Frustrated - head gasket leak early after top end rebuild

Well, I had to dig in and pull the top end off the XJ again, just two years and 5,000 miles after my rebuild in 2010. The gasket was wicking oil for some time in several areas around the head, primarily noticeable on the right side (#4 cylinder). I assumed it was the oil passage o-rings, but it looks like it was just the head gasket in general. There were slight oil stains outside the gasket all around the head, so I was hoping I'd find noticeable gasket failure. But I didn't. Just oil leaks.



For a short recap, 5,000 miles ago I replaced all gaskets with the top end gasket kit from Chacal, installed new piston rings and oil control rings, cylinders were honed, and valves were lapped. After reassembly, valves were of course properly adjusted, carbs were Colortuned and synced (with the YICS tool), and proper break-in procedure was followed. It ran well.

Then I started experiencing unusually high oil consumption. After changing to 4T 20W-50 (thanks, Fitz), oil consumption decreased. But still not where it needs to be. And then I started noticing oil stains on the head fins. Though I re-torqued the head bolts, I may not have done it soon enough. Could that have compromised the gasket early?

I monitored compression, and though low at break-in, it's now around 135 for all cylinders. But here's what I found on all my formerly clean pistons:



Lots of carbon buildup and flaking on all four pistons. But I'm puzzled, because the spark plugs are tan at highway speed when I do a plug chop. What am I missing here? I used copper spray-on gasket sealer (which I'm thinking about not using again, because I'm wondering if it broke down the gasket). But could it be a warped head? Incorrectly installed oil control rings? I don't want this happening again for a very long time after I get my new gasket set. Any thoughts? Thanks for reading though my ramblings.

 

valve stem seals?

 

Re: Frustrated - head gasket leak early after top end rebuil

Thanks Polock... shouldn't be valve stem seals. Sorry, I forgot to mention that when I lapped the valves I also replaced valve springs, seals, etc... the whole nine yards, top-end-wise. Though they are the original valves. Although I guess I can't rule out valve stem seals just because I replaced them.

 

+1 to the seals. That's not just plain old carbon build up. It should be way more uniform and not have so much crust. That's where most of your oil has been going. Did it blow any blue smoke?

When you did your valves did you check to see if the guides were worn?

If your compression was off more I might suspect blowby or issues with your rings. Are your cylinder walls scored at all?

When you get your new H Gasket check to see if it requires sealant-most of the new ones are specifically designed to be used w/o.

 

How many miles were on the engine before the re-ring?
Did you measure the cylinders before re-ringing?
You have to take several measurements, to be sure the cylinders are not elliptical. might be a little egg shaped and letting oil by mid stroke.
What were your compression numbers before and after rebuild?
Could very well be valve stem seals, since you have the head off any way, it's cheap insurance to replace them if that hasn't already been done.

You could have a warped head, but not highly likely. I personally do not like using the spray stuff on head gaskets. I also have never rebuilt an engine that I did not take the heads and block to a machine shop to have decked before re-assembly. There is an easy way to tell if you may need that done. You will need a piece of heavy plate glass that will cover the surface area of the piece to check. You will need a piece of 400 grit sand paper to cover the glass. Tape up or plug any area you do not want paint on. Spray a light coat of paint on the gasket mating surface. Let it dry, then lay the plate glass on the piece and sand. If you have ANY paint remaining on the block or head, take it to a shop to be resurfaced.

 

Re: Frustrated - head gasket leak early after top end rebuil

I agree that it could be valve seals -- but it seems weird that it's all four cylinders that look like this. And when I did the rebuild at 38,000 miles, I didn't have this kind of crusting. I replaced the valve seals just because I was in there, not because I had evidence of leaking at the time. Also, I'm certain I didn't mix up valves between cylinders, so I shouldn't have any "fit" issues that led to premature seal failure.

Regarding cylinder wall scoring, the walls aren't scored, but the honing pattern is still prevalent more so than I thought it would be after 5,000 miles.

