Topic: Valve Job Questions....

[sparkyman]

Valve job questions.... if anyone has a great link to instructions that would be helpful. I just ordered Hondaman's book, but it's going to be a while.

• • How do I know if my Valves are ok? They are pretty cruddy and a couple are rusty.
    How do I know if my Valve Guides are ok? (I'm just going to go ahead and change out the Valve seals since they're cheap)
    Is it going to ruin anything if I remove the Cam Tower studs? I'd like to finish the gasket surface.
    Is the 'fill the bowls up with gas' test the best way to check lapping
    Is there anything else I should be looking at?

thanks in advance

[BomberMann650]

disassemble the head and be careful removing the cam tower studs.
Clean everything - then you'll know what needs fixed for sure.
It's surprising how much carbon can build up on a valve and seat.  You don't want any of that crud there when you reassemble the motor.

I used a really bright flashlight to check the seal when lapping my valves.  It's surprising how much light will find its way thru.  *disclaimer* without the valve springs in place, total occlusion won't happen.  But it was enough to let me know if I had hi/lo spots.  Then once the springs were on, total blackout.  The valves will bed themselves during break in.  Lapping just helps things along.

[ekpent]

 As you lap the valves you will start to see a clean ribbon and there is also a type of blue dye that you can apply to see how things are bedding in also. On the last 750 head I did this winter I used a rubber hose chucked in a drill connected to the valve stem and with paste  lapped them in at a very slow speed with a very little bit of finger pressure. Maybe not the way the book says though 

[HondaMan]

Lift the valve about 1/4" off its seat, then measure the 'wiggle' it can be moved toward the center of the combustion chamber and back toward its port. This is Honda's "spec clearance" value. When the valves can move more than 0.0032" on the intake side, Honda says it's time for new guides: while this spec if the same for exhaust, they run OK to about 0.0050" of wiggle in real life. I have found that if they move more than 0.0025" (intakes) they start to run pretty hot: depending on how you treat your steed, this can either help keep them cleaner than normal, or overheat them. If they are more than 0.0040" (intakes) then it is DEFINITELY time for new guides.

If your 750 was made after 1972, chances are the guides are pretty loose. They switched to simple cast-iron guides early in the K3 or late in the K2 (depending on which factory made the head), which was OK when we had leaded gas: when the lead went away, so did their lube system. Ethanol turns the valve stems into lapping rods because the iron cannot descale the steel shafts without lead or at least some bromide, both which are missing in fuels with ethanol. So, replace them with bronze next time, and they will probably outlive the rest of the engine.

[sparkyman]

Your guides have a spec for play allowable in the manual. If the head is off, now is the time to have it milled flat. The head and block will have warped to some degree after thousands of heat cycles.

Drop your head and valves to a machine shop and have them check the guides and lap the valves in for you so they are dead right the first time. (My advice.

Part of me wants to take the head to a machine shop for this, and part of me wants to do this to learn for myself. I'm sort of conflicted about this.

[sparkyman]

Lift the valve about 1/4" off its seat, then measure the 'wiggle' it can be moved toward the center of the combustion chamber and back toward its port. This is Honda's "spec clearance" value. When the valves can move more than 0.0032" on the intake side, Honda says it's time for new guides: while this spec if the same for exhaust, they run OK to about 0.0050" of wiggle in real life. I have found that if they move more than 0.0025" (intakes) they start to run pretty hot: depending on how you treat your steed, this can either help keep them cleaner than normal, or overheat them. If they are more than 0.0040" (intakes) then it is DEFINITELY time for new guides.

If your 750 was made after 1972, chances are the guides are pretty loose. They switched to simple cast-iron guides early in the K3 or late in the K2 (depending on which factory made the head), which was OK when we had leaded gas: when the lead went away, so did their lube system. Ethanol turns the valve stems into lapping rods because the iron cannot descale the steel shafts without lead or at least some bromide, both which are missing in fuels with ethanol. So, replace them with bronze next time, and they will probably outlive the rest of the engine.

Thanks for this. The bike is a K8. Like I replied to Calj above, I'm sort of conflicted about doing this. I think lapping the valves and replacing the seals will be fine, cleaning it all out will be fine, I even think I can manage the head surface, but for some reason I'm second guessing the guides. I'll do some more research.

This is supposed to be my winter project, but it's only September and I'm moving right along. Maybe I need something to slow me down 

[sparkyman]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

[ekpent]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

More expensive then buying a known good one 

[uksparky]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

machine shop will charge about $300 to $400

[sparkyman]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

More expensive then buying a known good one 

Ha, fair enough! I purposely bought this one for the experience of doing it though. I'm going to do some more reading before I throw in the towel though....

[sparkyman]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

machine shop will charge about $300 to $400

That's not outrageous, but that will be a last resort I think.

[Stev-o]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

machine shop will charge about $300 to $400

That's not outrageous, but that will be a last resort I think.

I had a valve job done on my K3 last year, I believe it was around $200, no milling was done.

