Motor sticking wide open... everything looks good?

[showner3]

Just installed my new Mikuni pump. Charged battery, started it up idled good everything looked fine. Hit the throttle a couple of times went into 5000 rpm range motor stayed wide ope? Can't figure it out. Throttle is not sticking and the kill switch won't work when it gets stuck .

Kill switch works at idle and every other time just not when it sticks like this. Looked at throttle linkage everything moves freely. Carbs recently cleaned.

What am I missing?

[Jeffwil]

Re: Motor sticking wide open... everything looks good?

I have a Polaris 650 SL. I installed a new Mikuni three outlet fuel pump. I started it up and for a few a minutes it seemed to run at a reasonable speed and then the RPMs started taking off until it was nearly wide open. I killed it. Now whenever I start it the engine accelerates to what seems to be wide open and I must shut it down. Thinking that the new pump was overwhelming the carbs, I put the old pump and restrictor back in place. It did not change anything. It still loses control of idle. I have checked the main idle screw and backed it out just in case. No change. The throttle plates look to be in the proper closed position. It seems as if fuel is just pouring through the carbs in an unrestricted fashion. Any help would be greatly appreciated.

[BarefootPolaris]

Re: Motor sticking wide open... everything looks good?

Unfortunately, sounds to me like your diaphrams in your carbs have holes...This is a common factor for skis that have newly added pumps...I am not familar with the way you have added the pump, meaning if you added it to the existing or stand alone, however, when the diaphrams are exposed to too much gas, they can develop holes or rips...with a new pump installed, if you removed the restrictor, then there is a constant flow of gas being sent to the carbs and eventually into the motor once the ski is started...

First, I would break down the carbs and check them out...If the tops of the diaphrams are very wet, then you likely have a small hole or rip...If not, it could be something more serious within your electrical...I will try to keep an eye on thsi post, but if you have any other questions or issues, email me as I check my email multiple times a day: Barefoot311@yahoo.com ....I hope this helps and good luck to you...

BarefootPolaris

[BarefootPolaris]

Re: Motor sticking wide open... everything looks good?

Also, if your ski is out of water, you never want to rev it up beyond a midrange point (best to be determined once you know your ski) as this will cause damage because of the heating and lack of cooling...

[mikey20]

Re: Motor sticking wide open... everything looks good?

I would start looking for possible air leaks did you rebuild your carbs with rebuild kits or reuse your gaskets .That can happen with either being really lean or an air leak ,I would go over recent work and double check everything.To get it to stop try choking or priming the engine that should stop the engine from glow pluging and allow you to stop it.

[Jeffwil]

Re: Motor sticking wide open... everything looks good?

Well I have tried everything mentioned here. I have put kits in the carbs which did have diaphrams with holes in them. The **** kits came with no instructions so it was a bit of a guessing game. They also came with a pile of extra gaskets and parts that apply to the Mikuni 38 or super BN 46 as opposed to the Mikuni super BN44 that I have. I have tried it with and without the fuel line restrictor. Can someone confirm that the restrictor goes in the return line on its way back to the fuel tank? I have tried it with the old fuel pump and the new 4 port fuel pump. I have tried it with the low speed adjusters and the high speed adjusters turned all the way in.

The only thing I have found that keeps it from going wide open is to use the choke 3/4 of the way closed. This will allow reasonable RPMs.

This all started when the ski sat for two years without starting. When I tried to start it, nothing, no fuel fuel through the carbs. When I worked to get fuel flowing again I used some compressed air and perhaps I have damaged some part of the carbs that regulate flow. I replaced what I could see when I put the carb kits in but maybe there is something deeper. It sure seems like a carb problem, there is no regulation of the fuel flow to the cylinders...

Thanks to all who have contributed ideas...this was much appreciated..

[Jeffwil]

Re: Motor sticking wide open... everything looks good?

So I went over everything again including the carb kit installs and I am convinced that everything is right. Maybe I need to make the final adjustments in the water. Perhaps the over idle condition with go away with the water cooling and prop load. Since I can control the idle speed with the choke at about 3/4 closed, I don't think I'm that far off. I will try this as my next step.