Ignition problems + Poor Running

[adamcfc]

Had a few problems with my bike, would break down every time it rains, not very helpful! originally thought it must be water in the fuel tank as when the bike breaks down it idles okay, but smokes out white smoke and soon as the engine is under any strain it dies.

Although someone at a garage had a quick look at it after they did my MOT (passed ) and said they reckon its the air filter. I have a K&N racing one on there which was there when i bought it so have never removed it, but have been told the rain is being flung off the back wheel and drenching the air filter causing it to die and smoke white. So we cable tied some rubber from under the seat to the mudguard to protect the air filter for now, as i have a standard air-box on order.

Since then, i think its been running poorly, slow to pull away, is getting bogged down in gears and on slight hills really easily, wont go above around 9000 revs ( used to go up to the full 12k) and is suffering speed-wise about 25%.

Then today i pull up at my friends house, turn the ignition off and remove the key, and the bikes still running, with my friend holding the keys, i can ride off. The only way to stop the engine is to stall it now. I dont understand how it can run with the key out, the dashboard turns off but it still runs.

Any advice would be much appreciated :/

[Wafer_Thin_Ham]

Are you sure the K&N is your issue rather than something electrical. It would make more sense if you have electrical problems which could well be causing both issues.
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[adamcfc]

no im not sure its the filter, but i rode it halfway home from the garage when it was Pi****g it down and it started to die, so i got it back to the garage, they removed, blew out, and put the air filter back on making sure it was protected by this rubber, and i got home okay albeit running a bit poorly.

I dont know about the electrics, because its been doing this thing in the rain for quite a few weeks, and each time ive drained all the fuel out and filled it up again and thats seemed to fix it, and the electrics have always been fine up until today.

[adamcfc]

Just been out of it again, speeds getting worse, now only getting about 2/3 maximum :/ Any ideas?

[Teflon-Mike]

OK give us a bit more to work on here.
A/ what bike is it.
B/ You have two or three different 'problems'... please can we identify them individually here.

1/ You say it has A K&N filter.... is it ACTUALLY a genuine K&N or an ebay special 'cone' filter 'like' a K&N
Genuine K&N filters are pretty good; they flow lots of air, and last a long time, and aren't 'so' effected by inclement weather, though being stuck in the 'splash line' of the rear wheel, isn't helpful!
Cheapo paper 'cone' filters, are not so great, they dont flow much air to begin with, and clog quickly, and have a habbit of turning to paper mashe and not flowing at all, if drenched.

Now, because you sayA K&N filter, singular, I am going to hazard a guess your bike is a single cylinder jobbie..... but that doesn't help TOO much.... could be a scooter, which suffer enormously from having low slung engines two inches from the deck, and tend to get ridden in the gutter where all the rain water gathers. Could as easily be an XR650, which is slightly bigger, and has the air filter a lot further from the road, but likely to get splattered in mud, that will set like terracota on the filter.... WHILE cone filter that flows enough air for a 10bhp CG125 or scooter, will in all probability struggle to flow the air for a 45bhp CBR500 or similar.....

Help us, help you here....

2/ Next up, you say the bike is struggling to rev to 9K, where before it used to rev easily to 12K..... Clogged or paper mashe filter may be a likely culprit here.... BUT, are we talking reved on the side stand or are we talking reved under load, ie accelerating up the road hauling your weight with it? Different conditions, give different suspects.
AND how are you measuring the engine revs? I don't know many single pot engines that rev that high, certainly not many four strokes, so are we dealing with a two stroke? And fewer with a rev counter.

AGAIN, help us help you.....

3/ Engine carries on running after ignition ky removed. I presume by the comment that with your mate holding the keys and you saying you can still ride it, that it is actually running, and the ignition switch isn't isolating teh ignition, RATHER than 'running on' which is when an engine, thats normally very hot and or very worn, will carry on running, on 'pre ignition' or 'dieseling' the charge ignited by the compression alone, like in a diesel.... which normall stopps if you tickle the throttle or put it on load.....

THAT one peculiarly points to the ignition circuit, AND the ignition circuit ALONE, if it IS simply NOT switching off. Many small bikes, and particularly Hondas dont 'break' the feed to the ignition circuit to stop sparks, they 'Make' a short circuit earthing the ignition Low Tension feed, by passing the Coils, usually at the CDI...... from which one wire goes to the ignition switch, which in the 'off' possition 'makes' the circuit that diverts current from the coils...... with me?

YEs... means that THAT WIRE isn't making teh circuit it should when you turn the ignition switch to 'off'. So either the wire is broken, cut, or disconnected, or the switch is not closing to make the circuit.

Job for a multimeter and a wiring diagram to find the break in the circuit... IF its a small honda or has similar 'earth kill' ignition circuit.... we cant say for SURE without knowing what bike we are talking about here!

You know what I'm going to say, here dont you... you, help us help you!

4/ Breaks down every time it rains, & idea it was water in the petrol? THIS is rather err... well, breaking down in the rain, could be 1000's of things. Water in the petrol only ONE of them, WHAT made you think it may be water in the petrol, WHAT have you done to eliminate that possibility, what OTHER diagnostics have you done to prove/disporve that theory..... or was the suggestion that your exposed air filter was the problem by a mechanic, side tracked you and made you randomly jump ont a different tack?

Is water in the petrol STILL a possibility, or a red herring, what do you want to know?

Petrol is lighter than water and immissable (doesn't mix') with water. If you have water in teh petrol tank, it will normally settle to the bottom, where unless you run onto reserve or have an AWFUL lot of water in the tank, it will stay, the petcock taking fuel from the top of the outlet pipe, normally about half way up the tank, hence not dragging water into teh carburttor.

Have you checked the contents of the tank, removing the petcock, and draining the tank onto a jerry can, or similar, and letting it settle, to see IF there is any water actually collecting in there?

If you HAVE water in the tank, how is it getting in there? Failed seal on the fuel cap is an obviouse culpret, but this damp weather, so is condensation from damp air 'dewing out' on the inside of the tank walls over night in a half empty tank, on a bike that gets only short journeys, and spends a long time more empty than it does more full.

A blocked breather, or one that is full of condensation could also cause fue starvation problems. Have you investigated these?

Have you checked the float bowl of the carburettor, where water would again, if it gets in in smaller quantities, 'settle' and as the main jet usually sits low in the float bowl, WOULD suck water from the bottom, often getting 'mixed' with petrol, causing poor running and white smoke?

Take float bowl off and LOOK for beads of water in the petrol sat in there.

5/ your unshielded cone filter, COULD be the cause of many of your maledies; could have been turned to paper mache, could be clogged, could be too small for the engine..... But you say you haven't taken it off.

Do so....

does it fall to bits when you try? If so, probably NOT a genuine K&N!

Inspect. Is it clogged with mud and crud? Has it turned to paper mashe? Has it been contaminated with oil?

Blow it through the wrong way, see if it cleans up. Mean while try running the bike up withoiut it..... wont hurt for a short run, provided you aren't too brutal on the throttle, and it runs lean.

Does bike run better? Does it rev out? Does it make more power? If not what DOES it do?

With inspected filter, cleaned as best... put ot back on... (if its not disintegrated)... do symptoms return? If not dos it run better, what DOES it do?

Help us, help you.... lets 'nail' THAT variable, before looking at what else might be giving you jip!

We cant press a big button on our keyboards or type in a magic code to fix it for you, and we cant diagnose it by telepathy, you have to do some work and give us details, that help us know whats going on......

Like what bike it is!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[adamcfc]

okay, first let me thank you for the time and effort you have put in here,it is much appreciated. The reason for little description is ive already posted a large post describing the water the first time it happened, and explaining all about the bike, i thought people would remember it from there. I see now how much of a stupid idea that is.

[Teflon-Mike]

OK. Well it's definitely a 'muddle'; you need to be clear in your head, organised and logical, & you need to get to grips with the 'logic' and follow the 'logical chain' through each symptoms tree of possible causes, and not get muddled with over lapping branches for different symptoms.

The ignition fault
Lets start here.
If its an earth 'killed' system, as described, you need the wiring diagram and the multi meter, and you need to identify the 'kill' wire, from the CDi or 'Igniter Box' through the ignition switch, and 'buz it out'.

Means finding what colour wire it is from the wiring diagram, then finding that wire on the the connector blocks that go to the ignition switch and the CDi.

