Topic: '78 CB550 Bad cylinder

[LouB]

Hi Guys,

Love the site and the bikes. Have been looking for a CB project and found a '78 CB550 that would be a great project bike, but it has a "bad cylinder". The current owner bought it as a father/son project but had a mechanic look at it. Apparently, he took compression readings and one of the cylinders had "low compression". That was as specific as he got and he said that it was now "more of a project than he wants" and is selling the bike. I don't mind working on the bad cylinder, but I don't want to get into having to bore the cylinders, etc. I am going to look at the bike on Saturday and I guess my question is, what can I look for that would give me an indication that it is not something more than worn rings?? Also, he is asking $300.00, is it worth it anyway? I have plenty of time but I don't want to put a ton of money into either. Any advice would be more than welcome! Thanks.

[campbmic]

I'm by far not the best person to ask but I would recommend; turning the engine over or starting it up and listening to the engine for any knocking or ticking noises. These typically indicate thrown rods, rod bearings, or valve issues. I had a bad rod and when I would roll on the throttle it would increase in speed.

Aside from that, check the oil level before starting her up and see if it smokes. I believe bad rings in a cylinder would usually cause blueish smoke to come from the cylinder's exhaust pipe.

What condition is the rest of the bike in? A fairly mint roller is worth more than $300 even without an engine!  

[traveler]

I'm by far the best person to ask but I would recommend; turning the engine over or starting it up and listening to the engine for any knocking or ticking noises. These typically indicate thrown rods, rod bearings, or valve issues. I had a bad rod and when I would roll on the throttle it would increase in speed.

Aside from that, check the oil level before starting her up and see if it smokes. I believe bad rings in a cylinder would usually cause blueish smoke to come from the cylinder's exhaust pipe.

What condition is the rest of the bike in? A fairly mint roller is worth more than $300 even without an engine! 

I see modesty is not your strong point.   

~Joe

[campbmic]

HAHA, thanks for pointing that out Traveler, obviously I'm NOT the best person to ask seeing as I can't even type!

[traveler]

hehe...just messin' with ya.

I had to read it a couple of times to beleive it.....

~Joe

[Zig]

take a compression tester/plug wrench/squirt can of oil with you and do a wet/dry compression test.

[fastbroshi]

  See if you can chew him down a bit on the price, and even if he doesn't budge it would be a decent buy for a parts bike if you two had your hearts set on a 550.  Could just be the rings on that cylinder.  Not an uber difficult job.  You could do it with basic hand tools.

[LouB]

Thanks guys. I appreciate the info and advice. From the pics it looks like the rest of the bike is in decent shape. It's an Arizona bike so I don't think there's any rust. The chrome on the exhaust looks to be in really good shape. He recovered the seat already, so i could sell that and some of the other pieces parts that I am going to replace anyway and recoup a little of money. I thought about doing a dry/wet compression test, but how accurate is that? I guess that would be a good indication of whether it's just rings or not anyway. Well, I'll let you know how it turns out!  Thanks again!

[fergie]

yeah the dry/wet test should bive you an idea if its the rings or a bad valve.