Topic: Help...changed plugs and now...

[domer]

ok... 72 cb500, new caps (six weeks ago) new plugs today, changed oil today too... all the sudden it'll fire, but struggles almost like its trying to fire 2. plugs are d7ea, caps are ngk. ran good (not perfect, small carb issues) has not given me any other trouble in the 1200 miles/ year ive ridden it. plugs that came out were ok, 2 center cyl. were worse than the outer cylinders? center seemed carbon fouled. im too tired to check spark and all tonight, but the wires are still secure to the caps. i thought id throw this out here and see what else i should be looking for before i dive into this tomorrow....thanks.

[Gordon]

Well, checking for spark would be the first thing I'd do.  Maybe get some sleep and start there tomorrow.   

[dave500]

yeah fresh start,make sure a coil primary wire hasnt disconnected,look at the points,and go from there.

[domer]

all righty... so i have no spark on 2-3  or i should say 1 or 2 sparks, then none.
battery is charged, points and timing havent been touched... but was fine before the oil and plug change... caps are new... havent really done anything else.
any ideas what i might of done? or where i should start... im gonna break out the manual and get crackin but thought id get some advice from the pro's to boot...

[BobbyR]

OK these motors use "waste spark" 1&4 and 2&3 fire together, so have a pair out is common. The Motor is part of the circuit so if one plug does not fire the corresponding one will not fire. After a while corrosion builds up where the cap screws into the wire. Most of us have clipped a wee bit and I mean wee off the end of the each wire so the screw is biting into cleaner copper. If you have 2-3 out you can pinpoint the problem more easily. Cracked Plug maybe?

[domer]

plugs are good... swapped em around with the same result. snipped off a 1/4" of wire before i put the new caps on. made sure it was a nice and clean connection too. gonna test the coil now...

[domer]

all right tested on coil and it appears (if im doing this right) i have 14k on the high side, and 4.9 on the low side... can anyone tell me if it sounds like im f'n this up... or maybe just f'd.

guess i should say. tested the plug wires with the caps off, using fluke 12 set at k (ohm) and put the caps back on (bad?) and  tested the low side at just (ohm) or 0.0 . am i sounding like an idiot yet or did i do this right

[domer]

a little more beer and a little more research, i can see spark on 1-4 points, but not 2-3. gapped fine... everything looks pretty new, but i havent a clue how long its been there. bad condenser? im trying to test them, but im doing something wrong... 

[domer]

strange... filed the points a little for #$%*s and giggles. well god damn if it didnt fix it... odd timing that would pop up, but woo-hoo!!!  

[dave500]

well done,if the points are old and you plan to ride a few miles from home replace them,have a look at a "honda man"or other ignition upgrade,with the tank and side cover off undo and clean any and all connectors and re connect them.have you got a timing light?,the points will be slightly out out sync im guessing,,you said you had small carby issues?,its important to have your ignition absolutley spot on before you chase fuel problems!not pretty close,spot on,youll be going in circles with it otherwise.cheers.