eil
Forum Sage
Well, I worked on the motorcycle all weekend long but in the end, didn't really make any forward progress. 
I ordered new intake boots (at great monetary expense) and compared them to the old ones. Honestly, the new ones are not leaps and bounds better at first blush. They both have about the same amount of squishiness, the only real differences is that the old ones lack the rubber coating on the metal flange. Which I guess could contribute to them leaking when hot, if that's what was causing the lean condition. I put the new ones on anyway but it remains to be seen if they'll help at all.
Since it appears that I may have a charging problem, I spent the majority of Saturday cleaning electrical connections and grounds. Used De-ox-it and Q-tips, mainly. Found a couple of nice PO surprises and fixed those. My R/R appears to be original, so I'm certain it's shot. I plan a thorough test of the charging system in the near term, but not immediately. Until I'm sure I have the engine running right, I can muddle through with relatively short rides and keeping the battery topped up with a charger.
Wrapped up the day by installing the new choke cable and putting the carbs and airbox back on. Now, I know a lot of people say that installing the carbs and airbox on the 850 is waaaaay simpler than almost any other bike out there, but I still dread it every time. Mostly, it's because getting the boots and clamps exactly where they need to be is a real pain. (And yes, all boots are brand-new.) Every time I tried to tighten the airbox clamps, the bottom end of the clamp (and boot) would slide off the carb. I ended up jamming two pieces of wood in behind the airbox to push it forward as much as possible and that got everything lined up mostly right. I still feel like those airbox boots are going to just slip off the carbs one day while going down the road.
On Sunday, I tell myself I'm going to go for a test ride. Put on my boots, get the mesh jacket out. I start up the bike. As usual, it starts right up, no questions asked. But seems to be running just a little rough. Is it? I think it's always sounded like this. Anyway, I let it idle for a minute and then shut it off to check the oil. Oil looks good. On a whim, I whip out my IR themometer and check the head temperature in front of the exhausts. 100(F) degrees on #1, 200+ on the others. The #1 header is only slightly above ambient temp, I can touch it no problem. The others are way too hot to touch.
So cylinder #1 is not firing. And it's probably not been firing since I got the thing running again, because I never thought to test for a non-firing cylinder before. And because I don't know exactly what a properly-running GS850 sounds like. Guess I'm not going for a test ride. I started it up again and pulled the #1 spark plug boot. No change in engine speed or sound, so I guess that confirms it. Spent the remainder of Sunday trying to figure out which of these things is failing me: compression, spark, or fuel.
Compression: Surprisingly good. About 130-135psi across the board.
Spark: I looked up the wiring diagram for the ignition system and I see that the secondary winding of the coils runs through each spark plug and through the engine to complete the circuit. So if I have no spark on #1, #4 would not be firing either. Yet I know for sure that it is because its cylinder is getting hot and pulling the plug boot from #4 consistently stalls the engine. My only concern here is that... because the plugs #1 and #4 are in series, wouldn't pulling the boot from #1 also kill the spark for #4? Because this doesn't appear to be what's actually happening...
I unscrewed the innards of the spark plug boots and noticed the resistors were visibly toast. The metal terminals on each side were severely worn down by arcing or missing altogether. The one for #1 had a carbon trail along it, showing that current was now preferring to go around the resistor rather than through it. I replaced the resistors with equal-length pieces of metal (cut-off machine screws) and put the plugs back together. Cylinder 1 is still not firing.
Turned my attention toward the plugs themselves. Verified gaps, although I had already done this before. I noticed for the first time that these are not B8ES, they are BR8ES. Meaning they have resistors in-line as well. Thanks, PO. Verified with a multimeter that the spark plugs have 10k of resistance exactly. I feel that with the 5k resistors removed from the spark plug boots that this is not a big enough difference to cause a problem, so I will continue to run them for the time being.
Fired up the engine again, same results. Tried swapping the plug boots, same results: cylinder #1 doesn't fire, engine stalls with #4 removed. Measured the cap-to-cap resistance on the second coil (going to #2 and #3) and it was within acceptable Service Manual limits. But I could not get any kind of reading between boots #1 and #4. So, open circuit. Infinite resistance. But apparently not so infinite that a few thousand volts can't get through to fire the #4 cylinder.
So I know one coil is not good, but since the #4 cylinder is still firing, for the moment I'm going to consider it marginal. I will probably take the coil off the bike in order to give it a better visual inspection. I may also try swapping the coils to see if the problem stays. (Although at this point, I'm sure it will.) I am not looking forward to replacing these coils if OEM ones aren't available because all of the aftermarket ones I've seen are freaking expensive.
Fuel: Since swapping around the plug wires still revealed #1 cylinder failing to fire, I'm falling back to carburetor issues as the most likely culprit. The #1 carb was the only one of the three that looked gunked up in the beginning. I suppose I might not have cleaned it well enough? Float height is correct because I just set that. I know it's getting gas because a bunch of gas poured out when I removed the drain screw. I removed the carbs from the bike again, unganged the #1 carb, and started disassembling it. Removed all the bits and pieces. Could not see any plugged up jets, but I haven't dipped the carb body yet. I'll try to get that done this week.
So that is where she sits. I don't mind actually working on this bike, but I am starting to get very tired of constantly having to throw money at it. At this point, I really just want to ride it.
