Bandit 600/1200 CDI Interchangeability?

[bigMaybe]

Hey guys,

I'm trying to diagnose some issues with my gsf600s. I have a dead cylinder that seems to move around, meaning it was #4, then overnight it changed to #3 and #4, then after a carb rebuild it's now #2..  To rule out the CDI I'm hoping to borrow a friends from his 1200, same year ('97). I've looked around the internets a bunch and haven't been able to find a straight answer to this question: Are they interchangeable?

And just some background. The bike runs (not smoothly) on full choke, might idle like shit once warm, and dies when the throttle is pulled. I have spark on all cylinders. When I got the bike a couple weeks ago I deep-cleaned the carbs and replaced the capacitors in the CDI and it ran like a dream. Then it sat in the rain one night and this dead cylinder issue arose. If you guys have any other input I'd greatly appreciate it.

[ventYl]

short answer: definitely NO
long answer: B1200 has throttle position sensor from first day of production, B600 has TPS only since facelift in 2001 when Keihin carbs were replaced by Mikunis. TPS signal would be missing by CDI and wiring can be different. Most probably even connectors won't be compatible.

CDI fires two cylinders at a time (round robin 1 + 4, then 2 + 3, then again 1 + 4 and so on) so if only one cylinder is dead and every time it is different cylinder CDI should be OK and search for damage somewhere else.

Ignition coils on B600 have HT wire plug which requires HT wires with terminals. While these are quite expensive compared to plain HT wires of screw-in type some people tend to throw connectors out and then suffer from dead cylinders (don't know why they do it but most of B600 i've seen does not have connectors on HT wires). IF your HT wires do not have any connectors on ignition coil end (= they appear to be just screwed in with plain ending) THEN your problem is definitely related to these wires. Either buy new wires with plugs or find some way how to fix wires in ignition coils.

PS: No, Ignition coil HT wire terminal is not ended by screw at which you can screw the wire. There's just a pin and wire won't hold on it's own.

[bigMaybe]

Thank you for this detailed reply and saving me a headache.

I seem to have fixed the dead cylinder. I found the hose that connects the air box to the valve cover was disconnected. I find it strange to believe such a simple disconnection would cause a dead cylinder but it seems to run on all fours now. I'm not sure if this is normal but there is some oily-watery liquid coming from that hose, I can see it dripping into the air box.

I have picked up a new issue, however. When I rev it up, it drops slowly back down to about 2k where it stays. Research tells me this is a fueling issue so I'm going to fuss with the idle screw. I'll post back here with an update.

[ventYl]

oily-water liquid coming out of breather hose can be normal. especially if your oil is old (change interval is 6000 km or 12 months whatever comes first), airbox has drain hole with long hose in lower edge.

if bike takes significant amount of time (i.e. not immediately) to slow down to idle then you can either have play in synchronization coupling of carbs or your idle is set up too high (did you say your bike idles at 2k RPM? normal idle is around 1200 RPM IIRC).

[bigMaybe]

It did turn out that the idle set screw (not idle mixture screws) was set a little high. By adjusting that and the idle mixture screws I was able to get an, almost normal idle/rev drop. It seems to stall for an almost unnoticeable time around 2k before dropping to ~1k.

I took it around the block a few times and it eventually died as I came to a stop. It is not running smoothly. If I were to guess, the timing is off and or I have a bad coil. It hesitates and has a loss of power as if not running on all cylinders. I checked the temp of the of the headers and 1&4 were hot but not as hot as 2&3. Would it make sense to swap the coils and see if the header temps change?

I think my next move is a carb sync, compression test, and a coil swap. Any other suggestions?

[ventYl]

take a look at carb sync coupling mechanism if there's any play. with play in sync coupling you'll not be able to reliably set idle. it will be either high or bike will be stalling.

you may try to swap ignition coils but you still can sort out failures like CDI final stage transistors which requires usage of oscilloscope (and can cause weak or no spark). while doing the swap inspect HT wiring if it holds firmly in coils. unfortunately B600 stock coils have terminals which does not hold wires tightly so one may think that coil is faulty.

my own B400 was once running only on two inner cylinders. after i removed fuel tank i found that cause of two cylinders not firing was that HT wire screwed out of spark plug cap and dirt with old rubber grounded whole coil. after i disconnected spark plug cap engine ran on three cyls. I screwed wire back into cap and it instantly ran on all four.

If spark plug wires are of unknown age using new wires may solve your problems too. It's cheap and easy.