I'll probably just dig in to the valves again and see what's in there. Fun fun.

 

Did you measure the cylinder bore and the new pistons to determine and check clearence? Did you also measure the ring end gaps ? Hopefully they are in spec.
Some piston rings have a orientation mark on them and need to be tward the top of the piston. I don't know if yours are like that but it is possible.

 

Re: Frustrated - head gasket leak early after top end rebuil

Regarding piston-to-cylinder clearances, I have nothing written down to prove I did measure -- but I can't imagine NOT doing it. I just can't remember. But I do know I'm not going to let any of this get by me this time (if it did last time). I do remember putting the piston rings right-way-up, though.

I also remember the machine shop that honed them saying that they were just inside the limits of out-of-roundness. Maybe I'm just out of luck with these cylinders.

 

If you were borderline "Out-of-round" and had the Holes Honed, ... you should have taken a Compression Ring and "Measured" the fit at the Ring Gap.

Set-in - squarely in the Cylinder - you use the Piston to move the Ring down the Cylinder to observe Ring Gap.

When Ring Gap is outside the limit, ... Oil Control and Compression will suffer.
If the Ring Gap is too wide you have to Graduate to the 1st Oversize Ring Set.

Sometimes you can get caught BETWEEN Sizes.
The Standard Rings are to wide at the Gap.
The Oversize Rings too tight.

In that case you carefully file the ends of the oversize Rings a little to give you the correct specs at the Gap.

 

Re: Frustrated - head gasket leak early after top end rebuil

Thanks Rick, great explanation. I'm sure I've seen that in another post, which is why I can't imagine that I didn't measure ring gaps. But at this point I'm treating this go-around as if I didn't do anything right the first time, and I'm not leaving anything to chance.

 

Before you assume rings: how do the valves themselves look, the part of the stem you can see above the head when you look into the ports? Any of them "wet" with oil or carboned up excessively? If it's a valve guide leaking you should see it on the stem.

 

you really had oil leaking two places. anything from inside the combustion chamber should have been sealed in there if the compression was good. oil from the cams would never go into the cylinders, not all of them evenly.
is that two pictures of the same two cylinders? what did the other side look like? what's the head look like? i'd like to say that spray screwed you up but how did all that carbon get there, on all four, evenly

 

I haven't gotten into the valves yet to check that, fitz. I need to borrow the valve tool I borrowed to do these the first time. I'm curious to see what's in there.

Yep, Polock, that's two pictures of the same two cylinders (#3 & 4). The other two cylinders look basically the same, except that #1 is not quite as carboned up as the other three. But it's close.

The head was carbon-covered too, but just lightly sooty, not peeling off like the carbon on the pistons.

 

What were your initial compression #'s before break-in?

cause those compression #'s if they are all right around 135 and this is a 550 that is really good. If your rings weren't gapped properly or not staggered and somehow letting the oil get past then your #'s shouldn't be that good...unless it's all the carbon build up.

I would still check your V guides to see if they are worn. And when you get in there if you find any carbon depo's on the backs of the valves you have your answer.

 

You don't need to take the valves out to see what I'm talking about. You can see the "backsides" of the heads of the valves through the ports. You should be able to see any blackening, burnt oil, etc.

 

Oh, gotcha. I'll shine a light in there tonight. For some reason I forgot they were exposed in the intake & exhaust ports.

 

Re: Frustrated - head gasket leak early after top end rebuil

The intake valves look really good. The shaft of the valves visible in each of the intake ports are nice and clean. I couldn't see any sign of oil leakage.

The exhaust ports are a different story. I can't tell from shining the light in there whether it's just carbon buildup or whether it's residual oil on the valves. Everything is just sooty black.

 

Exhaust valves should have some carbon on them, they're exhaust valves. As long as it doesn't look WET ("oily" wet,) then the valve stem seals are probably OK.

Back to the pistons and rings for a sec.

When you did the hone/re-ring, did you check the piston-to-cylinder clearance against spec?

