Topic: '78 CB550 valve guides WAY out...

[jaydog]

Hey all,

Good news - absolutely determined why the engine was smoking!!

Bad news - Need to get some head work done. All the exhaust valve wobble way more than spec, it's almost comical. I have no idea how they could be so worn. The manual lists  0.1mm for a spec and one of my valves wobbles at least 2.0mm. The other three are somewhat less than that but man, it is way out of spec. The inlet vales all seem OK. Since is is a '78 "lean burn" and I the PO had pods on it I think it was running lean for a long time so maybe that's why...? It was smoking since I got it so I think the damage was done. There are 14,500 miles on this speedo but I received 3 other speedos with the bike so I am not positive on the miles it has seen.

So now I have a couple questions for you all.

1 - I have been trying to attack this on a budget so I have been doing as much myself as possible. Searching the site I find a some people who have replaced guides themselves by heating the head and pressing them out. I feel I could do that but I am wondering if this is worth the trouble since it seems I would need to have the valve seats cut anyway so maybe just have a shop do the whole thing. I guess I could save a few bucks replacing the guides myself but not sure it's worth it. Something I could take on or should I send it to a pro, like MRieck for the work? I don't know any local shops so I am going to google it to see if I can find a place I trust too.

2 - The exhaust valves themselves... The manual lists the specs at 5.43mm as a minimum. All my valves fall right about there, even 0.01mm less depending where and how you measure. Do I need new valves too? Seems to me like the guides were so worn maybe the valves took a lot of wear too. They appear in good shape, smooth and straight. What do you guys think?

Thanks!!

Jay

Not sure if the picture will be clear but I tried to get a shot of the worst valve guide. The guide doesn't even look like it's made for the valve it is SO much larger than the stem...

[bwaller]

For sure have the seats cleaned up, while you're at it do them all. If the exhaust guides are that bad, replace the valves too.

[dave500]

you might even find a good usable head?

[jaydog]

Thanks guys. I called around to a few local shops today. Had a hard time finding a shop that didn't go quiet when I said Honda, not HD. Anyway I am going to source some parts and get the work done once I find a good shop.

Good idea to see if I can find a decent used head. Ill go scrounge on eBay...

I am just happy that this is the only unexpected thing I have encountered on this project... So far...

[percolate]

Hey jaydog,

I have a spare head floating around in the garage. I think a couple fins have been damaged but not too bad. Came off a parts bike engine with about 16k miles on it. PM me if you're interested and I can try to send you some pics. Actually now that I think a little more, it might just be the fins on the jugs that were damaged. Dunno. Can't remember. And it's nighttime and it's cold outside. Anyway lemme know if your interested...

[Vinhead1957]

Find out where your bikeshop sends their heads out.  They often outsource this kind of work. As for new valves let them decide.  The rubber meets the road when you know exactly what you are working with.  Don't leave it to guesswork or iffy. It may be more money but it buys knowing what you have.

[percolate]

Hey I was just out in the garage and it is the jugs that have a couple broken fins. The head is dirty but in good shape. Oh and it's from a '77 550k.

[jaydog]

Thanks Percolate. I'll send you a PM. I have had some encouraging conversations with a couple local shops. I feel like have done all the work to prep the head so far and it is in good shape besides the guides. Now it just needs guides so I am inclined to complete the repair, but it depends on what I find of options on the job.

I appreciate you checking on it. The cold, cold garage is one of the things that has kept me from working sometimes this winter. I need to get a bigger heater. I have one of the single burner heaters that goes on top of a propane tank but I need to be standing in front of it for it to warm me...

[bryanj]

A used head, specialy from a forum member, is waaay cheaper than the work you need doing

[MRieck]

For sure have the seats cleaned up, while you're at it do them all. If the exhaust guides are that bad, replace the valves too.

If the guides are that loose the valves faces are hammered from valve rocking in the guide bore.

[jaydog]

I am certainly no expert, I've worked on some car engines before but this is my first Honda 550. The valve faces and seats look OK to me. They are pretty much like the intake valves and seats and those guides have almost zero valve wobble. When I get home tonight I'll try to take some photos of the exhaust valves and the seats for you guys with the experience to look at, I'm probably not looking for the right things 

Percolate has a head that is in good shape but the valves are still in it so we aren't sure if the guides are in any better shape than mine. Since it is from a '77 I have read that the '77 and '78 are prone to wearing the guides due to the lean carbs/settings.

