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Troubleshooting help - sudden loss of power

  • Thread starter Thread starter Roostabunny
  • Start date Start date
(sigh)...All I'm saying is it looks like oil. We know what oil can do to spark.
A plug can become oil fouled whenever it wants. He says he sees white smoke which is oil burning. I'm thinking he's basically running on 3 cylinders so I mentioned how to tell.
I'm not there. I can't see the bike for myself. If I'm wrong then I gave my best advice.
I'll bow out of this one.
 
KEITH KRAUSE said:
(sigh)...All I'm saying is it looks like oil. We know what oil can do to spark.
A plug can become oil fouled whenever it wants. He says he sees white smoke which is oil burning. I'm thinking he's basically running on 3 cylinders so I mentioned how to tell.
I'm not there. I can't see the bike for myself. If I'm wrong then I gave my best advice.
I'll bow out of this one.
Click to expand...
OK, so we're all agreed that looking at photographs is a difficult way to diagnose plugs. It's like trying to rely on the pics in the haynes book. Heck I'm staring at the thing and it's not obvious to me because whether it's oil or carbon, it's the first time I've seen it in person.

Tell you what, I'll bring the fouled plug when I pick up the compression gauge and let my wrench friend take a look. No hard feeling if he says it's carbon, and I'll still post my compression numbers, K? :-D
 
Hey fellas, I know it's too soon to panic, but that's not stopping me. I keep coming across the phrase, "where there's compression, there's hope" and the phase, "parting out" as I'm searching the forum for info on compression problems and head removal for a bike that's my ride to work.

I know, I know - check the darn compression and then we'll go from there. What are you doing to yourself?

I'm stuck in the house till late afternoon, and even then, the family schedule's so busy I might not get to check the compression until tonight or maybe even tomorrow afternoon. So, I'm over here pacing back and forth like a father-to-be 50's-style waiting to hear about the baby. Except I feel like I'm waiting for Rosemary's baby.

So I post to the thread.

Inexperience, impatience, and imagination are a terrible trifecta right now.

Thanks fellas, I feel better. :-D
 
what did you find when you took the diaphram cap off of #1 carb?
 
focus frenzy said:
what did you find when you took the diaphram cap off of #1 carb?
Click to expand...
Haven't gotten that far yet.

But my compression numbers are 130-120-120-120. Go figure - the one with the fouled plug has the highest number.

My buddy didn't think it was oil fouling on the plug - thought it should have been goopier to be oil.
 
Last edited:
Roostabunny said:
Haven't gotten that far yet.

But my compression numbers are 130-120-120-120. Go figure - the one with the fouled plug has the highest number.

My buddy didn't think it was oil fouling on the plug - thought it should have been goopier to be oil.
Click to expand...

check that spring!!!!! when the spring coils up on top of the diaphram the slide will not open to let air in and you will see rich mixture conditions even though the way it runs sujest the cylinder is not firing.

so you can see wet (gas)and carbon build up.
 
focus frenzy said:
hmmmm just a idea here, take the diaphram cap off the #1 carb and see if the return spring is where it is suspose to be or is coiled up on top.
I have seen this a couple times and one of those times the owner and given up and thought that one cylinder was toast and parted out the bike.
(I got the carbs on E-bay and discovered his mistake.

the other time my buddy was pulling his hair out on his Kat as it would not run right, it now runs like a scalded cat.
Click to expand...

I have to believe this. After all the step by step things I did with basically the same issues as your bike with "abrupt" change in power. It came down to this and a set of new plugs. But I think he's right about the spring getting off set. All I did was take the top off my #4 which was rich as yours and let the spring relax and then put the top back on. BACK with a capital B.\\:D/ My bike runs better than ever now.
Mind you nothing I did was not needed. Seafoam in fuel for a tank, had professional set valves and synchronize carbs for $200. All this was essential and needed BUT. I ended up with one rich cylinder like you and all I did was the above and it was "magic". Focus Frenzy is my latest hero:)

http://www.thegsresources.com/_forum/showthread.php?t=119930 Here is my thread trying to solve basically the same problem, caused by hard acceleration with success.
 
focus frenzy said:
hmmmm just a idea here, take the diaphram cap off the #1 carb and see if the return spring is where it is suspose to be or is coiled up on top.
Click to expand...
OK, um... after I got that cap off, I think I realized what you meant by "coiled on top". I think you meant that it was bent off to one side and not centered on that cone on the underside of the cap. I emphasize after, because I still don't know how it was. Didn't look at the spring till the cap was all the way off.

Anyway, this is how it looked, in case I'm wrong about the "coiled" thing. I opened up #4 as well and it looked the same to me.

I think the bogging was from the fouled plug, and I've got a new plug in there. I took it out for a spin just now and it felt smoother (I noticed significantly less vibration through my knees) but it's still not pulling as hard as I'm used to. I used to get a "boost" around 5500-7000 rpm, too and that's missing.

When I got back the #1 plug looked wet and had the start of black fouling on the edge of the threads.

Can I rule out oil fouling with good compression? I think I read on GSR somewhere that wetness (gas) and carbon fouling go together?
 
focus frenzy said:
check that spring!!!!! when the spring coils up on top of the diaphram the slide will not open to let air in and you will see rich mixture conditions even though the way it runs sujest the cylinder is not firing.

so you can see wet (gas)and carbon build up.
Click to expand...

He told you twice and it was a 5 minute job. Worked for me with the same problem. BTW you should eventually get the valves adjusted and the carbs synchronized too - you will be amazed.

