Stage 2 GP12R RPM drop at WOT

[Himes]

I have an intermittant rpm drop and nearly instantanous recovery (within the update period of an old tiny tach) on my GPR at WOT. The ski slows down and recovers within a second. Flat water, drag type deal. The compression is fine open and closed. I replaced the OEM CDI for another reason and had the same problem before I replaced it.

I am thinking a PV servo problem or maybe its time to run through the carbs to make sure the screens and check valves are okay. But I think a fuel delivery problem would be pretty consistant, which this issue is not. I didn't take the seat off and watch the PV couplers when it happened, I just got the other ski and took it out instead.

For those of you that have had this problem before, what fixed it?

[smackwave]

It does sound PV servo related. Is there any chance you have the servo cables reversed? It seems to me that's when I had a problem similar to what you're describing.

[Duke]

Disable the PV motor by disconnecting the plug. Move rubber boot off cable cover on motor and open valves all the way ( either clockways or counter can't remember easy enough to figure out). Ski will not have bottom but will give you max power on top. This should tell you if your problem is PV related or not.

[Pistonwash]

Disable the PV motor by disconnecting the plug. Move rubber boot off cable cover on motor and open valves all the way ( either clockways or counter can't remember easy enough to figure out). Ski will not have bottom but will give you max power on top. This should tell you if your problem is PV related or not.

+1 Then if you are not dropping rpm's defintely pull those carbs, the ski might be starving for fuel. When is the last time you inspected the carbs?

[800AMSOIL4U]

Make sure you are using enough octane also. It might be going lean on you.

[Himes]

It does appear to be a PV servo. Anyone got one lying around that they would want to get rid of?

Thanks for affirming what I thought, bros. I think I have got one more season left on my carbs before I rip into them.

I forgot how cool PWC forums can be

[smackwave]

It does appear to be a PV servo. Anyone got one lying around that they would want to get rid of?

Thanks for affirming what I thought, bros. I think I have got one more season left on my carbs before I rip into them.

I forgot how cool PWC forums can be

Curse the PV servo motor! PM me with your address if you can't find anyone closer and I can send one out tomorrow.

[Himes]

Thanks to Smack for sending the servo. It got from coast to coast in less than 3 days

Too bad it didn't solve the problem for me. Everything seemed alright, I felt one hesitation, the overheat alarm sounded and the ski died. I did a compression check and had closed compression ranging from of 142 to 147. I am hoping I find something in the carbs and they are overdue anyway.

I always thought that those Yamaha overheat alarms in early model skis were too late to prevent any damage, being that they are usually pretty far from the cylinders. Kinda seems like you would already have been close to a solid seize when they go off. I hope I am right about the carbs or fuel circuit being the problem.

[Himes]

Since the problem I am having does not occur at all times, the ski takes off and accelerates fine and only sometimes do I have the hestiation, it seems odd that it would be a carb issue, those are apparant usually across the range of operation.

If the water temp sensor is bad, could it cause the engine to die. Or if the istrument cluster has an issue, could that be the problem?

I checked resistance on all the plug wires and coils and they are fine. I idled the ski back to the dock after the overheat alarm came on and it ran fine. Plugs look good. Seems electrical, I am looking for ideas?

[Himes]

*I hear crickets with this problem*

I think that the water temp sensor is going briefly "true" and then returning to "false" causing the alarm to come and go intermittantly and briefly putting the ski in limp mode, thus causing a brief loss of power/rpm.

Has anyone ever had this happen before?

*back to cricket time*