I like to do as much work on my bikes as possible, but when it comes to machine work, I leave it to the Pro's.

[sparkyman]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

machine shop will charge about $300 to $400

That's not outrageous, but that will be a last resort I think.

I had a valve job done on my K3 last year, I believe it was around $200, no milling was done.

I like to do as much work on my bikes as possible, but when it comes to machine work, I leave it to the Pro's.

What did you have done for the $200?

[markreimer]

I had my K4 and also my 350F valves done at the machine shop. That included pressing out the old guides, pressing in new guides, cutting fresh seats as well as the valve faces. Cleaned the whole thing up too. $200 Canadian for each one.

[sparkyman]

I had my K4 and also my 350F valves done at the machine shop. That included pressing out the old guides, pressing in new guides, cutting fresh seats as well as the valve faces. Cleaned the whole thing up too. $200 Canadian for each one.

Hmmm, if I can find a price like that, I may go that route. I'll be paying Canadian, so that's helpful 

[Stev-o]

No disrespect, but you can't surface the head to a true level of accuracy because it can be off in 0.000s. Only a mill with a DRO can do a proper job.

Some contend that a sheet of glass covered with emery paper is a DIY method, but realistically, it's not even remotely accurate enough to get it "flat". But it's up to you the level of care and quality you pursue.

Here comes my confliction again! 

What is a fair price for getting the head done, milled/valves/seats/guides etc?

machine shop will charge about $300 to $400

That's not outrageous, but that will be a last resort I think.

I had a valve job done on my K3 last year, I believe it was around $200, no milling was done.

I like to do as much work on my bikes as possible, but when it comes to machine work, I leave it to the Pro's.

What did you have done for the $200?

Included bead blasting, replacing the guides, cutting valve seats and faces and reassembly.   

[ekpent]

 I thought all that would be more then $200.00. Pretty fair to freshen everything up I guess.

[Stev-o]

I thought all that would be more then $200.00. Pretty fair to freshen everything up I guess.

It might have been $250, I dont keep receipts!
[dont want the wife to see em]

My machinist isn't cheap but he is fair.  It was on the K3 Park Racer, I havent done a valve job on the H2 yet!
[I did replace the oil pump check valves though]

[754]

Sparky if you told us where in Canada  you may have already found a place..
I see no need for a DRO on a mill to surface a head.
Most are done on head machines. But I have done them on a mill..
 I know I could do it with a sheet of glass and a big enough sheet of every  but I have quite a bit of experience  at fitting things.,

[sparkyman]

Sparky if you told us where in Canada  you may have already found a place..
I see no need for a DRO on a mill to surface a head.
Most are done on head machines. But I have done them on a mill..
 I know I could do it with a sheet of glass and a big enough sheet of every  but I have quite a bit of experience  at fitting things.,

Yep. Winnipeg.

[jgger]

I thought all that would be more then $200.00. Pretty fair to freshen everything up I guess.

It might have been $250, I dont keep receipts!
[dont want the wife to see em]

My machinist isn't cheap but he is fair.  It was on the K3 Park Racer, I havent done a valve job on the H2 yet!
[I did replace the oil pump check valves though]

Good thing, I hear those valves and guides for the H2 are about as rare as a curly haired Chinaman!

[754]

One thing, check the end of the valves for pitting, you can only grind a very small amount off , as they are not hardened through.  Easy job on a valve grinder. .
 I think lApping helps on a high mile engine but doubt it flows as good as getting everything reground..

[sparkyman]

One thing, check the end of the valves for pitting, you can only grind a very small amount off , as they are not hardened through.  Easy job on a valve grinder. .
 I think lApping helps on a high mile engine but doubt it flows as good as getting everything reground..

I'm going to try to clean everything up really good in the next day or so to get a really good look at how far gone everything is. Hopefully then I can see if there is pitting etc...

[sparkyman]

One thing, check the end of the valves for pitting, you can only grind a very small amount off , as they are not hardened through.  Easy job on a valve grinder. .
 I think lApping helps on a high mile engine but doubt it flows as good as getting everything reground..

I'm going to try to clean everything up really good in the next day or so to get a really good look at how far gone everything is. Hopefully then I can see if there is pitting etc...

Soaked the head and carbs in Simple Green HD last night and rinsed them off. I have a better idea of what I'm looking at now. I plan on more cleanup tonight with a brass brush and some paint stripper.

The head seems to have a very rough finish on it. Very odd. The carbs so far look pretty good, we will see once I get to them in a month or so.

[sparkyman]

Looking at the surface of that head, someone before you was none too carefully removing gasket material. There's heaps of scratches and gouges that I would have removed before assembly.

Skip the brass brush and use stainless steel brushes. They're softer, better, and do a far better job on removing smutz and not tearing up your surfaces.

Yes, I was surprised to find so many gouges. It actually looks like some of them are from hammering a chisel in to remove the head. Definitely a hatchet job.

I had always been told to use brass to clean things up? I've already got some brass brushes, so I'll give them a shot before buying something else.