My compression numbers after the valve job jumped at WOT to 150psi for all 4 cylinders. My spring looked just like yours when fully extended but who knows what it looked like when under compression inside binding?
 
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BTW, I also took a shot of the original four plugs. Obviously, the closest one is from #1. Again, this is from a day ago, so original fouled plug, not current.

The plug that's in #1 now looks like it'll go the same way after a while.
 
A thought just occurred to me.

Last time I adjusted the mixture and synced the carbs was before I sealed up my airbox (cleaned, weather stripping on the covers, new boots, the works). My seals were mediocre and my boots pretty shrunken at that point.

I don't want to mess up the troubleshooting process, but I thought this might be relevant info.
 
My compliments on a really clean and well maintained engine.

I just checked my previously blackened #4 plug after my 50 mile ride that made me smile and it is perfect just like the other 3.

So I have to say:

Charge battery.
Check spark at offending plug - replace if needed.
You all ready checked the spring but make sure there is free motion in the diaphragm operated slide?

If this doesn't fix the problem then adjust the valves to spec. and recheck compression at WOT. Mine improved dramatically to 150psi across all cylinders and I had one sitting at 90psi.
Re-Sync the carbs.
Hopefully smile wider than before?

Your thread solved my problems so hopefully my thread will solve yours?
Happy motoring.
 
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twistedwankel said:
He told you twice and it was a 5 minute job. Worked for me with the same problem. BTW you should eventually get the valves adjusted and the carbs synchronized too - you will be amazed.

My compression numbers after the valve job jumped at WOT to 150psi for all 4 cylinders. My spring looked just like yours when fully extended but who knows what it looked like when under compression inside binding?
Click to expand...

OK, sorry to be clueless, but I'm still confused about the spring. What was I looking for? I thought I was looking for something that was out of place or assembled incorrectly.

I just took the cap off #1, did the same on #4, thought they looked the same, then after taking 10 minutes to fish out the carb cover screw that fell and bounced down between the starter cover and the oil pressure sensor (of course), I put them back together.

I adjusted the valves about 3K miles ago - should be alright there. But the mixture and sync... that might be worth looking at.
 
Last edited:
I just checked my previously blackened #4 plug after my 50 mile ride that made me smile and it is perfect just like the other 3.

So I have to say:

Charge battery.
Check spark at offending plug - replace if needed.
You all ready checked the spring but make sure there is free motion in the diaphragm operated slide?

If this doesn't fix the problem then adjust the valves to spec. and recheck compression at WOT. Mine improved dramatically to 150psi across all cylinders and I had one sitting at 90psi.
Re-Sync the carbs.
Hopefully smile wider than before?

Your thread solved my problems so hopefully my thread will solve yours?
Happy motoring.
 
OK. You can't trust plug pics to look how they look in person. I've mentioned the same thing a bunch of times around here.
But that plug looks oil fouled to me. That's a pretty good pic you have.
The black has an obvious shine to it. Carbon doesn't shine like that. Carbon doesn't shine at all. If carbon, and as dark as that plug looks, it would be a fluffy darker/black. Even the end of the center electrode is coated shiny black.
You have good compression but you're burning enough oil to foul the plug. I'm thinking a valve seal.
You can check the lead and plug cap connections but from what I've read here, the spark appears to be getting to the plug. I agree the pic could be deceiving and it could be something in the carb making it rich but I just don't think so. But now you mention mixture screw adjustments. Wouldn't they be set the same or very close?
Check out some sparkplug sites and compare them yourself. You'll see carbon fouled and oil fouled plugs.
If you dip that plug in water just as it looks in the pic, does the water bead?
 
bwringer said:
You can get NGK plugs at many auto parts stores -- Advance Auto, Pep Boys, and Napa all carry B8-ES plugs a lot cheaper than bike shoppes. About $1.79 - $1.89 each is normal US pricing.

Autozone does NOT carry NGK plugs.
Click to expand...
I picked up NGKs at Autozone??
 
KEITH KRAUSE said:
OK. You can't trust plug pics to look how they look in person. I've mentioned the same thing a bunch of times around here.
But that plug looks oil fouled to me. That's a pretty good pic you have.
The black has an obvious shine to it. Carbon doesn't shine like that. Carbon doesn't shine at all. If carbon, and as dark as that plug looks, it would be a fluffy darker/black. Even the end of the center electrode is coated shiny black.
You have good compression but you're burning enough oil to foul the plug. I'm thinking a valve seal.
You can check the lead and plug cap connections but from what I've read here, the spark appears to be getting to the plug. I agree the pic could be deceiving and it could be something in the carb making it rich but I just don't think so. But now you mention mixture screw adjustments. Wouldn't they be set the same or very close?
Check out some sparkplug sites and compare them yourself. You'll see carbon fouled and oil fouled plugs.
If you dip that plug in water just as it looks in the pic, does the water bead?
Click to expand...

Hard to get any water at all to cling to a plug, but what stays looks like it's beading. And the black on the electrode is downright glossy.

I looked at some sites. If "wet fouled" and "oil fouled" are pretty much the same thing, then I saw some of those that looked like mine.

Any way to test for leaky valve seals (aside from fouling more plugs, that is)? I'll also check #1 plug again tomorrow after a longer ride.

As an aside, a motorcycle wrench buddy set the mixture for me when I first got the bike, so I don't actually know where the screws are set. I have a set of o-rings from Robert Barr, and have plans to rebuild the carbs at some point, but I haven't set the date due to the need for shocks and then this.
 
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