I just picked up this ski. Dont know history. It has a primer kit and choke cable is disconnected. Looks like aftermarket air intakes on carbs. Starts and revs fine on trailer. Fuel lines are black automotive line except the last foot on the return to tank is still gray. Starts in water and runs up to just below 4k rpm then will die. If you let off quick it will keep running. If it dies it starts right up but wont rev past 4k. New plugs, no change. Seems to run rough below 4k. Fuel filter under hood is clean. It is also taking on water. It is missing one siphon tube in pump venturi for the auto bailer. Didn't look like shaft seal is leaking while idling at doc. Hull had about 4 in of water after messing around with it for about 15 min. What to check next? Running on one cylinder? Rave valves? Fuel selector sucking air? Carbs or carb filters? Rectifier?
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98 GSX Limited dies at 4k rpm
- Thread starter kartchns
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Also compression is 135 to 140 in each cyl.
JeremyD615
Well-Known Member
The carbs are your most likely culprit. Follow the carb rebuild sticky with genuine Mikuni parts and it should clear up your problem.
You should also go ahead and replace that foot of grey tempo line. It’s a few bucks and five minutes worth of work, so go ahead and get it done.
You should also go ahead and replace that foot of grey tempo line. It’s a few bucks and five minutes worth of work, so go ahead and get it done.
JeremyD615
Well-Known Member
You can eliminate all kinds of things, but you’re going to wind up back at the carbs... And it will have cost you even more to get there, if the motor even survives being run lean for that long. Any ski with an unknown history needs the carbs gone through, the fuel selector cleaned/replaced, and the filters checked and cleaned. The absolute worst thing you can do to these skis is continue running them lean...
Pulled the carbs. Thought I had to pull the exhaust to do so. What a mess. Once I started that, I couldn't turn back. The carbs have a primer kit and all the fuel line as hard and not tight. Choke plates are removed. I bypassed the primer kit and bypassed the fuel selector. Looked into one carb. Fuel filter was clean. Insides were clean. Looks like they have been rebuilt recently. Did not tear into the second one. Thought I must have been sucking air from the fuel selector or primer. Checked exhaust for obstruction and checked water regulator diaphragm All good as far as I can tell. I check the Voltage regulator and seems fine (no AC voltage and about 14V when running). Pulled one rave valve. Had some carbon on the gate, but seemed to move up and down when pushed. Took ski out on water and it does pretty much the same. Accelerates fine and then hits about 4K rpm and then dies. Restarts no problem. It may be running rich. Both plugs are new and a little wet and brown (have only run about 5 minutes). I am not sure what they should look like. Some smoke when run on trailer. Not sure how much these 2-stroke should smoke. All fuel lines are black. The gray one was on the other ski, so this has 100% auto fuel lines (incorrect statement in previous post that it still had a small piece of gray). I am pulling carbs again and going through them? What else to check? Fixed the water leak. It is a siphon tube in the jet pump. Need to replace a missing one.
GrupaNation
Member
Make sure your spark plugs are gapped correctly. Might not be your issue but is something that is easily overlooked.
GrupaNation
Member
I'm glad to hear its working for you, but those NGK plugs come at about .031 inch gap and I know for my 97 XP the tolerance is .020-.024. I could hardly get it to start on the trailer with the stock gap. It starts great after gapping.
Ckrawiec
Well-Known Member
I THINK that, even though the carbs look like they have been / maybe been rebuilt recently...the devil is in the details....you don't know (do you?) if MIKUNI parts were used. I did mine with SBT kits and the ski fell on its face (similar behaviour as you describe....behaves on the trailer, starts on the water, but would not throttle up)....I went BACKWARDS to all original Mikuni parts (that I had saved) and the ski is now a BEAST on the water....lots of giddy-up and go, no throttle hesitation, runs better than ever....my son even stated "its feel like the ski is trying to throw him off her back", the ski cuts and digs in hard on those turns....it never did that before.
GrupaNation
Member
https://www.ngk.com/product.aspx?zpid=9559
Website says .31 so I dont know where you got the information for .28
JeremyD615
Well-Known Member
I know the last 8 plugs that I bought were all gapped at .28 according to my gauge... There are two different BR8ES plugs available, so maybe the ones with the screw terminal are gapped differently... I know all of the 3961 plugs I just bought were .28 though.
Probably from working on them for 25 years but I only run the 3961 with the solid terminal so maybe they are different than a standard BR8ES. I got lazy gapping them 20 years ago ands since it never caused an issue for me I just stopped.
Either way, the rule of thumb is to set them to factory spec 0.20-0.24.
Let's not derail this thread for the OP. Lets just agree you should set them to 0.24".
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