Topic: CB550 - Rebuilt, then sat, then started... advice

[matic00]

Hi all,
So I'm looking for some advice, guidance, etc on my 1976 CB550.
Long story short-ish. About 10 years ago I took my decent running CB550 and tore down the engine to lap the valves, replace the rings, honed the cylinder and just give everything a once over (winter project). I buttoned it all back up and the bike was 90% complete, just needed to sort brakes, etc.... and then I had a kid, and it sat for almost 8 years, most of the time with no oil in it (i know, stupid). Last winter I got back into it, put some Marvel into the plug holes, rebuilt carbs and all the other maintenance items. It would turn over, i'd get spark, fuel but it wouldn't run. Figured out that when I put it back together (8 years ago) I had screwed up the timing with the camshaft. I sorted that out, rechecked valve clearances, ignition timing and did a compression test -  90/95/100/95. Seems low, but figurted maybe the rings just needed to seat, etc. (I also realized I forgot to hold the throttle open when I did it.)I started it and NOW IT RUNS, but the problem is it's not running great and it's smoking a lot.

My questions:
- If my timing was 90 degrees out, could i have bent the valves, and how could one tell if they are bent, just low compression?
- If the valves are jacked, I imagine a leak down test would help verify? I've never done one, but will look into it.
- The smoking, i imagine there would be some of that the first few times starting a bike after a new build, until rings seat, right?
- I'm going to do a compression test tonight now that the engine has run a bit, and see if it's improved
- I know I should take it for a proper ride, bring the engine up to temp and all that before panicking, but it's winter in MN, so...
- If I need to tear it all back down, I'd prefer to do it during the winter while I have the time

Any thoughts, guidance, advice?
Thanks!

[BenelliSEI]

Do the compression check again and see if the numbers are up. If you’re using an automotive style tester, the numbers will be low. Consistency is more important. Try that and see.

How much oil did you pour in? That will take a while to clear up. Using fresh gas?

[matic00]

Yeah, planning to do the compression test again tonight and see where I stand. The tester is a Bosch, not specific to motorcycles.
I didn't remember exactly how much i used, maybe a tablespoon per cylinder - and that was last winter when I decided to dig back into it. Fresh gas yes, just did a tank flush, carb kit, new fuel filters, etc

[RAFster122s]

If you changed the brass to that of a kit then that is likely the source of part of your problems. Aftermarket brass is junk. Put the OEM Keihin brass back in after cleaning thoroughly and it will help.

[matic00]

I assume you're referring to the carbs? I didn't do a full kit, just individual OEM pilots and mains. I think the carbs are fine other than needing a sync, the smoke from oil burning and compression is my biggest concern.

[RAFster122s]

Compression will come up once rings seat, how much is hard to say...

The cylinders drift off of center as the material the cylinder cooling fins were made of allowed that until broken in and stabilized. HondaMan indicates this is about a 10% loss in power and a align boring of the cylinders will restore this loss. Often the cylinders wear to become out of round. So, just re-ringing after honing will not be enough. Without carefully measuring the cylinders with inside bore micrometers you won't know if there is eccentric wear.

Smoking should reduce as the bike breaks in, anything you put in the bore for lube will take quite a while to burn off. Run it a couple hundred miles with typical break in speeds and loads and if the smoking has not stopped you are going to need to overbore and new pistons and rings.

[jgger]

For as long as it sat make sure nothing has taken up residence in both the intake and especially the exhaust. Just for fun

[matic00]

Appreciate the detailed response, I'll dig a little deeper and go from there. Is there a chance of bending the valves when I had the timing off by 90 degrees? I just want to make sure I didn't destroy anything - I'd rather tear it open now than wait until the spring to find out if the compression doesn't come back up.

Compression will come up once rings seat, how much is hard to say...

The cylinders drift off of center as the material the cylinder cooling fins were made of allowed that until broken in and stabilized. HondaMan indicates this is about a 10% loss in power and a align boring of the cylinders will restore this loss. Often the cylinders wear to become out of round. So, just re-ringing after honing will not be enough. Without carefully measuring the cylinders with inside bore micrometers you won't know if there is eccentric wear.

Smoking should reduce as the bike breaks in, anything you put in the bore for lube will take quite a while to burn off. Run it a couple hundred miles with typical break in speeds and loads and if the smoking has not stopped you are going to need to overbore and new pistons and rings.

[TwoTired]

A tablespoon is 15cc.  With the 550 at TDC there is about 10 cc of room in there.  Seems like a recipe for hydro lock.   You only need enough oil to wet the rings for an extra seal. Not enough to alter the compression ratio of the cylinder.

These are small engines.  You have to be careful when using automotive techniques applied to these small Honda’s.

[matic00]

Good point, hadn't quite broken it down like this. Thinking back it was probably less than a tablespoon, but regardless - more than likely too much. Thanks!

A tablespoon is 15cc.  With the 550 at TDC there is about 10 cc of room in there.  Seems like a recipe for hydro lock.   You only need enough oil to wet the rings for an extra seal. Not enough to alter the compression ratio of the cylinder.

These are small engines.  You have to be careful when using automotive techniques applied to these small Honda’s.

[Nurse Julie]

The rings could be stuck in the piston grooves, this would account for low compression and smoking.

[campbmic]

Just wondering, why is it a bad idea to no have oil in the engine when its sitting for long periods doing a rebuild? Im in a similar boat and tore my bike down about 3 years ago after a house fire roasted it. I drained the oil and tore down the top end. Im now in the process of rebuilding it. Just wondering why its bad to have it sitting with no oil?

[grcamna2]

I've found that the residual oil sitting in the top-end including the pistons/rings will slowly drip down away from the moving parts after sitting for a long time.
This can be catastrophic when first started after years of sitting when you first start it.
The camshaft/s pistons/rings cylinders and cam chain like to be re-lubricated with fresh oil before firing it up after extended sitting in storage.