Did you check the "side play" (actually up and down) of the rings in the piston grooves? There is a minimum/maximum clearance spec.

We've already discussed ring end gap.

 

Re: Frustrated - head gasket leak early after top end rebuil

Yes, I do remember checking the min/max clearance spec. when I did the hone and re-ring. I borrowed a bore micrometer and an O.D. micrometer from work, and everything there was in spec. I measured in several areas around the pistons and then in several areas in the cylinders (for out-of-roundness AND clearance) and everything checked out.

It's the ring end gap that I don't have an answer for -- yet.

The $100 question (in my mind) is whether that flaky carbon on the pistons is leftover from the break-in period (when compression was really low, PSI in the 90s) or whether it's still happening as a result of the poorly sealing head gasket. (In other words, should that stuff have burnt off by itself in 4,000 miles, or would it still require removal with a wire brush?) I've already checked with Chacal and oversized pistons/rings are still unobtainium if it would come to the need to re-bore.

 

Seca that is too low for initial compression. I recently rebuilt a 650 motor and the initial compression was ~125 across and after break-in ~150. Even though your rebuilding a 550 with a max of 135 it shouldn't be below 100 at initial.

Did you stagger your rings? If so then I would suspect your ring gap was too large.

Picking up used would be cheaper than a rebore.

 

A combination of Low Compression, Diaphragm Piston "Stiction" and-or Clogged AIR Siphoning Orifices on the diameter of the Main Fuel NOZZLES (Emulsion Tubes) ... would account for an abnormally RICH Mixture that would have produced a "Dirty-Burn"

If Fuel was allowed to EXIT the Main Nozzles in Droplet or Rivulet form, ... the Mixture would not produce a rapidly explosive ignition of the Mixture and the charge would not completely ignite during the Power Stroke.

Thus, producing Carbon Deposits that would collect on the Piston Crown and form a Ridge atop of the Cylinder Liner.
Additionally there would be a heavy accumulation of Exhaust Deposits on Pistons, Combustion Chamber, Valves and the Exhaust Port, particularly on the Exhaust Valve Stems and Valve Faces.

Primarily due to the Unburned element of the Exhaust adhering to the Valve Stem and Face because the Less Explosive Burn would result in Lower Operating Temperatures conducive to carbon build-up.

 

Re: Frustrated - head gasket leak early after top end rebuil

I have notice some 820cc kits floating around on ebay. Don't know what the quality is or if they are still out there but it might be worth checking into.

Massimo

 

for a 550???

I think the carbon is probably a result of the miles you ran while still running 10W-whatever and were experiencing a lot of "blowby." In hindsight, I'd say part of THAT issue was probably related to our present discussion.

If the valve stems behind the heads of the valves are "normal" then it's time to pull the jugs off again and investigate the rings/bores. I suspect either out of spec gaps or you may have installed something upside-down.

 

Re: Frustrated - head gasket leak early after top end rebuil

Thanks all. I appreciate your feedback. I agree that my initial low compression numbers raise suspicions, and my next step is checking out those rings for installation and end gap issues. I'll let you know what I find.

At first I was just irritated that my head gasket was leaking... now I'm thinking it was probably a good thing.

 

Re: Frustrated - head gasket leak early after top end rebuil

I'm one step closer to an answer (maybe the right one, or maybe just part of it).
The ring end gaps check out good. Here are the measurements with top ring first, second ring next (service limit is 0.039"):
Cyl #1: 0.018" & 0.018"
Cyl #2: 0.013" & 0.013"
Cyl #3: 0.015" & 0.015"
Cyl #4: 0.015" & 0.017"

I took the cylinders and the head to a local old-school Yamaha shop to get their observations. With the above numbers, my compression in the mid-130s, the clean valve stems, and piston-to-cylinder clearances being within spec, they saw no reason to suspect piston/cylinder issues.

They did have two potential reasons for the flaky carbon buildup on the pistons, though: me using too much assembly lube (so it would have been there from the break-in period), or the leaky head gasket.

