Hi people, Found this forum on search engine and thought i might try my luck getting some help.

Mods, Sorry if this is in wrong section, I placed it in what I seen fit best.

So heres the issue, I Used to experience issues with bike where when riding after about 10 mins the bike would jolt slightly and throw my weight forward as if i had dropped 3 gears and let the clutch out dropping several thousand rpm at the same time and its got much worse, I can now free ride at 60-70mph....lol Yes 60-70mph and no engine power. As it starts to jolt and throw me forward, i pull clutch to stop myself being shot off bike and no sooner than i know it, the engine has cut out and im helpless to get it started until i stop. bump starting sometimes works but not always, usually find the bike has stopped rolling before i can think of trying to bump start. I have tried opening throttle to keep it running once i have pulled clutch lever but the bike still insists on dropping revs and cutting out as if it was starved of fuel. when it dies it does give off one hell of a noisy back fire, a firework exploding in sky would best desrcribe the noise it makes.[edit: only if throttle open when it dies, it backfires]

What do people suggest is the issue.

My ideas follow:
Carb related?
Fuel Line maybe kinked/trapped? << lifted tank off slightly and looks ok.
Fuel Filter? (If it has one....im not too mechanically minded)Led to believe it might be gravity fed fuel but source wasnt 100% sure?
dirty fuel in tank being fed into engine?
Condensation at bottom of tank being fed into engine?
Not enough air mixture?
oil/fuel mixture wrong?
Blocked breather? << where is breather for me to check this....????

Recently changed the plug and its still the same issues.

Having severe difficulties getting it to even start now.

You all may laugh at this but foolishly I gave myself an electric shock by touching outer area of spark plug just the other day when bike cut out as I could here a different vibration/rubbing noise coming from that area and wanted to feel where vibrations were coming from.....lol, got thrown back 2 metres flat on my bum and still dont know anymore about the vibrations...very reluctant to touch the bike now after that but im told you can be shocked from it if bike electrics are on << is this true....?? that the shock wasnt a fault on the bike but just stupidity?

anyway, can anyone help shed some light...

Bike was last serviced over 3000 miles ago so its very much due a service, two new tires and f**k knows what else to fix it this time.

Regards,

A troubled public transportee in need of a fully working motorcycle.

 

Wow, you have covered just about everything that can go wrong with a bike in your list.
Don't know much about the 125 or location of the breather is, but some things are consistent to all bikes. When they cut out like that, which is wots causing the bucking.
Just follow your list in trying to diagnose the cause, it's fuel or spark related, so: Coils, plugs, carbies, air filter & fuel. Don't touch anything electrical while the bikes running ok!
Personally, it sounds like a fuel problem.

 

Yea Pretty much everything!

Only one plug which was replaced less than 250 miles ago. problem has only got worse. Not being too mechanically minded, how would one go about diagnosing a fault without knowing what looks right or wrong or not having any idea what to look for.

Further question, Could I add air filter to my list of potential culprits for my troubles? just i havent had that cleaned/changed since last service either?.....Just a thought.....[edit - just read quote again, you mentioned air filter....im a **** that didnt read it properly first time]

!!!Please let this be a cheap repair and nothing too nasty.....!!!

any help would be appreciated

 

You mention that the problem got worse after you replaced the plug?
Ok, start there, Take the plug out & have a look at it's condition, they are a good indicator of what could be the matter. Could be fouled, or something as simple as not having correct gap, cap not fitted firmly in place or even the correct heat range of spark plug, (Double check that its the right plug for your bike). Often its the simplest things that cause problems.
Here's wot to look for. Also, being a 2 stroke, fouled oily plugs are not uncommon.

 

Its not A 2 stroke bike, its 4 stroke. does that make any difference to your response?

 

I dont know nothing about a CBR125 nor have never seen one, but make sure the battery cables are clean and tight.

 

Nothing to do with battery cables as lights are nice and bright....even when it cuts out....battery is now starting to die as it wont start but battery isnt the culprit for my issues whilst riding.