550 Seca enrichment plunger question ?

How can I tell if enrichment plunger is sealing on the seat in the carb. I'm having a really rich condition at idle. I get black smoke out the exhaust. The choke is off all plungers are seated. The float level and the valves are in spec. Air filter and carbs are clean.

 

What, have I stumped you. I didn`t think it was possible with all the knowledge here. Or is this a dumb question.

 

When you check the plugs are all 4 black, or just one or two. Just one or two might indicate a leaking plunger, but probably not all four. Have you checked the pilot screws and are they all about the same? How about the air filter? When I bought my 700 it had a Uni foam filter. When I replaced it with a stock paper filter it made my bike run very rich. If the filter is stock, I would first check the pilot screw settings with a colortune plug.

I've done everything I know and mine is still rich with the pilot screws set less than one turn. I have a spare carb on the way and I plan to swap out the jets and see if that helps. One rider mentioned the same problem and finally determined that the pilot screws had been drilled. When he replaced them his problem went away. Can't trust the number stamped on the jet since a po may have drilled them.

 

How can you tell if the plungers are sealing on the seat? Short answer is... Once the carbs are attached to the motor, you really can't.

You can INFER that they are closed properly if you have confirmed that the elastomeric seals on the bottom of the plungers are in good condition and have also confirmed that the plungers are tight all the way down when the enrichment lever is "OFF".

But if you're looking for a way to TEST that there is no flow past the plungers in application, then I think you're out of luck.

 

BTW - How did you verify that the plungers are seated?

 

You can with the carbs off the bike, some disassembly required.

Are all four plugs equally showing signs of the issue?

 

What I get real rich at start up to the point that the plugs will be black and sooty . But I can color tune to a blue color but runs lumpy even after syncing. If it sits at idle for a half a minute I can go to WOT and no rise in RPMs. So if I keep blipping the throttle it will keep running. Or if I turn off the motor then restart its OK. I find that number 3 plug is the worst. I have tried to move the vac line from the petcock to another inlet to see if the problem follows but does not.

 

Did you pull them out and carefully examine them?

The pilot screws have new o-rings and no missing washers?

Did you replace the o-rings on the outside of the float valve seats? If one of those is leaking it will act like a bad float or adjustment.

Re-verify your float levels and check the above.

I know you haven't been fiddling with the carbs with out-of-spec valves; but have you done a compression test recently?

(Just fishing...)

 

I did check the seals on the plungers one was compressed this was number 4.

The pilot screws have new O-rings that came in the rebuild kit that included O-rings for the float valve seats.

Have checked float levels.

I will reinstall the best plungers I have this weekend and recheck float levels and see how this works.

Compression is good above 140 PSI

I got to get this thing fixed be for PD13

 

Compression shouldn't be that high, it's a 550. That may indicate that it's "wetting" itself. Anything above 135 is out of spec.

I think you're on the right track; be sure to inspect the enrichment plunger boots too (long unavailable, Len now has them) but I'd be focusing on the float levels. When you check them, "cycle" each float (fill, drain, fill, drain, fill) before checking. If you check them on "first fill" they can often fool you.

Oh, and not that it matters one bit, but the vacuum line for the petcock runs off #2 on the 550s.