Topic: may be a coil problem? unsure

[dilbone]

Hey guys and gals,

I've got a 75 CB550 and I've gone through all of the tune up procedures.  Cleaned all carb passages and jets, cleaned and set points gap, set timing, new plugs, sync'd carbs etc....

It runs fantastic...

Problem is that when I start it, it acts like it's running only on 2 cylinders for about the first 5 minutes or so.  After that first 5 minutes it appears to be fine.

Tonight I'll do a temp check of the exhaust and see exactly which cylinders aren't firing.

Is it possible though, that if I do find either 1-4 or 2-3 lacks firing at initial start up that it could be the coil even if as it warms they kick in and begin firing?



Thanks in advance

[bryanj]

Coils normaly work or dont but if intermittent usually fail when hot.

Having said that it could be moisture in the plug caps/lead connection drying out---try new NGK caps first

[tlbranth]

I've had problems like that that turned out to be a fuel delivery problem. If you have filters, could be clogged or petcock could be partially blocked. The answer depends mostly on which 2 aren't firing.

[dilbone]

thanks you two, I guess I have some investigating to do. 

I was kinda hoping I could just use this as an excuse to get a dyna-s and new coils...maybe not quite yet...
or maybe the new boots is a good enough excuse to upgrade the whole deal.

I don't have an inline filter and I have good flow with both lines out of the petcock...I'm leaning away from a fuel issue since it only happens on start up.

[ieism]

When did it start doing this, any changes to the bike?
Do you always turn the fuel petcock off when you park the bike?
Do you have good voltage at the battery?
If you give it more than half trottle, does it start running on 4 cylinders or is it still crap?
When you ride the bike untill it's warmed up, does it start up properly after that?


First thing to do would see what cylinders are NOT running. I wouldn't complete rule out a fuel problem. Even after cleaning the carbs you can still have a blocked jet somewhere/somehow, i've had that a couple of times....

I agree with bryanj, coils usually fail when hot. You could try cutting a little off the lead connection and putting the plug caps back on.

[TwoTired]

How old are the condensers?
If you switch sides on which the condensers sit, do the problems stay on the same cylinders?

Are you electric starting the bike?  Is the battery at full charge?  What is the battery voltage when it runs on only 2 cylinders?

Are the electrical connections clean and making good contact between coils and points?

Are the electrical connections clean and making good contact between coils and power source?

[dilbone]

well, I started it up last night after several kicks to get things moving before using electric start and she idled right away...even better than normal.  I did a quick hand check of all cylinders on the exhaust and they were all firing right away.

I guess, if you want to fix a problem just post a question about it and then it goes away...lol

I will check it periodically and see if I can get it to act up again so I can check on some of what you've all suggested.
Thanks for all the advice...I'll report back if I find anything new.
PS. the bike hadn't been started since mid march and it still popped off with little problem.  Probably better than it ever has actually with 2 months of sitting. Go figure...