Off With Its Head! - Perhaps

krusty · June 12, 2019, 07:15:28 PM

I have an 84 FJ1100 (one of three). It ran well but had no compression on #3. Did the usual tests and narrowed it down to either stuck ring/s (it had been sitting for a long while) or broken ring. ATM I am trying to get the head to release from the cylinder but it seems stuck. I can get about 1mm movement on the LHS and less on RGHS. Yes, the two front and two rear bolts are out. I don't want to go the redneck way and jam screwdrivers in. Anyone have any tips?
Past history is unknown. Looks as though the head has been off in the past as there was an allen bolt as one of the three that hold the ex camshaft. And when I removed the far LHS ex cam holder I lifted one of the bolts out and saw what I first thought was a spring around it. Closer inspection showed it was a 30mm coil of alloy thread, possibly a helicoil? I wonder what other joys await?
Another thing. The shims were well and truly stuck in the buckets. Got them out with an old hard drive magnet but they did not come out willingly. Is this unusual?

red · June 12, 2019, 07:43:21 PM

Krusty,

I count 12 studs holding the head in place. Index Numbers being 4,5,6, &7, on the fiche linked here:

http://www.2wheelpros.com/oem-parts/1984-yamaha-fj1100l-crankcase-assembly.html

Am I missing something?
.

krusty · June 12, 2019, 08:41:27 PM

Yep, all 12 head nuts are off.
Forgot to mention, engine is still in frame. Didn't want to take it out unless absolutely necessary.

oldktmdude · June 13, 2019, 06:36:56 AM

Have you removed the 2 copper washers from the outer most RHS studs? They are soft and can squash enough to grip the studs
and not allow the head to move sufficiently. The threads that pulled won't be a helicoil as they are usually stainless steel or a high tensile steel.
Regards, Pete.

krusty · June 13, 2019, 07:04:12 AM

Quote from: oldktmdude on June 13, 2019, 06:36:56 AM
Have you removed the 2 copper washers from the outer most RHS studs? They are soft and can squash enough to grip the studs
and not allow the head to move sufficiently. The threads that pulled won't be a helicoil as they are usually stainless steel or a high tensile steel.
Regards, Pete.

I couldn't get the copper washers off but I didn't try real hard. Will give it a go tomorrow. Above the bolt that pulled the thread there is a circular witness mark on the underside of the cam cover right above it so something has happened there in the past. I've never seen a thread pull out like that before, it just seemed to undo normally.

RPM - Robert · June 13, 2019, 09:23:57 AM

Make sure the head gasket is coming up with the entire head evenly or it will get stuck. Sometimes the case stud "protective" coating gets jammed up when trying to take the head off, causing it to be stuck.

I presume you have the timing chain guide out.

As far as the shims. Not unusual we usually use a small flat blade screw driver to pop them out.

krusty · June 16, 2019, 02:03:43 AM

An update. Eventually got the head off. A mate came over (the guy who gave me this bike after giving up on it as he dosen't like working on engines anything but engines) to give me a hand. With a lot of effort and copious amounts of RP7 the head was free. Main problem was the stud between 3 & 4 on the exhaust side. The dowel had rusted. Next was the cylinder which the rusty dowel also proved a pain to get past the thread at the top of the stud.
With the head off it was easy to see the cause of compression loss on #2 a broken valve. Even though I had done the oil in the cylinder test, it fooled me. The PO was also fooled and got conflicting results for the same test. Anyhow I need a new Ex valve.

A check of #2 bore showed no damage from the broken valve and there were just a couple of small, tiny even, indentations on the piston from the broken piece.
Everything needs a good decoke as it looks like its been a long time since it was last done, if ever. One thing that was puzzling is that the only plastic stud sleeve or the remains of it was on the offending stud and it fell off when I touched it - none of the other studs had sleeves. I spent some time cleaning years of grime (and RP7) off the studs and their threads, and found a cause for concern. The aforementioned stud has significant rust about halfway up. It needs replacing but I have some concern about how difficult it is to remove. Will this be a problem?
I measured ring end gaps. Top rings measured between 0.7mm & 0.9mm. The second compression rings were a little less, but still over max. Max is 0.6mm. So new rings will go in, which I had planned to do.
I spent this afternoon cleaning and decoking the pistons. They seem to be in good condition apart from carbon build up. The bores look good, no scoring or damage. I'll be borrowing a measuring tool to check wear and roundness. Also degreased the cylinder and I'll clean it up for repaint. Next job will be the head and valves sometime in the next week.

krusty · June 16, 2019, 02:05:50 AM

In my initial post I said lack of compression was #3. It was in fact #2. Temporary memory lapse.

krusty · June 17, 2019, 01:11:22 AM

I'm considering replacing one of the cylinder studs as it looks a bit rusty. It shows as one of 4 different types on parts diagram. The one I need is 36y-11363-00. They are appear to NLA from Yamaha dealers in Oz. I tried searching RPM but couldn't find it. Can this stud be replaced with one of the others? Any suggestions please? BTW its one 0f the plastic sleeve studs.

RPM - Robert · June 17, 2019, 09:47:03 AM

The parts have been superseded to a different part number.

We have them all in stock. Search "stud" in the search and they will pop up. The four on the ends are the same. 7 of the 8 in the middle are the same and there is one intake side to the left of the timing chain that is different.

I believe this is the one you need Engine Case Stud (Center)

The new studs also have no rubber coating on them.

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Off With Its Head! - Perhaps