New bike in preparation for colder climes and WTF is that mod all about...

I now have a replacement for the K75 and more suitable for "forthcoming
projects".

It's a 1985 Armstrong MT500 I picked up from eBay - there was a minor
disaster on the way back from collecting it when the cam belt broke and
stranded me on the M1 - well done CN, picked up and on my way home within
40 minutes and, crucially, before it pissed down.

Anyway, fixed the cam belt, took 20 minutes, changed the oil (the army
manual lies - 3.1L is hugely overfilled) and took it out for a spin.

All seems well - it was cruising at a good lick of 75-85 mph on the M1
before the cam belt went. Still odes it but seems a bit noisier now but
that might because I wasn't wearing earplugs.

The heated grip (note singular) works but there isn't a heated grip on
the throttle - no wiring going to it, not that it just doesn't work -
which is a bit odd

LN has picked up some panniers and frames (which can accommodate a 20L
jerry can - what's not to like!) from Lichfield so we should be sorted.
Alan Crowder provided a scottoiler and Lozzo is rummaging for some
missing bits.

Great stuff.

However, there's an unidentified electronic thing on both sides of the
Mikuni carb (in itself a very desirable mod) and electronic control box
and sensor hidden away under the seat - it has an LED on the outside
which lights with the ignition on.

See here for pics:
http://www.sweller.co.uk/1985 Armstrong MT500/

WTF is it?

 

High power resistors is what thems is.

 

Lucky it isn't an 'interference engine'!

Heater to prevent carb icing?

--
+-------------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+-------------------------------------------------------------------+

 

Extra weight. Bin the fucker.

 

According to the part number, the gold thing is a wirewound resistor
http://uk.rs-online.com/web/search/...hod=searchProducts&searchTerm=157-538&x=0&y=0

 

and the word "temperature" on the pcb would suggest it's part of the
heated grip?

 

that was my deduction on viewing the 1st picture with the RS resistor,
before even looking at the controller. Used to use loads of them as dummy
loads on various test rigs. Handy for keeping the coffee pot warm.

 

My guess it's on/off rather than pwm. LM324 is an op-amp isn't it? So a
temperature sensor somewhere, a relay, and the resistors strapped to the
float bowls for warmingness. The twiddle pot will be for adjusting the
temp. it kicks in at.

 

It's connected to the resistors, not the grips.

 

It's definitely on/off - the big blue thingy is a relay and the LED is
meant to come on when the relay is on (it's labelled "relay on").

 

I think you were lucky it didn't do more damage.

 

Yes, I think others have made better suggestions

 

As others have said, two wire wound resistors designed to get hot and
the controller box:

http://www.quasarelectronics.com/velleman/mk138-thermostat-kit.htm

I'd leave it on, might be helpful.

 

It's a low compression engine (so it can run on shit/stale/available
petrol) - the MT forum chaps refer to it as a "safe Rotax".

It seems breaking cambelts are not that unusual - I may keep one spare
under the seat.

 

Heatsink attached to carb, control box with 'temperature' marked on it?

I'd say it's a crude carb heater.

 

No cruder than the one on my B6.

 

One of these:

http://www.quasarelectronics.com/velleman/mk138-thermostat-kit.htm

I'd leave it on. Might be important since carb icing's an awful pain
and especially so if roads are slippery.

 

Seems a bit pointless as the temp range is +5deg to +30deg - or have I
missed something?

 

Would also be my guess

--
Malc

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

 

I was thinking the piston bashing a valve, for example.