Paging the SOBMWisti

I finally got round to looking at my old R100RT which has been standing for
a couple of months after it started running very roughly following a missed
gear change and consequent over revving. The inlet valve on the left is
stuck open. I will admit to a fairly high level of mechanical numptiness but
it looks like a fairly straightforward job to sort the bike. With winter
approaching I'd like to have the old heap running for when it gets really
shitty. So is it an easy job? Is there anything I should know that isn't in
the Haynes manual. Help please.

 

Yes. Pushrod head. Simple.

 

"Stuck open". You mean as in bent? This usually damages the p.bronze valve
guide too so it is worth having a FOAK do the valve/guide/seat for you.

 

Sounds like the valve stem got bent by the piston whacking the valve.
Time to get the head off and see how much damage has been done, usually
just a new valve is needed.
Dont attempt to straighten it, the stem has been weakened and could
break at some random time in the future causing serious damage.

 

Yes probably bent. The spring doesn't move when I turn the engine on the
back wheel (so the rocker ends up with about half an inch clearance).
Assuming it does need a valve guide is it that hard a job?

 

Worrabout the pushrod - that might be bent as well?

 

They have plenty of give in them. Usually. But it will be obvious when the
head comes off. One would naturally check all the valve train. The screw
and locknut followers can mushroom or split for instance.

All these parts are very cheap from Motorworks though.

Has anyone said Clumsy **** yet.

 

Me about 50 times on the way home.

 

All what they said above. If its not been converted to run on unleaded
then it may be worth doing the vales, guides and seats etc all at the
same time. Motorworks and several other people do an exchange heads
package deal. If the bike is up around the 70K plus miles then it may
be worth doing this anyway as the valve heads are welded to the stems
and with hard use and high miles they have been known to part
company.

Its all basically very simple engineering.

Boxerboy

 

Phil Hawkesley's BMW forum is a good place to look as well.
http://www.bmbikes.org.uk/Forum/index.php?sid=84bf49df3df4e4d19d9dfbee76c2ae85

There's lots of technical stuff there as well as helpful bods. You may have
to register to get the technical pages though.

--
Malc

Rusted and ropy.
Dog-eared old copy.
Vintage and classic,
or just plain Jurassic:
all words to describe me.