SlowRoad
Member
Posts: 368
Heart of a Legend with a whole lot of Soul
Hartselle AL
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« on: August 30, 2009, 11:16:39 PM » |
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I am working on a '75 550 Four. It is only running on 2 cylinders. Runs on 2 and 4, but nothing on 1 and 3. 1 and 3 both seem to be getting gas and spark, so I am at my wits end trying to figure it out.
Bike has new coils and points seem to be good. It is firing on one cylinder off each coil. I have tried switching wires and post on the coils with the same result. I always thought on the older models that if you get gas and fire it will run, but that is not proving to be true in this case. Carbs look good, put in new plugs, checked and double checked timing, checked compression and everything else I can think to check. Any advice from you guys that may have worked on them in the past?
Thanks
Tim
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Warlock
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« Reply #1 on: August 31, 2009, 05:08:50 AM » |
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Might try and check the diaphragm on the carb needles. I had several years ago some had went bad and it sounded like it was missing.
I guess these has the vacuum slides.
David
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 I don't want to hear the labor pains, I just want to see the baby |
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98valk
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« Reply #2 on: August 31, 2009, 05:35:15 AM » |
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open up the idle mixture screws and check the coils. coils where known to crack and leak out the oil.
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1998 Std/Tourer, 2007 DR200SE, 1981 CB900C 10speed
1973 Duster 340 4-speed rare A/C, 2001 F250 4x4 7.3L, 6sp
"Our Constitution was made only for a Moral and Religious people. It is wholly inadequate to the goverment of any other."
John Adams 10/11/1798
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SlowRoad
Member
Posts: 368
Heart of a Legend with a whole lot of Soul
Hartselle AL
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« Reply #3 on: August 31, 2009, 07:14:08 AM » |
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Might try and check the diaphragm on the carb needles. I had several years ago some had went bad and it sounded like it was missing.
I guess these has the vacuum slides.
David
David, I thought about that and took the top off the carb to find mechanical slides. The slides are operated directly by the throttle linkage. Thanks. Tim |
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« Last Edit: August 31, 2009, 07:16:02 AM by SlowRoad »
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SlowRoad
Member
Posts: 368
Heart of a Legend with a whole lot of Soul
Hartselle AL
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« Reply #4 on: August 31, 2009, 07:15:40 AM » |
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open up the idle mixture screws and check the coils. coils where known to crack and leak out the oil.
I tried opening the idle mixture screws on those two carbs with no difference. The coils are brand new and all plugs are firing when I checked them. Thanks. Tim |
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BigMac (SoCal)
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« Reply #5 on: August 31, 2009, 07:54:10 AM » |
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Check the condensers. Your points could be fine but the condensers could be bad. It's a common problem on those old honda fours with points. I had about 10 of them over the years and it does happen now and them.
good Luck,
Dave
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dreamaker
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« Reply #6 on: August 31, 2009, 08:24:26 AM » |
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Just to give you a little incentive, this was my '72 Honda CB500 four I built and traded for a street rod. Built it start to finish. I'm still looking for it, hope to get it back one day. Dan   |
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Ricky-D
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« Reply #7 on: August 31, 2009, 10:19:49 AM » |
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I agree with most all that indicate it's still an electrical ignition problem.
You can manually test the coils, wires, and points and condensers. There are specs for all.
Additionally I would insure the correct wires to the correct cylinders. it doesn't make much sense to me when you say "It is firing on one cylinder off each coil."
Highly improbable problem, being identical to two individual systems.
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2000_Valkyrie_Interstate
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SlowRoad
Member
Posts: 368
Heart of a Legend with a whole lot of Soul
Hartselle AL
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« Reply #8 on: August 31, 2009, 07:10:49 PM » |
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I agree with most all that indicate it's still an electrical ignition problem.
You can manually test the coils, wires, and points and condensers. There are specs for all.
Additionally I would insure the correct wires to the correct cylinders. it doesn't make much sense to me when you say "It is firing on one cylinder off each coil."
Highly improbable problem, being identical to two individual systems.
***
I think you just nailed it. It came in with the coils already wired. I just looked up a wiring diagram and I think the coils are going to the wrong plugs. I will try it in the next day or so and see if that doesn't get it going. Thanks to everyone for the suggestions. I have said all along that it will be something simple that I am overlooking. I will find out if that does it. Thanks. Tim |
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SlowRoad
Member
Posts: 368
Heart of a Legend with a whole lot of Soul
Hartselle AL
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« Reply #9 on: September 03, 2009, 03:20:59 AM » |
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 Well, I knew it would be something simple. It was the wiring from the coils to the plugs. I "ASSUMED" the guy had them wired correctly when the bike came in, but should have known better. Oh well, it's running good now so I can start on the other issues.  Thanks for all the suggestions. Guess I just needed something to jog my brain and make me start thinking.  Tim
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