valve clearance measurements

I checked my valve clearances today on my 82 750 seca with 4K and got some strange measurements.

Intake
.178-.127-.178-.178 mm

Exhaust
.203-.178-.203-.203 mm

sorry my gauge has strange measurement increments, metric was a second thought.

Is this ok? It seems a bit looser than spec especially on the intake side. Why is this happening?

 

Good question. Either it was set up loose or the valves aren't closing all the way; rust in there somewhere perhaps.

Have you done a compression test? That might tell us a lot.

 

no. I'll do a compression test tomorrow and post some results

How important is it for my engine to be warm for a compression test?

 

It would help, but it's not critical especially in this situation.

Do a "dry" test; a couple actually;

Then do a "wet" test (1-2 TBs of oil in the cylinder) and let's see what we see.

 

ok

compression test COLD throttle wide open

Dry
130-125-130-130

Wet
1st try
200-170-250-205

2nd try
300+ 255 - 250 - 250

 

I would try again with another gauge, however it is looking like you need new rings, at least.

 

Wow, 300psi compression!

 

ya, weird. My gauge maxes out at 300.

I would need some pretty high octane fuel for that


I think i put too much oil in the cylinder for the wet test. the turkey baster I used was deceiving.

 

The WET Test confirms your Valves are OK.

The Compression Test shows you ought to start thinking about Rings.
The 125 - 2Hole is Close to Bad.

Watch your Oil consumption and No Racing.

 

The motor has 4K on it; the rings aren't worn out, but they could be rusty as could the cylinder walls especially on #2.

If there's rust in the cylinders, then it could also account for the loose valve clearances.

Methinks you oughta pull the head and have a look. On a mill with only 4K it would be well worth a valve job and rings if the cylinder walls are salvageable.

 

this is just terrible news.

I'm not burning or loosing or leaking any oil.

how many hours to pull the head?

Can i reuse the head gasket?

 

Sorry; but it's a low mileage motor that sat. Something's not right in there, not with those compression numbers and the strangely loose valves.

You can have the head off in an hour; go read your manual through about 4 times on that procedure.

Basically you pull the cams, tie the chain out of the way, and undo the bolts and nuts. Reassembly is a tad finicky but nowheres near as bad as trying to line up FOUR pushrods with their cam followers and rockers as you lower it back on. (Norton.)

You might be able to reuse the head gasket, especially with that low mileage; however you may find the "flame rings" on it are rusted too. There are some o-rings on a couple of the bolt holes you should replace.

I'm just making an educated guess based on rude (Triumph) experience about the rust; I hope I'm full of it and you find a nice clean motor. Unfortunately, it's a real logical explanation for loose valves and low compression numbers on a low mileage motor.

There IS only one way to find out...

 

i just read the manual. It doesn't look bad.

I'm not sure I understand the part about tying the chain out of the way but hopefully I figure that out when I get there.


I could do a leak down test if that helps. But it looks like the amount of time its going to take me to drive across town to collect my tester and a air compressor I could have the head off anyway.

 

A leak down test will just add to the mystery. I'm afraid the best course right now is a good ol' visual inspection.

You tie the chain up to keep it from disengaging from the sprocket on the crankshaft. I like to use a mini-bungee or two to maintain tension on it, yet still easily unhooked.

Be sure to let us know how it looks; maybe some pics.

 

I sold a parts bike (Venture) that had been sitting for years. The new owner was going to use the engine in a project.

When he checked he found low compression on two cylinders. On a tear down he found that the rings on those two pistons were loaded up with sludge. The bores still had the original hone marks and measuring the ring end gaps showed no sign of ring wear.

He cleaned the crud off the rings and piston grooves, did a light hone on the cylinders to break the glaze and reassembled. Compression all fixed.

 

well, i got the head off. Only took about an hour because I already had the valve cover and tank off.

Looks like the head gasket took a beating and separated. I didn't remove the cylinder section because I didnt want to ruin that gasket too if i dont need to.

Close inspection did show a VERY slight rusty color on the cylinder walls. Unfortunately everything is oil soaked from my wet compression test.

I don't know what to look for so i took some pictures. I didn't know what to take pictures of so i just took random shots. Sorry the lighting is terrible in my garage. I'll get some better ones in the day light in a few days. Please make requests of what needs to be documented.

