Paging the old BMWisti

I've been offered an old BMW for what seems like a good price. It's a 1985
R80RT monoshock fitted with 1000cc barrels. It has BM|W panniers, a
'progressive suspension' modification, has done a genuine 20k and is in good
condition. I've never ridden a BMW (always had jap bikes) so what can I
expect ridewise and what should I look out for mechanically.
The owner wants around 1K.

Thanks in advance

 

It will be quicker than you think it is, but slower than you want it to be.

With it being an 85, does it still have the single front disk?

And did they change the heads to 1000cc heads, carb settings and also
change the final drive gearing to suit too?

Generally go on pretty much forever, but electrics can rot and at this
age the coil is well known for cracking

 

Thanks Gyp. The bike does have twin front discs and I believe the engine
conversion included the heads and carbs but don't know about final drive.
The owner has said I can use the bike for a few days before I decide and is
quite laid back about the price.

I'm imagining the engine performance is similar to an XS850 I used to own?

 

In that case try it for a few days and see how you get on. You'll find
it's pretty quick if you don't try and go fast IYSWIM. The supple
suspension and good torque spread means that you can make progress
pretty well, especially on B-roads, but if you try and ride it like a
sportsbike it'll get out of shape.

Champ will be along in a moment and state that people with crap handling
bikes always say this sort of thing, but to my mind it does the job it
was designed to do very well.

I've not ridden an XS850, but i expect the XS would be a bit quicker.

 

One of the classic faults is a leaky rear crankshaft seal - check if
there is oil showing at the engine/gearbox join (there's a small vent
hole at the bottom there - should be dry). Other than that, check the
usual shafty issues, head bearings etc. Basically everything you'd check
on an older used bike.

They do last surprisingly well but you need to keep on top of the
maintenance. Not that this is hard to do.

Sounds like a decent enough price if it's in good nick - RTs aren't as
sought after as RSs so they tend to be cheaper.

Oh, and regarding the coil problem Gyp mentioned. This is a known
problem and there is a company in Germany who adapt the 1100 coil for
use on older airheads, which cures the problem once and for all.

Which reminds me, I've promised Gyp for years to get one for him - Gyp, do
you still want/need one?

 

Buy it. Jeez, just buy it.

Only prob you'll find is that the thing is undergeared in 800cc trim,
and will be *really* undergeared with a 1000cc kit on it. Fuel
consumption's piss-poor for the performance, as well.

Mechanically? Sound as a pound. Make sure it's charging, as alternator
gremlins are not unknown and are definitely pricey to sort.

 

No, nothing like. At least 15mph slower.

 

Noting that even with a fully functional alternator and a high-output
regulator, it still didn't work very well

 

Yup my R80RT alternator failed and it was only about 18 months old.

 

Change the oil and made sure the valves rattle.

Possibly...

I need to get to the R65 to check that the coil is indeed shagged. But
when that's sorted the bike will need a full service and tyres and a
battery before it moves anywhere so I'm not in a rush to start that at
the moment.

Priorities at the moment are... sell the Harley, the P5B (it went
through the MOT a couple of weeks ago - do you have a parking space
needs filling?), the BX19GTi and the caravan.

Once that lot's gone, I'll maybe get a chance to start on the R65...

Does the chap still do them btw?

 

I did exactly this to an R80 (but the immediately earlier model)- put
1000cc barrels and carbs on it. It went like a rocket with the standard
R80 gearing but ran out of sensible puff[1] at exactly the same top end,
as you'd expect. Frankly, I preferred it that way, as I'm not one to
want to cruise at 125mph. The torque from the hybrid was phenomenal -
I'd never felt anything like it on a bike before.

The conversion eventually killed the bottom end, but it had already done
well over 100K miles by then. If I was doing it again, I'd rebuild the
bottom end too - BMW shell bearings are quite cheap.

[1] Sensible puff, means you don't want to over-rev an old bottom end
anyway - just ask my big ends. It was easy to over-rev it in the lower
gears if you weren't careful.
--
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
How much more suspenseful can you get?"
- House

 

Fair enough.

Not really - at the moment I've got two that need emptying...

Last time I checked he still did them and that wasn't too long ago.

 

Not so, see above. Depends what you need it for.

Not so, see above. I went from an average of 40mpg to 50mpg once the
full conversion was done, with standard gearing.
--
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
How much more suspenseful can you get?"
- House

 

The issue is that the job it was designed to do was invading Poland in
1939.

--
Champ

ZX10R | GPz750turbo | GSX-R 600 racer
My advice as your attorney is to buy a motorcycle
To email me, neal at my domain should work.

 

Interesting. 40mpg was what I used to get from a monolever R80RT, and
given that it only did about 105-110 flat out, I thought that was
dreadful.

My old heavy flywheel R100RS, with the optional high-ratio drivebox,
used to do 45-50mpg and much higher speeds.

 

Exactly. It is perfect for your average British B road

 

The big difference came about when I finally got the stubs sorted out
for the R100 carbs. The 100 barrels+heads on the 80 carbs were still
giving 40mpg. Looks like the 80 carbs were just a bit shit.
--
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
How much more suspenseful can you get?"
- House