500 EFI losing rpm's
 

I had the port engine rebuilt over the winter. It's a 500 efi, and when I take it up over 4000 rpms it will top out at 4500-4600 then start losing rpms. I can back it down below 4000 for a few seconds then take it back up and it does it again. I have changed the fuel water seperator filters. Just looking for suggestions where to go next. I will probably hook a fuel; pressure gauge up next to see what pressure I get.

Re: 500 EFI losing rpm's
 

Check fuel pressure. That is most likely the problem. Be careful, if it is pulling RPM it is because it is detonating!!

Re: 500 EFI losing rpm's
 

i agree sounds like a fuel problem 4 sure

Re: 500 EFI losing rpm's
 

Have You Changed The Silver Filter At The Top Rear Of The Motor?

Re: 500 EFI losing rpm's
 

Also is the other motor only going to 4600? if so you need to buz it higher after you find the problem.Its Proped wrong.

Rob

Re: 500 EFI losing rpm's
 

Last year they would run up to 5000+. So it's something that has happened since the rebuild.

Re: 500 EFI losing rpm's
 

So both motors are not turning up???

Is all the fuel system stock 500efi stuff???

Re: 500 EFI losing rpm's
 

I had the same problem last year with a 525efi.
There is a sensor assy on the crankshaft pulley mine was part #828358 2.
I would run wide open then it felt like I was rumming out of gas. I'd slow down for a while then it would be ok. It happened twice on poker runs.
Changed the sensors and never had the problem again

Steve

Re: 500 EFI losing rpm's
 

Oh ya I changed those filters first--- still did it !

Re: 500 EFI losing rpm's
 

Steve the 500efi doesnt have a crank trigger like yours.