Bandit Alley
GENERAL MOTORCYCLE FORUMS => GENERAL MECHANICAL & TECHNICAL => Topic started by: tom_eaton on September 05, 2006, 08:33:15 AM
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hi all,
i was riding along the other day, when the power seemed to drop all of a sudden. more riding revealed that power seemed to go on and off, as well as a different sound from the exhaust, when the power dropped the exhaust sounded more 'aggressive'.
sorry if this sounds vague but its the best way i can describe it.
any questions/ideas?
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Are you firing on all 4? :wink:
The B4 did something like that on the last trip up to the mountains. Turned out that her 3rd cylinder wasn't firing consistently. (After a plug change prior to the trip) The plug wire wasn't 100% on, and we found that the #3 carb seemed to have more fuel in it than it should. So, cleaned the carbs,... again. Then trimmed the #3 plug wire,... she seems immensely happier now.
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1) Check for consistent spark to all cylinders
2) Check plugs. They can tell the story as to which cylinder is having the issue and sometimes even what is causing it
3) I know this sounds stupid, but check the petcock to make sure it is locked in the "on" position..also, another dumb one, you have enough fuel?
4) You like yams?
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ok i'll check out the plugs. what am i supposed to be looking for if there's anything wrong?
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ok i'll check out the plugs. what am i supposed to be looking for if there's anything wrong?
If the plug is wet, it means that there's fuel in the cylinder, but no spark. That's the easiest thing to identify.
The rest of these, I'm going on memory from my Firebird days:
A tan ceramic piece ( right under the electrode) will indicate that the fuel mixture is right on.
Black (carbon) means rich or too cool. (or weak spark)
Oily ( not to be mistaken for carbon, which can be similar looking, or a wet plug) is BAD. Rings? valves? ( I don't recall off the top of my head)
White, means that the mixture is lean, or too hot.
Part of the plug missing ( don't laugh, it happens :sad: ) means that there's a foreign object in the cylinder, and impact damage has occurred. May also be from preignition, or plugs that are too long.
The other thing you can do, is if the problem is consistent enough, fire the bike up for about 30 secs, and then turn it off. You should be able to put a hand near or on each of the pipes -very- briefly, and see if they're all hot. If not, the non-hot one will point you to your problem cylinder/carb.
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ok i'll check out the plugs. what am i supposed to be looking for if there's anything wrong?
Well, if one plug is different than the other three, then that indicates the bad cylinder. From there you are looking mainly for color or any pitting.
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right then, riding and general spannering have led me to believe the #4 cylinder isnt right. ive done a complete plug change, but the problem isnt much better. the bike does seem to run better when its hot. i thought it might be a problem with the coils.
any suggestions?
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If you install the same plugs and still having problems, buy a new set and install them. I've had a few spark issues on the B12 and replacing them fixed it on one occasion.
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what i meant was i bought a new set of plugs and put them in!
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right then, riding and general spannering have led me to believe the #4 cylinder isnt right. ive done a complete plug change, but the problem isnt much better. the bike does seem to run better when its hot. i thought it might be a problem with the coils.
any suggestions?
If it was a coil, both your #1 and #4 cylinders would be manifesting problems.
Are you sure you have spark? Did you test when the plug was out? Also, Check the plug wire, perhaps even trim off 1/4" and reseat it into the boot.
The plugs are an indicator of what's wrong with your cylinder. That's why two of us told you to check the plugs when you pulled them out, not just change them. I noticed you didn't say. What did the #4 plug look like when you pulled it out? Wet? Carbonned up? Dry? That will lead you/us to the problem.
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all the plugs looked the same. i checked them when i took them out. every plug was carbonned up.
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all the plugs looked the same. i checked them when i took them out. every plug was carbonned up.
That's very strange to have them all look the same, but the cylinders behaving differently, but I'll take your word for it.
And the answers to all of the rest of my questions? Believe me, they're valid, I'm going through the same thing right now.
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i didnt test for a spark, ill have a look tomorrow, and will trim off the plug wire asap.
the plug was dry and carbonned up, the same as the others
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Lets go back to the basics, what kind of setup do you have? Aftermarket exhaust, jet kit, advancer, etc?
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right, aftermarket exhaust, engine is completely stock exept for 33bhp restrictor kit in the carbs. spark plugs are manual recommended ngk's. the carbs were tuned not more than 4 months ago. the problem first appeared while going about 90mph on the motorway.
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What is this restrictor kit? I know of the restrictions in overseas areas for power, but I have never heard of a restrictor kit.
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the restrictor kit is for power, it is for british licence reasons. i cannot ride a bike with more than a power of 33bhp.
as far as i know the restrictor kit is simply four washers in the carbs.
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How low was the fuel? My bike behaves like that when I get down to reserve... Simple things first!
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the fuel is nearly full. i keep it high otherwise ill end up forgetting and running out of fuel somewhere!
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We've fixed Dita, her problem was some "gunk" that had hung up the #3 carb's float. Of course her plug was wet, so it was easy to see that she was getting fuel. It did look like a no spark problem though, because of the fuel in the cylinder.
I think you're going to be looking at your carbs before this is over.
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Good deal, glad to hear that you fixed your problem.
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Good deal, glad to hear that you fixed your problem.
Thanks! I only wish we'd found it sooner. Nothing quite like the mountains on a b4 3 cylinder.
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Tom
If you haven't already figured out your problem, I have something for you to look at. I was riding around a few weeks ago and my bike (98 B6 with 1127 engine) started cutting out as if someone just tapped the kill button for a moment, and it was very sporatic. It took a while but I found out that there is a wire attached to the main wire from the negative terminal on the battery that has a small connector on it that plugs into the main harness, this connector was loose, and when I would hit a bump just right or something else, it would break connection and drop spark. I repaired this connection and that fixed the problem.
Later
Josh