98 sportster 1800 missing/poor performance

[kcr357]

After some frigid 60 degree weather the last few weeks, it finally got back up to the 80's again so I took my sportster for its maiden voyage. Ran fine from idle to full when I got in the ocean; waves were huge and after getting knocked around I went back to the intercoastal where it started backfiring/missing sporadically. After hangin on the beach, we went back in and neither motor would really run past 3k. The SB engine was especially bad, and was smoking pretty bad, smelled like lots of unburnt fuel. I tested the comp. when I bought it, all cyl. were 150. Fuel pumps don't seem to have ever been apart, the carbs I don't know. Anyone care to take a guess on the prob? The prior owner removed the oil injection, I put in 8 gallons of 40:1, there was maybe 15-20 gal. in the tank already, at what ratio I don't know. I don't think the plugs got fouled from the 20 mins idling to the ocean, but maybe someone that has a boat with premix can chime in....

 

[Dr Honda]

Check the neutral switch in the shift lever. They go bad... and the engines won't go past 3500 RPM when the MPEM thinks it's in neutral.

 

[kcr357]

nope, the problem manifests itself even at idle. Took out both plugs, they were pretty wet but not carboned up.

 

[RFoster130]

I would throw in new plugs for the heck of it and see how it runs.

 

[kcr357]

The carbs and fuel pumps are all A1 with the exception of the low speed screws, one side was half a turn too rich, and the other was about 1 turn too rich. I'm all about premix, but wish this thing still had injection with all the idle speed areas down here.

 

[parrothd]

Yep, probably fowling those plugs with the premix, maybe too rich with the way you mixed it, did you replace the plugs with new ones?

 

[parrothd]

I'd also check the rectifier..

 

[kcr357]

Yep, new plugs are in it. Didn't check the rectifier, I'll do that next time I have the cover off. Just check voltage running/not running?

 

[Dr Honda]

Put a volt meter on the battery. Start it up, bring the RPM's up, (around 5000) and watch the meter. If you see more than +14.5 volts... then your regulator has gone bad. When they go bad... the ignition will do strange things in an over volt condition.

 

[stfoulks]

Mine did this very same thing last season ... scared the crap out of me. I'm on lakes, so not dealing with the waves you do, but it seems like I was doing some hot dogging just prior, and when I opened the hatch, I saw a little more water in the bilge than I'm used to seeing. It seemed to magically clear up for me after about 30 min (I don't like those kinds of miracles). I chalked it up to something getting wet.

Since then, I've replaced the carbon seals and have a lot less water in the bilge... but I still wonder what got splashed.

Thanks for the voltage tip Doc, I'm going to check that out too.

 

[CaptSteve]

One other thing you might check is the fuel filter. I see this a lot on bigger boats. They run fine and then go out in rough seas and all the junk in the bottom of the fuel tank gets stirred up and they foul the fuel filter. You should check the inline filter and if that is fouled, you should also check the filter in the carbs.

 

[kcr357]

re

Ding ding ding, after checking all of the more complicated things, turns out I'm not getting any more voltage when running than when not running. At least I found the carbs needed adujsted and got to spend some time in the sun.

I'd also check the rectifier..