head teardown and new valve seals

silas · April 30, 2012, 03:12:41 PM

I've had my '90 for another year now on a PNO title. Finished rebuilding the carbs last week, and revived a corroded and burnt out fuel pump using the point set replacement from Randy. Worked like a charm. Got a free week now, and it looks like a total head teardown is in order. I had it running steady, but banger #4 showed signs of a steady oil leak and was chugging to keep up with the others. Sounded like the right side of the engine was a diesel.

I'm hoping this will be a simple valve seal and cleanup job. Already can see that other rubber items need replacing. Hope the metal bits are still in shape.

Any tips on what else to look for as I crack it open today?

silas · April 30, 2012, 07:29:14 PM

Looks like I need way more than valve seals...

Dan Filetti · April 30, 2012, 07:41:52 PM

How many miles on on this motor?

Do you know of it having a history of being particularly thrashed suck as track work, nitrous, etc?

I ask because these motor are fairly bullet proof -this damage is a bit surprising without serious abuse and/ or very high mileage or both.

Just curious.

Dan

silas · April 30, 2012, 07:54:27 PM

It's got over 54,000. It came to me nearly stock, but rather neglected. The carbs were a pain to pull apart. Not sure if they were ever serviced for anything at all.

The air intake was riddled with leaks too. I had replaced two boots from the airbox to the carbs when I first got the bike. Every single jet was crudded up, and the floats were sticking too. Pretty safe to say that this poor thing hadn't had a good balanced diet of fuel/air for a while, and then started binging on oil too.

I'm looking up head bolts now. Anyone recommend an online vendor? I don't think I need to plunk down $80 for the Ape heavy duty jobbers. I'd buy em from Randy along with the other goodies in my cart, but he doesn't appear to stock them.

racerrad8 · April 30, 2012, 08:25:08 PM

Quote from: silas on April 30, 2012, 07:54:27 PM
I'm looking up head bolts now. Anyone recommend an online vendor? I don't think I need to plunk down $80 for the Ape heavy duty jobbers. I'd buy em from Randy along with the other goodies in my cart, but he doesn't appear to stock them.

You will never get them out and are heading down a slippery slop. At least one will break off, three will pull the threads and you will be splitting the cases to get them fixed; http://www.fjowners.com/index.php?topic=479.0

Give me a call and we can talk about the engine and the repairs you need. I cannot determine by the pictures posted what issue you are having other than what you have described.

I will be here for a few more hours...

Randy - RPM

Harvy · April 30, 2012, 08:28:59 PM

Has number 3 even been firing.......those exhaust valves are soooooo shiny!

Harvy

Dan Filetti · April 30, 2012, 10:12:11 PM

Quote from: Harvy on April 30, 2012, 08:28:59 PM
Has number 3 even been firing.......those exhaust valves are soooooo shiny!

Harvy

Is #3 'shiny' or white from being way too lean? (my interpretation).

Others know a LOT more about this, than I do.

Dan

Harvy · April 30, 2012, 11:21:22 PM

Quote from: Dan Filetti on April 30, 2012, 10:12:11 PM
Quote from: Harvy on April 30, 2012, 08:28:59 PM
Has number 3 even been firing.......those exhaust valves are soooooo shiny!

Harvy

Is #3 'shiny' or white from being way too lean? (my interpretation).

Others know a LOT more about this, than I do.

Dan

Good point Dan....may well be the case.
I was just going on how wet No3 cylinder looks compared to the other 3 too.

Harvy

silas · May 01, 2012, 01:18:19 AM

I'd say #3 was running quite lean. Looks even whiter there because it reflected the flash.

Just spent an hour and a half scrubbing off the grime with some wire brushes and half a can of PB Blaster. Worked faster than I expected. Everything looks okay to me, but I'll take pics in the daylight tomorrow.

Randy: Thanks for the warning. Certainly don't want to break anything now. Been on a roll the last few days. I'll give you a call tomorrow.

silas · May 01, 2012, 01:30:54 PM

Here's the head cleaned up a bit...

The exhaust valves in #3 and #4 still have a bit of grime on them. The wire brush wasn't doing much after a while.

The exhaust valves on #1 and #2 appear to be permanently pitted. Couldn't quite tell if it was just a layer of corrosion welded onto the surface or what.

silas · May 01, 2012, 01:41:53 PM

So now I'm assuming I may need to pull the cylinder block off to assess the situation with the rusty bolts. It was already coming loose on the rear edge when I was breaking the head free. The front edge of the block was giving me a hard time just now, so I decided to give it a rest and get some advice...

silas · May 01, 2012, 09:42:10 PM

I got the cylinder block off. Just took some patience and a few more hits with a rubber mallet. Actually came off easier than the head. Here's what I'm looking at now after a bit of careful cleanup...

The bolts are tight. Only a couple look rusted down at the mounting points. Could I just work on removing the rust and keep them in place? They don't appear or feel any thinner than the clean bolts.

Here's the block all cleaned up. Forgot to get the "before" pics. The bottom didn't need much work, but the thin orange cylinder gaskets disintegrated under the scrape of a fingernail...

Here's this round's highlight... a lovely rusty placement dowel after I freed it from the block. I wrapped the block with some heavy linen with a hole cut to grab and twist the PB Blasted dowel. Took a while but it finally started twisting. Yanked it and then brushed out the socket with a neighbor's Dremel. A clean dowel fits nice and snug now.

Despite the messy dowel extraction, the top of the block needs resurfacing. The edge of #4 comes a fraction of a millimeter from being flush with the surface. The edges of the other three appear to have the same resurfacing pattern/arc as the rest of the block's surface, but #4 has a distinct concentric texture. Would this indicate that the block had been (lazily) resurfaced before? #4 was replaced already? Could it be resurfaced any further? Is there a limit to how much you can shave off these things?

Here's a close-up...

fj11.5 · May 02, 2012, 07:26:36 AM

nice work cleaning up the head,where were you when i swapped heads on my bike

,, your valves looked new compared to the pics i have on here

,, hope you get her sorted out

andyb · May 02, 2012, 08:31:30 AM

Did you measure how far the pistons were at TDC vs the top of the block? That'll help to tell you how much can be taken off.

Thicker base gaskets are available, so if you cut the top off 0.010, you'd just add that back into the thickness at the bottom to get back to where you started. Stock base gasket is 0.020".

silas · May 02, 2012, 02:20:06 PM

Maybe I'd start a side business cleaning heads if my OCD worked this fast all the time.

I didn't measure the piston height. There was a mm or two of grime on top of them, so I wouldn't be able to get a good reading until they're cleaned up too.

Just got back from talking to a local mechanic that does resurfacing. He said the block surface is fine, even with the little nicks and dings. He excitedly pronounced it to be perfectly even too. Wasn't worried about warping anyway.

What he did say is that it's just the #4 sleeve that is obviously out of spec. He measured that it's 10 mil below the surface. He recommended replacing or refitting it instead of resurfacing, and that maybe a better equipped shop could fit a spacer under the lip.

So, banger #4 has/had a number of problems. I replaced the leaky intake boot from the airbox to the carbs (along with #3). Then it was a gunky carb. Now this.

Despite all the mess, it's still pretty amazing to me that the bike was running at all. Can't wait to get everything back in shape and feel what it's supposed to ride like.

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head teardown and new valve seals