Topic: White exhaust valve!

[KrautKoffin]

Took my exhaust off to install a center stand so I could actually get some work done on the bike and found that my far left cylinder ( guessing number one) had a white build up on the valve stem. Only this valve, I'm guessing it means I'm running lean. I've never seen build up on the stem, always the face. Any input?



Thanks,
Jordan

[MCRider]

The rest of the port doesn't look lean. Maybe the valve was set too tight and was hanging open. Even a few thou will do it. Flash from the combustion blew up there and cooked the carbon.

You're doing a basic valve job I assume? That valve may test out that it's been leaking and my theory would be correct.

[TwoTired]

Leaky valve guide seals?

[lucky]

Looks normal to me.
Look at other engines and you will see what I mean.

Even when you tear down engines the exhaust
valves always look whittish like this most of the time . Very common.
The intakes usually look light brown to black.
The exhausts always look light brown to white.

And with the new ethanol fuels burning some water content this is
even more likely.

Like I say just look at other engines and you start to see what is normal.

[MCRider]

His concern/question was why is this one like it is and the other 3 are different.

So, would you (Lucky) be saying this one is normal and the other 3 are rich?

Maybe TT has it with this one being normal and the other 3 are oily from leaky stem seals?

[KrautKoffin]

Looks like I'll be rebuilding the head before I can put more miles on the bike 

[TwoTired]

Looks like I'll be rebuilding the head before I can put more miles on the bike 

For what reason?

[KrautKoffin]

Looks like I'll be rebuilding the head before I can put more miles on the bike 

For what reason?

The massive oil leaks and the different colors of valves. I can deal with the oil, but hanging valves or leaky valve stem seals scare me.

[MCRider]

Looks like I'll be rebuilding the head before I can put more miles on the bike 

For what reason?

The massive oil leaks and the different colors of valves. I can deal with the oil, but hanging valves or leaky valve stem seals scare me.

There are many levels of "rebuild". The basic should yield results you like. Disassemble, clean, replace stem seals, lap in valves, reassemble. The low mileage (it was low mileage wasn't it?) should give you guides and valves that are not terribly worn and can be reused. Let's hope. Just dirty.  IMO

[TwoTired]

Sounds like you are more interested in adventure.
Have you done a leak down test?

You can change valve guide seals without removing the head.  Have you determined that the oil passage orings and the head interface are leaking?
FYI: The number of people that can build an engine as well as Honda are few.  But, with enough time and money, nearly anyone can do it eventually.


...even me.

[MCRider]

Sounds like you are more interested in adventure.
Have you done a leak down test?

You can change valve guide seals without removing the head.  Have you determined that the oil passage orings and the head interface are leaking?
FYI: The number of people that can build an engine as well as Honda are few.  But, with enough time and money, nearly anyone can do it eventually.


...even me.

TT: you don't know the history. The OP has an exciting thread where he had to light fires in the cyls to get the pistons out. And the head is of course already off. The rest of the engine is apart as well.

[KrautKoffin]

Sounds like you are more interested in adventure.
Have you done a leak down test?

You can change valve guide seals without removing the head.  Have you determined that the oil passage orings and the head interface are leaking?
FYI: The number of people that can build an engine as well as Honda are few.  But, with enough time and money, nearly anyone can do it eventually.


...even me.

TT: you don't know the history. The OP has an exciting thread where he had to light fires in the cyls to get the pistons out. And the head is of course already off. The rest of the engine is apart as well.

You must have me mistaken for the other 100 new owners on here, I'm the one that asks a million questions before tearing the motor out or breaking anything. I haven't been able to access my bike for the past month so I've been asking as many questions as possible. The bike runs lean, is a pain in the dick to start, and the PO did a bunch of 'fun' mods like pods without rejetting, a 4-1 with no back pressure (and no rejetting), seat hack job, and some wiring expirements that failed.

TT, I will be doing a leak down/ compression test soon, I read your write up on it when I first got the bike.
MC, I was planning on pulling the head in a fee months during our short 'winter' here and fixing the lol leaks coming from the pucks and head gasket.

I appreciate your guys's advice this far, what would be your next step knowing the motor is still in the bike

[MCRider]

Wow, was I off base! My bad.

[Vinhead1957]

Go to the carbs first and make sure that number one is clean as a whistle. Running that lean main jet circuit.  Have you ever sync'd the carbs?