 

In the very last pic, see that valve that's all bare nekkid and dry? That one's been hanging open from the looks of things.

The good news: There's no really bad news here.

The bad news: You got some work to do but nothing is F*ed.

I will elaborate later my dinner is on fire...

 

Since you saved all the Labor Charges by removing that Cylinder Head by yourself, ...
You ought to treat yourself to having a Machine Shop inspect the Valve SEAT on that one Clean one you have there ... and report to you on the condition of the one opposite it.

If you have the Tools; you can remove the Valves and service the Head.
Wire Brush the valve Stems
Clean the Combustion Chambers
Lap the Valve Faces into the Seats.

You're going to need a Valve Spring Compression Tool.
You may need one or two Valve Faces and Seats cut.

I don't know how you want to get-into this, yourself.

 

how much does this service run at a machine shop?

I've done valve springs and seals on one of my cars before. But never any lapping and I don't know how to tell if any of the seats will need to be cut.


What would you call this diagnosis? Burnt valves? And more importantly, how would something like this happen?

 

carbon build up will not allow valve to shut & so dissipate the heat back to the head.
Carry out a visual inspection to se if the valve & seat are badly pitted.
To lap the valves you will need coarse & fine grinding compound & the tool to rotate then back & forth. When they are lapped you will see a dull line around the valve & seat.
Did you fit new valves to your car without lapping them in?

 

Last time I had a Head done ... it was to Burn-out all the Broken Cap Screws and re-tap the holes.
Install new valve Seals
Lap or Reface as needed: $265.00

The Exhaust Valve got hot enough to burn-off deposits.
What kept the Valve open?
Is the Valve SEAT scorched?

There are several reasons or more.
Buildup on the Stem
Tight Shim Clearance
Particulate stuck to the Valve Face of Seat.
Burned Seat.
(You found it early enough that the Valve didn't actually get Burned-away)

 

When I did valve seals on my car I didn't even have to remove the head.

I'm going to make contact with some machine shops today to see what they can offer.

If I can't find a reasonable price, what kind of valve spring compressor works best with these heads?


For the record, I put over 1000 miles on the bike since I got it, and I'm pretty sure it came this way. It ran good, always started, accelerated fast, and idled "pretty" well. The only problem was a random backfire on the intake side at idle.

 

Not a good vehicle week for me. My fuel lines went in my car today. Kinda stranded now.

Anyway, further inspection showed this lovely wear on my cam shaft.

 

URK. Somebody ran it out of oil (or low on oil.)

Get another cam from a reasonably low-mileage motor off eBay, and don't fret it. It'll outlast the bike. The journal isn't toast, it just has a couple of new oilways. Seriously, the damage isn't on the real bearing areas of the journal, it will survive. Just be sure when you smooth out the "ruts" you don't gouge up the nicely polished bearing surfaces.

You can disassemble, clean, and inspect the head and valves and decide then if you need professional intervention. You might just need to lap a valve or two, the special tool for that costs about $5. (A valve "stick.")

You need the type of valve spring compressor that is a "tube" with the sides cut out; there should be a pic in both the Clymer or factory manuals.

Really sorry to see this, that kind of damage on a low-mileage mill makes my tummy hurt. RPGoerlich got ahold of a 550 max with something like only 5000 or 7000 miles on it that two holed pistons.

The good news is you should be able to resurrect it without spending horrible amounts of money and once done it will last a good long time.

 

Update

Found and visited a machine shop. Showed them my cylinder head and the machinist suggested that he didn't really see anything wrong with it. He said that clean exhaust valves were normal on air cooled motors. He also wasn't concerned about the cam journal or cam and said he could polish it out.

He recommended getting the head resurfaced and a cleaning for $250 +. If I wanted he would cut the seats as well for a total of $450+

Too much $$ for me right now, and I want to see the valve seats for myself.



Found my valve spring and retainer removal tool (it puts them back on too but I don't weigh enough to compress the springs) and pulled one of the exhaust valves.

Valve seal looked good
Guide had no play
Lapped that valve so I could inspect the seat which looked flawless.

Did find an awful lot of carbon build up in there though for only 4000 miles. At least a mm thick. I need to find a safe way to remove it all, I think this may be related to my problem.


