FJ1100 -head and cylinder pics + Bunt valve

[mr blackstock]

G'day,
I finally got time to take the head off the FJ, she had lost all compression in No.2 awhile ago, I guessed a burnt valve.  She has already had the head off around 3 years ago to solve the same problem in the same cylinder?!  I am at a loss as to the cause.  Once I took the head off I saw the burnt valve, but also a lot of carbon deposits, chunks of it in no.2.

The pipes have always been sooty, but the plugs have always been brown.  Once I have a look at the valve seats I might learn more. 
Any thoughts?

[Bones]

What are the valve clearances like Gareth, to burn a valve out in that amount of time sounds like it might've been tight and not closing properly. When the valve was replaced was it lapped in or just installed, the mating surfaces might've been damaged and never sealed properly.

How's your oil consumption, might be due for new rings or a total overhaul. 

[Arnie]

Gareth,

I'd posit that you've been running rich for a long time.  Doesn't explain your burnt valve though.
You say your plugs have been brown the whole time, and that your exhaust is sooty.
Well these engines use a "lost or wasted spark" ignition where every time the piston approaches TDC, the plug fires.  This is fine and works well with onlly 2 coils, but it does give you plugs that look to be a step hotter than they actually are.  IIRC it would also explain your poor fuel economy

Back to your burnt valve....with all signs pointing to you actually running rich, perhaps you got the valves carboned up and they stopped sealing so well.  Any chance you're getting detonation (pinging or pinking) on those long regular commutes?

[FJ_Hooligan]

Have you ever had the valve seats re-cut?  The early years were known to warp their valve seats leading to burned valves.

Re-cutting the seats fixed the issue.

[Pat Conlon]

^^^ Yep, simply lapping the new valve won't cut it (Get it? I just crack myself up sometimes)

Also, the first 500 mile valve adjustment is important as the new valves seat and the shim/cam clearances tighten up.

I had a issue with a cylinder getting an extreme amount of carbon on an exhaust valve which caused that valve to burn.
The cause was traced to the choke linkage allowing a trickle of extra fuel into that cylinder causing the valve to carbon up.

[mr blackstock]

G'day,

Thanks for the feedback guys. 
The head was worked on by a mechanic when the first valve was burnt, I would have to assume he lapped in the valves he replaced.  I will have to have a measure up of the valve seats too to see if there is enough there to have the seats re-cut.

I used to check the valve clearances alot, they always seemed to be shrinking too much.  Perhaps the valve seats are receding...
The engine was bored out and a big kit put in awhile ago, the bores look good still.  Oil consumption was perhaps high, due I think to the bores being glazed.

I think that after I get it all back together I will lean it out a little...
The adventures begins.

Cheers, Gareth

[racerrad8]

Gaerth,

Can you please email me the head & cylinder pictures to my email. I see several things, but since I cannot enlarge the photos I cannot confirm.

Burned valves are almost exclusively because they did not have enough lash and the valve overheats and melts away. After the head work, did you stay on top of the valve adjustment for the first 2K miles?

You say they kept getting tighter/shrinking. That is most likely because the valves were ground through the hardened face and they are "cupping" to the seat.


I normally see this much worse on the intake side because the valves are not as hard and the fact people use crappy air filters.

Regarding the carbon, what valve stem seals did you use?

I see they are aftermarket pistons, Wiseco?
What was the cylinder finish grit?
What was the piston ring end gap set to?

Have you pulled the cylinders yet to look at the pistons?

Send me those pictures so I can enlarge them and I will expound on what I see after I confirm.

Randy - RPM

[mr blackstock]

G'day,

Thanks for that, I will get to that after work tonight.  I will include some pics of the valve seats and valves, took them out last night.  They do not look very good either.  The last ime the head was worked on, I bought OEM valve seals, the pistons are Wiseco, and I have no idea on the cylinders. 

The Wiseco kit was put in 5000km before I bought it, I have perhaps added 30,000kms.  The bores look alright I think, I can see cross hatching, last mechanic said they were glazed from the assembling mechanic using oil during assembly.

I will send the pics tonight,

Cheers, Gareht

[CutterBill]

...last mechanic said they were glazed from the assembling mechanic using oil during assembly.

What else are you supposed to use? 

[mr blackstock]

Assembly lube.  It seems alot of people use too much oil on the bores and once the engine warms up the bores get glazed.  This is what I have been told, but for the rest of the engine it would be fine I guess.

[ribbert]

Assembly lube.  It seems alot of people use too much oil on the bores and once the engine warms up the bores get glazed.  This is what I have been told, but for the rest of the engine it would be fine I guess.

