GS550 bogging, still running a bit lean

[geol]

The mechanical advance starts advancing from idle and reaches full advance at about 4K rpm on the GS1000 I guess. You should observe it as it sounds like you need to remove the advance from the bike and clean/lube it. I think I suggested this previously. The strobe shouldn't appear to be "flashing" and should just be illuminating the timing marks and advance mechanism. Of course, it isn't perfectly steady but should not have a noticeable flashing effect.

[cp___32]

The mechanical advance is working. When I set the timing I first did it following Basscliff's instructions to manually advance it with your finger while doing static timing. I had bogging so I set it the way the factory manual said to do, where I use the 1-4 timing line set to when the test light just illuminates. Since I've got a Dyna S I have to set the timing for the 2-3 180 degrees from when 1-4 initially comes on and I did that. When I double check the timing using the timing gun it's set properly. When I rev it starts to advance. I can't recall exactly where it hits initially but as I rev it hits the advance mark spot on and stays there through the RPM range. I've tried advancing and retarding the timing to see if things get better but they don't seem to regardless, only worse.

As for when the strobe is flashing, I tried to connect an LED they way you do for static timing and then mount it to the handle bar so I could watch it blink as the coil fired (opposed to pulling a plug wire and using a spare plug, this way I have the engine running properly) but the bike wouldn't start with it connected and when I started the bike and then connected it using an alligator clip it would bog and kill the bike.

That's why I used the strobe. I wasn't using it looking at the timing cover, I was sitting on the bike, looking at the strobe and revving the bike to see if the rate would speed up as the revs increased. To see if I was having a complete drop out of spark on one or more of the cylinders while the revs climb.

As I said before, it does from idle to about 2800 RPM, and then it looks like the sparks get cut in half for frequency and then pick up again after 4K. When I let off, I see the same sort of behaviour.

[cp___32]

I've played with the timing a bunch. Pulled the advance mechanism and lubed it up. You can see it moving freely as the revs climb. I played with the timing and tried the bike at both extremes and everywhere in between. I still can't figure it out. With the timing set back to normal, choke doesn't seem to help.

What about the diaphragms on the CV carbs? The way the bogging happens, it almost gives me the impression that maybe those big cylinders are getting stuck in sliding up until there's enough pressure to draw them up? I checked them when I cleaned the carbs. No nicks, scratches or dents. The boots at the top were perfect and I sealed the lip with a bit of grease so they stayed in place when the lids were installed.

I'm also getting random hanging of the throttle when I stop sometimes. Cable isn't hanging anywhere it'll just rev around 2K, so I'll just nudge the throttle screw (not even turning it) and the revs will drop back to where they should be at idle. Sometimes just releasing the clutch slightly while stopped will get them to come down as well.

Would a problem with the CV parts on the carbs sticking cause symptoms like I'm having? I didn't lube the slide pin figuring fuel would do that. Is there a test for that I can try?

[tom203]

The odd flashing of the timing light in this bogging range suggests that ignition is not firing correctly in this rpm range, but magically clears up . I doubt the slides could stick so consistently.

[geol]

I am not sure why a Dyna S could malfunction during only one range of rpms. If the timing light isn't strobing with the rpm increase, the plugs are not firing. As I said, I can't imagine how that could happen with a Dyna S as you would think if the Dyna S were the cause, it would occur through the rpm range. I would call Dynatek and ask them if they had any ideas.

[cp___32]

I had questioned the Dyna-S a while ago and actually sent it back to them for testing. They sent it back saying they ran it through it's paces (hard) and it worked no problem. So unless something happened between 4 years ago and now after sitting I'm really not sure.

What I need is conclusive proof of one type of malfunction. I still am not sure if it's a carb issue causing the bogging which is causing me to lose spark or if it's a spark issue causing the bike to run rough in that range. I'll keep digging to see what I can come up with. About the only thing I can think now is maybe the battery is hurting at that range for some reason.
Any ideas, please keep em' coming.

[roeme]

Hmm. I think you need to set up a mobile lab to debug this further

I'm a noob, and just throwing up some ideas here, possibly outlandish:

- Miniaturized Voltmeters are unbelievably cheap on ebay. Like 2 bucks delivered, and they're essentially just a three-digit display with two wires poking out. You could temporarily duct-tape one to your dash, and then be sure what your voltage is at these rpms.
- Maybe get an cheap USB scope with some storage and at least four inputs. Wind some wire around each high tension cable. Plotting afterwards would give a clear picture about ignition pulses, I'd say much clearer than watching a strobe.
- ...also, with the scope one could check out various other stuff, though I can't think of anything else right now. What else would be useful the have measure on these engines?

That's for the electrical part, can't think of anything for the rest...maybe stick an O₂ sensor into the exhausts, and record readings, correlate with rpms read from the scope...hrm

[cp___32]

I picked up a scope and checked the carb behaviour. Unfortunately the scope doesn't have sound but you can see the vacuum cylinder flutter and back flow of fuel into the camera lens. That coincides with the bogging.

I had sealed the diaphragms with a little dialectic grease when I put the caps on the carbs. They were in good shape and had no rips or holes.
Since I don't have a properly running GS I have nothing to compare to but I was hoping this video might shed some light on a diagnosis.

I couldn't get the scope to bend around enough to see the leftmost cylinder so the video shows the other three starting from the right.

Any thoughts would be appreciated.

http://youtu.be/a5OqSU8gYz0