Unplugging either end from the loom, you then use the 'Ohms' setting on the multimeter to test continuity, by seeing if you get nil resistance from the pins on the connectors at either end.

If not, you need to check the actual 'pin' on the connector block, by 'spiking' the wire.... pushing the point of the test proble through the insulation of the wire, just a little behind the connector, and testing continuity from there to the pin...... make sure pins actually connected to wire. And do that with both pins on bolth connector blocks.

Then you need to test the switch. Again with the Ohms setting.

You need to use wiring diagram to work out which wire goes to 'earth' from the ignition switch...

When the switch is in the 'off' position, you ought to have continuity between your kill circuit wire and that pin. In the 'On' position, you shouldn't. As for the feed wire from CDi to switch, repeat testing continuity through the switch.

THEN you need to find the corresponding pin on the harness that the earth from the ignition switch plugs into, and again with the Ohms setting check that you have continuity from that pin to 'earth' both on the battery AND on the frame.

Following the logic chain. (Presuming its an 'earth kill' system) if the circuit isn't being made, engine wont turn off.

Circuit is made from CDi unit through ignition switch to earth.

If the wire from CDi to Ignition switch carries current, and the pins on the ends of that wire are connected, that's not a problem, its doing what it should.

If the ignition switch carries current when it should (in the off possition) and doesn't when it should (in the 'on' possition) THAT is 'good.

If the return wire that completes the ciruit from switch to earth, is good, THEN the ignition should switch off.

If any thing in that 'chain' doesn't check out OK.... Thats where the problem lies.

If it ALL checks out OK..... then fault has to lie upstream of that, and the only real place it can lie is in the CDi 'ignitier box'.

Quick test: find pin on the CDi that connects to ignition kill circuit, and by-pass all elce with a bit of spare wire, and engine running, make a circuit from that pin to a good earth, like the battery neg terminal, and see if holding wire from bat neg to that pin 'kills' the engine.

If not, then the CDi is definitelty at fault. If so, then go BACK to the kill circuit, becouse you have missed something.

For NOW just concentrate on nailing THAT single fault, and putting it right.

You are dealing with far too many variables here, to try and sort everything all at once, and dealing with stuff in random order will just muddle confuse and confound.

Lets NAIL this Ignition anomoly first.

BECOUSE, the further 'logic' is that is you have a 'duff' CDi unit, that's breaking down, then as that controls the sparks, if its not advancing the timing as it should, or is providing weak sparks, not amplifying the trigger signal from the engine to the coil 'enough'.... THAT could be giving you poor running problems. ALSO if the unit is suffering from water ingress..... could MAKE it break down, and fit with your damp running symptoms......

Its an area where we have branches of the fault tree over lapping quite significantly.......

SO, rather than working around them randomly..... HIT this one, isolate it, and prune the branches around the over lap.

If it IS the CDi... then well, we have a number of 'issues' to work through..... like WHY has the CDi gone faulty? Is it becouse of water ingress? Is it becouse some one has fucked with it trying to 'de restrict' the bike, or has a duff regulator, caused over voltage to burn out some of its circuits?

AT THE MOMENT.... we have a plathora of porblems and or pottential causes......

So start, with THIS one, as its right in the midle, and eliminate variables.

Thomas Eddison; took 10,000 attempts to make a practical lightbulb..... he said I didn't 'FAIL' to invent a light bulb, I merely 'discovered 9,999 ways NOT to try and make one.....

So don't get disheartened that you cant go straight to and 'fix' it... everything you check and fix that DOESN'T need fixing, is one more item PROVED not to be 'THE' problem.... might have to go through an awful LOT of non-problems to find the one that is..... but stay focussed, stay organised, think clearly and deal with ONE thing at a time, and you WILL get there..... ultimately there can only be SO many things it can be!

Crack out the Test meter, and go find a wiring diagram...... see what you come up with.

Best of luck.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[N cee thirty]

you've got a shit cone filter on thats never done any good on a 50cc

i had one on my rs and it ran shit

get a standard airbox and your bike will be mysteriously fine
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[adamcfc]

Thanks mike, I have a multi-meter, and now a wiring diagram, see link .. https://s675.photobucket.com/albums/vv118/hmmmnz2/randoms/?action=view¤t=reijurs2colour.jpg

I dont know what colour the wire would be that you first talk about, the kill wire from the CDi. Im not too good with the electrical side of things, but thanks for talking me through it.

Would I be right in saying its the double dark red line from the Ignition key to the Coil?

On the other hand, today I removed the air filter and rode the bike, there was no change in the poor performance so the air filter isnt restricting flow. I took the carb off, cleaned and put back on, to make sure no crud blocking jets or fuel flow, no change. I also took the spark plug out and I have a photo, it looks fine to me, am i right? The fact that these havent fixed it pushes me more in the direction that the problem is now electrical (e.g not producing a powerful enough spark a high revs).

Thanks, Adam

https://img228.imageshack.us/img228/6150/p1010127b.jpg

https://img829.imageshack.us/img829/6655/p1010129o.jpg

[adamcfc]

@Rob, the air filter was on when I got it and never really thought of changing it. I will be getting a standard air-box through my local garage because i cant find any on the internet :/ Would you say theres much difference performance-wise, am I going to lose power from downgrading in effect.

[N cee thirty]

you'll more than likely get more power

the box was designed by the manufacturer to do the job

water won't get through the main airbox like it is doing in your cone filter
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Teflon-Mike]

[adamcfc]

Okay, so theres a RED wire coming from the battery, though a fuse, to the connector block, then turns ORANGE and goes to the ignition. because the starter button doesnt work in the 'off position' but does in the 'on' position, i can say the RED wire is fine, I also know its always live.

Actually that doesnt make sense looking at the diagram :/ im just confusing myself here.

It seems to be, that there is power going to the ignition system (the coil?) all the time, as even with no key in, i can bump-start the bike in the 'Off' position. This is further backed up, as when the bike is running, and i turn the key to 'Off' the bike doesnt stop, (becasse the ignition system isnt having its power cut, as its always on?)

So i need to check the Ignition circuit, and the possible problem could be there is no earth at the moment? for example

[Teflon-Mike]

Ok.... its hard work, and I am probably not helping being so wordy, but I THINK your beginning to get the idea.

You NEED to sort this ignition fault FIRST.....

Then we can work through the filter, mixture and spark plug issues, and YES..... your ideas are sort of starting to follow!

OK.... look again at your wiring schematic. YES you have red wire, thats battery 'live' feeding your electrical equipment....

BUT the red wire going from the generator to the coil is NOTHING to do with all that....

The Ignituion circuit is totally isolated from the battery and equipment. Its a 'stand alone, and self powered system. You could probably bump start your bike without a battery.....

THIS is how it works, and its very common, system on the 125 Super Dream I have out side works the same way, as does the system on my DT, and my Montesa.

There are magnets inside a drum, on the end of the crankshaft. This is called the 'Rotor'. sitting inside the rotor 'drum' is a plate, with a number of coils of wire around them, usually around an iron 'core'. This is called the 'Stator'..... rotor, has magnets, attached to crankshaft, rotates. Stator, has coils, attached to crank case, stays stationary....

Now, as the magnets pass the coils of wire, or the iron cores down the middle of them, the magnetic field 'induces' a current in the coil, 'MAKING' electricity.......

So.... rotor spins, staor stays still. electricity made.

Now, different coils, or 'windings' go to different curcuits on the bike. Yellow wires on your schematic go to the 'Regulator'..... those come from coils, which when the magnets pass them, creates an alternating current, goes up and down from - some volts to + some volts depending on which end of the 'coil' the magnets passing.

Regulator is actually a 'regulator rectifier' and using a few diodes and transistors and stuff, clever circuits turn that AC electricity into a 12v supply.... probably closer to 14v actually, to charge the battery, but doesn't matter.

NOW, another set of windings, in the Stator, make the electricity to 'energise' the coil. This will probably be an AC current too, and as the magnet passes one end of the winding you will get a voltage increasing from 0 volts to I don't know, perhaps 26v and then reducing again to zero volts over half a Rotor rev. Then it will go the other way as magnet passes the other end, going from zero to -26v.

Now, your engine needs a spark, something like 8 degreed before TOP dead centre, every revolution. SO.... if you arrange the stator winding and the magnet in the rotor, so that its passing exactly over the middle of the winding core at about 8 degrees before TDC, then at that moment, when you want a spark, you'll have 16v on the coil.... and thats all you need.... dont matter about the rest of teh revolution, you just want them volts on the coil at the right time to make the spark, and as such we can treat it as a simple DC feed.

