Sportster 1800 port engine low speed issues

[go_panthers]

I have a 1999 Sportster 1800. I've searched the forum, but haven't been able to narrow down the issue.

I rebuilt the carbs on both engines over the winter. I have also replaced the fuel filters and oil filters as part of my normal spring maintenance. I took the boat to the lake today for a test run. Starboard engine is running great. Port engine is giving me a little bit of trouble.

It will crank normally with the choke pulled, but will not idle or run well at less than about 4000 rpm. If I crank it and give it 3/4 throttle (along with the other engine idling and pushed to 3/4 throttle), it runs well. Bring both engines down to about 3500 rom, and the port engine will just fall off and die.

I pulled the plugs. The starboard engine's plugs look pretty good. A little shiny and brown. The port plugs look grey and dry. I checked the fuel lines for any loose connections, and played a little with the low speed screw with no real impact.

Any advice I could get with troubleshooting this would be greatly appreciated.

 

[go_panthers]

Just to add a little more info. His boat has external fuel pumps, which I've never rebuilt. Should I?

 

[Dr Honda]

Sounds like the pilot circuit is plugged still. OR... the high speed check valve is leaking, and you are sucking the carb dry.

 

[go_panthers]

Sounds like the pilot circuit is plugged still. OR... the high speed check valve is leaking, and you are sucking the carb dry.

Thanks. Is the high speed check valve the little clear plastic piece?

 

[Dr Honda]

Yes. The clear plastic "Reed" that is mounted on the back of the jet block. It should sit flat. If it's bent up at all, at rest... that's the prob.


When it leaks... and you go to idle... it's easier to draw air though that, than to suck the diaphragm to open the needle, and pull in more fuel. (so the carb goes dry)


BUT... if the bypass ports are plugged up in the pilot circuit... you will get the same effect. As the throttle is closed... the fuel can't be drawn though.

 

[go_panthers]

Yes. The clear plastic "Reed" that is mounted on the back of the jet block. It should sit flat. If it's bent up at all, at rest... that's the prob.


When it leaks... and you go to idle... it's easier to draw air though that, than to suck the diaphragm to open the needle, and pull in more fuel. (so the carb goes dry)


BUT... if the bypass ports are plugged up in the pilot circuit... you will get the same effect. As the throttle is closed... the fuel can't be drawn though.

You were right, as usual. I reseated the check valve, as it wasn't quite centered, then removed the low speed jet and it was clogged. Not sure how that happened, but it is idling fine now with the low speed needle out 1.5 turns (spec is 1.25 +/- .25).

Ran it through its paces at the lake and the idling and throttle response is good.

Thanks for the help. I'll start a new thread with a minor (I think) issue at WOT.