Hi all , recently bought a beta techno 1997 , the bike seems fine mechanically and rides fine up until I've been out on it for an hour or 2 , the bike breaks down and will not start again , then I replace the plug and it will start and run fine again but I know this isn't normal , this has happend on 3 consecutive occasions since I bought the bike I replace the plug and it will break down after an hour or 2 , wondering if anyone has had a similar problem or if anyone has any idea what could be the problem ? Cheers

If your spark plug fails its likely a bad plug cap

Remove it and test resistance, it should be 5000 or 10,000 ohms

If its slightly different don't worry but if its radically higher it fraps the resistor in the spark plug itself and you get no spark

Just tried this I'm getting around 6000 ohms , any other ideas ? Cheers , george .

G'day, is the spark plug black when you remove it? (This is the key to your issue)

Let us know and we can go from there.

Cheers,

Stork

Faulty HT coil can cause these symptoms, See if you can borrow a known good coil. Alternatively find an autoelectrician with a PICOscope or similar who can check the coils output and waveform.

Edited July 29, 201313 yr by dadof2

Ya those things get a worn needle and seat, maybe you are just running rich and it's fouling plugs

Yes when I remove the plugs they are black , and I had thought about it being the coil breaking down when hot maybe but I know they are quite expensive just want to rule out anything else before I go down that route , cheers .

You are missing something

If it dies, then you put a plug in it and it starts

It doesn't have an ignition problem

A new plug won't fix the coil

You need a gap tester, if its jumping the gap after the bike stops then its not the ignition system

Or if you don't see spark, hold the plug in your hand and kick the bike

G'day, If the plug is black you have a rich issue. Check you have the correct spark plug first. (An NGK BP7ES). Check the air filter first, if it is very dirty or over oiled it will do this. then . After that, check the float level in the carb and needle and seat for damage. That is your most likely trouble. Search these forums for instructions on how to do these things and ask if you need help. Float level checking does hold a few traps for first timers! However, stick to this sequence of events -always the easy things first!

Cheers,

Stork

A couple of members have posted "if plug is black you hve a rich issue". I do agree to some extent and certianly its best to check / fix the simple cheap things first. I know an expoerienced mechanic who replaced the coils and CDI on a 4 stroke Kawasaki (at considerable expense) when the real cause was the cold start enrichment valve not seating properly.

A failing coil can however cause exactly the symptoms, including sooty plug you have, its as if giving it a rest whilst changing the plug gives it time to cool down or whatever and work again.

The soot (conducting carbon readily ionizable) on the plug actually helps the weak coil to fire right up to the point so much is deposited it provides an alternative path (to jumping the plug gap) along the centre electrode insulator.

Cheers

Certainly correct but I'm a believer in finding a way to measure, that is diagnose

Once again I say Gap tester, it answers all question as to having spark or not

No speculation

G'day,

No coil = No spark = engine will not run and foul spark plug. Providing the plug is the correct heat range this is the only cause.

Cheers,

Stork.

Basics first, how does it run when it's running? If it runs properly you can ignore the next batch of questions.

Are you using it as a trials bike or playing enduro racer? Is the choke properly off. I've seen bent choke rods holding the choke open a bit. Is the ignition timing set properly.

OK the laundry list;

Wrong plug heat range. A lot of people think the plug heat range affects engine temperature. They're wrong. Plug heat range is to make sure the plug tip stays hot enough to burn off contaminants while staying cool enough to not cause spontaneous combustion. Common. Plug fouls, bike stops, runs fine with new plug.

Wrong fuel/oil mixture. People new to trials bikes often mix extremely rich mixtures for a trials bike that merely clog up the works. Typical mixtures in a modern water-cooled "electrofusion" bore engine run 70-1 to 100-1. Very common. Exhaust will be smoky. Again plug fouls, bike stops, runs fine with new plug

Incorrect jetting. Standard Mikuni on that bike is probably a 30 Pilot 145 Main. Needle in the middle groove. Possible someone richened it up to play motocrosser or to try and compensate for bad gas. Wear of the needle and seat are also possible as well as damaged jets if someone ran a wire through them to clean them. Float level can also be way off due to bad adjustment or a damaged float filling with fuel and sinking. Somewhat common

Plugged exhaust. If the mid muffler and/or final silencer are full of goo it affects the engines ability to breath. Weak running and fouled plugs can result. Somewhat common. Often will have a very smoky exhaust after a prolonged high speed run. Can ignite fire in exhaust system that will burn after bike is off.

Ignition timing off. Either set incorrectly or due to a sheared flywheel key. Uncommon but can happen. Engine will run soft off the bottom.

Oil leak. If transmission oil is finding a way into the area of the crankshaft through a case defect, bad primary side seal or leaking center gasket it can foul the plug. Uncommon but possible. More likely with an older engine. Usually smoky exhaust

Choke stuck on. I once saw a bike that had the bent choke rod holding the valve just slightly open. Bike was hard starting and ran rich off the bottom. How the rider bent it I don't know. Weirdest thing I've seen. Very rare.

These are the first places to hunt.

Edited August 4, 201313 yr by dan williams