Bike Lurching/Surging/Coughing Problem - Help!!

phillc · #1 23-Aug-2006, 21:02

So my 2002 900ss is playing up big time.

It has developed what can only be described as a surge or cough when under power. No other way I can describe it really. Usually, whenever the revs get close to 5,000rpm and above, there is a sudden, short loss of power, then it picks up again. Sometimes this will happen once in a while, every mile or two perhaps. Other times it happens almost constantly.

I've tried to figure out if it happens when hot or cold, doesn't seem to matter. Tried to figure out if it's with full or empty-ish fuel tank, doesn't seem to matter. Tried to figure out if it happens at different rev ranges and usually it is between 5k and 6k rpm, but this morning it was particularly bad and happened all the way from 3,000rpm upwards.

So far I have done the following:

- drained the fuel tank totally. And there was a significant amount of water in the bottom - about 1 inch in the bottom of a 1 litre plastic drink container.

- change the fuel filter. Did both of these at Cadwell on Tuesday. I had 15 trouble free miles on the way home, before the problem started again.

- Changed old spark plugs for new. Fortunatelly my 900ss and my DD bike use the same plugs and I had a spare set.

- Put the standard pipes and airbox back on. The problem was still there, just that the "buck" of the bike didn't seem so bad with the standard pipes on.

All of the above has been to no avail. Problem still happens.

Someone suggested that it could be my potentiometer, but the SS ECU doesn't have one.

I'm supposed to be riding to Normandy on Friday evening for the bank holiday weekend. However, at this stage I'm not sure the bike is up for it. Looks like my weekend could be stuffed.

Any ideas? I guess it's too late to get it into a workshop now, but is there anything else I might try?

Help!

KeefyB · #2 23-Aug-2006, 21:07

Fuel tank breather partially blocked??

phillc · #3 23-Aug-2006, 21:20

Quote:

Originally Posted by KeefyB

Fuel tank breather partially blocked??

Now there's an idea........

I had this blocked once before and it caused this:

http://www.kapital-sales.co.uk/desmo...Tank%20001.jpg
http://www.kapital-sales.co.uk/desmo...Tank%20009.jpg

I'll check the breather pipe because I did notice this afternoon a "hissing" coming from around the fuel cap. I did think perhaps it was something I'd done in not putting it back together correctly after changing the filter.

Any thoughts on the best way to clean/clear the breather?

KeefyB · #4 23-Aug-2006, 21:26

Cant remember how the breather is routed on the I.E bikes,but when my wife had a carbed SS,I cleaned out a blockage by pushing a lengh of 4mm electrical cable down it.

Oh yeah,I remember those pics.Incredible!

Jools · #5 23-Aug-2006, 21:27

Errrrr...you weren't copying me were you?

I had exactly the symptoms you described on my ST2 for the whole of the first morning at Cadwell.

I changed the fuel pump, fuel filter, spark plugs...cleaned up the usual green connector suspects, drained the tank etc... almost exactly what you did.

I checked all the breathers as well, Still can't crack it

Pity, cos when it clears and pulls hard it's going like a train, better than I remember it ever going before.

thought about the TPS, but like your problem it seems to happen across the rev range not at a specific spot.

I'm gonna replace the battery next, because the battery is not holding it's charge. It's OK when you take it off charge, it'll start the bike no problem and it'll start the bike all day after that, but leave it overnight and the solenoid is clicking...I have a theory that if the battery or charging circuit is stopping the right voltage to flow across the TPS, or not providing enough voltage to the ECU then all sorts of crazy stuff could be happening to the fuelling or the sparks.

Don't know if this theory would explain why it's worse round right handers though

phillc · #6 23-Aug-2006, 21:28

Quote:

Originally Posted by KeefyB

Cant remember how the breather is routed on the I.E bikes,but when my wife had a carbed SS,I cleaned out a blockage by pushing a lengh of 4mm electrical cable down it.

OK, maybe I'll try a twisted piece of lock wire or similar. Thanks for that.

I should also mention that I spent some time this evening checking that the fuel line wasn't kinked anywhere, thus reducing the flow of fuel.

Any further ideas?

skidlids · #7 23-Aug-2006, 21:29

how about getting it plugged into a diagnostic machine in case its a sensor of some kind.
The guys from MotoRapido were kind enough to plug theirs in to Dallas's bike on Monday at the trackday and it revealed a rpm sensor fault.

Jools · #8 23-Aug-2006, 21:31

Quote:

Originally Posted by KeefyB

Cant remember how the breather is routed on the I.E bikes,but when my wife had a carbed SS,I cleaned out a blockage by pushing a lengh of 4mm electrical cable down it.

Oh yeah,I remember those pics.Incredible!

I dunno about SSie's either but on the ST the breather is a little round can about the size of a 10p piece and about half as deep with an air inlet sticking out the side. It's a one way valve and it sits on the bottom of the fuel pump assembly.

Jools · #9 23-Aug-2006, 21:33

Quote:

Originally Posted by skidlids

how about getting it plugged into a diagnostic machine in case its a sensor of some kind.
The guys from MotoRapido were kind enough to plug theirs in to Dallas's bike on Monday at the trackday and it revealed a rpm sensor fault.

Bugggerit...if I'd known they had one of those at the trackday

phillc · #10 23-Aug-2006, 21:35

Quote: