Yeah those 2 filters do not stop fine rust particles, like you get in steel tanks. There is sometimes a similar plastic filter inside
the petcock, and sometimes a gravity bowl at the bottom of the petcock.

I have had numerous machines where the carb is rebuilt, and the petcock replaced or rebuilt, and even the tank flushed, but
those pesky tiny rust particles keep showing up in the carb. Not just in the bottom of the carb float bowl, they get on the
float needle and cause it to leak. A well-cleaned plastic tank does not do that, but steel tanks, often.

Good news is most ATVs have had plastic tanks for a long time. Not so much with Honda and Honda-clone OHV engines, and
many many m/cs and generators. Those makers insist on steel tanks. With E10 gas, they get rusty and condensation goes to the bottom.

 

Right. I took the plastic tank off shoved a jet wash nozzle inside and washed it for ages rinsed out the inside many times and flushed. It's clean as a whistle. Petcock flowing fine.

jumped on bike started. Running like **** still see YouTube video I posted previously. It's not the tank!

 

OK, very rare that the tank filters block. The problem with dirty ones like you had is dirt gets through and blocks the jets. Have you cleaned the carb out since you cleaned the tank? Look out for water in the float bowl, you will be lucky if you got all that jet wash water out of the tank. Check the battery isn't overcharging, as the 300 is DC ignition and an overcharging voltage reg can put very high voltages into the CDI and coil. It can also kill the plug. I have just heard the video, could be just where you had the mike, but the engine sounds terrible. I think you have cam problems, this also could be your trouble.

 

thanks merryman, i haven't cleaned the carb out again, but will do so again for luck. How do i check for overcharging, have a meter i guess im looking for like 15 plus volts across battery?

Just had a local mobile bike repair guy out to check it, he too commented on the knock and using a tube reckons its little end knock. Reckoned it was mechanical as it's smoking a bit and it was revving ok but no power. Its cam or little end who knows.

Plug is relatively new and electrode looks fairly flat.

I have a spare CDI i would wire up to see if that helps.

 

15v at the battery is an absolute max, shouldn't be more than 14.5v Strange you have such good compression if the little end has gone and it smokes. US readers will now be wondering what a little end is.

 

Thanks Merryman off to test voltage in a minute not sure about the spam spam bit?!

 

Sorry, tried using asterisks as a joke and the website spam filters stuck that up, my dodgy internet connection took a while before it let me edit it out.

 

ok interesting!

Checked battery voltage before starting... 12.2volts

Revved it up and wow 18.4.volts back to idle still about 17volts plus. Have you discovered something here? Is my regulator screwed. I have two spare CDI's which may fit (brand new but connections need changing)

 

Omg i just found this thread which refers to your observation on the voltage and my knocking noise!

https://www.instructables.com/id/Tro...you-KLF300-AT/

And i had to replace my ignition switch recently as it kept switching on/off all the time. Anyway would this be affecting my bike in the way it's gutless and underperforming.