Now, your coil. This is actuallyt TWO coils, and works a bit like a transformer. First winding, the 'Low Tension' or LT winding, has a LOT of winds of wire around it. As electricity passes through this coil, creates a magnetic field... that magnetic field then induces a current in another adjacent winding, bit like the magnet in the generator passing the windings on the stator. This is called the High Tension Winding, and its connected to the spark plug.

Ratio of the number of turns of wire on the LT winding to the HT winding deturmins how how the voltage is 'bumped up' or 'reduced down' from the supply voltage, we said was 16v.

To get a decent spark, we probably need something like 16 THOUSAND volts, so to bump up the voltage that high, we'd need 1000x the windings on the LT coil to the number on the HT coil.

Unfortunately that would create a very high resistance winding that would use a lot of power, and due to the effect coils have in a circut, it would 'react' very slowly......

Coils, apart from being electro-magnets have another property, and they are some times called a choke, or an inductor.

If you put a voltage on a coil, then CHANGE the voltage, they react and 'induce' an opposite 'reverse' voltage to opose the change.... so if you are trying to increase the voltage, as in or case the generated supply grows from zero to 16v, the coil will react and provide a back voltage to opose it, slightly..... faster teh change, greater the back voltage.

THIS is the clever bit. IF we 'energise' a coil, slowly, letting volts increase accross it really slowly (and quarter turn of the generator, in electrical terms is SLOWLY!) we'll get volts on it.... BUT if we then SUDDENLY flick a switch and take the volts OFF the coil, like switching off a light bulb..... the COIL reactes, as the 'field colapses', with a HUGE reverse reaction voltage, trying to oppose the suddent and huge change in volts..... that reverse voltage will be a LOT bigger than the original 16v becouse of the speed of colapse, SO, we dont need so many windings on the HT coil to bump that voltage up to the level needed to make a spark....

But its SWITHING OFF the coil, that makes it spark, NOT switching it on...... first bit of backwardsness in the system!

Next up..... powered solely from that one winding in the generator.... you get power to the coil ONLY when the rotor is spinning.

Your starter circuit, electricity from the battery turns electric motor. That motor turns the crank-shaft, rotor on teh end of crankshaft, spinning around stator, makes electricity, fires sparks.

Turn ignition 'off' engine dies, rotor stops spinning, no more electricity no more sparks......

BUT with direct feed from the magneto to the coil, tuning off the suply from the battery, wont do anything to stop sparks. Only way to stop sparks would be to either:-

a) Stop the rotor spinning (Stall the engine)
b) Break teh circuit between generator and coil. coil gets no electricity, no spark made, rotor stops spinning
c) DIVERT electricity from generator to 'earth' short ciruiting the coil, so that the power has easier 'path' not jumping the spark plug gap.... no spark, engine dies, generator stops making electric.

What YOU have is option C), that red & white wire, feeding to earth, short circuits the ignition, and kills the engine.

Ignition switch in the 'off' possition, it MAKES the circuit that diverts electric from the generator, straight to earth, bypassing coil.

Ignition switch in the 'on' possition, it BREAKS the circuit that diverts sparks electric, so the current has no where else to go, but jump the spark plug electrodes and make the sparks making engine run.

NOW, isentify THAT white RED wire on teh coil...... for now forget the multi-meter wirk.

Start the engine, and try short circuiting that white red wire to earth, doing what the ignition switch should.... I find for such tests a jump lead with a nail in the jaw of one end useful. I clip the free clip to battery negative, then with the nail in the clip the other end to push into the back of the connector block against the back end of the connector inside to make the circuit..... shoudl short the coil, and turn engine 'off'.

Try it.... should work, which then tells you that the 'fault' is upstream of the coil, in the wire or connectors or the ignition switch, NOT making that circuit you have just created with a jump lead and nail (or your own improvisation!)

THEN using multi-meter, you can trace the wiring and find out WHERE that circuit is broken or not being 'made'.

MEANWHILE, if ficing that permenantly is going to take a while, you MIGHT be able to improvise a 'kill switch' circuit...... something a tad more tidy than nail and wire.. maybe twistie connections and tape..... to make your own kill circuit, with a switch on teh handlebars or yoke, so you can run the bike up, and do a plug chop.....

