Author Topic: 1982 CB650 Running on 3 Cylinders...  (Read 3517 times)

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Offline wildrum88

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1982 CB650 Running on 3 Cylinders...
« on: March 10, 2012, 11:23:03 AM »
Hey y'all just got my cafe back in running order for the spring after sitting in the cold colorado winter, and trying to figure out a small problem with cylinder #3. So, last year i bought the bike and started making all kinds of improvements (mistakes) and ended up cross-threading the spark plug on cylinder #3 somehow. Well, i figured i would just re-tap the spark plug hole with the spark plug itself. Turns out this didn't work out exactly as planned. The weird thing is that #3 runs some of the time (you can hear it popping in the exhaust when accelerating, and seems to work after about 30 mph) and it is definitely getting spark, but when idling it stays rock cold, i did the spit test and it is the only one that didn't evaporate. Just checked the plugs and #3 had soot on it (running rich) but all the rest were white (lean). The plugs were brand new as of October 2011, and getting new plugs seemed to have solved my problem for a short while. I did de-foul the plugs and put them back in only to find the same problem. So i guess what I'm getting at is what the *^%* is going on with #3 and can i fix it? Thanks for your input!!

Offline wildrum88

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Re: 1982 CB650 Running on 3 Cylinders...
« Reply #1 on: March 12, 2012, 04:30:44 PM »
**update**: Today i re-tapped the spark plug hole on #3 and started her up, only to find i was still having the same problem which leads me to believe it is a compression problem (broken rings, etc.) My next step is to do a compression test to verify and then re-evaluate. I also found that the spark plug from #3 was dripping wet with gasoline which means its not a carb problem, right? I also switched plugs around to make sure it wasn't just the spark plug, and that doesn't seem to be it. What do y'all think? Please get back to me

Offline cb650

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Re: 1982 CB650 Running on 3 Cylinders...
« Reply #2 on: March 13, 2012, 04:32:16 AM »
Could be to much fuel.  You running pods?  Event though you cleaned the plugs you should try new ones.
18 grand and 18 miles dont make you a biker

Offline wildrum88

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Re: 1982 CB650 Running on 3 Cylinders...
« Reply #3 on: March 13, 2012, 11:20:53 AM »
yep I've got k&n pods. it seems like when i rev the engine in neutral the #3 pipe starts to heat up but not nearly as much as the others, and after taking it for a spin it is hot but the plug is sooty. this must mean too much fuel, can i fix that simply with the air/fuel screw? i also just realized last night that it appears the previous owner put a 650sc auto fuel valve on and i have the 650 standard and switched the fuel vent tube and vacuum tube running to carb #3, could this have anything to do with it? thanks for the advice ill grab some new plugs today.
 this is the 650 standard: heres the one i seem to have:

Offline LesterPiglet

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Re: 1982 CB650 Running on 3 Cylinders...
« Reply #4 on: March 13, 2012, 11:24:39 AM »
Is #3 plug sealing properly. Run the plug out of the cylinder and make sure there is a regular spark. Swap the plugs over and try it.
'Then' and 'than' are completely different words and have completely different meanings. Same with 'of' and 'have'. Set and sit. There, their and they're. Draw and drawer. Could care less/couldn't care less. Bought/brought FFS.


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Offline wildrum88

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Re: 1982 CB650 Running on 3 Cylinders...
« Reply #5 on: March 13, 2012, 01:05:31 PM »
Problem solved!! im ecstatic to say that it was the fault of whomever the last owner was and not me...phew. Seems as though switching the vent tube and the vacuum tube on carb #3 did the trick. She's back up and running on all four