Thanks for the help and comments everyone!

Jay

[alejandro javier]

hola saludos . para reconstruir la tapa de cilindros use esta guia ( perdon por no escribir en ingles)

[Tracksnblades1]

Thanks Percolate. I'll send you a PM. I have had some encouraging conversations with a couple local shops. I feel like have done all the work to prep the head so far and it is in good shape besides the guides. Now it just needs guides so I am inclined to complete the repair, but it depends on what I find of options on the job.

I appreciate you checking on it. The cold, cold garage is one of the things that has kept me from working sometimes this winter. I need to get a bigger heater. I have one of the single burner heaters that goes on top of a propane tank but I need to be standing in front of it for it to warm me...

Just guides…?

What about your valves..? Loose guides usually mean worn valve stems and non concentric valve faces and seats..?

A good shop will ask the right questions…..🤔

[scottly]

Thanks Percolate. I'll send you a PM. I have had some encouraging conversations with a couple local shops. I feel like have done all the work to prep the head so far and it is in good shape besides the guides. Now it just needs guides so I am inclined to complete the repair, but it depends on what I find of options on the job.

I appreciate you checking on it. The cold, cold garage is one of the things that has kept me from working sometimes this winter. I need to get a bigger heater. I have one of the single burner heaters that goes on top of a propane tank but I need to be standing in front of it for it to warm me...

Just guides…?

What about your valves..? Loose guides usually mean worn valve stems and non concentric valve faces and seats..?

A good shop will ask the right questions…..🤔

Look at the date....

[newday777]

Thanks Percolate. I'll send you a PM. I have had some encouraging conversations with a couple local shops. I feel like have done all the work to prep the head so far and it is in good shape besides the guides. Now it just needs guides so I am inclined to complete the repair, but it depends on what I find of options on the job.

I appreciate you checking on it. The cold, cold garage is one of the things that has kept me from working sometimes this winter. I need to get a bigger heater. I have one of the single burner heaters that goes on top of a propane tank but I need to be standing in front of it for it to warm me...

Just guides…?

What about your valves..? Loose guides usually mean worn valve stems and non concentric valve faces and seats..?

A good shop will ask the right questions…..🤔

Look at the date....

Post 11 was the start up today by the new guy

[Little_Phil]

He/she is suggesting using guide 12231-KFO-305 for 550K exhaust. An ebay seller is selling this P/N as being the same as 12231-429-305. Looks different to me.
Original guides to 12023-324-405 (12023-323-300) are still available.

[MauiK3]

Perhaps Hondaman has some good information he could offer on this thread? He did my CB 750 head.

[MRieck]

Perhaps Hondaman has some good information he could offer on this thread? He did my CB 750 head.

There isn't much more in the way of info to offer. Loose guides need to be replaced along with the valve. A valve job has to be done as the valve centerline shifts when a new guide is installed. The new guide will need to be honed (best method for final fit) or reamed to final size. The shorter intake guide can be used on the exhaust side to reduce the amount of guide in the port. That also applies to the CB750.
 I'd recommend Kibblewhite valves as the OEM valves are soft in comparision. Also recommend the Kibblewhite Viton  guide seals ....far superior to OEM seals.

[bryanj]

My only answer to the problem is send it to Mike, his work is superb

[rotortiller]

Valve stems that are worn will have a shoulder where the guide does not touch or rub. It is easy to see and feel with a finger nail, if you can feel it I would replace. Stems can be also checked for roundness, trueness and dimension. Valve stems that have all the dimensions within spec and that are suitable for the new replacement guides are fine. The valve tulip area and valve seat can be inspected for condition visually and dimension to see if they are pooched from the looseness. New guides get reamed to size with the valves, new seats can be cut after reaming as required. If it measures and looks good it probably is. A shop can tell you that or you can figure it out. A verdict cannot be passed with guess work and it is very easy to waste someone else's money. Bottom line is if a used part is serviceable you can install it again. Ponder this, if crankshaft bearings are worn out and the crankshaft is good, what would you do?