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I AM DONE! PLEASE HELP 98 Sportster 1800

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blackwellchris2000

blackwellchris2000

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Ok, so heres the background- I have a 98 Sporster 1800 with the twin Rotax's. The left engine (as you are seated in the drivers seat) started having a problem a few weeks ago. Initially when running at full throttle it would die from 7K RPM's down 6K and then all the way down to about 4K and in order to get the power back up, you'd have to throttle all the way down for it to "pick back up". Then you could run it wide open again for a few minutes, but then it would do it all over again. So we checked the fuel filters and cleaned them out, and we did find a cracked spark plug. We replaced it and took it out on the water and the next few times it ran PERFECTLY! Well now it's acting up again. It now drops from 7K down to 4.5K and then goes back and forth from 4.5K and 6K......just back and forth very quickly. Checked the fuel filters and plugs again but no dice. Oh by the way, that carb was replaced new less than 6 months ago by the previous owner and we have documentation on that.
UPDATE: Pulled the carb and cleaned it up and did a once over on everything (it wasnt that bad) . Now when it gets up to about 4700 to 5000 it starts having the same issues....but are you ready...now its happening to BOTH motors. Please help, cause i'm outta ideas! :boxing_smiley:
 
it does have only one tank but i have no idea whether or not it has any kinda selector switch. Do u think maybe a rev limiter issue? The way it started doing it, and stopped doing it, and then started again, and now to both motors is just friggin nuts and makes no sense to me at all!
 
depends if you could upload or send me an audio file I would be able to tell, it depends on the sounds they make, is it a very fast boucing sound or just revs slow up and down, does it sound like it is boucing off the rev lim?? an audio file would really help.
 
not actually at the boat now but it is a quick up and down spike of the motors but not as quick as a rev limit is. Maybe about a second from up to down
 
its the yellow 1in sq. look'n things, bolted to firewall of boat, in engine bay.

If these are bad, and its not carb problems, then what happens, is its not convert'n AC to DC, inturn..erratic motor behavior..."similar" to when drive'n under bridge with radio on, it gets "static"..same symtom/situation...
 
My buddy/co-owner of the boat (forum member Chicksdigit98) is out on it now test running it. Can he do it while in the water. Are there any negative rammifications of taking them off or leaving them off for that matter
 
make sure the battery is charged. With red wire disconnected, it not charg'n it, so...shouldnt take more than 5-10 minutes, to know if this fixed it or not..:cheers:
 
blackwellchris2000 said:
ok, trying to get ahold of em now to try it but dummy wont answer his phone lol! Any other ideas if this doesnt solve the problem?
Click to expand...

Clip plug wires back 1/4in, replace the o-ring in inline filters, check/clean the fuel pump.

I had same boat...so, if not rectifiers, then fuel related, stud.
 
blackwellchris2000 said:
not actually at the boat now but it is a quick up and down spike of the motors but not as quick as a rev limit is. Maybe about a second from up to down
Click to expand...
From this yes it does not sound like a rev limiter, a rev lim would be like a pin-ball machine when it gets trapped in a tight area and bouces off of each side, I think even you would know if that was the sound, Timmy seems like a good place to start, however it is odd that both engines went at the same time
 
i was actually starting to think fuel pump as well. It would almost explain it all but u figure if it was bad then it wouldnt really run at all. But if it's on its last limb then it kinda makes sense.
 
timmyboy76 said:
tell'n him to replace the rectifiers, if, by disconnecting the red wire, solves the problem.
Click to expand...
sorry Timmy I got lost on the twin motors....lol... I hate these small motors I was like this guy the first time I messed with a 2 stroke, where the heck is the stator,reluctor, and rectifier......I was so lost the first time. I thought you where telling him to replace them in pairs, like the stator and rec. sorry for the confusion
 
tell me about it, i know my way decently around a car or regular outboard, but all these jets, and raves, and what not....just gonna take some getting used to i suppose
 
timmyboy76 said:
Clip plug wires back 1/4in, replace the o-ring in inline filters, check/clean the fuel pump.

I had same boat...so, if not rectifiers, then fuel related, stud.
Click to expand...

Do these have a fuel shutoff valve Timmy? The slow up and down rev could also be a vac/air leak but not very common with it being both motors. Check those items Timmy stated first
 
whats a trip, is that, all it has is a "reserve" rocker switch on panel...no on/off switch.

No worries, stud...learn'n the 951 from ur thread...:cheers: THink Blackwell has right idea..aka (BALLS), to hit up seller for $$$$
 
hell no chance of that, dude man sold us the boat for 2K so he wouldnt lose his house...so there aint no more water in that well i can guarantee that! If i can ever get ahold of my buddy i will try the rectifiers and see if that does the trick. Then if not i guess i will try the fuel pump, and then start working my way down the rest of the stuff u guys gave me. Its a shame considering how nice and clean a boat it is and how well it ran for the first couple of months. That thing is a BLAST when its right
 
timmyboy76 said:
whats a trip, is that, all it has is a "reserve" rocker switch on panel...no on/off switch.

No worries, stud...learn'n the 951 from ur thread...:cheers: THink Blackwell has right idea..aka (BALLS), to hit up seller for $$$$
Click to expand...
Your a funny guy...I called them 5 times and threatend to take them to court, they dont care buch of good ole' boys from the sticks, then they turned around the story after I told them what was wrong and told my the 4 wheeler had a ton of problems...lol. go figure.....no worries I will just put tons of money into it like everything else
 
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