CB550 Antics

J

jryftc

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So I've been posting around on here a lot about this CB550 I've been riding for a few reasons, mainly because I've never really used forms before and two just to get some ideas about what other people are thinking. So essentially, this is what I got going on.

Picked up a CB550 5 weeks ago. 24,000 miles on it, in ready to ride condition. I test ride the bike up there, no problems. Check it for basics things like visual damage, all four cylinder firing, checked recharging system with a multimeter, starting up idling low, and of course quick test ride. Just about as intrusive to someone else's bike as you can be in their driveway.

Take her home, 5 hour drive. When I get back, I noticed that cylinder three isn't firing. A quick clean of the sparkplug solved that. So now we have the bike in good shape. I take the bike around my neighborhood, with/without a passenger, for usually around 45 minutes to an hour a few times a week. Fairly light riding honestly, but also going on the occasional longer ride with a buddy when we get a chance. Stuff's generally going well at this point.

Week 4 into owning the bike. I noticed that the acceleration seems "boggy." My buddy straight cooks me off the line, and from wrenching / riding Honda's for the last year and change, can tell things should be more responsive. Then today, I went on a ride, and about an hour into it, my bike started popping. It was hot and there was traffic, so I figured I'd stop and let her cool down, see what happened. I let the bike sit in the shade for a fair amount of time, and things were still in the same shape. It got to the point where I couldn't accelerate out of first gear from stop, and I actually stalled in two intersections. I also couldn't make it up hills. It was like the power was out of the bike. The acceleration just got weaker and weaker.

I was reluctant to put a wrench on this bike at first because the previous owner works on strictly old Honda's a lot, and it seemed like he knew what he was doing. Mainly though it was because I also dealt with a basket case CB450 this winter, and by basket case I mean this thing was fucking evil. Having summer months for riding in the future, the thought of pulling a "ready to ride" bike apart wasn't something I wanted to do. But after today's experience, I realized I need to sack the fuck up and figure this out.

From what I've done, I think it's carburetors. Running lean, I need them a bit richer, because pipes are burning gold-blue color. Plus the popping. Fuel flow something in there I think is may be fucked. Air screws tuned the wrong way, bad mixture, something along those lines. Maybe one off float height? I don't know. The other thing that was in the back of my head was oil getting past the piston/rings. I say this because I did see a little bit of white smoke today, but fingers crossed it isn't that. The bike runs too well for some top end repair bullshit, reiterating that I rode the bike hard for a month, and less than a few days ago was doing like 65, putting around reliably, minus the boggy acceleration.

Regardless, let me get your two cents. If you sat through this, thanks for reading the novel I just typed up for y'all. Cheers.

Joe
 
jryftc said:
From what I've done, I think it's carburetors. Running lean, I need them a bit richer, because pipes are burning gold-blue color. Plus the popping. Fuel flow something in there I think is may be fucked. Air screws tuned the wrong way, bad mixture, something along those lines. Maybe one off float height? I don't know. The other thing that was in the back of my head was oil getting past the piston/rings. I say this because I did see a little bit of white smoke today, but fingers crossed it isn't that. The bike runs too well for some top end repair bullshit, reiterating that I rode the bike hard for a month, and less than a few days ago was doing like 65, putting around reliably, minus the boggy acceleration.
Click to expand...

Pipes bluing is generally a symptom of too much heat -- and that's what you get with a lean mixture. But the air screws can't be "turned the wrong way" unless you tried to adjust them and turned them the wrong way (backing them out leans idle mixture, screwing them in enriches mixture), or unless you cross threaded them. Float height is not something that can be "one off" unless it's off by one mm. It's also not something that will just happen. Stating that "The bike runs too well for some top end repair bullshit" is belied by your description.

If you're "reluctant to put on a wrench on this bike" take it to a shop where they know older bikes (and find one with a mechanic who is also older; green MMI grads aren't usually the best when it comes to working on old bikes -- no offense to recent MMI grads, especially those who have been wrenching on old bikes for years). Be prepared to spend whatever the going rate is for an hour or so to diagnose, and then whatever it takes to fix it.

Or... lose the reluctance to pick up a wrench. If you ran the bike hard for a month (how hard? did it overheat? did you rev it past the red line?) and you're getting these symptoms, it could be a number of things. First, buy a manual and read it. I'd look into carburetion first. Check your plugs. If they are sooty, they're running rich, not lean -- this will cause some of the bogging down and popping as well. When you said your #3 plug had to be cleaned and then it started firing again -- what did you clean off it? Sooty deposits (rich)? Or oil (rings, valves, gasket)? Have you looked at your other plugs to see what shape they're in? Bogging and low acceleration can be from not all cylinders firing. Or plugged jets (partially clogged jets can also cause heat issues). How are your points? Clean and flat contacts? Fouled points can cause you to drop two cylinders (2-3 or 1-4).

Welcome to having an old bike. Lose the reluctance to wrench or open your wallet, those are your only two choices, really. Read the manual, it'll also have a troubleshooting section.
 
Yeah, there were a few things weird. I believe its carburetion. Two of the plugs were wet. The others were sooty. Inside of the carbs looked dirty as well. Will give those a clean. Go through and check the float heights, etc. I think the two in the middle had off floats letting in too much gas, fouling the plugs. Believe it or not one of the pilot jets was falling out when I took off the bowl, and the oil was low, so I changed that as well. Never checked any of these things when I bought the bike, just put it on the road. Guess that's what I get...
 
I usually found it that original parts from the carbs work the best. I replaced the plugs, gave the carbs a cleaning, and set the floats back to standard height (12.5mm) and the air screw jets back to their standard (1.5 turns). Put it all back together and cylinders two and three still aren't firing. I noticed that when the bike runs, the 2 and 3 points have consistent strong spark between them, but the 1 and 4 points have less...curious if this has anything to do with the issue...
 
For your spark issue, swap the coils over. If the problem follows the coil, it's the coil. If the problem stays with the same wires from the points it's the points / condensor.


White smoke is (usually) burning oil. Check to see if your engine oil smells like gas and is overfull. Gas can leak past the carbs into the cylinders and then down into the sump, or if there's a crankcase vent that goes to the bottom of the airbox, it can leak in that way.
 
Replaced coil bike runs well again. Thanks to anyone who gave me their two cents on this thread, appreciated.
 
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