02 125 ELPTO good hole shot but backs off.

[Tim Wagner]

This is the 3rd season for me and this motor. its been good and has always ran around 5200RPM and 40-42 MPH.
This season, it developed a high speed miss so I put in new plugs (the same as what has been in there). Gapped them to .040. but they are not 10's like the book says, they are 20's and thats what has been in there since I bought it.
That didnt stop the miss so I went and tore all the carbs off, tore them apart 1 at a time and cleaned each one. (I numbered them so they went back on the same cylinder) there isnt too many parts in there and its pretty simple to do. I was pretty careful also not to do screw up the floats or the needles. I also dumped a pint of sea foam in tank. there was roughly 20 gallons of fuel in there.
All is back together. did the link and sync to the carbs and am sure the butterflys are opening flat a WOT.
it idles fine, cruises fine but on the hole shot it cranks to 5200 RPMs and then for some reason it fades back to 46-4700 and only goes about 33 MPH tops. Its happening, you can clearly hear it.
Oh, the miss is gone.
I put in a new filter and reuilt the fuel pump. that didnt help.
i put new gas in a separate tank and ran it off that and that didnt help.
I even replaced a the 2 fuel lines coming out of the fuel pump, and the one going into the motor up to that crazy line with the "Y's" in it. that goes into the fuel pump. That didnt help.
I squeezed the bulb at WOT and it didnt help.
It does it every time though. You nail it and you can hear it scream. You can watch the RPM's come up of 5000 and for a second you think you got it and it fades back to 4700 like you backed the throttle off.
WTF??

 

[Tim Wagner]

Re: 02 125 ELPTO good hole shot but backs off.

A couple added notes because I know its coming.
1. I never touched the timing so Im really not thinking its there how ever Ill verify it.
2. I havnt done a compression check either
3. I regapped the plugs to .035 and that didnt help.
4. the old plugs I took out had a way bigger gap than .040 but I wrote that off beings they were so old and had a million hours on them.
WILL RUNNING IT LIKE THIS WHEN I GO TO CANADA ON SATURDAY DAMAGE THE MOTOR?

 

[mickab]

Re: 02 125 ELPTO good hole shot but backs off.

hey Tim, im currently dealing with pretty much the same issue with my motor. I have a 94 merc 150 xr6. I have done all the things you have done with the same results. its currently at the shop right now and should know something in a day or two. so when I do ill let you know and it may help you. as far as running it, I wouldn't, cuse it still could be a fuel issue which if it runs lean at that rpm for whatever reason could cause a bigger problem.

 

[Tim Wagner]

Re: 02 125 ELPTO good hole shot but backs off.

Thanks for the reply.
Im headed to Canada on Saturday for a week. I NEED the boat.
I cant be stuck on Lake St. Clair without my big motor. Plus I troll with it.
I tuned the idle mixture myself and I know its not lean.
Plus I looked over the plugs from my testing exploits and they dont show signs of running lean either.
This motor is what they call a 2+2 which means it only runs on the top two cylinders under 2000 RPM's and those are the only two carbs with low speed idle mixture needles.
Ill probably troll 500 miles on the week.