See... we work through the logic, one step at a time..... Ignition fault first, becouse thats a key feature to other diagnostics.... THEN we move on and do the next thing, which is look at your sooty plug, again, having fixed the ignition so we CAN kill the engine on a switch (maybe not the one that the factory put there, but still a switch) with the engine under load......

Making sense to you? Wordy still, I know, sorry.. I'm verbose, but, read it through get it clear in your head whats going on, its all pretty simple.. REALLY!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[adamcfc]

Didnt have time today to properly have a go. But i messed around for 10 minutes. I pressed a wire into one of 4 ports coming out of the ignition coil i believe, the red and white one. Then touched the metal fram with the other and it killed the bike. This is with the ignition key on, so im bypassing the ignition barrel and killing the bike fullstop?

Please dont spend hours of your time with a long reply as I will need further help and i dont want to bore you, but im not 100% sure what to do with the wire and multimeter tomorrow. e.g do i remove the ignition barrel? do i have to cut all the loom covers and cable ties off and expose all wires? what do i set the multimeter to?

Thanks, Adam

[Teflon-Mike]

[adamcfc]

Fixed the Ignition fault!

[adamcfc]

https://img89.imageshack.us/img89/2158/1000656y.jpg

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Undid the screws on the bottom of the ignition barrel, to fine the blue wire had been snapped of its solder point. Stripped back the wire, and re-soldered it and that fault is now fixed

Now, the running problems are getting worse still. Riding from cold now, the first few minutes its limited to 25 mph, and has some serious misfiring. When its warm it gets better, the misfiring disappears and it does about 38, but this is still far below and the revs are still feeling limited.

My dad has suggested to run the bike in the pitch black somewhere, to see if any sparks are escaping from anywhere?

You also mentioned a plug chop, im able to do that now but can you expand on what i should do. Do i need to put a new plug in first?

Im far from an expert but it seems like the spark is breaking down or is weak at higher revs and under load, is there any tests i can do?

Your help really paid off with the ignition fault, thanks again, Adam

[Teflon-Mike]

Whe-hey! Some-times you get lucky!
But there you go. that's the way it goes.
If it had been at the other end at the connector block, often the wires inside the insulation snap, but the insulation stays in the connector, and its not so obviouse, which is when the multi-meter pays off, working it through, narrowing down, item by item where the fault must lie.

ANYWAY: Your Dad's idea about loosing sparks, is fair enough, sometimes you can see electrical leakage as 'arcing' around the HT Lead or plug cap. Only trouble is, that most likely to happen when the engine is under most 'load' ie when you are going fast, and accelerating, and its pound to a pinch if it arcs, it will be some where you cant see from the saddle.

However, dark night, if its bad, can sometimes 'show' tel tales.

Meanwhile, working through...... Plug 'chop'.

YES it is 'best' to start with a brand new spark plug. That will be clean, have good corners, and any colouration will be from your chop run, no guess work.

If not, you need to use a good plug and clean as you can get it.

Two strokes, and especially more highly tuned two strokes are very plug sensitive, and they errode the electrodes alarmingly and like fresh plugs frequently.

ALSO.... and I do NOT approve.... de restricted peds are a mugs game, becouse going faster is evidence itself you are breaking a LOT of laws, for bugger all reward... its still a ped..... BUT.... chances are its not got the right grade of plug in it, for whats been done to the engine.

Hence I'd checl teh spec sheets and buy two new plugs, one the suggested grade, one a single number up, and try both, see what gives best results.

Between trying them, I'd do the plug chop thrick, running bike up, and JUST before you finish accelerating, killing the engine with the ignition switch, and coasting teh last few yards back to your drive way, to remove and inspect plug against a plug colour guide.

Plenty on the web or in the Haynes manuals..... you ideally want one for a two stroke motor.

Compare colour of plug against photo gide, and follow the instructions.

Black and sooty means ritch running..... blocked / cloged air filter, incrorrectly adjusted carb etc, over oiling.....

Make ONE chance at a time, clean plug, do another chop..... see what difference it makes....

Repeat until the bikes running 'sweet' again.

Best of luck!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'