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MG MGB Technical - WTB: crypton synchro check

Hoping to find one in great cosmetic condition as well as perfect operating condition.
GMA Alpern

Please tell me what it is. I am completely in the dark.
Sandy
Sandy Sanders

It's a device like a toy hovercraft that sits flat on the carb intake and has a vertical glass tube with an aluminium float in it. A centre rotating valve allows main airflow to be set so that it diverts a measurable amount to the tube and so lifts the float and produces a reading. The device is then transferred to the other carb and the idle screw then adjusted to get an identical float reading.

A brilliant device which is easy to use and very accurate. I've had mine for years and it is still in pristine condition but I won't part with it !!
Iain MacKintosh

I'm sure the Crypton item is better quality, but the gunsons Carbalancer is probably more readily available, cheaper and just as good for getting the correct balance for the occasional use it should get. In my experience once you have setup the carbs correctly, and don't fiddle about with them afterwards, twin SUs keep their tune very well.
Paul Hunt 2

Sounds like a Uni-Syn, although probably made to a little higher standard. The Uni-syn is shown on this Moss catalog page. http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=37191

Bill Young

Actually it doesn't look anything like a Uni-syn. Here's a link to one in poor condition.

http://cgi.ebay.com/Crypton-synchro-check-Carb-balance-tool_W0QQitemZ8038346326QQcategoryZ30921QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
gary

Seeing this thread remind me I have a matched pair of vacuum gauges that my brother bought to use on his Moto Guzzi V twin.

When attaching them to the breather ports on my SU HIF carbs I have never been able to get a reading.

Does anyone the range of vacuum that might be expected?

My connections have always been a bit of a bodge up. If I was sure that the gauges covered the correct range I would try and make decent connectors.
David Witham

When using motorcycle balancing gauges it necessary to install restrictors in the the lines going to the inlets. Without these you get readings that pulsate so fast as to make results useless. Restrictors are available
from any motorcycle shop with a good parts supply. Ray
RAY

Sorry Folks,, mine is called Moto-Meter Synchro test and is I had described it. It also look a much more accurate instrument that the Crypton one with the pointer shown in the photo and is obviously direct acting very like a hospital flow meter. As Paul says though once set a good pair of SUs will stay in tune indefinitely.
Iain MacKintosh

I must be a scrounger from way back. The ebay meter doesn't look to be in bad condition to me, just needs polish or paint.
Tom

Hi

please forgive a stupid question...

I have a set of vacuum gauges for my motorbike (http://www.carbtune.com/). I have not gotten around to using them on the bike yet, but I did take a look at using them on my 77 UK roadster, couldn't see anwhere to connect them and ended up with the length of hose pipe held to ear "sounds about the same" test.

Is there somewhere to connect this type of gauge to the carbs that I didn't notice?

Cheers
Darren
D Lewis

The vacuum gauge is used for mixture, timing, other settings and diagnostics. You can connect a vac gauge to the brake servo take off. The synchro test is only used to balance carb air flows on multiple carb engines.
Iain MacKintosh

The vacuum gauges Darren mentions are parallel gauges that let you compare the vacuum at each carb in order to balance them. I'm not sure where you'd be able to hook them on an MG.

I like the SU Toolkit sold by Moss and probably others for balancing and tuning carbs. The kit consists of some tubes and wires and a jet wrench. The tubes are placed into the tops of the carb pistons, and into those tubes are placed the wires. With the engine off, align the wires to each other. Slacken the carb linkage. Now, start the engine and set the idle speed by adjusting both idle screws until the idle speed is correct AND the wires are still in alignment. By aligning the wires you are synching the carbs -- no Unisyn or similar device needed. This kit also has the advantage that you can check the synch throughout the entire rev range AND quickly and easily compare the rise and fall rate of the pistons.

The wires also give you a quick & easy visual guide for the "lift the pin 1/32 in." test. Just lift the piston by the thickness of the wire.

If you can only afford one SU carb tool, this kit contains everything you need.
Rob Edwards

This thread was discussed between 17/02/2006 and 18/02/2006

MG MGB Technical index

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