Topic: 1974 CB550 - Starting After a Decade

[TPIGroove]

Hello all. My 550 restoration is coming along, and I've finally hit the point where I can see if the engine will run. I've replaced the plugs and wires, rebuilt the carbs and tuned them to the original specs, set up the air filter and airbox to stock, oil change, everything. The hard part now is getting it to run and idle as it should. I've managed to get it started and running on its own power, but starts are hard, and I need to hold the idle around 2000 RPM, it starts to die around 1500. I'm starting it with the choke closed, and while I held the RPM to warm the engine, I opened the choke and it sputtered and died. I have the carb screws set a little over one and a half turns out. I'm not sure if it's because it's sat for so long, or if the less restrictive exhaust is hurting it. Any ideas where to look before I start fighting it some more?

[desertrefugee]

Unless you're confident the carbs are done correctly, that'd be my first suspicion.   Did you replace the rubber inlets to the head?  Could be suffering from vacuum leak(s).   Definitely sounds carbish related.

[Deltarider]

[...] and I need to hold the idle around 2000 RPM, it starts to die around 1500. [...]

This is normal. The CB500/550 engines are quite coldblooded. Although chokes on models with the oldstyle carbs can be re-opened within a few seconds, the idle has to be kept @ around 2000 rpm, say for the first mile and maybe even longer. The Owner's Manual is clear about that. When the engine has warmed up, go for an idle of 1100-1200 rpm. You can use the big idle adjuster knob for that. Next cold start you will need a raised idle again however, be it by keeping the throttle twisted a bit inward, or by giving the idle adjust knob a few turns.

[TPIGroove]

Went out to try and start it again, now I can't get it to quite catch. Adjusting the choke from full closed to partial almost got it going, though. One other thing I notice is that cylinder 3 seems to be most consistently firing, that pipe was warm while the others were cold. While checking the pipe I saw that apparently one of the studs was broken flush with the collar on that pipe, so there might be a leak there. Would that have a major enough impact?

Unless you're confident the carbs are done correctly, that'd be my first suspicion.   Did you replace the rubber inlets to the head?  Could be suffering from vacuum leak(s).   Definitely sounds carbish related.

How supple should those inlets be? When I had them off they seemed flexible still.

[desertrefugee]

Generally speaking, if they're not hard as a rock, but as you describe have some "suppleness", they're probably ok.

Did you pull the slow jets and clean them, i.e. daylight shows through?

[Stev-o]

One other thing I notice is that cylinder 3 seems to be most consistently firing, that pipe was warm while the others were cold.

Have you confirmed that you have spark on all four cylinders?  What is the condition of your points, condensers and spark plugs and caps.   If you havent done the "3000 mile tune up", you need to start there.  And if you have, did you use genuine parts? There are a lot of sub-standard points and condensers out there that cause running issues.

[TPIGroove]

One other thing I notice is that cylinder 3 seems to be most consistently firing, that pipe was warm while the others were cold.

Have you confirmed that you have spark on all four cylinders?  What is the condition of your points, condensers and spark plugs and caps.   If you havent done the "3000 mile tune up", you need to start there.  And if you have, did you use genuine parts? There are a lot of sub-standard points and condensers out there that cause running issues.

I've done a full tune up. The engine was running earlier, all sparks were firing, I just noticed 3 seemed to fire more in my second start attempt.

[xhevi]

Sounds like something is off on the pilot circuit. It also could be then when you bench synced the slides are set too low.

Below are few issues I have run into with my 76 550:

1) New NGK plug caps that go bad, 4 in the last few months.

2) New manga coils that would not fire at high rpms. If you have a timing light hook it up to each plug wire and rev to ensure you got spark at all rpms.

3) Bad new condensers.

I would also go over the wiring from the points to coils and all connections in between.

If you have the original coils maybe the plug wires are shot.

[dave500]

stock coils have solid core wire that never fails,go right over the ignition again before you #$%* with the carbs again,if the caps aint new get new ones,if your not setting the points with a timing light your running blind,also with the carbs,if you took the rack apart how accurate is the static or "bench sync"?get the ignition squared away perfectly before you #$%* with the carbs,also what carbs are on the bike,type one?or the later PD type?

[TPIGroove]

Alright, biggest hurdle was overcame. Turns out it had so much trouble starting because I barely had enough gas in it before. Just gave it an extra gallon and it starts right up. Still running rough though, lot of fun smells and smoke coming from the exhaust, and she's shuddering pretty bad. I'm gonna get new boots to be sure, maybe replace the gasket for the engine piece the carb boots attach to. I've got a nasty exhaust leak too, and while I plan on replacing all of that how severely would it affect the engine running? For the carbs, totally rebuilt to stock configuration (cleaned and everything) and bench synced with a 1/8 punch so all the gaps were the same. I got new Magna coils, did a continuity test and they're all good, new wires, plugs, caps. Did a resistance test on the caps, too. Did static timing, set the gaps, set the valves.

Since I'm going into the exhaust, should I replace my setup with something else? It currently has a 4 into 2 with no muffler, and while I liked the sound one of the pipes is butted up against the oil drain plug, which was just plain inconvenient the other day. What exhaust setup would you recommend? Is there a good 4 into 4 aftermarket, or should I just go 4 into 1 and readjust the carbs?

[RAFster122s]

Hindle and Delkevic are good choices that are not too costly... Ripple Rock Racers in Canada makes the Hindle.