[TwoTired]

I appreciate your guys's advice this far, what would be your next step knowing the motor is still in the bike

Let see.  Cb750, can't get the valve cover off, to get to oil leaks.  Operational issues and poor treatment by P.O.

I'd want to know how big a bite the engine needs, in time, effort, and money to be serviceable, or to start shopping for another engine.  Compression test for sure.  Leak down test, even better.
If the comp test/L/D test shows a healthy core, then I'd just focus on seals. Clean and find oil leak source(s).  If above the head gasket interface, leave the head in place when you pull the motor to fix the oil leaks.

Put engine back in and massage the carbs to atone for induction and exhaust choices.
The electrical stuff is simple for me to return as Honda intended, and they run pretty well that way.  Electrical fixing is just divide and conquer each circuit in turn.
When you run out of circuits to correct.  Go ride.  (I don't know what other maintenance the bike needs to ride safely.  But, owner's manual checklists ought to be involved.)

[thirsty 1]

I would be more concerned about the ones that are not white. Remember its a exhaust valve with 500f + running temps. I would think that your carbs are way out of balance. The more engines you pull apart the more you will see this. I'm not saying that it couldn't have been tight, but it just looks fine to me. miles? Check your carb settings and ignition settings. If it's been resurrected from the dead I'd start over with cleaning everything and resealing (including lapping).

This is my head off of my 400f with 35k and it ran great when I pulled it apart for another repair. My valves were set at .002. Sorry it's a crappy picture and I was checking for leaks so they were wet when I took this pic, but they were white when I pulled the head.

[lucky]

I would be more concerned about the ones that are not white. Remember its a exhaust valve with 500f + running temps. I would think that your carbs are way out of balance. The more engines you pull apart the more you will see this. I'm not saying that it couldn't have been tight, but it just looks fine to me. miles? Check your carb settings and ignition settings. If it's been resurrected from the dead I'd start over with cleaning everything and resealing (including lapping).

This is my head off of my 400f with 35k and it ran great when I pulled it apart for another repair. My valves were set at .002. Sorry it's a crappy picture and I was checking for leaks so they were wet when I took this pic, but they were white when I pulled the head.

Yes... this head with valves looks normal.

What you DO want to look at is the EDGES of the exhaust valves for small cracks,
or burned away edges.

[lucky]

If a valve guide seal is leaking it can just be one drop of oil per night into the combustion chamber.
IF the valve guide seals are old and dried up and leaking a little you would see smoke on start up .

What happens is the rubber cup with spring around it, (valve guide seal), usually gets a crack in the rubber cup. But the oil still has to get past the entire valve stem and guide to find its way to the combustion chamber.
The early CB750's did not have valve guide seals at all.

[lucky]

His concern/question was why is this one like it is and the other 3 are different.

So, would you (Lucky) be saying this one is normal and the other 3 are rich?

Maybe TT has it with this one being normal and the other 3 are oily from leaky stem seals?

That is possible.

[lucky]

If you go to http://forums.sohc4.net/index.php?topic=94278.0
you can see at the bottom of PAGE1 and top of PAGE 2 a new valve guide seal and a tool I made for changing valve guide seals without removing the head.

This procedure is only for engines that you know do not have other problems.

[KrautKoffin]

If a valve guide seal is leaking it can just be one drop of oil per night into the combustion chamber.
IF the valve guide seals are old and dried up and leaking a little you would see smoke on start up .

What happens is the rubber cup with spring around it, (valve guide seal), usually gets a crack in the rubber cup. But the oil still has to get past the entire valve stem and guide to find its way to the combustion chamber.
The early CB750's did not have valve guide seals at all.

I don't have any white smoke at all at start up or running

[lucky]

If a valve guide seal is leaking it can just be one drop of oil per night into the combustion chamber.
IF the valve guide seals are old and dried up and leaking a little you would see smoke on start up .

What happens is the rubber cup with spring around it, (valve guide seal), usually gets a crack in the rubber cup. But the oil still has to get past the entire valve stem and guide to find its way to the combustion chamber.
The early CB750's did not have valve guide seals at all.

I don't have any white smoke at all at start up or running

If the compression is ok and the valves are set right , I would not worry about it.
Make sure when setting valve clearance that you try inserting the next largest thickness gauge to make sure they are set right.
For instance, if it is the intake and it is .002 thousandths the try a .003 to make sure. The .003 should not fit.
A tight valve is what causes problems. A loose valve will just tick a little but will not cause any damage.