Runs 5 seconds and dies, need choke to run.... why?

[98mkiv]

I have a bone stock Kawasaki 750SXI Pro.

With the ski in the water, the ski will die 5 seconds or so after starting. I can keep it going if I pop the choke on every ~3 seconds and then it will die again after 3-5 seconds if I don't blip the choke.

Good compression
Reeds are good
no obvious issues
ski is corrosion free

i just bought the ski, so I don't know the history. It needed a carb rebuild when I got it as the diapragms on the meter side were age cracked, so I rebuilt the Mikuni carbs (including the fuel pump). I was told by the person I bought it from that it had this same stalling problem, so I don't think it's related to the carb rebuild. Spark seems fine, runs on the trailer pretty much no problem (or maybe it just takes longer to use the fuel with no load).

Any ideas what would cause this problem.

 

[Vumad]

Did you use genuine Niki in rebuikd kits and test the carbs?

Pulling choke = mix is lean. Usually clogged Jets or weak pump.

 

[98mkiv]

I agree.....

The pump and all other components are new, they are not genuine parts, but looked decent, and the in water test is what I'm doing....

 

[mike b]

Does the ski run longer out of the water or same 5 seconds no matter what. If it runs fine dry I have heard of electronic shortages due to water in old Start stops switches. Probably not your problem but shouldn't take more than 5 seconds to check it out and test it lol. Good luck

 

[Vumad]

I agree.....

The pump and all other components are new, they are not genuine parts, but looked decent, and the in water test is what I'm doing....

New parts dont mean good parts. I put new sbt kits in my gp1200 and it still never ran right. That was before i knew abput popoff testers.

I put new sbt kits in my superjet and did a popoff test for the first time. The fuel pumps leaked, and that was with allen head screws torqued tight ANDgease which shouldnt be required. I put the 8 year old mikuni parts back in and the leaking stopped.

I had only replaced my carb kits because i figured they were old. The brand new sbt kits tested out worse than used miku i kits. The o rings in the sbt kits do not seal like genuine mikuni kits.

I realize that with a stock kawi you likely have a keihen carb, but that does not negate the fact that fuel pumps and needles can jot be assumed to be working properly just because the kits are new. You should test even with brandnew genuine parts.

 

[bandit88]

The only SXI with Keihen's is the 95, all others have Mikunis. When you rebuilt the carbs, did you clean all of the passages and jets? The Mikuni rebuild kits are the only way to go but I dont think that is what is causing this issue.

 

[98mkiv]

Does the ski run longer out of the water or same 5 seconds no matter what. If it runs fine dry I have heard of electronic shortages due to water in old Start stops switches. Probably not your problem but shouldn't take more than 5 seconds to check it out and test it lol. Good luck

Definitely not the case here. Runs longer out of the water than in, and the start/stop operate normally.

 

[98mkiv]

New parts dont mean good parts. I put new sbt kits in my gp1200 and it still never ran right. That was before i knew abput popoff testers.

I put new sbt kits in my superjet and did a popoff test for the first time. The fuel pumps leaked, and that was with allen head screws torqued tight ANDgease which shouldnt be required. I put the 8 year old mikuni parts back in and the leaking stopped.

I had only replaced my carb kits because i figured they were old. The brand new sbt kits tested out worse than used miku i kits. The o rings in the sbt kits do not seal like genuine mikuni kits.

I realize that with a stock kawi you likely have a keihen carb, but that does not negate the fact that fuel pumps and needles can jot be assumed to be working properly just because the kits are new. You should test even with brandnew genuine parts.

parts are good qualty, I'm thinking I either made a mistake reassembling the pump, or the jets are clogged.

 

[98mkiv]

The only SXI with Keihen's is the 95, all others have Mikunis. When you rebuilt the carbs, did you clean all of the passages and jets? The Mikuni rebuild kits are the only way to go but I dont think that is what is causing this issue.

good point, but it's odd that both carbs are clogged up. could be I suppose. I'm leaning more towards a mistake on my part during reassembly of the fuel pump since that would cause an issue with both carbs where one carb might run a bit better or clear a bit but both of them completely clogged shut? maybe....

thoughts?

 

[mike b]

Definitely not the case here. Runs longer out of the water than in, and the start/stop operate normally.

If it runs fine out of the water it could be electronic issue when it gets wet which would exclude carb issues in my mind. We had a blaster in town with a bad switch and only would start for a second then die. Something to consider if out of the water and in the water run different was what I was saying above.

 

[DAG]

Do you have a primer? if so prime fuel into during the 5 seconds it does run and see if you can get it to run longer by keep adding fuel. Or if you dont have a primer get some starter fluid in a spray can and do the same. If it runs you have a fuel system issue. Also wound not hurt to unplug the start stop switch in the harness (white/black wires). But plug them back in before going out for a ride

 

[98mkiv]

Ok so some interesting progress here:

1. double checked the carbs - all assembled correctly. Jets clean, etc - nothing obvious - assume the carbs are right.
2. Disconnected the return line - can blow thru fine - no obstructions.
3. tank check valve - works fine. Tank pressurizes when capped, check valve allows air into the tank.

so here's where it gets interesting:

If I remove the return line at the tank and run it into a little bottle, the ski runs. Fills up the bottle slowly.

reconnect to tank (remember there is no restriction on the return, it flows freely!) the ski will not run. Makes no difference if the tank cap is on or off (e.g. pressure or no pressure in the tank).

Your Thoughts!??!

 

[Magyar68]

did you use the same color Springs from the rebuild Kit? were the Float arms re-adjusted during the rebuild?

 

[danjs750]

Mine do exactly the same thing, and that was the bearing of the pump and the pto almost sticked. When they became hot after 5-10 second running, the engine will die, but with choke is still running... but when i was running (5-10 second) it was like 30% of the total power that 750 can have....

 

[danjs750]

And on my yamaha banshee the last time i have sticked the crankshaff bearing , that was the same thing... the atv won't run long time without choke... but still lack of power when running.