Author Topic: CB550 Top End Rebuild (Read 18861 times)

bryanj · « **Reply #100 on:** June 17, 2019, 01:17:05 AM »

Check that the exhausts are tight in the head you would not be the first to chase a noisey tappet then find a slight exhaust gasket blow(got that tee shirt!)

flatlander · « **Reply #101 on:** June 17, 2019, 02:40:56 AM »

good call bryan!

calj737 · « **Reply #102 on:** June 17, 2019, 03:46:52 AM »

+2 on exhaust flanges.

CJK · « **Reply #103 on:** June 17, 2019, 11:51:08 AM »

Flatlander - Thanks for info about newer valve cover. I think I set tappet clearance correctly.

- Place correct feeler gauge between top of valve stem and bottom of tappet.
- screw tappet down just to point where feeler gauge can slide out, but next size gauge will not fit.
- tighten 10mm nut to secure

I will check exhaust flanges for any leaks. I put the copper crush gaskets in there and tighten down pretty good. I’ll check for any leak.

Any guidance on engine break-in following a top-end rebuild?
I would assume first 500 miles should be taken easy and oil changed.

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flatlander · « **Reply #104 on:** June 17, 2019, 12:56:46 PM »

there are different break-in philosophies. i'm in the fast and hard camp but other opinions are available

with that disclaimer out of the way... avoid idling and avoid keeping it at the same rpm for longer times. so start it up, get riding immediately and keep varying the rpms throughout the gears. like on your local twisties. accelerate and decelerate on the engine. warm the engine up doing this, 5-7 miles up to 5k rpm, another 5-7 miles up to 7k, then use the full rpm range. get back home when you have up to 50 miles on the clock, then change the oil and filter.
then keep riding the same way, meaning avoiding sustained rpms if you can but otherwise you can ride it like normal. don't baby it, give it the spurs once warmed up. change the oil and filter again after about 200 miles. after that you can stick to the normal oil change schedule.
the point is to get the rings to seat properly and you won't get that without load. that's why all the accelerating and decelerating. so have some fun, avoid city and highways and head for some small exciting roads. the oil changes are important to get the metal dust out early.

Fezzler · « **Reply #105 on:** June 17, 2019, 04:44:17 PM »

Apologies for lurking, but what a thread! (And this top end was completed in frame?)

CJK · « **Reply #106 on:** June 17, 2019, 05:19:12 PM »

Thanks flatlander, that all makes sense.

After I get the carbs vacuum synch’d and then get carbs tuned, I’ll be sure to work it through the full range of RPMs with a huge grin on my face

Fezzler - I’m grateful to have so many experienced minds (Bryan, Cal, David, and Flatlander) helping me through this. This forum was one of the reasons I purchased a Honda SOHC motorcycle, it’s been a journey and learned so much through it. It’s been awesome.

I’m not sure I understand your question, can you re-phrase?

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Fezzler · « **Reply #107 on:** June 17, 2019, 06:03:44 PM »

Apologies. I'll try again.

Is it correct that you completed the rebuild of the top of the engine without removing the engine block from the motorcycle's frame?

I attempted my first project after seeing Dino's Hack-A-Week series, asking a bunch of questions here, and getting a lot of terrific help from some unbelievably nice, helpful and knowledgeable folks on SOHC4. I still have a lot to learn, and my first bike isn't perfect, but it is a very fun Sunday rider and occasional commuter bike.

They instilled in me enough confidence to attempt a second restoration with the training wheels off some.

CJK · « **Reply #108 on:** June 17, 2019, 06:28:10 PM »

Oh, I understand what you're asking...

Yes, I left the bottom end mounted in the frame, while the top end was off. I stuffed shop towels around the rods to prevent anything from falling down in there, then I put a plastic trash bag over the top to make sure dust did not get down in there.

For a first rebuild, I've been pleasantly surprised with it. I'm sure the next one will be much easier

bryanj · « **Reply #109 on:** June 17, 2019, 11:11:06 PM »

Fezzler, dont forget the 500/550 you can strip the top end in the frame but the 750 you can not(without a frame mod kit!)

CJK · « **Reply #110 on:** July 12, 2019, 09:58:32 PM »

Bad news:
the engine seized on me during its first test ride since the rebuild about a mile from home.

Good news:
no injury other than my ego, morale, and wallet.

I must have made a mistake somewhere along the way and forgot to check something or tighten down to spec.

Not sure what the extent of the damage is, but I won’t be able to open it up for a couple weeks as I’ll be traveling.

I was decelerating at the time, engine was at maybe 3-4K RPM from about 6K max. Engine felt odd so I pulled in the clutch to remove load, felt a clunk and the engine died. Tried the kick starter to see if it would even turn over, but it was seized.