Apologies to Len, but they had a leftover OEM top end gasket kit (surprised them AND me) that they generously sold me for $75(!). I went ahead and got new rings, also, although I probably could have reused the ones I just took off.

My final task (besides getting these pistons cleaned up and remeasured for ring groove clearance, Fitz) is to take the cylinders and the heads to a machine shop and check flatness -- maybe take a couple thou off to make sure I have a good flat gasket surface. Might even see if they can check for cracks, just in the off chance...

 

Very nice efforts and results. Your ring gaps are very good. Nice that you have an 'old-school' Yammy shop-non existent most places.

I would agree with their assessment given all the data. Although I don't think the A lube is significant. The leaky HG is never good, but I've only dealt with those on water cooled motors.

Yes to the final task. A few thou off creating the nice perfect flat surface would be a fine idea. When putting a head back on I follow the sequence but break it into one additional stage so instead of 7 ft-lbs, & 14ft-lbs, I do 5, 10, 14 and just as added insurance I stop before I do the last torque down and wait 20 minutes then the final torque. An old mech told me it lets the metal relax and seat better with the final torque. Be sure to soak parts in fresh oil and follow break in procedure like it's new and after you're done I suspect it will be...like new that is.

 

Re: Frustrated - head gasket leak early after top end rebuil

MercuryMan, thanks, and good advice on the torque. I'll do that in the stages you suggest.

If you saw the assembly lube I used (the heavy black stuff) when I reassembled the valves, you might not be as skeptical. Suffice it to say I won't be using it again in the top end of a motorcycle engine! I also won't be using the spray-on gasket adhesive on the head gaskets. Several have advised against it.

 

Add insurance.

Spray the Head Gasket with Permatex Hi-Tack Spray-a-Gasket (Copper)

Shoot some in a clean Tuna Fish Can.
"Paint" the Mating Surface on the Block and Head with the Sealant using a small Artists Brush to make the job neat.

Incrementally torque the Head to specs.
Run the Bike until it reaches operating temperature.
After the Bike cools; Re-torque the Head Bolts.

It wont leak.

 

Rick, that's actually the stuff I used that I'm now very skeptical of. It leaked. But I want to make sure there's not a flatness issue or cracks in the head (though I know that's very remote) before I blame the Spray-A-Gasket.

 

The last head gasket I got specifically stated "no sealant" although I have used it in the past with other gaskets but these were old style pressed and had no such instructions for 'no sealant.' The newer ones seem to have either been already coated or they are using some other method for achieving a good seal-of course you are right to make sure your mating surfaces are perfectly planar flat, otherwise no seal is possible.

 

Re: Frustrated - head gasket leak early after top end rebuil

Well, that answers that question... the machine shop said the cylinder head required 0.005 in. removed to get it flat. They said the cylinder block was good, however.

With the Yamaha manual listing a "less than .002" warpage tolerance, and a 0.010" warpage limit, how much stock removal could I get away with before I have to replace the head? (I'm assuming of course that it's never been machined before. I got it at 28,000 miles and it's approaching 44,000 miles now.)

I'm also getting conflicting advice: old school Yamaha shop says don't use any gasket sealer, and the machine shop and Rick say definitely use it. Hmmm. Decisions, decisions.

 

With a freshly Planed Head you can just throw-on the Gasket and hope that the Crush Sections stay gas and oil tight.

But, if you are going to wind-up that baby and live over at the right-hand side of the tach, adding Gasket Sealer or Gasket Shellac is Race Prep.

Permatex High-tack Spray-a-Gasket is well known to the High Performance Community.

Indian Head Gasket Shellac is "Old School"

Indian Head is the choice for Liquid Cooled bikes.
It's messy.
Prevents leaks.
Hardens and bonds to fill gaps and prevent leaks.
Makes removal of the Head a pain in the ass if the Head needs to come off,, again.

 

So I checked with the manufacturer of the head gasket I used last time which had "no sealant required" printed on it and they said it had already been coated at the factory. The guy I spoke with also said there are new ones with a bi-metal layer that 'swells,' his words, and they don't need sealant either. I'm not sure how that would work but who knows.

