Morgan CarbtuneII test
Morgan CarbtuneII test
When I was a poor student riding and servicing my 400-4, I set about making my own carburettor synchronising manometer using mercury from old tilt switches, a piece of plywood and some model aircraft fuel tubing. I drilled out some M5 bolts and soldered in brass tubing for adaptors. It worked well, if a little fiddly to store and set-up, and I had one of the sweetest running 400-4's around. Dealer friends could not believe that my 'Blue Peter' device was actually more accurate than their 'arm-and-a-leg' vacuum gauges. (it was, and still is, take my word for it)
It was a matter of intense pride, that I shouldn't give in and purchase one, when I first saw John Morgan's advert for 'Mercury Carbtune' in the press. Instead, I built my 'ultimate weapon' in the form of a water filled manometer. To those who've done a bit of physics, water is about thirteen times less dense than mercury and will remain less expensive and less toxic for some time to come. (if the water regulator does his job) This means that the standard carb balance figure of 2 CmHg (centimetres of mercury, that should have given my dealer friends a clue!) translates to a reading of twenty-six centimetres of water.
This device worked. It was ultra-sensitive but quite traumatic in use. If one of the pipes fell off, the water had a nasty habit of injecting itself into the engine.
Recently I saw John Morgan's latest offering, the 'Carbtune
II'. 
Stainless steel rods being sucked up plastic
tubes? Now, there was a novel wheeze. It just couldn't work could
it? Curiosity got the better of me, and I just had to have one.
I sent a fax off to Belfast on Tuesday afternoon, and the postlady
delivered a neat cardboard package on Thursday morning.
The system does indeed use a set of stainless rods, but they run in close-tolerance brass guides, working rather like an inside-out tyre pressure gauge. I was all for getting the bike out straight away, but there was one small job to do beforehand. To damp down the inlet pulses, a restrictor has to be incorporated into each hose. This is done by inserting fine bore plastic tubes. With only a short DIY delay, I was up and running. Two sets of adapters are provided, 5mm and 6mm. With these screwed in to the manifolds and the gauge mounted on the handlebars, with the thoughtfully provided reusable cable tie, we were in business.
To my amazement, the little rods did their stuff and I was able to set up my four carbs in a matter of minutes. The system has the usual advantage of mercury gauges in that you can easily compare the four columns as they rise and fall, but there is no mercury to spill out and the system is robust enough to keep in your toolbox. The little instruction book is a model of clarity and useful tips.
For unfortunates who own bikes where the vacuum
tappings are difficult to get at, John Morgan can supply (for
£8) an extension kit comprising tubing, adapters and blanking
caps, which can be permanently attached, allowing you to resite
the vacuum connections to a more convenient place.
I'm giving my home made version to the kids to play with!
Supplier
John Morgan
Unit 33c
Townsend Enterprise Park
Townsend Street
Belfast
BT13 2ES
Carbtune II
Twins £35 Fours £45 P+P £3
Graham Curtis 17 Feb 1998