Topic: Pinned rocker shafts cb500

[calj737]

Why would a warped head cover even be considered a candidate for this?

Its not about a warped cover, its about shafts out of round or out of spec. And they are a diminishing product since they are not being remanufactured. Some type of "fix" may become necessary for an owner who has one, but no source for a replacement. Simple as that.

I see not a thing wrong with ideations on how to repair or upgrade stock parts to address wear or design flaws. I just wish I had the expanse of time to tinker with these ideas on how to provide a fix, and at a reasonable cost.

[alacrity]

Funny. I began a response with PRECISELY the same phrase, "It's not about a warped cover...."  Haha.
Here's video I just shot showing the problem precisely.  This just came in via eBay. Seller said it was in very good condition.  Cam journals are perfect, the rocker faces are all good if not great.  This one has the short shafts.  And on the intake side, same place my current one has a problem, I have this really ugly fat wiggle.  So this cover is garbage until I can figure out a machining/bushing solution.

video is here:  https://vid.me/e9RD

[FunJimmy]

Funny. I began a response with PRECISELY the same phrase, "It's not about a warped cover...."  Haha.
Here's video I just shot showing the problem precisely.  This just came in via eBay. Seller said it was in very good condition.  Cam journals are perfect, the rocker faces are all good if not great.  This one has the short shafts.  And on the intake side, same place my current one has a problem, I have this really ugly fat wiggle.  So this cover is garbage until I can figure out a machining/bushing solution.

video is here:  https://vid.me/e9RD

It look simple enough but what tolerance does the inside bushing have?

[alacrity]

No idea. I am neither a machinist nor engineer.  Just a creative mechanic with a problem that needs solving

[FunJimmy]

Sorry. I wasn't very clear with the previous question. The outside shaft/bushing clearance is obviously loose as shown in the video.
It looks like a simple fix as the OP (and others) have suggested but what condition (clearance) does the other (inside) shaft bushing have?
I would expect them both to be out of tolerance and that would complicate the simple bushing replacement suggestion.

[alacrity]

It seems to me that the inner tunnels retain their shape because of all the metal around them... the supporting structure is stronger.  These all seem to have a problem in the same place... around the Number 1 piston intake side.

[RAFster122s]

I've wondered if it would require you to mill for a bushing for the entire path of the rocker shaft. Could you get away with milling or drilling and reaming from the outside to only cover 1/2 of the #1 and #4 rocker shafts?
Once they start wearing their oval shape into the cover, then you start wearing the rocker arm adjusters and the rocker faces as well as the cam.

Being able to fit the longer shafts into #1 & 2 and #3 & 4 could stablize the shafts by their longer length.

Maybe my idea is full of smelly excrement...just seemed like it could be a viable fix.  But, to make it viable cost wise you would have to have access to the machines and have the training to do it, or have someone who basically wanted to work for free for a better good of CB owners.  Not likely.  Given the one resource that we all have which is limited and non-renewable is time.

David

[calj737]

The length of milling has little to do with the expense.

[RAFster122s]

Cal, very true, the setup is the huge time sink, but the cutter lengths are a challenge and I was just thinking of how to minimize the length needed for the bushing operation.  Maybe a solution before they go bad is to rework it so they can accept long shafts instead of short shafts. It won't be as easy to wear a long shaft due to the moment arm involved and the added surface area.


But, as long as you can get the '77 and '78 cam/rocker covers, that is by far the best solution.


I'm looking for one of the late covers but don't have a lot of funds for one to outbid anyone when they go for well over $100 on ebay.


David

[scottly]

This same topic came up a few years ago, and the least expensive repair appeared to be using set-screws from the outside of the cover to force the shafts down into the bottoms of the bores, where the wear is the least. IIRC, the question was if there was enough material for threading the screws to support the load of the valve springs? I offered to see if it was a feasible repair, but no one was willing to sacrifice a cover to the cause.

[That 70s Bike]

Problem is Honda didn't design it to sabotage...they just took a long time to figure out a good fix.
Like most any company, they learn from their mistakes or they go out of business.  Honda apparently has been able to learn enough to continue to have a motorcycle company.

Not wanting to argue...and I'm not going to.  Just merely pointing out a fact that hind sight is 20-20. 
These bikes were made in a era where the methods and materials and knowledge was growing at a healthy clip. Honda started using thermoplastics long before other companies and learned how to do them well. It lowered their production costs in time.  They employ other techniques and methods to improve over time.  They never set out to put out an inferior product, few companies do...it could be argued today that several companies or entire segments of industry do produce product that is inferior or has designed obsolescence to sell future units.  That mindset changed a few decades ago...

If anyone has a later ('77-78 CB550) cover they want to sell, I have my hand up wanting one...

David

Indisputable fact is: during this time the 750's shafts were locked from movement. They knew why they did this and why they did not for the CB-500/550 for 6 of the 8 year run. Foresight not hindsight.

[calj737]

I've got one of each (early and later model) sitting in boxes. I'll have to examine them now that my curiosity is up for some measurements and ideas.

And no, the later model is NOT for sale. 

[strynboen]

Problem is Honda didn't design it to sabotage...they just took a long time to figure out a good fix.
Like most any company, they learn from their mistakes or they go out of business.  Honda apparently has been able to learn enough to continue to have a motorcycle company.

Not wanting to argue...and I'm not going to.  Just merely pointing out a fact that hind sight is 20-20. 
These bikes were made in a era where the methods and materials and knowledge was growing at a healthy clip. Honda started using thermoplastics long before other companies and learned how to do them well. It lowered their production costs in time.  They employ other techniques and methods to improve over time.  They never set out to put out an inferior product, few companies do...it could be argued today that several companies or entire segments of industry do produce product that is inferior or has designed obsolescence to sell future units.  That mindset changed a few decades ago...

If anyone has a later ('77-78 CB550) cover they want to sell, I have my hand up wanting one...

David

Indisputable fact is: during this time the 750's shafts were locked from movement. They knew why they did this and why they did not for the CB-500/550 for 6 of the 8 year run. Foresight not hindsight.

yes ,,,but at same time 400 vas made vith absolut no problems..just a sleigtly better oiling system(sprayers in the cam areia)..but ok a smaller engine ..less pressure at the../valvet lifters.

[alacrity]

again - what value is there in raking Honda over 40 year old coals?
Let's figure out how to FIX the problem now...

[BomberMann650]

There have been a couple of simple tricks shared on here.  Tricks to keep the good valve covers good at least.

Though not everyone knew about the extra o-ring method before.  As evidenced by the wandering rocker shaft on my recently acquired motor core. 
Oh well, I bought it because the cooling fins had nary a mark on em.