So if you get an 'old school' HG then definitely seal it, but if you get a new one I wouldn't or I'd go real light on sealant. No problem with the one I replaced w/o sealant. I was extra careful to make sure both surfaces were totally clean and smooth. Of course I would trust Rick and a machine shop over a single mechanic any day.

To the milling question. Let me first state I have not done this on an XJ motor so I can't tell you 100% for sure it's no problem. But .005" is half the warpage limit and isn't very much to remove at all. Especially when you consider that gaskets are .02 to .04 usually. Taking .005" off would change your compression ratio from 9.50:1 to 9.513:1, which is really almost no change at all. I can't see any problems with that much if it's all they need to remove. I'm suprised the machine shop can't take your specs and give you a safe limit-they should know.

 

if the limit is from .002 to .010 and your at .005, why even mess with it.
wonder why it's .002 and not 0 ?

 

I've used it on many, many head gaskets; primarily to prevent "seepage." The key for head gasket use is to: -Not overdo it, just a thin coat; and -Let it DRY thoroughly (set your kitchen timer for 15 minutes.)

I haven't seen a motorcycle head gasket with "no sealant required" printed on it; just automotive. Unless so specified, I'd use High-Tack. But go easy.

And be sure you use NEW o-rings around the RH head bolt gallery dowel pins, even if you just replaced them.

Oh, and I gotta agree with Mr. P. If you were at .005" and spec is .002 ~ .010" it wasn't all that bad to begin with. But from the sound of things ("requirED") they've already done the work. If all they peeled off was .005" you're fine.

Polock, it's probably .002" instead of zero because nothing is TRULY flat (nor truly round.)

 

He is messing with it because of the title of his post. He has exhaustively checked everything else and doesn't want a further issue with a leaky HG.

Plus if .002" is the warpage tolerance and .010" is the limit. I think that means you want the head to not have any more than .002" warpage for assembly and if it's beyond .010" then you can't machine it-it must be replaced. I don't think it's from 'a' to 'b' type spec.

Might be semantics but a head with .010" difference doesn't seem right to me, can't see that working-sounds like a leaky sieve to me.

And no nothing is ever 'perfectly' flat, but the last head I had shaved was close: .0003". Also measuring across the surface is one thing but a sudden irregularity can be much smaller (like 1/2 of spec), be easily missed and cause problems.

 

Did this bike have any head leaks prior to the first Rebuild in 2010? Can you confirm that your torque wrench is reliable? Just some random thoughts?

 

Re: Frustrated - head gasket leak early after top end rebuil

Thanks all, I appreciate the continuing feedback. I'm leaning more and more toward using the gasket sealant again, feeling like the head flatness was the real issue. But it surprises me how many people I've talked to are divided on whether or not to use the sealant. It's split right down the middle.

Adrian1- Yes, I remember that the head was beginning to show slight oil stains before the first rebuild, at 38,000 miles. I attributed it to age/mileage, and that's what began to motivate me that it was time for a top-end rebuild. You bring up a good point about the torque wrench. I don't know if it's reliable (it's the old-style needle type), but this time I'm going to either borrow a calibrated one from work or buy one of the same "releasing handle" type.

I'm still pulling the valves to check seals (which I had replaced) and guides (which I had not replaced) again, but I'll still sleep better knowing the head's flatter.

 

Making progress, that's what we like to hear.

Several of you veterans know who I am: I was the "checking cylinder compression" thread-guy quite awhile ago now for my 650. I was split right down the middle as well regarding gasket sealant. Twice I used the copper spray a gasket sealant (yes I said twice, its a long story). The last time I used Indian Head sealant Rick mentions (yes I said "last time", its an even longer story) but thought it was too big of a mess. The copper tacky spray sealant others have mentioned was easier.

I'll continue to follow this thread. I can relate to it without a doubt.

