[Ace44]

Tore down my CB500T to address some oil leaks, and to investigate why my I could never fit a feeler gauge between my right exhaust cam and rocker. Well I guess I've found the ugly truth. For some reason one of the two PO's replaced the right exhaust valve with a different, taller valve for who knows why. This in my mind explains why I never had clearance for a feeling guage [taller valve] and why the damn thing never ran right. An always open exhaust valve sounds like it would do it.

So I'm using this post to ask a few questions, I'm thinking of buying a used exhaust valve on fleabay and getting a machine shop to lap all of my valves. Ok to just replace the one bad valve? First time tearing an engine down...

Secondly how the hell do I remove the valve stem seals? I've tried to grab at them with pliers but they keep slipping off the metal ring imbedded within the seal, any trick to remove them?

Finally does my hypothesis sound right? Would a too tall exhaust valve cause a bad idle and running condition and cause white smoke to be burnt when running?

Below are the pictures of the removed valves and an example picture of the stem seal I cant remove. Thanks!

 

[PoiPio]

Seal factor is... oh boy, what to do now if no seals are available. See if this makes sense. The valve guide is worn at a fore and aft feel pulling it to the back wheel, change directions to the front wheel direction. The angle of the valve opening is that pushing down and that curve of the cam pushes it to that one side.

So when this happens, the stem of the valve opens or moves the lip of the seal. This lets oil enter and be sucked in via the intake stroke. Vacuum like electricity finds the shortest path, and this weak area brings a liquid into the firing chamber, lights off oil, and you see a momentary puff of smoke and go away after startup.

The oil will run down the guide and stem, flow down the stem, and sit around a closed valve with a ring of oil. It is about to be washed off with the gas entering, the boom, the smoke, the eventual stop. Say you want to buy a used car/bike. Find an incline, lift off the throttle, you are following the vehicle behind. Then when it accelerates a puff of smoke occurs and clears up. That's worn valve guides.

Startup the vehicle and it puffs like a chimney and does not stop, that is poor ring seal, and/or a wide ring gap past its serviceable limit. That gap and/or weak tension at the oil scraper (middle) ring, can no longer push the oil into the oil control (deliberate open gaps) of the ring to dump into. This is a worn ring. Make sense?

Theory above, the even now to happen to the guide seal. Run without, why put it together at all. One 'think' I didn't point out, but it is going to make all the sense in the world is buy a tank bag. The burning of oil when running is not noticeable with worn guides. We are back to every 4th stroke is sucking out oil and burning it one stroke at a time. Thus the oil cans and where to put it while stopping for gas.

Find seals before swine. Pork feed is now light sweet crude thrown at them.

 

[450roo]

I have tried a few times to remove the valve seals but most times the old seal did not survive. There are valve seals available on the net, but make sure they look like the ones on your engine, I have seen seals advertised as for a Honda cb450k but pictures showed they were definitely not. While the head is off the bike it makes sense to replace the valve guides if needed.

 

[Ace44]

Seal factor is... oh boy, what to do now if no seals are available. See if this makes sense. The valve guide is worn at a fore and aft feel pulling it to the back wheel, change directions to the front wheel direction. The angle of the valve opening is that pushing down and that curve of the cam pushes it to that one side.

So when this happens, the stem of the valve opens or moves the lip of the seal. This lets oil enter and be sucked in via the intake stroke. Vacuum like electricity finds the shortest path, and this weak area brings a liquid into the firing chamber, lights off oil, and you see a momentary puff of smoke and go away after startup.

The oil will run down the guide and stem, flow down the stem, and sit around a closed valve with a ring of oil. It is about to be washed off with the gas entering, the boom, the smoke, the eventual stop. Say you want to buy a used car/bike. Find an incline, lift off the throttle, you are following the vehicle behind. Then when it accelerates a puff of smoke occurs and clears up. That's worn valve guides.

