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[cheesemonger]

Fairly new to motorcycles. Have a 2007 Bullet 500 purchased a year ago which had only done 1500 kms. Now after another 3000 or so the top 14/15 inches of the exhaust pipe has lost its chrome colour and is golden. There's a little blueing for the first inch and then it's kind of red/gold. Is this normal or could I have a timing problem. Thanks Martin (Christchurch NZ)

[Leon Novello]

Hi Martin: They will all discolour slightly. Severe bluing is usually retarded timing or weak mixture. An amber/straw colour is considered normal. Expensive motorcycles have a dummy outer cover over the pipe so it remains cooler and stays shiny. There are compounds available to polish off the bluing but it will also remove some chrome if used too often.

[ric]

If your bike is running on handbook recommended ignition setting then you might be running slightly retarded.

The figure that was recently being printed by REI for their iron barrel engines is the same figure first quoted by the Redditch factory back in the 50's.
The bike may not have changed much, but fuel certainly has and it requires a slightly different amount of ignition advance to complete an efficient burn inside the combustion chamber than that available from the pumps back in the Fifties.

[jefrs]

What you are seeing it the tempering colours of the chromium plating, which is lower than that of the steel pipe under it, just as well. This is happening to my bike too, it is fairly normal. Weak mix.



Post-war austerity fuel was basically rubbish, little better than available in India even now, and required 6.5:1 compression to stop it 'pinking' (detonation). By the end of the fifties petrol had improved allowing 8:1, 9:1 or even higher compression. Through the 60s we got a tiger in the tank and even 105-octane petrol, which was nice. That allows things to be run far more advanced without multiple spark plugs. We don't have that stuff now but do get 95-99RON (97/99RON is 92/93octane in the USA)

Unfortunately India still has 88RON petrol, so the bike leaves the factory basically set up to run on rubbish. The good news it that it can be fixed. The engine is supposed to run lean but it can be richened up and advanced far more than poor fuel will allow to make the motor work harder but big but - advancing the ignition is a way of ensuring the fuel is all burnt by the time the piston reaches bottom dead centre to prevent 'knocking' and embuggering the big end, so the fuel is ignited before the piston reaches top dead centre, this is to overcome the slow rate of burn of poor quality fuels; it actually wastes power. Using a high quality fuel enables the ignition to start closer to TDC. You will have noticed I seem to have contradicted myself there - advancing the ignition on high quality fuel can be counter-productive. Pinking and knocking are two different but related things.

The bike can be made to run much better but no, the bluing won't go away. In any case it's something of a status symbol.

[cheesemonger]

Thanks - Leon, ric and jefrs - great information!

[Tim NZ]

Check that the points gap is at least 0.014", max 0.016". A reduced gap retards the ignition timing and leads to bluing of the header pipe.


Put a drop of oil on the points pivot, and a wee dab of grease behind the heel of the points. Lack of lube at these points accelerates general points wear


A quick squirt of Chain lube in behind the points plate to Lube the AA unit is advised, from time to time.

[PeteF]

It's pretty rare to find one without some bluing on the header and the golden colour is almost always there.
Worth checking the points though and have a look at the plug colour. If it's white at the centre electrode it will be running a bit lean.

[jefrs]

If you have a lean-burn or EFi then the plug colour won't tell you much other than gross defect like oiled up, the plug should look paler than ye olde Haynes manuals show.



As TimNZ rightly says you can adjust the A/R a little on the points gap; I have a 0.016-in diachrom spatula for doing that but if you make the gap too small then the charge in the condenser will jump the gap and produce false weak sparks. If you oil the points rotor as you should then be a bit leery of getting oil on the contacts, hence the diamond coated feeler gauge to remove pitting. The drop of oil on the end of the dipstick (or screwdriver) is more than sufficient. You most certainly do not want the points dripping with oils and the nylon part of the points is practically 'self-lubricating' (plastics like a hint of silicone rather than mineral oil).

Are there not a pair of A/R springs and weights behind the points plate? - they like a little lubrication too.



But that's getting complicated. Imo leave the ignition timing alone and maybe make the mix a little richer by raising the carb needle a notch (is that possible, I don't know which carb you have).

[cheesemonger]

Thanks Tim NZ (sold me the bike?), PeteF and jefrs - all good stuff. Points gap is good at .4mm as per the book and plug ash coloured with just a liitle soot on the insulator. Its not a lean burn of EFi engine. The carb needle is set in the middle slot, though I've ordered a slightly richer throttle slide to (maybe) rectify an occasional problem where the bike dies when the throttle is suddenly opened at, for instance, traffic lights or blipped when changing down. Unfortunately the bike is just now being being pulled apart with a likely main bearing failure. During a post xmas ride it developed a rough sounding noise (other than the usual clatter from the valve gear) which seems to be coming from the crank case. Bugger!

[PeteF]

Plug sounds about right although you can't "read" plugs like you used to with modern fuels.
Main bearing failure is all to common I'm afraid - make sure you replace with better quality (the originals are pretty crap) Also, while it's split, have a really good look at the big end. It's false economy not to replace (or upgrade) that at that sort of mileage.