Cylinders 2 & 3 Seem Intermittent

[lake_harley]

Based on header temp reading, using a heat sensor gun, the #2 and #3 cylinders on my '06 600 Katana are not always firing. Once the engine is reved it seems the engine smooths out and the temps come up on those cylinders too. I'm fairly confident it isn't carb related since I have vacuum gauges on it and the vacuum is very close on all cylinders once the valves on the gauges are adjusted to get rid of almost all of the needle bouncing.


I realize #2 and #3 share a common coil, but am a bit confused how a bad coil would give intermittent failure. I'm going to replace the spark plugs (like I routinely do on most older bikes I've bought) and check the plug caps. In the meantime is there something else that I'm overlooking that might cause a cylinder, or cylinders to "drop" intermittently, particularly under 4,000 or 5,000 RPM?


Thanks, in advance.


Lynn

[maniac1886]

I call coils. Electronic failure almost always starts with intermittent, random, or erratic Failure.

[lake_harley]

I just checked the resistance values for the primary and secondary sides of the coil for 2 & 3. The primary side was in, or close, to spec. I'll blame my Ohm meter for not being the most reliable in reading exact values. The secondary side was different. Providing the contacts of the meter probes were actually touching, as it felt they were, down in the spark plug caps, I didn't get a reading....like in open circuit. I'll do some more checking before ordering parts, but at this point I'm guessing a bad coil as well.

Thanks

Lynn

[lake_harley]

Replacement coil arrived and I installed it. Things were better but still suspected a carb issue so pulled them again, went through them a bit more thoroughly, drilled out the pilot screw plugs, cleaned and adjusted the screws out to 2 1/4 turn out. When I checked them at disassembly they were only out 1 3/4 turns and had read they might be better a bit farther out. Had to deal with a petcock issue as well and got that sorted. Rode the bike about 9 or 10 miles and I'd say I'm pleased with it's performance. Now waiting for new rear brake pads and oil filter order to arrive to get it ready the rest of the way for state inspection and licensing. I think I'm going to really like this bike. It is a good balance of a lot of qualities.

Lynn

[shpielers]

. I think I'm going to really like this bike. It is a good balance of a lot of qualities.

Lynn

that's a kat! Good at almost everything, matter of none. Very versatile. Glad you got it sorted out. Might want to sync the carbs since you adjusted the A/F screws.

[lake_harley]

Might want to sync the carbs since you adjusted the A/F screws.

Carb sync has already been done. Revs and drops back to a smooth idle very nicely. They were actually very close as they were, but it did take a little tweak to get them reading the same.


Lynn

[lake_harley]

After taking care of a couple other things on the bike, I decided to put in a fresh set of plugs. I recently had to change the #2/3 coil and wires, and while I was installing the plugs I noticed a questionable spot on the #4 plug wire's insulation. I re-checked the secondary resistance and found that even though it recently checked within spec the wiggling around evidently broke continuity in the wire. Drat! Now it'll be another few days waiting on parts.

While I'm waiting for parts (again) I thought I might check the valve clearances. The bike shows ~11,xxx miles. What's typical for the 600 Katanas in terms of valve clearances changing? Some bikes just stay in spec forever it seems, almost to the point that checking clearances is a waste of time. I'm guessing if I do have to adjust any that I'd better also re-sync the carbs. It never ends.....

Lynn

[shpielers]

Yes resynching after a valve adjustment is required.

I adjust mine every ~12k miles. I've never had any get out of spec, but they will drift away from where i set them in the middle of the range.

[lake_harley]

I guess I'll take advantage of having so much apart already and check the valves now. Not much point in putting the bike all together and wondering if they really are within spec. I freely admit I'm lazy, but I generally can be shamed into doing the right thing.

I'm guessing the best way to get to that one bolt on the front of the valve cover is to loosen or remove the oil cooler, but I'll refer to the manual that's linked elsewhere in this forum section for guidance. It's probably also covered in the manual, but will the cover come out the front of the frame or does it have to be jiggled out toward the back. To me if looks like the throttle cables may hamper bringing it out the back. The crossmember and coils are already out of the way.

Lynn

[shpielers]

There are two bolts up top of the oil cooler, remove those, and you can slide the cooler out of the bottom bracket and let it rest on the front wheel/fender. The lines are flexible.

Cover jiggles out towards the back. I remove the carbs, and hold them off to the side (throttle cable still connected, choke cable disconnected) whilst jiggling it out. Choke cable is very easy to take off/reinstall. Throttle cable is more of a PITA, so I just leave it on.

[lake_harley]

Thanks for the advice. Getting the valve cover out looked like it was going to be tight, at best, so every little tip helps and is appreciated!

If I keep chipping away at these little things that need attention then one day all that will remain to do will be to go for a ride.

Thanks!

Lynn

[shpielers]

If I keep chipping away at these little things that need attention then one day all that will remain to do will be to go for a ride.

LMAO
Story of my life

[lake_harley]

Well, here's the latest installment of my long running saga. I admitted to being lazy, so I didn't check the valves as I said I was going to. After replacing the #1/4 coil and wires I fired up the bike and had a cold #4 header pipe. Long story short, I backed way up and pulled things apart again. I finally checked the valves which were all still within spec, pulled the #4 carb apart and re-checked for jet blockage (none found), did find a questionable wire/plug cap on the #4 wire that I had just put on (eBay)and replaced the cap and then re-checked the secondary resistance which was OK. It seems like I double checked everything I had done before and also verified that all 4 cylinders had compression. After I put it all back together it fired right up and all 4 header pipes were within about 20 or 30 degrees of one another. It runs smooth and revs to the moon like it should. My best guess is that the #4 wire and cap on the replacement might have been the culprit, but I thought I had changed the plug cap and trimmed the wire before my latest work session. After a while it all seems to run together as far as what was done when. I guess it doesn't matter as long as it runs right.

So....a few miles of test riding just to make sure all stays OK, re-install all of the fairing parts and finally state inspection and licensing. Yay!


Lynn

[shpielers]