Basic Fault Finding.

[Guest]

Remember this:

Most faults which cause an engine to stop working, or work intermittently, are ignition-related. It is rare for a bike to suffer a sudden

fuelling problem. So don't start dismantling the carbs when it starts misfiring.

If your engine refuses to fire, or stops firing altogether:

Check kill switch

Check fuses

Check battery leads

Check sidestand ignition cut-out (especially if it's a Kawasaki) and/or clutch lever ignition cut-out

Intermittent or rough running:

Check all of the above - loose fuses or a slightly loose battery lead will cause this. Ditto a dodgy connection to a kill switch. However,

if the bike suddenly loses power on one or more cylinders:

Check which cylinder(s) are missing. If it's a single cylinder which is failing, then the problem is likely to be HT/spark plug/plug cap

related.

Swap over the cap and/or HT lead (if possible) to see if the fault transfers to another cylinder.

Understand this: it will not be a coil or ignition pick-up problem. Four-cyinder engines are wired so that cylinders 1 and 4 work off one

coil and ignition pick-up and cylinders 2 and 3 off the other.

Find out if these pairs are dropping by feeling for the hot exhaust pipes - and obviously, take care! They're hot! If you have a fault that is causing 1 and 4 or 2 and 3 to fail, then it has to be coil or ignition pick-up related.

It's more likely to be coil - swap over the coils and see if the fault transfers to the other pair of cylinders.

If it doesn't, then the fault is in the ignition pick-ups. Check for a bad connection on the wiring, but prepare yourself to buy a new

pick-up unit (and they're never cheap).

Fuelling problems:

:

Bike runs fine, then dies, and will not re-start for a while. Then it restarts, runs, and dies again. And so on.

Partially blocked fuel tap? If the bike uses a vacuum tap, pull off the fuel line from the tap and switch the tap to the Prime position.

If you get a good fuel flow, replace fuel pipe and try it on this setting.

Blocked or partially blocked vent hole in filler cap? Remove filler cap and see how the bike runs without it. If you've recently removed

the fuel tank, check you haven't pinched one of the fuel lines when you refitted it.

Bike runs rich, on one or more cylinders

Check for sticking choke control

Check you haven't left a rag or something else under the seat or tank which is blocking the air intake

Check the plugs - if it's just one cylinder that's misbehaving and running rich, it could be a misplaced pilot jet or main jet.

Brakes:

I get a strange vibration through my brakes when I put them on.

This is a warped disc. It *is* possible to have the disc trued in a hydraulic press. Often it's better to replace the disc with a new

one - maybe a PFM pattern.

My brakes feel spongey. I've bled them and it makes no difference.

Check pad thickness. Sometimes very worn pads give this effect. Or - check the brake hoses. If they're very old they bulge under pressure.

Another cure - loosen master cylinder cap, tie brake lever back to bars with bungee cord or gaffa tape, and leave overnight. All the air

finds its way up the hose and to atmosphere. Works a treat.

Chain:

I try and adjust my chain, but it's looser in some places than others.

This is a "tight spot" and is common on worn chains. Adjust at the slackest point of the chain. Buy a new chain soon!

Should I change my sprockets at the same time as the chain?

In theory, yes. In practice, no. The pedants say that sprockets and chains should be changed together. In fact, the rear wheel sprocket

wears very slowly. The gearbox sprocket, as it has about one-third as many teeth, carries three times the load and wears much faster.

You'll find that a front sprocket may need changing with the chain, but that a rear wheel sprocket will last for two chains. Obviously,

this is variable according to thrash and maintenance quotients!

I'm supposed to adjust my chain with someone sitting on the bike. How can I do this by myself?

Difficult. Set the tension with someone sitting on the bike, then get them off it, and measure the tension with them off. Then simply set

it to this tension thereafter.

Electrics:

My battery keeps flattening. What's wrong?

It could be a duff battery, or a duff charging system. Test the charging with a multimeter connected across the battery terminals. With

the engine revving it should be about 14 volts. For a quick test of whether the alternator is working, turn on the headlight, rev the

engine, and see if the light brightens. If it does, the alternator is working - but the regulator/rectifier might still be up the Swannee,

meaning no charge.

There's a rattle from my engine which gets worse the more you rev it. What's up?

Most likely a rattling camchain. The most likely scenario is that the tensioner has stuck, unless it's high mileage in which case the

chain could be knackered. If you own a Honda, it could be both. Suspect the tensioner first - replacing a tensioner unit is generally

quick and cheap, whereas replacing a chain isn't.

How can I tell if the dealer has done the service work?

Put very little blobs of Araldite on the tappet covers or cam cover/cylinder head joint. If the blobs are still there and unbroken, then

the covers haven't been disturbed. If you've been charged for a valve adjustment, you've been ripped off. Mark the air filter, and ditto

the oil filter (scratch a mark in it with something sharp).

[Rich748]

I get a strange vibration through my brakes when I put them

 

Do you put them on just for fun then?!

[Stealth]

Check which cylinder(s) are missing.

 

Bugger me - my last bike was like that all the time - only ran on 3 cylinders.

But then it was a Triumph ......

[cyberwolf]

pmsl

[houdini]

triples are the best