintenance records & all performed "by the book", (they also changed out the gray fuel line). Brought home, pulled pump & shaft for refurb, flushed/vacuumed out all fluids from tanks & lines & replaced with fresh, validated oil pump operation & clean out mud dobber nest. Compression test very good (see pics).
Before start up, fresh plugs & a "squirt" of syn oil in cylinders. Started up within 5 secs. Not knowing the sound of a running 787, I erred on the side of caution when that loud knocking noise occurred @ startup & immediately shut down. Installed air box, no quieter. Mechanic stethoscope was unable to pinpoint source. "Word on the street" is that rotary valve motors are inherently noisy. This noisy? Is this normal? Have short vid with good sound p/u but unable to post. Can use some help on that also.

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lavasioux said:
Nope, that's not normal or good.

You have no output connection, correct? The shaft isn't connected and clanking?

Something isn't right.

Good luck!
Click to expand...
Correct, no output shaft/pump.
I can only assume that this noise is not a normal occurrence(?). The dozen or so vids I saw the noise was present but not @ this particular level, but the events were always outside under flush. I'm in an small enclosed shop, just me & those freakin dirt dobbers.
Process of elimination> An old school trick I learned years ago, take a cutoff wheel, cut insulator to the shell, drill/punch holes/remove center electrode of spark plugs so as to relive some compression from the pistons but still labored. Impellor removal tool> socket>swivel & a strong high rpm drill motor. Have my buddy put down the beer & operate drill motor while I listen with mechanics stethoscope. Worked in the past, see if it reveal's any clues tomorrow. ( keep those modified plugs there a PIA to make), then the flush run if there is no solid determination.
There is something thou that sticking me in the side, the pump.
Previous owner stated that he lost ALL thrust before the sale. No mystery here, the liner was completely trashed. No thrust=compromised cooling capability & we both know what that can cause.
UPDATE: CoP's. Pulling head. With only 40.3 hrs & documented recommended oil used, those cylinder walls should be in pristine shape.
If not.....
Will provide pics.
 
Just an observation but from the video it looks like the cylinder cover has been removed in the past. Looked like the paint was half missing from the cylinder cover bolts. I wouldn’t have thought there would be a need to be in there in a 40 hour machine. I thought I could see the exhaust moving where it connects to the exhaust manifold but that’s probably just normal vibration. I’m sure you have checked all obvious bolts. I’m worried that the cylinders have been bored with oversized pistons and the rave guillotines are bouncing off the piston
 
burtshaver2021 said:
Just an observation but from the video it looks like the cylinder cover has been removed in the past. Looked like the paint was half missing from the cylinder cover bolts. I wouldn’t have thought there would be a need to be in there in a 40 hour machine. I thought I could see the exhaust moving where it connects to the exhaust manifold but that’s probably just normal vibration. I’m sure you have checked all obvious bolts. I’m worried that the cylinders have been bored with oversized pistons and the rave guillotines are bouncing off the piston
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I picked up on that also, the missing paint, unsettling to say the least. Rave valves were pulled, rather clean for 40 hrs,(too clean), no missing material. All three bellows/internals in good shape. Engine #s match to original title. Getting close to write this off for the summer for complete rebuild but more determinations are needed.
Been here before but only with Kawi's & Yami's. Rotary Rotax is a whole new territory.
 
AquaEye said:
I picked up on that also, the missing paint, unsettling to say the least. Rave valves were pulled, rather clean for 40 hrs,(too clean), no missing material. All three bellows/internals in good shape. Engine #s match to original title. Getting close to write this off for the summer for complete rebuild but more determinations are needed.
Been here before but only with Kawi's & Yami's. Rotary Rotax is a whole new territory.
Click to expand...
I had one Yamaha 701. I should never have gotten rid of it. 9 years I had it and not a single issue, just drive
 
Nope, not a normal noise at all. Someone had that head off and absolutely no reason for that at 40 hours unless something was wrong.

I would pull the head first since it uses o-rings.
 
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