Great topic.

Mechanics and engine builders don't feel strongly about what oil you run in your engine but this subject gets them going, along with run in procedure.

Perhaps Randy could tell us how he goes about it and the difference between his race engines (legends cars) and road engines.



Noel

[CutterBill]

Assembly lube.  It seems alot of people use too much oil on the bores and once the engine warms up the bores get glazed....

Saying that the cylinder bores have too much oil is nonsense.  Have you ever seen the inside of a running engine?  I have, and the amount of oil being thrown around is amazing.  As soon as you start up an engine, oil is being flung everywhere.

For the record, I have never heard of any engine builder using assembly lube on the cylinders.  Crankshaft, yes, but never the bores.  Just oil.  Actually, the only time I use assembly lube is if the engine is not going into immediate service.

Ok, so what causes glazed bores?  It's quite simple really, and is well understood by people who research this stuff.  What you want to do (with new rings) is force them out against the cylinder bores during the very first few minutes of starting the engine.  The way to do this is by using a very heavy throttle, wide open if possible.  Accelerate hard, run the bike thru the gears, then slow down (to a stop if you can) and do it again.  The first 10 minutes are critical.  Note that "heavy throttle" does NOT mean "high RPM."  Short shift at about halfway to redline, but use as much throttle as possible.

The worst thing you can do to new rings is to "baby" the engine, using light throttle and very low revs.

I'm probably not explaining this well, but I'm on my first cup of coffee and I'm not awake.   

[mr blackstock]

I did not say cylinder bores have too much oil, I said people use too much oil on the bores, by definition that means a person has manually put oil on the bore, that means they have put it together.  I made no comment on how much oil is flung around inside a running engine. 

I have been told by more than one mechanic that If you are assembling an engine that has just had a hone or likewise work, to use assembly lube, as it usually contains a high level of molebednum disulphide or a lithium equivelant.  I have been told that the assembly lube is best as it prevents first start damage until oil can get to the surfaces, which is a nano second away, but the use of the lube ensures good initial ring "bed in"  I may have been given wrong info, that happens.

As always, everyone has an opinion, and there is more than one use for any given object, oil and otherwise.

[The General]

I can remember throwing a handful of Ajay down it`s throat at the speedway, but obviously things have changed since then. On the road I`ve always done the heaps of throttle but not high revs thingy. But I also let it have high revs with little throttle, after a small settling in period to allow for what I was told in tha old days to be Crankshaft flex (esp on single cylinder performance bikes) and that little lip being formed mocroscopickley at the top of the cylinder.
But yeah I too am interested to learn best practise these days of big words in oils.     

[mr blackstock]

I did a little bit of "google" research, I was curious about the process, and I came across two methods regarding cylinder wall preparation, "oiled up" and "dry"  I added some extracts, anecdotal, but interesting.  The only mention of assembly lube being used seems largely in reference to valve trains, rockers, pushrods, etc. not cylinder bores, I must have been mistaken.

http://www.enginebuildermag.com/2014/10/break-in-oils-and-assembly-lube-needs/
"Regardless of which product you choose, a thin coating of assembly lube should be applied on all high-friction, high-load surfaces such as cam lobes, lifter bottoms, pushrod ends, rocker arm and valve stem tips, as well as all the rod, main and cam bearings.  The assembly lube will stay on the surfaces of these parts and provide the much-needed lubrication until oil pressure can take over. Motor oil (straight weight or a multi-viscosity oil) can be used to lubricate less critical surfaces such as the cylinder bores....As soon as the engine starts, it needs to be revved to 1500 to 2200 RPM and keep there for 20 to 30 minutes while the cam and rings are seating. Varying the RPM helps seat the rings more quickly."

http://www.thumpertalk.com/topic/607578-installing-new-piston-rings-in-boredhoned-cylinder-dry-or-wet/
"If you are going to be starting it in the near future, put it together dry, if it is going to sit for a few months before being started, put a little oil on everything. My family business was part of an experiment performed by a major engine manufacturer on what was better, wet or dry assembly. The companies final conclusion was that engines put together with dry rings and dry cylinders not only made more power, but also lasted longer, and burned less oil throughout the life of the engine. This company wouldn't assemble them in the factory this way b/c they didn't know what engines would be put into service right away and what ones would sit in a warehouse for a while. They didn't want anything to rust in an engine that was sitting."

So I guess use either oil or not on bores, hell some suggested using ATF liquid. 

Cheers, Gareth