Topic: Cb 550 Starts then Dies

[shinneh]

I'm kinda new here kinda been lurking around. I frequent here often for info and inspiration.

Having a coupla problems, some I know what to do with, others...eh.

Problem, finally got the non running cb550 to fire up and run, but only while I'm holding the starter button. I let go of the button and the bike dies. Now I feel it necessary to say that the button is not so much a button, but the wire of the button being grounded to the handle bar when I want it to turn. And also that I didnt have a battery directly connected, I had a car battery with jumper wires going to the pos and neg wires. All electrics work fine.

Also, this happened the other day, while trying to get it running one of the carbs is overflowing gas, no biggy as it's prolly the floats. Problem is the bike back fired something fierce and caught fire to, well.. alot. After alot of water (damned fire extinguisher failed) being sprayed the fire was dead with no real damage except a blackened carb and blackened gas tank (with a small dent from when I ripped it off the flaming bike and threw it into the yard). My problem with this is what should I do with the motor if water made it past the carbs into the firing chamber?

Ontop of that the bike will "start" up pretty quick after hitting the starter but die when ya let go. My manuals were among the things that caught fire so I'm lost on that portion for a little while.

The bike is a 74' cb550 but I think the motor is a 77 or 76. I've replaced the points, 3 of the spark plugs (one I can't get to, in the process of grinding down sockets to fit in there a get it) I've set the gap correctly, I believe. And as well as set the timing statically. I get a blue spark from all wires, kinda thin though but blue. (Not sure how thick it ought to be)

Thanks in advance.

[kslrr]

Have you:
Set the timing and points gap?
Checked and set the valve clearances?
Removed and totally cleaned out the carbs (I am assuming it has sat for awhile)?

The dying when the starter wire is removed may mean the PO (Previous Owner) screwed up the wiring somewhere.

Also, be carefull using an external battery.  Not paying attention to when you are connecting the jumpers or if the battery is still in the car can destroy the bikes voltage rectifier.

[Gordon]

The only way you can hurt the bike's electrical system by jumping it to a car battery is if you reverse the polarity.  Doesn't matter if it's currently connected to the car or even if the car is running at the time.  So as long as you had the polarity correct, don't worry about that part. 

As for the rest of it, you leave a lot of questions unanswered.  Have you done a complete, 100% thorough tune-up?  Have you cleaned/ rebuilt the carbs?  What (if any) changes have been made from stock that might affect the intake, exhaust, ignition or combustion of the engine?

If you haven't done everything listed in your manual that encompasses regular maintenance of the engine, then do that and see how it runs. 

[TwoTired]

Plugged up slow jets, funk in the carbs,
....assuming you know how to use the choke.

[shinneh]

Gap and timing (as prev mentioned) were indeed set. Uhm, forgot to check valve clearances. Completely took apart carbs, soaked in carb cleaner and blew them out with compressed air at my shop. Before doing this to the carbs the bike wouldn't start with the carbs on the bike.  The car battery was removed from the car (as the bike was kinda in the house). Had choke on all the way. In relation, bike would not start at all with no throttle but would immediately start with half to full throttle. But giving any throttle yielded no response at all. I see alot of light through both the jets, so I'm hoping they are good. If they are the culprit I'll just buy new ones. I'm thinking though this is an ignition problem some how.. but then again I haven't checked the valve clearance.

[Gordon]

but then again I haven't checked the valve clearance.

Check the valve clearances and then see how it goes. 

It may not be part of the problem, but then there's not much sense in looking for another cause if you haven't ruled out the simple ones first. 

[shinneh]

Haven't gotten to the valve check yet as I'm stuck at the shop longer than expected. But I forgot to mention the changes made to the intake/exhaust. Currently I have no air box, and no air filters on the carbs at all. I know that would cause a problem but the damned thing should start at least. There is also a 4-1 exhaust which I have taken the baffle and cone off for repairing.

In thinking things through I'm not sure i have the points gap set correctly. The specs in the book and my feeler guage didn't speak the same language so I'm not sure if I did it correctly. I will say that if they are wrong then there is not enough gap. And that for me to get a light to turn on when setting the timing for 2-3 cyclinders I had to increase the gap a little. I'm certain that this has something to do with it so now I need to figure out what gap i need.