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Discussion Starter #1
Hi all,

Just bought a 2000 GTX with 201 hrs. Went through the entire fuel system, removed carbs, cleaned and pressure tested and pop off pressure checked. All good and appears to be well maintained. Removed and checked condition of pump and impeller. Clearance is well within spec which verifys po's claim of new impeller and wear ring with 8 hrs use before storing machine.
Water test shows 51.5 mph @ 6600 GPS on light ripples, no current 200 lb rider full fuel, temp 75* ,200 ft asl. Return pass was 50.5 mph @ 6570 rpm.
Slightly rich at slow speeds and after a 15 min. tour at idle through a no wake zone it took about 30 secs. to clean out at full throttle.
Machine is completely stock and high speed needle is closed , low speed needle set at 1.5 turns out as per BRP manual.
It starts immediately hot or cold and has a new battery.
Didnt have an opportunity to check plugs immediately after the full speed test but after the entire 2 hour session of moderate riding the plugs were dark tan with the pto plug appearing to have a little bit of oily goo on one side of the porceline below the center electrode.
Compression test shows equal at 120 psi warm. Takes about 5 seconds to pump up to that and when I compare it to my stock snowmobile 2 stroke engine it seems to take awhile to pump up. Rather than 3 or 4 strokes to reach max it takes comes up about 10 psi per stroke. This may be normal for a 6:1 compression PWC compared to a 9:1 sled.
I am waiting for gaskets so I have not looked at the cylinders yet or rave valves.
Under normal circumstances is a re-ring the normal course of action if the cylinders are in spec or is it better to just bore and go to an oversize piston?

Do these 951's tend to run rich in the bottom end when set at the stock settings or is there some tricks you experienced tuners use to get them running crisp ?
Am I correct in assuming I am 6 or 7 mph shy of a well tuned stock 951 carb GTX?
Any help would be greatly appreciated!
Thanks,
Rob
 

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Did you check the RAVE valves to make sure they are opening all the way?
 

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Discussion Starter #3
No, not yet but thanks for the good suggestion. I dont know how to check them yet but will read up on that tonight. I will have time tomorrow to verify they are functioning properly.
How about the compression. Can anyone tell me how a new or low hour top end should react during a compression test?
Mine only pumped up about 10psi per stroke rather than 2 or three strokes to reach the maximum reading. This seems rather lazy to me when I compare it to none marine 2 strokes.
Would rings alone fix this?
Thanks,
Rob
 

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Discussion Starter #4 (Edited)
Compression is now OK, my Gauge was broken!

Went to my shop today and got my Mac compression gauge to retest our GTX. It pumps up in 3 strokes to 140psi and 3 more strokes to a max of 148-149 both sides. Takes about 3-4 seconds to achieve max psi now. Sorry about the original misinformation about the compression only being 120 and slow to rise!
I am happy with the reading I am getting now and am glad I didnt do the top end due to a faulty compression gauge...
I have just cleaned the rave valves and they had significant oily residue build up and some carbon deposits. I will water test again and see if the bottom end is cleaner and see if it is now pulling more rpm then 6600. If not I will start to work with carb tuning.
Does anyone have a good baseline carb jetting/setting for a GTX 951.
It is a bit of a pain to get to the carbs so I am hoping to get it right in as few tries as possible.
Thanks,
Rob
 
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