I ordered new intake boots (at great monetary expense) and compared them to the old ones. Honestly, the new ones are not leaps and bounds better at first blush. They both have about the same amount of squishiness, the only real differences is that the old ones lack the rubber coating on the metal flange. Which I guess could contribute to them leaking when hot, if that's what was causing the lean condition. I put the new ones on anyway but it remains to be seen if they'll help at all.
Since it appears that I may have a charging problem, I spent the majority of Saturday cleaning electrical connections and grounds. Used De-ox-it and Q-tips, mainly. Found a couple of nice PO surprises and fixed those. My R/R appears to be original, so I'm certain it's shot. I plan a thorough test of the charging system in the near term, but not immediately. Until I'm sure I have the engine running right, I can muddle through with relatively short rides and keeping the battery topped up with a charger.
Wrapped up the day by installing the new choke cable and putting the carbs and airbox back on. Now, I know a lot of people say that installing the carbs and airbox on the 850 is waaaaay simpler than almost any other bike out there, but I still dread it every time. Mostly, it's because getting the boots and clamps exactly where they need to be is a real pain. (And yes, all boots are brand-new.) Every time I tried to tighten the airbox clamps, the bottom end of the clamp (and boot) would slide off the carb. I ended up jamming two pieces of wood in behind the airbox to push it forward as much as possible and that got everything lined up mostly right. I still feel like those airbox boots are going to just slip off the carbs one day while going down the road.
On Sunday, I tell myself I'm going to go for a test ride. Put on my boots, get the mesh jacket out. I start up the bike. As usual, it starts right up, no questions asked. But seems to be running just a little rough. Is it? I think it's always sounded like this. Anyway, I let it idle for a minute and then shut it off to check the oil. Oil looks good. On a whim, I whip out my IR themometer and check the head temperature in front of the exhausts. 100(F) degrees on #1, 200+ on the others. The #1 header is only slightly above ambient temp, I can touch it no problem. The others are way too hot to touch.
So cylinder #1 is not firing. And it's probably not been firing since I got the thing running again, because I never thought to test for a non-firing cylinder before. And because I don't know exactly what a properly-running GS850 sounds like. Guess I'm not going for a test ride. I started it up again and pulled the #1 spark plug boot. No change in engine speed or sound, so I guess that confirms it. Spent the remainder of Sunday trying to figure out which of these things is failing me: compression, spark, or fuel.
Compression: Surprisingly good. About 130-135psi across the board.
Spark: I looked up the wiring diagram for the ignition system and I see that the secondary winding of the coils runs through each spark plug and through the engine to complete the circuit. So if I have no spark on #1, #4 would not be firing either. Yet I know for sure that it is because its cylinder is getting hot and pulling the plug boot from #4 consistently stalls the engine. My only concern here is that... because the plugs #1 and #4 are in series, wouldn't pulling the boot from #1 also kill the spark for #4? Because this doesn't appear to be what's actually happening...
I unscrewed the innards of the spark plug boots and noticed the resistors were visibly toast. The metal terminals on each side were severely worn down by arcing or missing altogether. The one for #1 had a carbon trail along it, showing that current was now preferring to go around the resistor rather than through it. I replaced the resistors with equal-length pieces of metal (cut-off machine screws) and put the plugs back together. Cylinder 1 is still not firing.
Turned my attention toward the plugs themselves. Verified gaps, although I had already done this before. I noticed for the first time that these are not B8ES, they are BR8ES. Meaning they have resistors in-line as well. Thanks, PO. Verified with a multimeter that the spark plugs have 10k of resistance exactly. I feel that with the 5k resistors removed from the spark plug boots that this is not a big enough difference to cause a problem, so I will continue to run them for the time being.
Fired up the engine again, same results. Tried swapping the plug boots, same results: cylinder #1 doesn't fire, engine stalls with #4 removed. Measured the cap-to-cap resistance on the second coil (going to #2 and #3) and it was within acceptable Service Manual limits. But I could not get any kind of reading between boots #1 and #4. So, open circuit. Infinite resistance. But apparently not so infinite that a few thousand volts can't get through to fire the #4 cylinder.
So I know one coil is not good, but since the #4 cylinder is still firing, for the moment I'm going to consider it marginal. I will probably take the coil off the bike in order to give it a better visual inspection. I may also try swapping the coils to see if the problem stays. (Although at this point, I'm sure it will.) I am not looking forward to replacing these coils if OEM ones aren't available because all of the aftermarket ones I've seen are freaking expensive.
Fuel: Since swapping around the plug wires still revealed #1 cylinder failing to fire, I'm falling back to carburetor issues as the most likely culprit. The #1 carb was the only one of the three that looked gunked up in the beginning. I suppose I might not have cleaned it well enough? Float height is correct because I just set that. I know it's getting gas because a bunch of gas poured out when I removed the drain screw. I removed the carbs from the bike again, unganged the #1 carb, and started disassembling it. Removed all the bits and pieces. Could not see any plugged up jets, but I haven't dipped the carb body yet. I'll try to get that done this week.
So that is where she sits. I don't mind actually working on this bike, but I am starting to get very tired of constantly having to throw money at it. At this point, I really just want to ride it.
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Other than that, it was mostly crimping blade terminals onto wires. Charging system tests good now, and after a short ride the battery seemed to be staying charged. (Bonus: the headlight, indicators, turn signals, and brakes all seem to be much brighter now!)
