You don't have a backfire problem, you have a carb problem. You need to figure out where is the fuel coming from and see if you can stop it. Then go get new plugs. Unfortunately once those NGK's get wet they are toast.

With as many problems as I have had with mine I'm becoming really familiar with the symptoms. Unfortunately the cure still eludes me.

I know is not much to on but good luck! and welcome to the forum.

 

Thanks for the welcome LEC.
I think I have solved the fuel problem when i tapped on the outside of the carbies as there is no more fuel coming from the overflow pipe and hasnt been for a couple of days now. When i took the plugs out they were not wet and looked in good condition. I have checked to make sure i have fuel flowing from the tank and all is good.
One thing i wanted to check on is to make sure i have the ht leads on the correct plug as my manual does not say. Which coil to what plug ? sure i have them ok but just want to make sure .
Thanks

 

Gday, coil on the left[ clutch side] goes too cyl no' 1+4, other coil 2+3, cheers

 

Thanks spark11k . That is as i have got them. Didn't think i had them set up wrong as it would be hard for the ht leads to reach any other way. Just trying to eliminate things and make sure i wont do any damage when trying to fire it up. It has got me beat at the moment why it wont start and why it backfires so loud when i crank it over.

 

i'm with lec - fouled plugs

 

Are you ure its not just flooding? Try holding the throttle completely open and turn the engine over a couple of times with the starter. Then try maybe half choke no throttle to start the bastard.

 

Thanks for everyones help. I have solved the problem and finaly got the old girl going. Turned out to be a 2 part problem and unrelated to the work i had been doing on it. One of the floats was stuck and hence the petrol in the overflow , a few taps with the hammer fiixed that . And the other was a fouled plug that had gone un-noticed. Once again thanks for everones help.