Not much other details to share as I pushed it back (uphill the entire way, of course), parked it, and walked away.

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DaveBarbier · « **Reply #111 on:** July 19, 2019, 05:38:24 AM »

Bummer! When will you be able to open it up? Check the oil filter for metal.

wolf550 · « **Reply #112 on:** July 19, 2019, 01:56:28 PM »

reminded me of my last top end rebuild
after putting back together went for a ride
heard what sounded like my cam chain loosened and then chunk!
when i opened it up the gear was off the cam and bolts were gone
forgot to tighten the cam gear bolts i guess

Stev-o · « **Reply #113 on:** July 19, 2019, 02:39:51 PM »

Sorry to hear...

CJK · « **Reply #114 on:** July 19, 2019, 04:09:35 PM »

Thanks all, it’s a bummer and I was pretty upset for a while. However, I didn’t get injured and I’m sure there’s lessons learned so I’ll chalk it up to another learning experience.

I should be able to open up the engine next weekend. I’ll be happy if the work I had Mike do wasn’t for nothing.

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CJK · « **Reply #115 on:** August 25, 2019, 07:20:11 PM »

It took a bit as I’ve been busy with work and I haven’t wanted to know...but I finally opened it up.

This wasn’t the first run. It was the first time on the street.

Below is cylinder 1...looks like it’s now a Stage 2.5 paper weight and the piston is ruined too.

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dave500 · « **Reply #116 on:** August 25, 2019, 08:50:53 PM »

dropped a valve,keepers let go?thats a big bad bummer I feel for you.

CJK · « **Reply #117 on:** August 25, 2019, 09:35:07 PM »

Quote from: dave500 on August 25, 2019, 08:50:53 PM

dropped a valve,keepers let go?thats a big bad bummer I feel for you.

Honestly, I have no idea.

@MRieck did all the head work for me and I have no reason to doubt his workmanship.

calj737 · « **Reply #118 on:** August 25, 2019, 09:44:26 PM »

How do the other 3 cylinders look top and bottom?

CJK · « **Reply #119 on:** August 25, 2019, 09:50:48 PM »

Quote from: calj737 on August 25, 2019, 09:44:26 PM

How do the other 3 cylinders look top and bottom?

Exhaust Valves definitely made contact with pistons heads on 2/3/4.

I had an adjustable cam sprocket. Maybe I didn’t tighten it down enough and I lost timing which led to this?

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dave500 · « **Reply #120 on:** August 25, 2019, 11:23:25 PM »

yeah if all made contact it wasn't a keeper let go,either as you said cam bolts slipped or way to close clearance?if the clearance was too close id imagine both inlet and exhaust valves would collide with the pistons,being only the exhausts id guess the timing went off,or was set wrongly?was the valve clearance to pistons checked?if only those eye brows were bigger?

CJK · « **Reply #121 on:** August 26, 2019, 05:12:13 AM »

Quote from: dave500 on August 25, 2019, 11:23:25 PM

yeah if all made contact it wasn't a keeper let go,either as you said cam bolts slipped or way to close clearance?if the clearance was too close id imagine both inlet and exhaust valves would collide with the pistons,being only the exhausts id guess the timing went off,or was set wrongly?was the valve clearance to pistons checked?if only those eye brows were bigger?

I checked valve clearances with the clay method on top of pistons and they did not touch.

To set timing, I followed the manual exactly (Cylinder 1 @ TDC, cam notch parallel to head) and it ran very well in neutral when I was tuning it. This was the first time under load and it drove for about a mile before I suspect the cam sprocket slipped back several degrees, retarding the timing and sending the #1 exhaust valve into the piston.

When disassembling, this is where the timing advancer and cam notch were at. Timing advancer is a 3-5 degrees before F, the notch is probably 10-15 degrees behind where it needs to be.

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flatlander · « **Reply #122 on:** August 26, 2019, 05:29:00 AM »

remind us what cam you have?
and can you make another pic of the cam slot orientation, this time at TDC?

CJK · « **Reply #123 on:** August 26, 2019, 05:54:56 AM »

Quote from: flatlander on August 26, 2019, 05:29:00 AM

remind us what cam you have?
and can you make another pic of the cam slot orientation, this time at TDC?

1979 CB650 cam

Sorry, top end is disassembled so I can’t take anymore pictures to show timing and replicating it wouldn’t be accurate. The engine wouldn’t turnover until I removed the chunk of the valve that was stuck in the head.

Here’s another I took with better light.

bryanj · « **Reply #124 on:** August 26, 2019, 07:10:26 AM »

Looks to me like it would be close to spot on if on T mark

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Author Topic: CB550 Top End Rebuild (Read 18861 times)