Also, where do the yics ports exit within the intake port? I was looking into them with a flashlight and they all seemed like dead ends.

 

Since you have the Head off and the Machine Shop told you not to sweat the Cam Journal, ... keep doing what you can by yourself.

Wire Brush the Combustion Chambers and Valve Bottoms.
De-Carbon the Head and Valve Stems.
Install NEW Valve Seals
Lap all the Valves.

Those Double Return Springs are a fight.
Don't let that get in the way. Find a strong teenager to help with compressing those springs.

A smart whack on the top of the Valve Stem with a Ball Peen Hammer will loosen the KEEPERS.
A strong Magnet helps-out when you have the Spring compressed.

Mark two CARDBOARD Sections: IN & EX 1 -- 2 -- 3 -- 4
Push the Valves through a stabbed hole with a screwdriver.
Let them be held tightly by the Cardboard so there is NO Mixup.

Goggles
Wire Wheels
TIGHT Fitting Leather Gloves.

I chuck a Wire Wheel into my Drill and put the Drill in my Vice.
Run the Drill at High Speed with the rotation downward.
Wire Brush each Valve Stem and Face ... free of ALL Buildup.

Heavily MASK the Valve Seats and remove Buildup from the Ports.
Vacuum.

Lap all the Valves.
Buy a Double-ended Tool.
The Suction Cup on an Automotive Lapping-Stick is too large and causes difficulty.
If necessary, ... the Large Cup can be trimmed-back.
If the Cup slips-off use a little-bit of Denture Gel.
Oil the Stem.
Rotate the Valve to and fro when inserting it through the New Valve Seal.

Wipe the Valve Faces and Seats clean of Lapping Compound.
Don't use water.
Use Kleenex and WD-40

When you have all the Valves back in the Head, ... SEAT the Valve Stem Keepers by Tapping on the End of the Valve Stem with a Ball Peen Hammer.

 

Which cam is that? If it's the Exhaust cam I have one for the 750 Seca.

 

Its the exhaust cam. I am going to try to run the one I have but if that doesnt work out or I change my mind I'll keep you in mind.

Thanks

 

finally had some time to pull the valves, clean the head, lap the valve seats and reassemble.

All the seats looks very nice. no defects of any kind on the seats or the valves. lots of carbon as I mentioned before which I removed and am hoping is related to my problem.

further inspection of the cam journal revealed a spec of something stuck, or some sort of build up on the journal, enough so that my finger nail can catch on it. Is there any safe way to grind this with a dremel?

 

I wouldn't.

That cam is torn up. Take Richard up on his offer; the journal isn't in bad shape but the cam is pretty nasty.

 

Sorry, wasn't clear. Its the bearing surface on the head itself that has the build up.

 

+100-squared on the Fitz recommendation......

 

Sorry; you're right, I didn't catch that detail.

However, the cam still looks scary, the journal isn't damaged in a critical area.

The machine shop offered to polish out the journal for you didn't they? I would let them do it if they're not going to hammer you an arm and a leg for it.

Get the replacement camshaft, and take it, the head and the caps to the machinist.

 

A trip to the machine shop means removing the valves again doesn't it.


Anyway,

I can't get the shim buckets back over the valve springs. I don't think the valve springs are perfectly centered. Any suggestions?

Also one of the shim buckets is rainbow colored from the heat. Cool, not cool?

 

strange days

checking shim numbers and I can't read some of the exhaust ones. All I can read is a Y2 something something. So I measured them with my micrometer and... the ones that do have numbers don't measure up.

checked the intake shims and they do measure correctly.

 

Use the actual measurements of the shims (assuming you have accurate calipers) as the basis for making your "needed shim" calculations, rather than what is printed on the shims (whether you can read those imprints or not).

The imprinted number is what they should have measured, when new.

After lots of pressure and lots of miles, they may not still be that thick.....


Your measured valve shim clearance is an actual measurement, though.

The amount that you need to open up (or close up) that clearance is going to be based on the real, actual, measured size of the shim that currently inhabits that bucket, rather than the "marked" size.

 

there are pieces of the old head gasket dried onto the head and jugs. Any tips for cleaning this off?

Ive been working at it with a razor blade with minimal success.

 

NAPA sells head gasket remover spray - - be careful !

Pick up a tub of elbow grease too !

 

great thanks.