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Author Topic: Am I the only one this dumb? Carb issues not the carbs.  (Read 1205 times)

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Offline octalz

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Am I the only one this dumb? Carb issues not the carbs.
« on: June 30, 2010, 07:13:00 pm »
'77 cb750A
I've been fighting issues with the carbs every since I got the bike running after 20+ years in a barn. I knew I had to clean them when it ran crappy right out of the gate, so I did. That solved about 1/2 of the running bad.

It would idle OK but when I take off from a light it falls on its face and starts running on 3 cylinders. If I crank the throttle anyway the rpms come up and the fourth cylinder kicks in and it runs smooth. So If all I want to do it run 3/4 to WOT I'm set. Not real ridable to work and back.

Next I read for hours on this forum to learn what I could about the carbs. Now I feel like I know quite a bit about what effects what at what throttle possition, etc. Thanks eveyone who contributes here. After the third time through them I was 100% certain that the main jets were clear, the needles were set right and clean, the floats were set right and working. I was happy. Put them back on and again... fixed about 1/2 the issue. I had even pulled the petcock out of the tank and checked it.

Last night I'm working on it at 11:00pm (kinda pissed at the neighbors anyway) and happen to be standing in front of the bike looking down at the motor while flipping the throttle and to my surprise there are all kinds of sparks jumping all around way down in the hole by plug number 3. At an idle, no sparks. At 1/4 throttle and above sparks all over. when the RPMs come up they go away again. Now I know I need coils and wires but I just have to know if that's my "carb" issue. So I wrap the snot out of number 3 plug wire with electrical tape and go for a spin. It runs like a new bike. No miss at all.

Now the part I need help with. Where's the best place to get new coils & wires? It looks like I may have to take out a second mortgage to afford them.

Thanks
Dave
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Offline BLUE71TURBO

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #1 on: June 30, 2010, 07:17:18 pm »
 Sounds like you only need new spark plug caps.   ;D
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Offline scottly

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #2 on: June 30, 2010, 07:24:09 pm »
No, you are not the only one dumb enough to confuse an ignition problem with a carb problem. I fought and fought with a Carter carb on a car when I was a kid, and the problem turned out to be bad resistor plug wires. As Blue71turbo suggested, your problem may well be in the resistor spark plug caps. 
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Offline Popwood

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #3 on: June 30, 2010, 07:29:50 pm »
+1 on the caps. Cheap compared to coils and wires which normally outlast caps by a geometric multiple. Unless you can see bad wire insulation, read that cracked/bare, I'd say the cap replacement should be your first fix. Good luck!
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Offline octalz

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #4 on: June 30, 2010, 07:32:52 pm »
OK, I just yank them off the end of the wires? Tried that once with my old chevy and ended up re-securing the wire ends on every one. I'm just paranoid that I'll end up fighting crusty old wires forever. I guess I have nothing to lose by trying.

Am I right that the wires are permanently connected to the coils? Why would they not do them like a car and make it so we can replace just the plug wires?

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Offline scottly

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #5 on: June 30, 2010, 07:53:06 pm »
DON'T YANK THE CAPS OFF THE WIRES!!!!! They screw on, with a pointy screw inside the cap.
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Offline CBGhia

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #6 on: June 30, 2010, 07:57:29 pm »
you can cut 1/4 or 1/2 inch off of the wires and screw the caps back on.  It really helped my bike. 
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Offline ev0lve

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #7 on: June 30, 2010, 07:58:39 pm »
Do the caps first. It's not hard and they'll come right off with a reasonably hard yank (at least mine did). Cut back about a quarter inch and screw your new NGK caps on. Enjoy  ;D

If you have a multimeter you can confirm they're good or bad. Only one of mine was bad but I had problems all the way up/down the line.

Z1 has all the bits - coils, wires, points and condensers included if you end up going there.
http://www.z1enterprises.com/catalog.aspx?pid=HPIG0
« Last Edit: June 30, 2010, 08:00:46 pm by Iggy »
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Offline octalz

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #8 on: June 30, 2010, 08:00:40 pm »
DOH... That would have been embarrassing. Thx.

Think I'll get some caps and take a closer look b4 I rip and tear.
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Offline scottly

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #9 on: June 30, 2010, 08:06:10 pm »
Check the FAQ about measuring spark plug caps ;)
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Don't fix it if it ain't broke!
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Offline octalz

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Re: Am I the only one this dumb? Carb issues not the carbs.
« Reply #10 on: July 03, 2010, 06:50:19 am »
This forum just proved it's value to me. I'm not usually the type to broadcast to the world what I don't know but it certainly pays off here.

I was prepared to just park the bike and buy new coils next pay day (anywhere from $120 - $240) but you guys suggest maybe I try this $3.10 part instead. Now $18 later I have a new bike. $18 because I bought 4 plus shipping. Total savings of at least $102.

I think I should try to start a trend. Come payday (next Friday, so hold me to it) I'm going to donate 10% of my estimated savings to this site.

Think of the money you guys have all saved each other and noobs like me. Now imagine 10% of that going back into the site. :o
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