My cb125 k5 1973, runs fine but a few weeks ago, the battery boiled, the accid levil is still ok but it loses power, (lower than 7v = broken.) all the lights broke aswell (blown up) the new battery boils again. even after running for a few seconds Now, 10 min. later, turn the egnition on, NOT START, a sissing nois (like kooking)can be heard at the battery. what can it be( the rectifier? and if so, how does it look like and where is it?) thanks bart rosseel (belgium)

Seems you have a dead battery. Could be anything related to the charging system (alternator, control, wiring) or the battery itself. It takes a methodic process of testing to determine the cause(s).

Start by having battery tested and charged. If the battery checks ok and holds a charge then "likely" the problem is with the charging system, but it's a multistep process of elimination and very few parts store do a complete full load battery test.

If the battery test fails then you'll need to replace the battery and then promptly have the charging system tested to verify its working or you'll have another dead battery.

Once the battery and charging system has been verified functional you need to have a parasitic current test done. Excessive parasitic draw can ruin a new battery in a few months depending on your driving habits. Is this a daily driver or every other week or longer?

Check all ground connections to chassis and engine.

It could be your battery,your alternator or both

When you disconnect the battery in the PT Cruisers you have to rub the connectors (terminals) together and leave off for 10 minutes, it will reset it and believe me this is the solution. I had it done a week ago after replacing my batter a few months ago and losing my power windows as well. Who woulda thought?

not your fuel or pump you probably have a loose ignition coil check them out if they are lose or are not in sincro they will back fire

Make sure the battery is good and fully charged . You will get the code if the battery is bad on the transmission.Check the ground wire from the engine to the frame of car. Must have a good one. Check to see if the battery cable is getting hot. The gauge inside the car could also be bad. A few things you should look at

either the belt is slipping or the alternator is losing juice at a lower rpm....i take it it was checked in park,or taken out and tested by a machine which spins fast?

You need to explain the problem better....  You are saying that the machine is not boiling the water and the problem has gotten worse ?  It sounds like you may have a loose or corroded wire(s) running to the heating element which would explain the intermittent nature of the loss of heat... If you are not handy with tools and electricity, take it in to a coffee machine or appliance repair place and tell them the problem.

Check for a clogged catalytic converter.

Does it have spark , fuel pressure ? If the starter spins the engine an does not start an run , you have a fuel delivery problem or a ignition system problem . There are videos on youtube showing how to test for these .