Startup the vehicle and it puffs like a chimney and does not stop, that is poor ring seal, and/or a wide ring gap past its serviceable limit. That gap and/or weak tension at the oil scraper (middle) ring, can no longer push the oil into the oil control (deliberate open gaps) of the ring to dump into. This is a worn ring. Make sense?

Theory above, the even now to happen to the guide seal. Run without, why put it together at all. One 'think' I didn't point out, but it is going to make all the sense in the world is buy a tank bag. The burning of oil when running is not noticeable with worn guides. We are back to every 4th stroke is sucking out oil and burning it one stroke at a time. Thus the oil cans and where to put it while stopping for gas.

Find seals before swine. Pork feed is now light sweet crude thrown at them.

Ok... so I understand your explanation about how an oil leak can be attributed to worn valve guides, and I understand your explanation about how a constant amount of oil coming out is bad/worn piston rings. Your last paragraph says that a worn valve guide isn't noticeable when riding [ie doesn't produce a noticeable amount of smoke]
So... you are thinking that its my rings that have gone bad? I presume? Not even gonna try and decipher your last comment. Thanks for the response however. The rings are brand new looking and a nice crosshatch is on the cylinder walls, but I'll check if its over the service limit/needs oversized pistons as the ones in it are the original pistons just shined up clean. Perhaps the previous owner who took a crack at this thing when a little ham on the crosshatching?

I have tried a few times to remove the valve seals but most times the old seal did not survive. There are valve seals available on the net, but make sure they look like the ones on your engine, I have seen seals advertised as for a Honda cb450k but pictures showed they were definitely not. While the head is off the bike it makes sense to replace the valve guides if needed.

Oh I definitely have replacements, but can't figure out how to remove them without absolutely marring up the valve guides, were they stuck on pretty good on yours?

 

[PoiPio]

The problem is the valve seat cut. It's when that guide is changed, I'm not sure if the arch range of the cam to follower will be that wide [built in] to set that small gap needed?

See how difficult with that little bit of a growth of valve stem, is not having enough to adjust out? Your out, 'if you decide to take this mission' is to listen to turtle, meaning if it was my bike? Probable buy that 450 valve is one. If sold, I'd have at least the top of the valve ground down, will still clear the spring retainer when in operation, do not even lap any valve.

Twist? The seal can't be that hard to get off. Last thing you want is to crack the guide. Here is my trick for wiping off carbon with a paper towel. The ratio is 1cup vinegar to 1 ounce of hydrogen peroxide. Must have the oxy mixed in to help the vinny. I found vinny alone just does not cut it [pun].

So it's dip the valve in a cup of mix, up to where the stem is not carboned up. The head goes in a bucket of vinny and oxy. This will expand any rubber [useless] and see if that pops off easier. Second bird killed is the carbon in the head and ports, will soften up [sitting for a few days], as you pull it up, give a towel wipe, and see if the carbon needs more time.

Steps refreshed:
1. Buy the correct valve.
2. Retainer and valve keepers on both OEM and aftmrk valve. Notice height, then match height to the OEM.
3. Do not mess with any replacement or cutting of seat or guide.
4. Assemble head and wet test.

Cylinder to piston clearance: 0.03 - 0.06mm.
Valve stem to Guide clearance:
EX: 0.018 - 0.042mm
IN: 0.012 - 0.036mm

I sort of showed a smoking habit can exit two ways and not answer either or. I more answer in the 'why' it occurs, where you have to decide which it is. So now I check the second part of the top end rebuild as who is still 'within its serviceable limit?'

I'll take the 0.06mm feeler gauge, and ever so soft, insert it at the piston skirt and position it at the bottom of the bore. Figure that's the fast and easy way to see if the piston is past it's serviceable limit and just buy a set of rings to close the gap, no bore, new pistons and all that machined crap.

