Thread: 96 GTX Inconsistent Performance
10-13-2007, 07:39 PM #1
96 GTX Inconsistent Performance
Here's the deal:
I bought this ski from a friend that rebuilt the motor - bored and recranked it....big overhaul....rebuilt carbs, new prop, new fuel lines...he's been rebuilding skis for 11 years, mostly SeaDoo's...very meticulous.
After the rebuild, he had been in the process of tuning it when he had to put it aside to move to a new house. He needed to rejet the carbs due to a freer breathing flame arrestor/air filter
It sat in my backyard for about a year and a half unused and I brought it out of hibernation. I'm in South Florida so no winterizing issues.
He opened up the carbs to rejet them, and we fired up the ski on the trailer out of the water and it ran very well. It didn't look like there was much old gas in the tank and before putting it in the water, I topped it off with about 8 gallons of 93 octane gas meaning there was a lot more old gas than expected.
In the water the ski started easily but most of the time wouldn't run above 3500 rpm and sounded like it was missing. Going to full throttle would kill the engine. Idle is smooth and it will eagerly go to 3500 rpm but run with the miss.
Occaisionally, I was able to get WOT. 5000-6500 rpm, the engine was really sweet. If I let off the gas, then usually I was back to the 3500 rough rpm issue.
As the first day running wore on, I was getting more and more top end 54 mph runs. Compression using my cheap Harbor Freight tester was 120 psi on both cylinders.
The next day, I siphoned out as much of the remaining gas as possible and today took it for another run with 89 octane and a bottle of fuel injector/carb cleaner. Same 3500 rpm issue, but later got more frequent WOT runs. I dumped the fuel/water strainer a couple times and that seemed to help.
Sometimes at WOT the engine would die for no apparent reason.
We started doing plug chops at WOT and found the plugs to be a bit lean and after 4 chops the plugs were the right color as we richened the mixture slowly. More often than not, I was able to enjoy a pretty good idle to WOT response, but got the 3500 rough max rpm issue again but maybe only 10% of the time instead of 90%.
So that's where we are now. This ski is a cream puff. Looks great, rides great and when the engine is running well, performs great.
Any ideas? It seems like we are getting close, but that 3500 rpm issue is troubling. Thanks!
10-13-2007, 08:36 PM #2
- Join Date
- Jul 2006
- upstate NY
If you are sure that the fuel is good now and the carbs are clean I would check your rave valves and make sure it didnt blow the bellows off. Also check the rear electrical box and make sure the grounds are clean on the coil. You could have a burnt head gasket you really need to investigate.
10-14-2007, 07:57 PM #3
sounds like the rectifier might be the problem. have you changed the fuel lines in the ski yet? if they are deteriorating, they will clog the internal filters in the carbs and cause it to run lean. you should be seeing 6800-6900 rpms at full throttle.
10-14-2007, 08:22 PM #4
Sounds like the jetting carb problems I had on my old 580cc after a rebuild. Didn't you say he rebuilt the carbs??? Most of the time a set of air filters by them selves do not need bigger jets. Try going back down.
Check popoff pressure too. I have the guage for sale if you need it.
10-14-2007, 10:13 PM #5
10-14-2007, 10:30 PM #6
Idle is great, starting hot and cold are great, but that 3500 rpm thing is messed up. When I can get the top end, the low and midrange are fine. I can't get to WOT when the mid range is stumbling. The engine bogs down and dies if I go to WOT.
10-14-2007, 10:49 PM #7
10-17-2007, 02:18 PM #8
- Join Date
- Dec 2006
- Cartersville, GA
10-17-2007, 04:56 PM #9
- Join Date
- Feb 2006
- Warner Robins, GA Home of the 2007 All-Star Little League World Champions!
Ditto on the rectifier...especially if it is the original one.
10-18-2007, 07:58 PM #10
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