Topic: "Fried Intake Valves" 1976 CB550

[bryanj]

Down on the left side by the rear brake light switch is a rubber boot in which the wires from the points (blue and yellow) connect, not uncommon for them to get disconnected.

Cam chain tension has no effect on ignition timing at all as points are on end of crank not cam.

You need a manual and an OLD Honda man to run through everything methodically.

Air fare is a bit much to come and help sorry

[Can550]

When turn the key, all required lights (neutral, oil, headlight, tail light) turn ON

There is good spark (after putting new spark plugs).

When turned over, I noticed cylinder 4 both valves adjustment bolts come up together at the same time.

He referred to timing of cam chain being out a tooth or so (which I have no clue about)

I will check rubber boot by the brake light switch (isn't it on right side when sitting on bike?)

Thanks


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[calj737]

He referred to timing of cam chain being out a tooth or so (which I have no clue about)

That would not be very likely at all unless someone removed the valve cover, removed the chain from the sprocket, and installed the cam physically rotated out of position to TDC, then adjusted three of four cylinder's valves correctly, but not the fourth.

There are any number of reasons that your starter motor didn't start. For starters (pardon the pun), did you pull in the clutch while pressing START? Your bike very likely has a Clutch Safety Switch and requires this. Did you check the Y/R wire at the solenoid for 12v with START depressed?

Too many of your posts seem oriented towards a catastrophic failure that will require untold service/repairs/rebuild. If you are getting bad advice from "locals" stop asking them. Grab a manual, grab a meter, and isolate 1 thing at a time. To run, your bike needs: Spark, Fuel and Compression. In that order.

Pull the tank off. Get a donor/test tank of fuel to diagnose your issues and tune the bike. Clean all the varnished gas from your tank, petcock, and be prepared to fully and properly clean the carbs. This will require more than simply "spraying" them with Carb Cleaner. Disassembly of the carbs (still attached to the rack but detached from the bike) will be required. Doing this will also allow you better access to the coils and other electrical connections.

With the carbs off and while you rebuild/clean them up, begin checking the electrical/igntion. Learn something about your bike before you commence adjusting the valves. Download the correct manual, and clean up the ignition and points and set the timing properly. Then see if the solenoid (because you've cleaned up the connections) will spin the starter motor. If so, reinstall the carbs now that they're clean.

Then fire up the bike. Finish off the 3K Mile Service interval and ride your new bike.

[BomberMann650]

When turned over, I noticed cylinder 4 both valves adjustment bolts come up together at the same time.

Both valves close (tappets up) when the cylinder is ready to combust.

Intake down, intake up, BOOM!, exhaust down, exhaust up, repeat.

[scottly]

Do a compression test and/or leak down test. The leak-down test will tell if the valves are sealing, and the cranking compression test will help identify if there is a cam timing problem.

[Can550]

Thanks everyone for all the guiding and advising posts. I'll attach few photos to show you what I found once it was topless

Pictures will speak thousand words and I'm now quiet!

Cam is broken, sprocket is damaged, rocker arms are marked/ scratched.

One of the bolts that seat sprocket on to camshaft, came loose, was hitting and ultimately broke into half and was sitting right there ( luckily did not fall down) plus some particles of broken bolt which were carefully removed.

To move forward, I need a cam with all rockers, close the top and try cranking it. Await valuable input and if some is selling required parts, pls let me know.

Guess it is not going to be ready soon




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[scottly]

Ouch!!

[Can550]

I'm terrified
Don't know what next?
Damn I spent four days taking parts off, scrubbing, cleaning, polishing them

Even ordered a set of tyres, bought oil, filters and brake pads, all led bulbs and a headlight. I'm sad


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[scottly]

Is the camshaft itself broken in half, or is the broken off ear where the sprocket bolt goes the only breakage?

[Can550]

Ear is broken (to the best of observation). Are you suggesting it can be salvaged ? I don't even know how much these go for used and or new


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[scottly]

No, I wouldn't try to salvage the cam; I was asking to determine the cause of the breakage. From the looks of the damage, I'm guessing the sprocket bolt backed out until it hit the cam cover, snapping the ear off. If the shaft itself was broken, one might suspect that oil starvation may have caused the cam to seize, breaking the cam and breaking off the ear. If the bolt backed out, most likely due to improper assembly, the damage may only be to the cam itself, rather than the cylinder head and cam bearing surfaces.

[bochnak]

Now would be a good time to check cam timing. If cam timing is good, then the valves should be OK too.

You can still perform a leak down test with the cam out. Just support the cam chain in case the crank wants to spin on you.

[calj737]

I would not continue rotating that motor with that kind of damage visible. You have no idea what has dropped into the lower end (gouged aluminum) and is possibly tearing up the lower end bearings.

Not only do you need a new cam, possibly a new sprocket, but you will also need to remove the head and inspect thoroughly the cam chain tensioner.

To find a replacement set of stock rockers and a cam will be hit or miss. Likely, whatever you find will have some amount of wear on them. The best course of action is to have a set hard welded (pricey) and use an aftermarket cam. The issue is, this will become expensive given that you still don't know the condition of the motor beneath. 

I would encourage you to remove the head and tensioner. Inspect the piston tops. You may well have damage to them from the cam being out of time, and its also possible you now have bent some valves. Inspecting the pistons will be a clear indication of this.

Regrettably, you have bought a bike that probably needs more money sunk into for engine repairs than the purchase price of the bike. It's not at all the end of the world. You just need to understand whats in front of you from an expense/time perspective. Its all very easily repaired, the cam being the most expensive portion. But you won't be riding this Spring with that motor unless you hustle and spend some dough (more).

Repairing it, you can do much of that work, even if you've never wrenched on a bike. There are hundreds of folks on this forum with projects who have started with worse, knew less, and went farther their first time. So you too can do it. I think theres a member (Trad) living in CA who has a cam for sale, might even have rockers... ( http://forums.sohc4.net/index.php/topic,164474.0.html ) It's a 650 cam and it will fit your bike. You'll just need a different tach gear and gauge.

[lrutt]

I'd also replace that cam chain as it has seen a lot of stress. Pretty strange failure to be honest.

[calj737]

Ear is broken (to the best of observation). Are you suggesting it can be salvaged ?

The ear can be welded back on. The cam lobes show significant wear, and I wouldn't reuse it as is. It is a viable candidate for hard weld, and will be a suitable core after the ear is welded on.

[DaveBarbier]

Other options are to get another 550 motor that runs and drop it in your frame while you fix/upgrade this one. Or...of course there's the 650 swap which drops right into your frame too . Sometimes it's cheaper to get a whole bike that's been sitting instead of getting individual parts. My 650 donor cost $300.

[Can550]

I feel this is exactly what happened. You are right on that. Seeing the spot where broken bolt was sitting.

I have found one camshaft locally, waiting to talk to seller in case he has rocker arms from same setup so they match.

If it is pricy, then I'll put bike in a corner and wait to come across a cleaner running motor. Thanks


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