Tri z cutting in and out on wot??? Help

[1972mercury]

I just finished rebuilding the whole engine this fall was running a 470 in summer and today was 9 degrees so I bumped it up to a 490 ran it and plug looks perfect but when I started going wot in 4th or 5th gear it just would cut out for a second or 2 then it would rev up normally for a couple seconds then go back to cutting out and it would keep doing this until you let off the throttle what could be the problem???

[200xranger]

I have been having the same issue. fairly new rebuild. only in 5th wot. some say carb, some say tranny. Never could get any real leads on a cause. it would almost shake the teeth out of my head haha. going to investigate further this spring. good luck

[ATC-Eric]

Sounds like a fuel delivery issue. May be time to rebuild your fuel pumps. I ran into the same issue with one of those generic mikuni pumps you can buy cheap. It would cut out on wide open pull because it was drinking fuel faster then it could get it. Check to make sure all your lines are free and clear.

[1972mercury]

Sounds like a fuel delivery issue. May be time to rebuild your fuel pumps. I ran into the same issue with one of those generic mikuni pumps you can buy cheap. It would cut out on wide open pull because it was drinking fuel faster then it could get it. Check to make sure all your lines are free and clear.


I did replace all the fuel lines with that blue hose but I was starting to think maybe it was the fuel pump but wasn't sure that was only thing I didn't rebuild I'll have to buy a fuel pump rebuild and keep everybody updated.

[ATC-Eric]

Even if it isn't the pump the kits are cheap, and its good piece of mind. Hopefully that does it for you.

[barnett468]

I just finished rebuilding the whole engine this fall was running a 470 in summer and today was 9 degrees so I bumped it up to a 490 ran it and plug looks perfect but when I started going wot in 4th or 5th gear it just would cut out for a second or 2 then it would rev up normally for a couple seconds then go back to cutting out and it would keep doing this until you let off the throttle what could be the problem???470 to 490 is a big jump, i would simply put the 470 back in and try it or at least go down to a 480 and try.

put a clear line from the cylinder to the fuel pump. if you ever see gas in it, the pump is leaking which will cause big perf probs.

[El Camexican]

470 to 490 is only 2 sizes up, I would not consider that a "big jump".

Do the rebuild, its cheap http://www.jetsrus.com/individual_parts/002_223_su.html, just pay attention to how things came apart. It will likely run great with the 470 or even a smaller main once you get the pump right.

[DohcBikes]

If it ran great before you changed it, my opinion is that you try changing it back first. A quality carb rebuild kit is never a bad idea with a rebuilt engine.