 

Re: Frustrated - head gasket leak early after top end rebuil

2 to 10 mil is probably what the factory accepted when they built it.
guy #1
guy #2
first of all #2 isn't married
but it isn't as silly as it sounds because surface finish is important too.
Fitz, a telescope mirror is flat to within 1/4 wavelength of light, that's perfect in my book

 

Well maybe P but I've had machine work done on an I-4 truck motor, a 1 cyl dirt bike, and a I-4 motorcycle (1 water cooled and 2 airheads) and all three had a minimum warpage of .002" which is .05mm. So .01" is 5 times more than any I've seen and that is .254mm-doesn't that seem like a lot of difference??

Your handyman links are funny.

Yea that's pretty darn flat.

 

Fitz, I got a whole new top end gasket set, so I'll be basically replacing everything I just replaced 5,000 miles ago.

So would it be your recommendation to use the High-Tack on all the paper-based gaskets in the set, as well as the head gasket? I'm thinking of cylinder base gasket, cam chain tensioner gasket, etc.

 

Re: Frustrated - head gasket leak early after top end rebuil

Polock,

The man in the second vid...is that a Vanheusen? Funny!
Gary

 

I would. BOTH sides of "one time" gaskets like the cylinder base gasket; and one side only of "multi-use" gaskets like the ignition pickup or clutch covers.

 

Re: Frustrated - head gasket leak early after top end rebuil

I was able to finally dig into the valves over my Christmas vacation. All the valve stems looked great, and measured round and within size tolerance using a micrometer. I was not able to measure runout, since I don't have a v-block or an indicator.

All the valve seals looked good, but as I said before I'll go ahead and replace them again since I got them in the top end kit.

The #1 exhaust valve felt a little loose, rocking a little in its valve guide (compared to the feel of the other 7 valves in their respective guides), so I should get ahold of a hole gage and measure the guide to get a proper clearance measurement.

I'm curious how loose a valve has to be in its guide before oil would leak past a good valve seal and into the cylinder. Anybody know? Not that I'm trying to avoid replacing the guide if it's bad; just trying to determine if the extra guide clearance could have potentially contributed to my increased oil consumption, or if it's unlikely.

 

The 'by the movement' test is essentially that the valve shouldn't move 'more than a little.' Basically there will always be a perceptible amount of movement, but it should be very slight. This is done by holding the valve off its seated position and trying to move or rock it perpendicular to the guide. I wouldn't worry about run-out-it's unlikely that's an issue. It's a little concerning that one is different from the others, but be sure you're doing the test the same way for each one. If you are still unsure you could take the head to the shop-they shouldn't charge you much to just measure the guides-considering you've established a relationship with them, they might do it for free or very close to.

With the amount of all over leakage you had, one 'past spec' guide is not going to do that. They have to be fairly loose past spec to leak, but the spec is where it is because if they are past they will get worse pretty fast-lot's of movement there so stress can build up.

 

Re: Frustrated - head gasket leak early after top end rebuil

Thanks Merc... the fact that one was moving perceptibly more than any of the others also concerned me, and I think I'll take your advice and just have the machine shop measure them. If the one guide's bad, I'll probably have them do the replacing and reaming, too.

Yeah, from what I've seen, I doubt it's the valves at all that caused the burnt oil crust... but I don't plan on being in there again for a really long time.

I'm more inclined now to think it was a combination of too much assembly lube, really low compression after the rebuild, and maybe rings installed the wrong way (who knows -- everything looked good).

 

Cool - you were right. I called the machine shop, and the inspection of the guides is free. If I need a new valve guide, they'll install it, ream it, and touch up the seat -- all for $12! Wow, what a deal.

 

Re: Frustrated - head gasket leak early after top end rebuil

@ SecaMaverick

OT: You a rotary man?

 

Since the Head has to be serviced at a Machine Shop, ... you might as well have the Head ... reconditioned!

Valves and Seats Lapped or re-faced.
Valve Seals replaced
The Mating Surface straight-edged.
The Mating surface planed a couple-thousandths.