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Offline danarchy77550f

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wont startup
« on: July 23, 2014, 07:38:46 AM »
Hi Guys,

 Recently finished a rebuild on my 77 CB550F after having my primary chain fail.  I had to replace the upper case because of damage so i had to rebuild it from the pretty much every bolt. 

Its buttoned up now but im having trouble firing it up.  It will back fire every once in awhile

I have spark
new gas
cleaned out floats and jets
electronic ignition ( existing )
I adjusted the valves after i noticed gas shooting out of carbs
.002 intake .003 exhaust
im going to check compression after work
i static timed it and it checks out
starter is working
battery is at full charge each attempt
carbs are sucking in and exhaust is pushing air out

im at a loss as to what else could be wrong, please help!
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Offline calj737

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Re: wont startup
« Reply #1 on: July 23, 2014, 08:21:08 AM »
Is it possible you have the coils reversed? Blue wire from ignition runs to 1/4 coil (left side). This is very common and usually the timing is the cause of backfiring during starts.
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Offline danarchy77550f

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Re: wont startup
« Reply #2 on: July 23, 2014, 08:57:57 AM »
i never touched the coils so they should be fine, and i know the ignition leads to a blue and a yellow wire, i will try switching them up because they were backwards on my friends 750
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Offline goldarrow

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Re: wont startup
« Reply #3 on: July 23, 2014, 10:03:00 AM »
you indicated it back fired, by anychance you have the advancer cam flipped 180 degrees out?
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Offline danarchy77550f

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Re: wont startup
« Reply #4 on: July 23, 2014, 10:18:44 AM »
is that the center black part?
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Offline TwoTired

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Re: wont startup
« Reply #5 on: July 23, 2014, 10:21:19 AM »
Quote from: danarchy77550f on July 23, 2014, 07:38:46 AM

I adjusted the valves after i noticed gas shooting out of carbs
.002 intake .003 exhaust
im going to check compression after work

Good plan to check compression.

Did you heed the warning in the shop manual about fitting the cylinder cover back on without bending valve stems?


If there are still no bent valves...
The mechanical spark advance mechanism can be assembled backwards, which would make spark timing 180 out of phase.

I'll ask how you connected the spark leads.  One coil connects to 1&4 the other to 2&3.  It's not a left side/right connection scheme.
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Offline goldarrow

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Re: wont startup
« Reply #6 on: July 23, 2014, 10:24:54 AM »
Quote from: danarchy77550f on July 23, 2014, 10:18:44 AM
is that the center black part?

yes.

also you mentioned electronics ignition, is this Dyna S, they are famously know to have switched blue and yellow wires around.  few things to check but all are easy to do
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Life Is Full Of Challenges - And My Backyard Is Full Of SOHC4's

CB550 K0
CB750 K0, K2, K23 JDM, K45, K5
And the little ones z50r, xr50r, st90


750k5 http://forums.sohc4.net/index.php?topic=114817.0

Offline danarchy77550f

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Re: wont startup
« Reply #7 on: July 23, 2014, 10:27:46 AM »
The valves shouldnt be bent, they are on dead center.

the bike was running for two years on the ignition so it shouldnt be backwards but i will double check
the coils are running to the correct cylinders
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