Author Topic: Flooding carbs on Post War models.  (Read 4486 times)

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Offline KiwiJohn

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Flooding carbs on Post War models.
« on: 25 May 2005 at 23:42 »
I am embarassed to admit that I have recently resorted to questioning the pedigree of the designer of the Amal carbs fitted to my 80 Plus,  quite unfairly as it turns out.

Fuel flowed from the carb bodies when the engine was at idle with the mixture so rich that plugs fouled in just a few minutes.  I was convincedthe float valves were the culprits but they were (almost ) innocent.

The real culprits were incorrect washers fitted to the jet block. These are big fibre washers of about 33mm diameter and the ones in my carbs have a centre hole of about 19mm.   These washers appear to block the  passage to the idle jet and replacing them with much narrower washers appears to have cured the problem!  Yippee!    :D  :D  :D

Now all I have to do is make the generator work and wait for the next problem to show itself.

Offline alwyn

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Flooding carbs on Post War models.
« Reply #1 on: 26 May 2005 at 08:41 »
Good luck John, you're winning - keep us posted.
Alwyn
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Offline KiwiJohn

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Flooding carbs on Post War models.
« Reply #2 on: 26 May 2005 at 09:21 »
Having apparently solved the cursed carb problems I spent an hour in the garage this evening and appear to have succeeded in converting my 80 Plus to 12 volt.

The first step was to buy the biggest 12 volt battery that would fit in the dummy battery box that is molded in the pattern of the original battery.  Fortunately I found one that is a rather neat fit,  rummaging around in my junk piles I found a suitable 12 volt brake/tail lamp globe, a small Edison screw bulb for the speedo and a nice sealed beam unit from an Austin Maxi I dismantled a couple of decades ago.

I had to buy a voltage regulator and the one I got is a Bosch unit, solid state of course that has just two connections,  'D'  and  'DF'.  Obviously 'dynamo' and 'dynamo field',  I connected those to the terminals on the dynamo but testing with connecting the battery to the 'D' terminal showed a current flow with the engine stopped which is not good.   Easily fixed though by fitting a 10 amp diode in the lead from the 'D' terminal to the ampmeter.  Unfortunately this diode drops the charge voltage by about 0.6volts.

A quick start of the engine showed a definite current reversal at 13 point something volts and a satisfying reversal of the ampmeter.  Unfortunately the engine has to be running quite briskly for this which might cause problems if I take to doodling around town at night, otherwise I think it will be quite satisfactory.

Converting to 12volts in this way has both pros and cons.  One of the obvious disadvantages is that the motor must be running faster before the generator cuts in.  Noone has explained to me if there is any strain on the field windings.  As for the armature, although the voltage is higher the current is lower under normal operation and one can expect about 30% increase in power output without running into any problems.

If I do cook the generator windings I can always buy 12 volt windings for it, it might even be practical to hand wind the field windings but I wont worry about that until, and if,  the field winding cannot take the strain.

The horn works really well! :D



Next up, brakes would be nice!

Warning! Information that has been kindly sent to me indicates there may be other problems with the Lucas generator through this conversion.  I might have to pay a price and so might you if you do the same!

 

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