Head rebuild and rings?

[Bengt_Phorqs]

Are there any signs of iminent head failure?  

Something to consider.  Don't forget the old adage "if it ain't broke, don't fix it".

[weasel01]

Are there any signs of iminent head failure?  

Something to consider.  Don't forget the old adage "if it ain't broke, don't fix it".

Likr I was saying before the bike runs great "except" for the gaskets leaking around the base of the jugs at the block and pushrod tube.

What got me thinking about the heads is the left side exhaust vale is rattling pretty loud at startup but then goes away after warm up?

[montmil]

Ampy, you're most likely just hearing "BMW music". When cold, they rattle like death's own bones but after warming up, well...

It could be the rocker shaft mounting blocks need to be snugged up a bit. There's a thread hereabouts concerning that. Try search or perhaps someone will know where it is.

My bikes have just a smidgen of discoloration around the cylinder to block union, plus the PR rubbers, but I've learned to live with it. No drips. Just visually not perfect... like me and Mike!

[weasel01]

Ampy, you're most likely just hearing "BMW music". When cold, they rattle like death's own bones but after warming up, well...

It could be the rocker shaft mounting blocks need to be snugged up a bit. There's a thread hereabouts concerning that. Try search or perhaps someone will know where it is.

My bikes have just a smidgen of discoloration around the cylinder to block union, plus the PR rubbers, but I've learned to live with it. No drips. Just visually not perfect... like me and Mike!

That's good to know....I dont really know anybody around here with a similar bike to compare it to.

[Yikes]

I'd recommend just fixing the problem you have- leaky pushrod tubes and cylinder base seals.  All you really  need is the replacement head and valve cover gaskets, pushrod seals and maybe some cylinder base sealant.  Pulling the heads and jugs to do the job is really not that complicated and can be done in a day.  Capital Cycle recommends replacing the rings every 50,000 miles and that could easily be done when the cylinders are pulled, but if there is no problem with power or compression, I'd just replace the seals and gaskets.  If the heads become too loud to live with or compression becomes a problem, it's easy enought to pull the heads and jugs again to fix the valves or replace he rings.  But if your bike is running good and the leaks are the only real problem, just fix the leaks.
 [smiley=2cents.gif]
John McC

[CE144]

Good question.

I'm not a mechanic, but I don't think heads actually fail.  They just get less efficient with wear.  A compression or leak down test might tell that story.

In my case, as a new owner of an old bike, I'm looking to do one major repair/maintenance project a year.

2 years ago I did the carbs.

Last year, I sent the gear box to Tom Cutter for a rebuild that fixed the missing circlip issue.  I also rebuilt the front brake caliper because the pads didn't retract.

This year I did the PR seals... and decided to do the heads and rings while I was at it.

Chas Gross
Ellington, CT
1987 R65

[Bob_Roller]

I just went through the receipt that I had from having my heads overhauled in 1998 .

I had both surfaces of the head machined to true them up .

Replaced all 4 valve seats .

 Replaced all 4 valves .

Replaced all 4 valve guides .

All springs and retainers .

Glass bead blast both heads .

Cost was $502US, not including shipping .

Work was done by San Jose BMW .

[nhmaf]

The heads won't fail - but the valves will.   Generally one has some advance warning of impending valve deformation -> valve clearances close up fast (like, within 1000 miles from last adjustment).   Once one detects valves closing up by .002" or more within that interval, it is time to stop and do the deed:  pull heads, clean, replace and recut valve seats and new valves with new valve guides & keepers.  Then, with just normal maintenance she should be good for 100K+ miles..

When valve clearances close up - the engines run quieter, not noisier - so when your normally "tappy&happy" airhead engine starts to sound like a japanese bike with hydraulic lifters (very quiet) it is DEFINITELY time to pull out the feeler gauges and check those valves right away!

[Bob_Roller]

When I got the old valves back with the heads, I was amazed how worn they were .

The exhaust valves were worn to a thickness of about .025 inches, I was told, that I had about 5,000 or so miles left before the valve would have collapsed into the exhaust port in the head .

Every time I adjusted the valves, the clearance had closed up around .003 inches .

I have an '81 model year bike, one of the worst years, for valve recession, I've been told .

[weasel01]

I definitely do have a very pleasant and even tappity-tappity sound when its warm ... it sounds great and at speed it has the pleasant drone of an aircraft engine.

And I'm 245lbs and still feel like the bike has plenty of power....pulls me around with intent..not a neck breaker but nice.

It's just at a cold startup the left cylinder has a louder than normal tappity sound originating from the exhaust side.

Sometimes it comes from the right side but mostly it's oriented to the left I hear it mostly at idle and during a deceleration.

after the first 5 minutes it completely goes away and the bike just sounds cool as all getout.

[Bob_Roller]

Have you ever had the valve covers off and done a clearance check ?

[weasel01]

Yes they are accurately set at .004 intake and .008 exhaust.

Set them maybe 500 miles ago and just rechecked when I changed the timing chain a few weekends ago and they were unchanged...

[Landlubber]

aussie,

Not so much head failure mate, it is the valves and the seats that wear.
Pull a plug one day and get a decent little LED torch and have a gander at the lip of the valve head, it should have quite a good deal of metal around it, if the edge is thin, time to do something about it, because if the head comes off the valve, the rest is history.

I would be looking after 50k on any airhead, and just watch yearly after that to see the wear pattern.

A new set of seats and valves from an engine recon fella here is about 200. Cheaper if you use cheaper parts, but why.....only use good gear if you expect it to last, and NO Chinese copy castings.