Topic: Valve Guide replacement? Need help

[Cleric40]

Hi All,

While working on restoring the head on the cb500,  I got to replacing valve seals and ran into a huge setback. First off, I couldn’t get the exhaust valves out because it appears the valve shafts have a slight bend to them. They seem to seat OK, but I can’t get them out. Next the valve guides are cracked or broken towards the top. All 4 guides will need to be replaced 

I have been searching/researching how to replace these suckers, but from what I have read it looks like a huge PITA.  From what I have gathered it’s a pretty complicated job that involves pressing them out and then re-cutting valve seats?  Some say you can heat them up and they come out easy. Any input or procedure here would help out a lot.

I have also read that many suggest getting a donor head off ebay or somewhere. Can someone shed some light on what cb550 heads are interchangeable? Anyone have one willing to sell? 

Thanks in advance!!

[Restoration Fan]

If you're already going to have to replace the guides anyway, why not try and pull the valves out?  I would put some Marvel Mystery Oil on them and gently rotate them as you try to pull them through the guides.  If it damages the guide, who cares?  You're going to have to replace them anyway.

As far as replacing the guides, I have no experience with it but MReick is a magician with these heads (I've personally seen his work on some of Bill Benton's bikes).  You might want to PM him and see about sending it out to him.

[Cleric40]

Hi Restoration,

Thats kinda what I was thinking as well but before I went yanking on them I thought I'd run it passed the experts here on the forum.

Would the valves be salvageable with a slight bend?  Could they be re-straightend out?  Could be a dumb question but figured I'd ask

Thanks!

[Restoration Fan]

Hi Restoration,

Thats kinda what I was thinking as well but before I went yanking on them I thought I'd run it passed the experts here on the forum.

Would the valves be salvageable with a slight bend?  Could they be re-straightend out?  Could be a dumb question but figured I'd ask

Thanks!

I just went through this last week on my 78K build my son is doing.  Our #2 intake valve shaft was slightly bent.  Once you got it into the guides, it appeared to be just fine in it's normal travel area but I went ahead and swapped out the valve for another one.  But I had the advantage of having Bill Benton living near me and he had some replacement ones. 

Personally, I didn't want to take a chance using that bent one so we opted for the replacement route.  You can buy replacement ones online but people like Bill Benton also have them available to sell as well.  You can PM him to see if he has some for your year & model.

[70CB750]

My 750 F3 exhaust valves were mushroomed and i had to grind ends to get them out. Also guides were shot and I replaced them and recut seats, tooling is expensive to recut at home and it is not for everybody I will admit.  Still did not start the engine cant tell if I did a good job or not.

Anyway , different head should be your best option, there are no good F3 heads out there - my only other option was to outsource it and it was not possible for my budget.

[MRieck]

Hi All,

While working on restoring the head on the cb500,  I got to replacing valve seals and ran into a huge setback. First off, I couldn’t get the exhaust valves out because it appears the valve shafts have a slight bend to them. They seem to seat OK, but I can’t get them out. Next the valve guides are cracked or broken towards the top. All 4 guides will need to be replaced 

I have been searching/researching how to replace these suckers, but from what I have read it looks like a huge PITA.  From what I have gathered it’s a pretty complicated job that involves pressing them out and then re-cutting valve seats?  Some say you can heat them up and they come out easy. Any input or procedure here would help out a lot.

I have also read that many suggest getting a donor head off ebay or somewhere. Can someone shed some light on what cb550 heads are interchangeable? Anyone have one willing to sell? 

Thanks in advance!!

Replacing the guides is as follows. The ports have to be bead blasted to remove carbon, The head is heated and the guides driven out with the proper driver. I let it cool down so I can clean the guide bores well than reheat and drive new guides in. The new guides have to have the ID's honed for proper fit. The seats have to be recut as the valve in no longer centered on the seat after the guide has been replaced.
 The bent valves are no good....you need new ones.

[Cleric40]

Hi MRieck,

Thanks for the info, that's what I expected and have read. Sounds like more than my budget can afford.

I will look for a replacement head and hope it doesn't have the same issue