And I'm talking the how-to feel that feeler gauge. It either slides under the door or not. That push is not buckling the leaf of the blade going in. That gap can read 0.059999999999999999 an that 0.06 will not fit in. So if it wont even slip in between that gap, it's not out of spec. And for the visual as far as a feel for it, the push is as if the head of your digit pushed into a straight razor... that's the soft push, Only the squid's touch does it bleed and buckles the blade.

Signed,
Throw away bike builders, get the junk back up and running in the cheap seats club

NOTE:
I just refreshed a 30yr old sitter. The carb's rubber boots sit on top of the engine and is not exposed to fresh air. It is heat sunk so the supple is cooked out of it. Could not budge the carb bank due to the hardness in that type of environment. Had to literally razor cut the boots to get the bank off the engine. I think that is where your are at is it's as hard as a stone.

When I used the vinny on a rubber tipped float needle, the vinny expanded the tip right off. So to loosen the spring next time I dipped just the bottom where the spring is and the vinny/ox loosed those up and reused them. Still going after shaking it down and found no gas or oil leak, just one fork seal leak. Of course changed both seals as set like any other sets on the bike like tires?

 

[450roo]

Ok... so I understand your explanation about how an oil leak can be attributed to worn valve guides, and I understand your explanation about how a constant amount of oil coming out is bad/worn piston rings. Your last paragraph says that a worn valve guide isn't noticeable when riding [ie doesn't produce a noticeable amount of smoke]
So... you are thinking that its my rings that have gone bad? I presume? Not even gonna try and decipher your last comment. Thanks for the response however. The rings are brand new looking and a nice crosshatch is on the cylinder walls, but I'll check if its over the service limit/needs oversized pistons as the ones in it are the original pistons just shined up clean. Perhaps the previous owner who took a crack at this thing when a little ham on the crosshatching?



Oh I definitely have replacements, but can't figure out how to remove them without absolutely marring up the valve guides, were they stuck on pretty good on yours?

Yes brute force to get the old seals of off!

 

[Ace44]

The problem is the valve seat cut. It's when that guide is changed, I'm not sure if the arch range of the cam to follower will be that wide [built in] to set that small gap needed?

See how difficult with that little bit of a growth of valve stem, is not having enough to adjust out? Your out, 'if you decide to take this mission' is to listen to turtle, meaning if it was my bike? Probable buy that 450 valve is one. If sold, I'd have at least the top of the valve ground down, will still clear the spring retainer when in operation, do not even lap any valve.

Twist? The seal can't be that hard to get off. Last thing you want is to crack the guide. Here is my trick for wiping off carbon with a paper towel. The ratio is 1cup vinegar to 1 ounce of hydrogen peroxide. Must have the oxy mixed in to help the vinny. I found vinny alone just does not cut it [pun].

So it's dip the valve in a cup of mix, up to where the stem is not carboned up. The head goes in a bucket of vinny and oxy. This will expand any rubber [useless] and see if that pops off easier. Second bird killed is the carbon in the head and ports, will soften up [sitting for a few days], as you pull it up, give a towel wipe, and see if the carbon needs more time.

Steps refreshed:
1. Buy the correct valve.
2. Retainer and valve keepers on both OEM and aftmrk valve. Notice height, then match height to the OEM.
3. Do not mess with any replacement or cutting of seat or guide.
4. Assemble head and wet test.

Cylinder to piston clearance: 0.03 - 0.06mm.
Valve stem to Guide clearance:
EX: 0.018 - 0.042mm
IN: 0.012 - 0.036mm

I sort of showed a smoking habit can exit two ways and not answer either or. I more answer in the 'why' it occurs, where you have to decide which it is. So now I check the second part of the top end rebuild as who is still 'within its serviceable limit?'

I'll take the 0.06mm feeler gauge, and ever so soft, insert it at the piston skirt and position it at the bottom of the bore. Figure that's the fast and easy way to see if the piston is past it's serviceable limit and just buy a set of rings to close the gap, no bore, new pistons and all that machined crap.

