99 Sportster 1800-one engine fades intermittently at WOT

[go_panthers]

I was at the lake today testing the fixes Dr Honda recommended for my low speed issue. Those are fixed. Here is my next challenge:

Cruising the lake at almost wide open throttle. Both engines synced at 6500 RPM. After about a minute (that's a guess), one of the engines faded back to about 4000 RPM and leveled out there. I pulled the throttle back on that engine and pushed it back and the engine went back up to 6500 and stayed there. This happened twice over the course of about 60 minutes of testing.

Any thoughts on the cause for this?

 

[Dr Honda]

It's going lean !! Don't keep running it, or you will roast the engine !!

You could have:

1) a lose hose, and are sucking air.

2) a filter could be plugged.

3) High speed jet is plugged.

4) There is a prob with the fuel pump on that side, and it can't keep pressure.

5) Pop-off is very high.

 

[howie099]

My boat did the same thing if I gained speed to fast one engine is would drop RPMs and I would have to baby it back up and than I was fine luckly this happend at the end of the labor day weekend last year. I knew the carbs would need to be serviced since the orignal owner never has them service since they bought it. My issue was just the internal fuel filter was clogged on that engine pretty bad. I was supprised it even ran when I looked at the filter. Since I took the carb apart I just celeaned it out fully and replaced the rubbers why not it's apart and for $40 it makes me feel better even though my carb looked like brand new inside. I just serviced the other carb this year since one was clogged and it pulls from the same fuel tank the other will follow. I hope you just have dirty or clogged carb. If it's the fule pump they are easierto replace. I would put some external Fram G2 fuel filters on the baot also so the internal fuel filters stay cleaner also repalce that gray tempo fuel line from the pulse line on the engine to the pump if you didn't that will gum up and kill the fuel pump unless you run 100% gas in your boat. That is the only gray tempo line on the boat the rest are marine grade fuel line.

 

[go_panthers]

It's going lean !! Don't keep running it, or you will roast the engine !!

You could have:

1) a lose hose, and are sucking air.

2) a filter could be plugged.

3) High speed jet is plugged.

4) There is a prob with the fuel pump on that side, and it can't keep pressure.

5) Pop-off is very high.

I have checked all the hoses on the low speed issue, they are all new.

Filter was new as of the winter carb rebuild. I didn't open up that side of the carb when I checked the low speed jet, so that is not verified.

High speed jet looked good when I had it open to check the low speed one.

Could be the fuel pump. It is external. And I have not touched them since I bought the boat 4 years ago.

Pop off should be good. Spring and lever were checked when I had the carb open.

What are my fuel pump options?