How can you tell if you're running on one cylinder?

Ok, heres a silly question. How can you tell if the bike is only firing on a single cylinder? I'm sure you'd see a loss of power, rough running etc., but that would probably describe a whole raft of issues.

Can you tell just from the sound - if so, what would it sound like?

The reason I'm asking is that I'm just getting the bike (2002 SV650 naked) back out after a few months off over the winter. I'd warmed it up a few times before, but yesterday it was hard to start initially. After it warmed up the idle had dropped to about 500rpm. I took it for a ride which seemed to generally be ok, but running about 35 at ~4000rpm (I think it was in third gear) I noticed that the power delivery was sort of pulsing - like it was firing about 3times /second 'ish.
Anyway, I'll put a can of carb cleaner through it sometime this week and check the plugs, WD40 the HT leads and see what happens, but I was just curious about what symptoms single cylinder operation would give.

Cheers,
Vic

[rictus01]

extremely poor pickup, rough as old harry, smell of unburn petrol from exhaust and one cold down pipe (DON'T ACTUALLY TOUCH IT TO FIND OUT!!!!).

Ever been karting? If so you'd recognise the noise.

Slightly smoky method... spray some WD40 on the exhaust header for each cylinder, if the cylinder is running (and so the pipe is hot...), lots of smoke.

Originally Posted by rictus01

extremely poor pickup, rough as old harry, smell of unburn petrol from exhaust and one cold down pipe (DON'T ACTUALLY TOUCH IT TO FIND OUT!!!!).

spot on descriprion, in my case it was a bad connection on the rear cylinder HT lead

[dizzyblonde]

Originally Posted by rictus01

extremely poor pickup, rough as old harry, smell of unburn petrol from exhaust and one cold down pipe (DON'T ACTUALLY TOUCH IT TO FIND OUT!!!!).

Easy way round that, it may be a bit of a filthy habit, but spitting on them is better than burning your fingers. See if it sizzles.

However the SV rear downpipe is a bit hard to spit at

Originally Posted by dizzyblonde

Easy way round that, it may be a bit of a filthy habit, but spitting on them is better than burning your fingers. See if it sizzles.

However the SV rear downpipe is a bit hard to spit at

When spitting make sure its not a greenie they tend to dry and stick on

Originally Posted by BanditPat

When spitting make sure its not a greenie they tend to dry and stick on

Peasant!

I usually try something a bit more sanitary and flick some tap water onto the headers.

When running on one cylinder the bike doesn't have enough power to maintain 55 MPH up a modest hill unless you downshift so that the engine is revving at around 8K.

Most likely you've got a carburetor that is acting up. Lift the tank and pull the airbox and start the engine briefly. If you see gasoline dripping out of one of the overflow lines (the hoses between the two carbs that have open ends on them) you've got a stuck needle valve in the carb attached to that hose. Pulling the carbs and cleaning the contaminants under the needle valve should fix that.

If you're not seeing any gasoline you've probably got a clogged jet. You can test that by placing your hand loosely over each carb throat and restricting the air flow. If you do it on the one that's firing the engine will stall almost immediately. If you do it on the one that's not firing the engine will actually start running better (i.e., running on both cylinders). This is because the additional vacuum is pulling a bit of fuel into the intake. If that's the case you'll have to clean the jets and all the little orifices to restore normal operation. Fun!

Thanks everyone.

Some good tips. I'll check some of that out tonight.
Incidently, I was talking to one of the dealers looking for some carb cleaner - It's quite common here for people to park the bike up over winter then have the crud in the carb come spring time. They were telling me they'd been having a lot of customers with carb probs since the petrol companies switched over to E85 fuel (here in Oklahoma). Sometimes with just 6weeks of not being run! She suggested taking it for a long run (2 to 3 hrs) and see if that will flush the carb and burn some of the crap out. I'll have to find time to do that before long (It'll be fun even if it doesn't help