VB Ignition Timing

[martin.cooper]

Hi All,

My 55 VB is a bit of a pain to start.

The mag gives a nice fat spark, and when running, the engine plods along nicely, and will pull well up hill with no problems, but when I come to restart from hot it can be a bit of a b*****r!
What should I be setting the timing at BTDC? I assume it needs to be set with the mag fully retarded?

In the summer, after a bit of a slog up over the moors, in roasting heat, I stopped and nothing other than a bump would get her to fire....could it have been a problem to do with fuel vapourisation? Should I fit a heat spacer between carb and inlet manifold?

Finally, what are peoples opinions about the effect on plugs with modern fuels containing ethanol? I have been told to run with a hotter plug than book standard to try and prevent fouling...this comes from a pal that races a classic outfit.

Cheers, Martin

[Knud.Degnbol]

Get a new condenser/capacitor or what you call it. It sits inside the armature.
Knud

[nevhunter]

re the ethanol, there shouldn't be a problem unless the tank is fibreglass. The engine should run a bit cooler and as the ethanol content rises you would need to retune the carburettor to enrichen it and you would get a lower gas mileage, under those circumstances. The VB wouldn't run a very cold plug anyhow would it?
With plug heat range, it's usually the revs, compression ratio, and throttle position that dictate the need for a colder plug. NOT the size of the engine. (Assuming your mixture is right). Nev

[john.nash]

Hi All,
My 55 VB is a bit of a pain to start.

The mag gives a nice fat spark, and when running, the engine plods along nicely, and will pull well up hill with no problems, but when I come to restart from hot it can be a bit of a b*****r!
What should I be setting the timing at BTDC? I assume it needs to be set with the mag fully retarded?

In the summer, after a bit of a slog up over the moors, in roasting heat, I stopped and nothing other than a bump would get her to fire....could it have been a problem to do with fuel vapourisation? Should I fit a heat spacer between carb and inlet manifold?

My VB was the same
Started easily cold, but woebetide you if stalled or you stopped after it wa hot. It had to be left to cool down for a bit.
There was a spark visible at these times; but not much of one.

My Magneto required a recondition, which was done by Merv:
http://forum.arielownersmcc.com/viewt ... ?f=23&t=52

So, I'm with Knud here.

[martin.cooper]

I know its nothing to do with the size of the engine, the feeling is that the standard plug as per specified back when the bikes were new in the 50s, are now not as suitable for fuel with an ethanol content of 5% which is what we put up with here...A hotter plug seems to improve things (looking at the colour and deposits off a used hotter grade plus vs say an N4)
I have checked the jetting and it is std.

I will try a new capacitor

[nevhunter]

Any magneto that has an original coil is running on borrowed time. I have had plenty of bikes where the spark fades after about one ond a half hours running. when the magneto is rewound and the condenser checked and replaced if necessary, you have a completely different motor.
I had a veteran V twin that I had rebuilt for a guy with intermittant hard starting that I suspected was experiencing magneto problems. It took 1 and! 1/2 hours on the test bench, before it broke down and gave an intermitent spark. up to then it performed flawlessly. Nev

[Knud.Degnbol]

Have a look here: http://www.edknet.de/Download/LUCAS%20MAGNETOS.pdf

Knud

[Keith.owen]

Hi,
Just another thought - do you have an insulating washer ( a thick gasket made of tufnol or something) between the carb and the inlet manifold? When carbs get unduly hot this often produces a similar effect.

Keith