98 GTX RFI won’t turn over 4200 rpm

[Blacknsilvr]

Hi all!!

As the title states, ski won’t turn over 4200 rpm. I’m assuming it’s in a fail safe mode, because it stutters like a rev limiter. I’ve verified that the stator, and my osd heavy duty rectifier are both operating as designed.

This is a new problem and that popped up after I rebuilt the engine due to a rod bearing failure. (Engine was turning 6800 ish rpm at the time of the failure).

Fuel injectors have been cleaned and flow tested.

Verified the rave valve solenoid and lines are functioning properly.

TPS has been reset and idle speed adjusted.

Crank position sensor checks to be good.

So my question is, is there a possibility that the ski is actually charging correctly, but the mpem is not recognizing that it is, and throwing it into fail safe?

I’ve traced my powers and grounds to the mpem, all are showing battery voltage, and good grounds.

I’m open to any and all ideas on this deal, it’s got me stumped pretty good.

Thanks in advance!!!

 

[Blacknsilvr]

Bump??

 

[shamrock246]

Are the rave valves opening?

 

[Blacknsilvr]

Are the rave valves opening?

Yes. I have thought about taking the caps off the next time out, to see if that changes anything.

 

[etemplet]

I had one that did that. Right under 4200 then evey now and that it would take off and run 6900. Once I let it drop back down below 4000 rpm it wouldn't rev. It was the rev limiter in the MPEM. I swapped MPEMs and the ski ran great. I kept the MPEM for testing.

 

[Blacknsilvr]

I had one that did that. Right under 4200 then evey now and that it would take off and run 6900. Once I let it drop back down below 4000 rpm it wouldn't rev. It was the rev limiter in the MPEM. I swapped MPEMs and the ski ran great. I kept the MPEM for testing.

I read several of your replies that said it fixed yours. I did try another mpem, and it did the same thing. But it’s exactly like yours did. If I hold it long enough, it will push through and go to max rpm’s.

I did clean out the rave valve solenoid, and the vent line that goes back to the rear of the ski. Vent line was stopped up, but I doubt it fixes the problem. This ski has been a PAIN. IN. MY. ASS……..

 

[etemplet]

When I swapped MPEMs mine responded right away. Hmmmmm..... Check your wiring from the mag, three yellows and black and red. You may have a bad ground. I also found bad connections to the ground and the wiring under seat (the coils) I didn't read it all but did you swap the coils out. I'm lucky as I have lots of spare parts but I have to say... swapping parts is no way to fix these skis. gotta figure out what is wrong. Have you check the timing? clean the plugs and points of contact on the number 4 plug on the MPEM. You might have a plug issue Be gentle they break real easy. Good Luck !

 

[Blacknsilvr]

I’ve hit all of the easy stuff. Ignition leads and boots were bad, leaking spark. I replaced that, no fix. Had a brand new spark plug go bad, didn’t fix it.

This will be the only RFI ski I will ever own lol.

 

[etemplet]

One thing I've never replaced on a ski is the wiring harness although I've been tempted. I may have a harness for a RFI. Sometimes I think the pins cause problems. I once spent 30 hours or close to it troubleshooting a RFI. It was the first thing I suspected but I was not able to verify like I wanted. It was at night and I pulled the rotary valve cover to check the timing and the disc came off with the plate so I couldn't tell where it was located upon removal. I checked the rotary valve shaft for looseness... it was a little loose but I couldn't turn it so I let it go and retimed the engine. All the other hours I spent were getting it to almost run and going deeper and deeper. Finally, I pulled the engine and split the cases. Full of brass and no teeth in the gear. I had restored that ski and rebuilt the engine so I knew no much could be wrong with it. Basically, somebody put gas in the oil tank. After I installed another engine I rode the ski and there was a hot plug on the electrical. I cured that by replacing the MPEM. I knew when I put the engine back the ski would be fine.... goes to show. LOL I'm building a RFI for my wife. I love them. Start right up, no issues for the ladies. You can leave it sit for months and months and months and it will start right up. Just gotta get it right. LOL I love challenges... I just can't let go. LOL Too bad you don't live by me.


This is my next one. It's clean and ready for the engine.

 

[Blacknsilvr]

I’ve got my suspicions on the #4 harness, but everything ohms out good. That may be next on the list.

I do agree, they start right up when you hit the key. I do like that. I’ve got a 2.5 200 rfi merc on my go fast boat, zero issues.

My ski looked just like that when I got it. I put several hours on it after I got it running until the sbt engine ate a rod bearing. This all popped up after I rebuilt the engine. I’ll be mentally get it dialed back in, it’s just fighting me. I can’t backdown from a challenge either.

 

[burtshaver2021]

One thing I've never replaced on a ski is the wiring harness although I've been tempted. I may have a harness for a RFI. Sometimes I think the pins cause problems. I once spent 30 hours or close to it troubleshooting a RFI. It was the first thing I suspected but I was not able to verify like I wanted. It was at night and I pulled the rotary valve cover to check the timing and the disc came off with the plate so I couldn't tell where it was located upon removal. I checked the rotary valve shaft for looseness... it was a little loose but I couldn't turn it so I let it go and retimed the engine. All the other hours I spent were getting it to almost run and going deeper and deeper. Finally, I pulled the engine and split the cases. Full of brass and no teeth in the gear. I had restored that ski and rebuilt the engine so I knew no much could be wrong with it. Basically, somebody put gas in the oil tank. After I installed another engine I rode the ski and there was a hot plug on the electrical. I cured that by replacing the MPEM. I knew when I put the engine back the ski would be fine.... goes to show. LOL I'm building a RFI for my wife. I love them. Start right up, no issues for the ladies. You can leave it sit for months and months and months and it will start right up. Just gotta get it right. LOL I love challenges... I just can't let go. LOL Too bad you don't live by me.


This is my next one. It's clean and ready for the engine.
View attachment 68597

And they are amazing on fuel, my 1999 GSXRFI uses roughly half the fuel that my 97GSX uses, same engine

 

[etemplet]

And they are amazing on fuel, my 1999 GSXRFI uses roughly half the fuel that my 97GSX uses, same engine

I haven't kept one long enough to burn more than a tank, generally break in. I know the DI's a great on fuel consumption. What I really like about the RFI is... it's not a 951 and no carbs. I love them for women that can't start or ride a carb ski. LOL Just hit the button and go.