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1989 900 Supersport running on one cylinder

Posted: Tue Apr 01, 2014 5:33 pm
by TheDuctor
Hi guys, not been on for a long time as I didnt get muchuse out of the bike last year unfortunately. I've just got it out from winter lay up and I have started the riding season with a problem. The bike started fine and ran fine up until I stopped about 2 miles up the road for petrol. When I restarted it though it only ran on one cylinder. I got it home and put my extensive knowledge, know how and tooling abilities to work. After hours, ok it seemed like hours, I had exhausted my knowledge, know how and tooling abilities. Through swapping plugs and ht leads over I narrowed the problem to the front, or horizontal cylinder. I put that spark plug in the rear cylinder and that ran ok. I did notice that the wire in the pic from the back of the rectifier(?) was totally loose and not to mention the fuel line joint!! Could either be the cause?

Re: 1989 900 Supersport running on one cylinder

Posted: Tue Apr 01, 2014 9:24 pm
by bmw851
Nah, none of those things shouldn't make it run on one, reckon the Flux Capacitor is stuffed.................... :fart:

Re: 1989 900 Supersport running on one cylinder

Posted: Tue Apr 01, 2014 9:42 pm
by TheDuctor
Yeah, the capacitor definitely seems to be fluxed. Well and truly fluxed!

Re: 1989 900 Supersport running on one cylinder

Posted: Tue Apr 01, 2014 11:08 pm
by higgy
better check the muffler bearings and the constant entropy seals while you are at it, they do tend to act up when ignored :beer: :beer:

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 4:30 am
by Mc tool
Geeeeze and I thought I was bad at the smart arsed replies :D
Ductor you gotta sort the ..................................wait a minute.....are you taking the piss :D :mad: :D ( shit ! I nearly fell into that ! ) ...........yeah , make sure you didn't put the petrol in upside down :-P

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 9:21 am
by TheDuctor
Thanks guys :banghead: :lol:

Anyone got any real suggestions though :D

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 11:22 am
by bmw851
OK with a heavy Irish accent alay the I.T. Crowd

Have you tried turning it off and on :drunk:

Himself

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 11:25 am
by TheDuctor
I'm going outside to stick myself in the ear with a blunt pen

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 11:32 am
by bmw851
Is that like cutting someone's heart out with a spoon, ok that that does it, no more merciful beheading's, no more scraps for the leper's and Christmas is cancelled.

No pleasing some some people, but that's what he said........................ :truck:

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 11:42 am
by paso750
assuming you still have the original Weber carb that broken Y piece is the split to the carb and the return line. You should have fuel everywhere.
What`s connected to that blue wire only you can check.

When you`re finished poking yourself in the ear with a pen swap the CDI units. If the non running cylinder remains the same swap the coils. If that doesn`t change anything measure the pickups to verify that no wire might be broken.
Then measure the voltage at the coils at ignition on and engine running. If it`s lower than the actual battery voltage do the wiring mod (see FAQs).
You should then have spark on both cylinders (or if one coil, HT lead, spark plug or CDI unit is defective at least swapping the parts from the horizontal to vertical cylinder then should make the other cylinder run). If every ignition part is ruled out as possible source of the problem you should check carb synchronization.

G.

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 11:57 am
by TheDuctor
Thanks Paso750. There was indeed fuel all over the engine and the floor. The blue wire runs to the battery negative terminal. I guess I'll start the elimination process at the weekend. I did try swapping the HT leads over and the same cylinder still wasn't running, so that's one thing I guess.

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 12:01 pm
by bmw851
Um err G, if I'm not mistaken the N terminal on the battery is disconnected, god knows what that blue wire is meant to be attached to, and it would have been pissing fuel under pump pressure if the battery was connected with the split Y piece, so I think the post date has some relevance, if not I'm very scared indeed, and will go poke myself in the eye with a blunt stick, just because I can. :shock:

Himself

I'm going outside with my blunt stick now

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 12:08 pm
by bmw851
That hurt........... :banghead:

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 12:25 pm
by TheDuctor
In no way is this an April Fool! I disconnected the battery terminal because I was trying to get at the coil

Re: 1989 900 Supersport running on one cylinder

Posted: Wed Apr 02, 2014 9:50 pm
by bmw851
OK not April fools joke :(

Then in that case the broken Y piece would be the most obvious and foremost problem to start with, fix it 1st before anything else, I may be a bit mechanically challenged myself, but if the bike started fine and was running along alright until you stopped and filled it up and tried restarting it, and I assume there would have been a strong smell of petrol by then? and it cut to one cylinder and died that should be the culprit, fuel starvation pure and simple.

If that doesn't work, move onto the next suggestion, one thing at a time. :D

Cheers

Peter