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Discussion Starter #1
So let me tell you a story.....

I pushed home a dead ‘98 my neighbor gave me. Less than 13,000 miles. It hasn’t run in maybe 2 years. I’ll try to keep this short.

Original owner is now 80. I actually shared an office with him when we both worked and can remember when he bought it new.

A few years ago he decided to sell it and took it to a Honda dealer to “tune up” or do something to something in preparation for sale. He had quit riding by this time and would only start the bike and let it run to keep it in good shape. He stored his bike in his entryway. He started the bike and let it idle and walked away, he completely forgot about. When he found it it was dead. Rolled it in his garage and covered it up.

I got it home. Dead battery replaced with new battery. Checked oil. Looked good. Checked coolant. Had to add about 1 quart. Gas tank completely dry. Added fuel. Fuel leaked out everywhere. Shoved drain pan under bike. Lifted rear of tank and learned about the shutoff valve. Vacuum petcock leaked and fuel was coming out the carb overflows.

Ordered rebuild kit for petcock and completed that. While I was waiting for parts I rigged up a fuel supply and tried to start the bike. I pinched shut the vacuum line to the fuel petcock. Bike wouldn’t start but would fire. Overflows in carbs quit leaking gas.

Procured starting fluid and removed air-box cover. Gave each carb intake a squirt and bike started. Ran very poorly.

After the bike warmed a bit I could keep it running at about 3-4000 rpm. Even lower but obvious miss and wouldn’t idle. I independently squirted starter fluid into each carb inlet. I got an obvious and strong response in revs except cylinder #3. #3 was dead. No response for #3.

After running the bike a took exhaust header temps using a laser temp gun. #3 was twice as hot as the other 3 cylinders. About 350 ish vs 175 ish F.

Pulled plug #3. Looked good. Hooked up to coil could see spark.

Out with all the plugs and completed compression test..... all 4 cylinders even at about 135. Throttle wide open and holding the vacuum slides open with a finger.

Put new plugs in. Put bike back together with fuel tank on properly.... same thing. Bike runs crappy. Misses. Exhaust header 3 temperature way hotter and out of family with other temps.

The bike fires for plug #2 and #3 at the same time. I believe the spark I was seeing was for the number 2 power stroke and not the #3 power stroke. I believe the spark occurring for #3 is at the exhaust stroke and is burning the fuel in the exhaust system explaining the high header temperature.

Soooo.... my question is what initiates and controls the ignition spark for cylinder #3 power stroke? I’m suspecting a crankcase or camshaft position sensor, both or ignition timing module or something.

I don’t have a manual yet and am not sure if this bike has these sensors and where they are.

Any my thoughts on my next move?
 

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You can see that there are only two coils. Each coil services two cylinders. The Honda's have long used a "lost spark" system (I think that's what they call it?) where by, one cylinder is under the power stroke..and the companion cylinder is under it's exhaust stroke, but it's spark plug is fired anyway. They are not a "single fire" system. At a guess it will be wise to ensure that the spark plug wires and running to the correct coils so that there is a the correct firing order in place. The coil pairings are #1/#4 and #2/#3. The spark plug wires are not all the same length, as I recall, so mixing them up might be somewhat difficult, but it's still worth looking at.

The high cylinder temp for #3 is interesting. I've never measured pipe temps, but have done the "touchy feely" pipe test to check for hot or cold pipes to see what is firing and what is not. If you've got fire in the hole with a high temp I'd normally say it's a possible lean condition. Interesting issue. Sorry I can't be of more help.

T.
 

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#3 may be running too lean. Carb jets probably need cleaning after sitting for so long.
+1 Sounds more like a blocked/restricted idle passage in #3 carb, and possibly an air leak - maybe a compromised intake seal? That combination can drive you to frustration looking for a single source. Rebuilding the 21yo carbs w/new gaskets/seals may be worth consideration.
 

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Clean idle circuit, pilot circuit and jets, and both air corrector circuits accessible from the bell mouth.
I'd guess clogged pilot jets are the main problem.
 

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what hanksxxx and all above said +1
might have to replace the carb insulators"intake boots" aswell mine wer rock hard on my 97 carbi after 69k and many heat cycles.
its a funny thing my carbi bird starts like a FI bike never needs choke either for the most part , take your time and get the carbs and intake system sorted first then move on
dont for get the O rings in the fuel intake lines there 4 two on each fuel tee , dont ask me how i know , partzilla has all the parts

https://www.partzilla.com/catalog/honda/motorcycle/1997/cbr1100xx-ac
 

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Discussion Starter #7
I’m proceeding to pull the carbs to clean them up. I’ll keep you posted as things progress at a relaxed slow pace. ...
 

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Check crankcase chances are it's full of fuel because of the carbs hanging open. If it smells of gas dump it and the filter change them both.
 

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Discussion Starter #10
Check crankcase chances are it's full of fuel because of the carbs hanging open. If it smells of gas dump it and the filter change them both.
Your exactly correct.... I found that out a few days ago. New oil and filter is already installed. I’ll change it again as soon as I get it running a bit.
 

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Glad you caught it early. There's been a couple birds that have dies from this affliction. The FI are just as susceptible, the FPR fails and does the same thing. Keep and eye on that weep hole. The ethanol we have to run these days is not nice to rubber parts out here in the desert. You should be good for a long while if you ride regularly. But if you park it for long periods be mindful of the effects.
 

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Discussion Starter #12
Well.

Carb kits were slow getting here and they didn’t make it before I went on vacation up in the cool country.

Today I finished the carbs and put the bike back together. I pulled a vacuum on the petcock to fill the carb bowls before hooking up the vacuum line.

The bike fired right up and runs perfect.

I just completed a test ride and all is well.

Winner winner pizza dinner.

Thanks to all all for your thoughts and advice.

:cheers:
 

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Your very welcome glad to see another BB back on it's flying wings. Now be sure to always gear up and definately wear a face shield otherwise you'll be picking bugs out of that ear to ear grin shes going to be giving you.
 
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