And I'm talking the how-to feel that feeler gauge. It either slides under the door or not. That push is not buckling the leaf of the blade going in. That gap can read 0.059999999999999999 an that 0.06 will not fit in. So if it wont even slip in between that gap, it's not out of spec. And for the visual as far as a feel for it, the push is as if the head of your digit pushed into a straight razor... that's the soft push, Only the squid's touch does it bleed and buckles the blade.

Signed,
Throw away bike builders, get the junk back up and running in the cheap seats club

NOTE:
I just refreshed a 30yr old sitter. The carb's rubber boots sit on top of the engine and is not exposed to fresh air. It is heat sunk so the supple is cooked out of it. Could not budge the carb bank due to the hardness in that type of environment. Had to literally razor cut the boots to get the bank off the engine. I think that is where your are at is it's as hard as a stone.

When I used the vinny on a rubber tipped float needle, the vinny expanded the tip right off. So to loosen the spring next time I dipped just the bottom where the spring is and the vinny/ox loosed those up and reused them. Still going after shaking it down and found no gas or oil leak, just one fork seal leak. Of course changed both seals as set like any other sets on the bike like tires?

Hey PoiPio, thanks for the very informative response, I've bought a cheapo used correct valve off fleabay and I'll probably either get a local machine shop to lap the all of them or I'll just home gamer DIY just the "new one" it if they aren't open after Christmas. Thanks for the recommendation about using vinegar and peroxide combined, ill use that tomorrow.

You've been in this "business" for a long time I'm guessing, thanks for passing down some information to me. I appreciate the help.

 

[PoiPio]

Ace, anytime, and yes I've been at since I was 14; from making my own lawnmower driven bike, to pitting for a race team for years, meaning currently. I sent off my nephew's crash bike all rebuilt new, yesterday. These were my bread and butter years, so I can put some of these bikes together in my sleep/blindfolded.

Schooled myself on fuel injection. So I can pretty much walk up to any year bike and figure it out to run again. I offer my experience, and sign off as NOLTT. Those who listen my not struggle as hard at it, but mostly they don't.

Signed,
NOLTT (no one listens to turtle)

 

[Montanabill]

Another interesting post full of responses.

Beware using too much force getting the old valve seal off. On other bikes I have broken valve guides popping off seals.

When you get your new valve guide seal and valve installed.... install the valves, torsion bars and cam in the head and check to see if you have clearance. Do this before you assemble the engine etc. Someone could have recut the seat and that will really cause problems if they went too deep.

Try to find some valve lapping compound and you can lap your own valves in after you have cleaned the carbon.

Do you have a master link and riveting tool to put the cam chain back together....i have seen them butchered by people using a hammer and back up piece of metal.

If the clearance on your pistons is too loose the bike will smoke.....a lot. Get some extra long feeler gauges and lay them in the cylinder then try to slide the piston thru. Find out your measurements you need to hit and buy the guages from a tool truck individually or possibly on line. I have bored multiple cylinders in multiple machines starting in 1973, Not a perfectionist but a line mechanic that has made a living fixing other peoples motorcycles.

Amazon.com: Stainless Steel Feeler Gauge Measuring Tool Dual Marked Metric and Imperial Measuring (0.038-1.02 mm,25 Blades) : Industrial & Scientific

Amazon.com: Stainless Steel Feeler Gauge Measuring Tool Dual Marked Metric and Imperial Measuring (0.038-1.02 mm,25 Blades) : Industrial & Scientific

www.amazon.com

 

[DD23]

Cats paws then....van Norman ?

 

[Montanabill]

I have used several different varieties of boring bars and even precision hones which with care can do a good job without the danger of over boring.

For general info about some boring bars. Even if someone else is doing the work it helps to understand and if the shop knows you are going to measure the work after they are done they will do a better job......Also if you give them a dozen donuts when you drop the work off they will remember who you are.