Topic: Engine teardown help CB550 F1

[-CB-Jamie-]

So I recently finished my cafe racer build and got the bike on the road only to find it was blowing out a hell of a lot of blue smoke and going through a lot of oil. A 40-50 mile trip would bring my oil level from the top mark of the dipstick almost to the bottom mark on the dipstick. The bike pulls amazing though which makes this problem even more frustrating. I did everything I could like valve clearances etc but it's still the same so I decided to bite the bullet and tear down the top end.

My Plan is:
1. New head gasket, new valve stem seals and O-rings where required.
2. Clean the valves and ports of any carbon buildup.
3. lap the valves.

One question, can I reinstall the pistons without new rings and without honing or is this a must? (because as far as I can see they look ok)
Also a big bore kit would be a possibility if I need to go down the road of new pistons/rings etc as it seems to be an almost cheaper option.

I did find one o-ring between the head and the cylinders that could have been causing a problem. I think oil could have been getting past it and into the cylinder.

So I'd just like to post pics of everything so the kind people of this forum can tell me if I'm missing anything and advise me as I'm far from an expert.


Thanks,
Jamie

Pistons


Bad o-ring


Underside of head (1-4 from first to last)





Intake valves (1-4 from left to right)



Exhaust valves (1-4 from left to right)







Bores (1-4 first to last)

[calj737]

You can not determine whether your motor needs machining from "looks" alone. Based upon the info you provided regarding smoke and burning of oil, I'd say at a minimum you need to have the cylinders and pistons measured with a mic and determine if they're in spec. Also, the valve guides and seals and springs.

Did you happen to perform a compression test pre-teardown? That would have been helpful too.

If you do re-use those pistons, I would definitely hone the cylinders and buy new rings. Your head and valves do not "look" healthy to me. Very fouled and a lot of carbon build up. You could easily have both a mechanical problem (mentioned above) as well as carb/ignition problems too (poor A/F mixture, weak spark, etc.). First, you must start with a known good motor from established mechanical clearances. Then proceed to tuning. Bet your plugs look like your exhaust valves...

Any pictures of the cam and rockers?

[-CB-Jamie-]

Ya I'm in the process of trying to get a loan of a bore gauge to measure the cylinders, I should b able to get a loan of a micrometer as well.
I did a compression test a few months ago alright, my values were in the 105-110 psi from what I can remember, each one was within the 10% of each other anyway for definite.
I'm quite happy with the tuning of the carbs and ignition, carbs are balanced and mixtures correct, this bike has been rebuilt from the ground up pretty much.
My plugs are actually quite clean, I'll post pics tomorrow as I'm in work at the moment

[calj737]

my values were in the 105-110 psi from what I can remember, each one was within 10% of each other

That's good that they were within that range to each other, but from the pictures it appears the overall compression was poor.

this bike has been rebuilt from the ground up pretty much.

Is that everything except the motor? The head and cylinders don't appear to be consistent with that description.

[Bodi]

I would say a light hone (for ring seating) and new rings would be good if the bores and pistons are in spec.
The guides or valvestems are suspect to me, get them measured. The clearances are miniscule, measuring the guides is not easy. Intake ports look oily, especially 3. There are aftermarket guides available with seals on all 8 stems (I think the OEM exhaust guides are unsealed) but opinions vary on using exhaust seals in engines where Honda didn't.

[rb550four]

I would like to know what if anything was done to that motor too. How long did it sit locked up before you got it loose and fired it up?
  The valves show lead deposits on them . That indicates no work was done to the head. First cylinder pic shows striations like the rings were encrusted  and cleaned themselves out the hard way.
The second cylinder pic looks like that was the cylinder that took on the most water (was the plug out of that one?) and fused the rings to the cylinder.
From these pictures , I would say that nothing was done to this engine after it was broke free,  except being made to run .
 Kinda makes you wonder where all the crap in those rings went to right? And what else may be worn down in the lower end?  Hmmmm.

[MiGhost]

You can not determine whether your motor needs machining from "looks" alone.

Actually, Those pictures tell quite the story.
Heavy blow-by on the pistons indicate bad rings, and possibly worn cylinders. Cylinder #2 shows some serious pitting that will likely need to be bored out to clean up (if even salvageable). Cylinder #1 shows signs of ring seizure causing the wear marking lines.
Heavy buildup, and dark, wet, discolored ports make the guides, and seals highly suspect.

I do agree that the way to go is to check, and measure to find out the true condition, but machine work is a likely probability.

[-CB-Jamie-]

this bike has been rebuilt from the ground up pretty much.

Is that everything except the motor? The head and cylinders don't appear to be consistent with that description.

Yes sorry should have been more clear that's everything except the motor.

I got this bike about two years ago and it wasn't locked up, it turned over freely, I reckon from what the previous owner said though this bike was lying up for about 10 years previous to this. I had no problem getting it to fire up and so this is why I went ahead with my build without touching the motor.

When I got this bike running and on the road a few weeks ago it ran extremely well, idle was perfect and it pulls away much better than I expected, the only problem I had was the smoke, other than this I would have been very impressed with the performance.

Anyway had an hour this morning so cleaned up the valves with a wire brush, I measured two of my exhaust valve stems with a digital vernier and they were in spec. I then proceeded to measure the valve stem clearance as per the service manual and what I got was not good. The manual states 0.030mm - 0.050mm for the exhaust valve and I got about 0.130mm. So it's looking like my guides may be a problem. I will try to get the measurements for the rest of the valves and everything else that I can and post them here in the next few days.

Should have a loan of a small bore gauge later that I should b able to measure the valve guides with as well and possibly a micrometer as well for measuring the valve stems. I may not be able to get a loan of a bore gauge big enough for the cylinders unfortunately.

Bodi: there was 8 valve stem seals in the motor, both the intake and exhaust valves had them. I thought the 550 has 8 seals but the 400 and 350 only had them on the intakes??

Anyway here's a few pics.... sorry about the quality these are only taken with a phone















The plugs aren't in order unfortunately, don't know which plug is from which cylinder

[calj737]

The only things I see that cause me concern, outside the valve measurements, is the blue sealant around the cover, and appears to be some wear on the cam lobes. That could easily be caused by oil starvation (sealant clogging oil passages) or improperly adjusted valves (guides badly worn) or both.

Since you're into the cylinders also, I'd pull the oil pump and inspect it closely for measure and obstruction.

Looks like you've got some machine shop work ahead of you.

[Vinhead1957]

Check the valves for straightness too!   Roll them on a flat surface and make sure the head rolls true.   To me your oil consumption is valve seal related but you really can't rely on the eye! Hondamans book would be an asset to your build.  Mic the cylinders to be sure