The plot thickens.....

My first haynes manual was the Jaguar Series 3 XJ manual, it was flat
wrong in so many ways it wasn't funny - they took the Series 2 manual an
"updated it" (I use the term loosely) - I certainly used all the above
phrases with regards to that volume. Yes it was $40 compared to $120 for
the factory manual but it was def a waste of money.

I've heard the same comment made by at least 4 other people regarding
different makes (car and bike but I'd be scratching my head to remember
what brands) <shrug> They can't ALL be terrible I guess

JL

 

The CB250RS one was great.

The R-series one is pretty good, but a bit too general: they try to
cover every model from 1970 to 1996, and it makes it quite difficult
to follow.

The only really wrong thing I've found so far is the instructions for
adjusting the steering-head bearings on late model GSes, which is
wrong, wrong, wrongitty wrong and leads to really crappy handling.

Oh, and there's a couple of funny bits in the wiring diagram ...

-----sharks

 

Well, it turns out the cause of the sudden 2+ mm valve clearance was the
hardened valve seats (both of them) in the RH cylinder dropped out a bit
when the motor overheated.

They didn't fall out completely, but moved a couple of mm, so when the
valves closed there was 2+ mm of clearance. I guess the chuff chuff was
because the seats didn't drop straight out, by at least one of them sat
at an angle, so the valve wouldn't close properly.

Either both valve seats dropped more or less simultaneously, or the
exhaust valve seal dropped first and the motor stopped on the overlap,
allowing the inlet to drop out as the motor cooled. Both seem unlikely,
yet it happened.

However.

The engineer who had a look at them (with a view to fitting new valve
seats) says (and I'm getting this second hand from a mechanic who says
he doesn't understand metallurgy - Hell, I can't even spell it) the
alloy in the head seems to have gone off with the overheating, and seems
to have lost some strength. The engineer thinks he could fit new seats,
but they wouldn't stay put. So I'm looking for a pair of replacement
heads. Something that already has hardened valve seats would be nice,
but the ones from the 90's airheads won't fit.

Might be a while.

Moike

 

I would like to say that's good news now you know what the problem is.
Bugger bugger.

 

Wow. Nasty.

What doesn't fit? I thought they were as near as damnit the same engine?

Time to get on the Airlist, my friend ...

-----sharks

 

Ring Ray Peake he may have some 07 5543 5962

Boxer

 

http://www.micapeak.com/lists/AIRHEADS

WARNING: Americans. Mostly a nice bunch, though. The resident
gurus are pretty good. The resident nutters are pretty bad. Working
out which is which will be left as an exercise for the reader.

I know they went from 97mm stud spacing to 99mm stud spacing in '77
or so, is yours older than that?

Are you on http://autos.groups.yahoo.com/group/OzBeemers/ ?

-----sharks

 

*bugger* moike.

Maybe you should just fit standard heads and use that lead replacement
additive next time if the inserts are going to be a problem?


G-S

 

aahh.. airheads. yep. Haven't joined them though...

Mine is a '79. I didn't know about the change in stud spacing, but then
I tend not to bother finding stuff out until it is useful, and I wasn't
expecting to be head-hunting.

Moike

 

So whats the difference supposed to be Moike? The 80G/S I had was fitted
with 90 barrels and heads, so why can't your 90 accept 80 or 100 heads?
Unleaded 100 heads would be the go if you could procure them.

For those out of the picture, 900s have cast iron liners, 800s and 1000s
(different stroke to the 750/900) have Galnikel coating direct onto the
alloy barrel.

Do what John said, call Ray Peake and get it twin-plugged at the same time.

Al

 

Or call Phil Marshall over at K&R in Mentone.

I'm surprised Chris & James at BMW Ringwood don't have an answer
though.

I'll make some calls to the local BMW club and see if there is
anything available.

SteveB

 

I would suggest you take the heads to a competent workshop , one that
does a lot of heads and have them offer an opinion ( Repco are often
quite good) , Im willing to bet there will be a suitable insert with a
larger outside dia for the job , locking into the head is easy with the
right tools and its certainly going to be affordable , although you may
get larger valves as a consequence and may have to accept the
performance improvement .

 

Actually, with respect, you appear to have misspelled 'incompetent'.

Mileage between individual workshops may vary, but it is my
experience that they are not only fundamentally incompetent,
but they are in no way prepared to take responsibility for
their actions either.

Case in point: completely fucked a Massey Fergueson (sp?)
TEA (petrol) head that was in for something simple - machine
the surface flat I think - to the point where it had to be
binned, and their response to "what are you gonna do about
it?" was to shrug their shoulders and walk away.

G

 

If it was poor spelling then I might have stipulated another workshop ,
I have in the last several months had a set of vg30 heads done , a 4
litre falcon head and block decked and "O" ringed and a Yamaha r1 head
decked as well as 4 clevo 2v heads ( about 4500$ worth so far), the
more specialized stuff I do my self with a mates machines but for basic
work the repco shop in Browns PLains Brisbane is excellent , unless of
course the chubby bloke who can lift lots and is an awesome machinist
leaves I might be singing your song , the basic advice about the new
insets is correct however as I am certain they can be replace by as I
said a decent trades parson ,

 

Dave at Albion motorcycles in Brisbane does lots of inserts and head repairs

 

I'd agree with this. Often you can get quite radical work completed that is
every day for them, and is under warranty. There is plenty of bike mechs
that have no idea about what can be done.

Hammo

 

That's not been my experience.

YMMV.

Hammo (oh, Sydney)

 

We have had a dozen or so heavy vehicle heads done by Repco over the
last 5 years by Repco and haven't had a problem with one of them.

Your experience doesn't sound typical to me.


G-S

 

As I said use my Repco shop or find your own chubby machinist .

 

I have had the heads on a R60/2 (1969) a R100GSPD (1993) and a R100RS (1990)
done by Ray Peake and never had a problem, he only works on BMW Motorcycles,

Boxer