Testing Time

( Grace P., 2012, The Royal Enfield, Issue 2)

- Running rich or feeling lean?

- We test a nifty gadget for checking carburetter settings 

Tingkering and fettling, they are lovely words aren't they? They imply a sense of competent non-threatening servicing, to be enjoyed with a mug of strong coffee and dulcet tones of Radio 4 serenading in the background, within a snug and purposeful shed

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Hold that thought for a moment. It’s wonderful when your motorcycle is working perfectly and requires no major maintenance work. One’s leisure time can then be spent perfecting its running and keeping its cosmetics in shiny good order. Bliss. No rush to get that engine back together from an exploding big-end, or that clutch replaced before the annual club summer rally and ‘drinkathon’; instead, some quality fettling time, with little risk of failure and ridicule from your chums.

One such fettling task is adjusting the carburetter on the old faithful, a nice tweaking job if you have the right tools. 

Many people suggest using a ‘plug chops’ technique to set up the fuelling on old motorcycles. A technique that involves riding the motorcycle under load at four different speeds between idle and full throttle, then, killing the ignition abruptly and coasting – hopefully – quite elegantly to halt. Next, scalding your fingers by quickly pulling the hot spark plug and examining its burnt colour, and finally refitting a new clean spark plug for the next run. So that’s 4 runs with 4 different throttle openings and 4 new spark plugs, one for each run. Are you still with me?

Not an easy or safe task, and to be honest, not that useful these days with our unleaded petrol and all its additives.

Alternatively, for a relatively small sum of money it is possible to purchase a Colortune kit to actually look inside the combustion chamber, gasp, and thus see the actual colour of the combustion flame front. It becomes easy to understand and adjust the fuelling, noting the visual effect that adjustments have on the colour (and therefore fuel/air ratio) of the combustion.

I obtained my Colortune from www.frost.co.uk who also stock low cost adaptors, so it can be used on other vehicles too. The 14mm size is usually the most useful one. Before using the Colortune kit and making adjustments, firstly warm up the motorcycle so it can idle without using choke, and then remove the spark plug. As you can see from the example in the photo, this motorcycle seems to be set up fairly well anyway, with the plug electrode displaying a nice beige tone.

If the plug is dry and sooty then you may have a fault with excessive fuelling; if it is oily then it’s possible that engine wear may make adjustments difficult. 

 In place of the normal spark plug you screw in the special Colortune Transparent plug. It only needs to be just a fraction more than finger tight to take care not to over-tighten it! Next, screw the HT extension lead into the Colortune plug whilst the other end connects to the spark plug cap. The insulator on the Colortune plug is glass rather than ceramic – the area around the white centre – so you can look down into the centre of the plug and actually see the combustion taking place.

With the engine running just above idle speed you can clearly see and orange glow on the inside of the spark plug.

 Just a fraction of a turn anti-clockwise on the air-screw on the side of the Amal Concentric carburetter enables you to trim the colour of the combustion to the correct blue hue.

Too far and the colour will turn white, indicating and unwanted lean burn situation. 

 

You can use the Colortune to check the combustion at other engine speed too, rather than just at idle. The instructions that come with the kit describe what to expect at various throttle opening, to perhaps diagnose an incorrect main jet or slide, or even a defective accelerator pump on such equipped carburetters.

I tend to prefer using my experience and ‘feel’ to set these up, or if it’s a very complex problem by using a Dyno rolling road with an air/fuel ratio print out at a local specialist.

However, for most simple classic motorcycles the Colortune should be more than adequate. It’s especially useful when faced with twin carb equipped engines. Each air-screw can be set spot on using the Colortune, then, the idling balanced using an air gauge.

When you are finished, simply give the Colortune plug a clean with some brake cleaner using the small brush provided in the kit, then pack everything safely away for the next time it is needed. I use and old wooden wine box to ensure all the various parts are kept together.

“Look after your tools and they will last a lifetime” as my old dad used to say.

Using the Colortune kit is a rewarding yet simple bit of fettling, when carried out in the comfort of a well-ventilated shed.
Go on, treat yourself to another cuppa with the feeling of the job well done! 

Paul Grace

(Full Magazine is available at: http://www.magcloud.com/browse/issue/402366)

Motorcycle Restoration

Are you considering undertaking a motorcycle restoration or maybe you have already started your 'project'. Whatever your motivation you are probably about to become involved in a labour of love.
Once you have become enamored to restoring motorbikes, it is a passion which stays with you for life - even when the practicalities of day-to-day life mean you have to swap two roaring wheels for four more sedate ones.
A wedding ring and the patter of tiny feet would, once, have meant packing the bike leathers away for good. But over the last 20 years, the number of ‘mature motorcyclists’ has rocketed - and the popularity of motorcycle restoration is greater than ever.
When embarking on bike restoration, it is important to consider the following: Pick a motorbike you know you will be able to restore - taking a look around our website will give you a feel for the sort of products around to help you.
Like any restoration project, make your goals achievable: decide how much work you are prepared to do, how often you intend to use the bike and what you really want out of the bike.
There are many motorcycle fan clubs out there, and a quick look through local ‘what’s on’ columns during the summer inevitably throws up bike events when dozens, if not hundreds, of pristine two-wheelers will be on show. It is also recommended to join online communities and forums and Facebook groups to extend your network of support.
Once you have chosen the motorcycle to restore - and that really can be the fun part with so many different places to look - a hints and tips book or car manual is an invaluable companion for when you reach frustrating moments during your labours.
There will be times when you may feel stumped by a problem you had not expected - and that’s where we at Frost can help. We pride ourselves on being able to give advice and scouring the UK looking for the right restoration tools and accessories to help make your labour of love that little bit easier. Be it the Yamaha 500 V4 from more recent times, or an Ariel Huntmaster from the decades which went before, here at Frost we can help you.
We also stock the equipment and products you need to make sure that once complete, your bike remains in the condition you have lovingly restored it to.
We know what it means to feel the thrill of the open road on a restored motorcycle - and that thrill only gets better when you know it’s thanks to you that the bike you’re riding is only back on the roads because of you and your efforts.