Hissing gas cap

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thanx atom3624. its not cross threaded and the tank has two pipes coming out of it one for inlet and one out to the carb. there is a vent hole in the cap and i did put a small screwdriver thru it to chk if its clean and then blew some air form my mouth it was difficult to blow air thru it but some did pass, very little under a lot of pressure. now do i hav to enlarge the hole on the outside of the cap or the two holes on the inside of the cap where the thread i locked into the cap so the cap does not fall out. there are two small holes next to the thread too.???
 
i have not got a clue:w00t:what your on about with so many holes

if you have lots of holes in the cap, then the cap must be vented :D

if your worried about venting,drill a small hole in the tank

and screw in a small nipple and attach a piece of fuel line to vent to the rear

K....
 
Thanx sorry for te confusion but there is one hole on the outside of the cap and two on the inside of the cap. But wil try to vent the gas tank.
 
Youre right,two holes inside,rubber valve and one hole outside.I had the hissing problem yesterday,the hole was too big it the top of the cap and the rubber valve was too far open.had to order a new cap in the end.
 
If you take your cap off, the inner part comes off, carefully leaver it, under that is a white filter, fine screwdriver will pop this out, this part was blocked on mine, cleaned it, and the hole in the top off the cap and it was sorted.

hth

Jason
 
well i put in a new 668 carb and ran it with the cap open its sound ok but need to run it for a full tank just to be certain.
 
hi guys again there i put the new carb and it still cut out after 5 mts of running can i make a new vent hole in the grommet next to the inlet and return pipes??????
 
Is the end of the return pipe sat at the top of the Tank or the Bottom?

sorry if it seems a daft question, But not long ago bought a non runner with these symptoms and that was the problem.
 
top of the tank just to return fuel, the pipe that takes petyrol into the carb sits at the bottom of the tank with clunk.i had same problem on mine.first i made the whole bigger in the cap,didnt work,then i made the hile bigger in the felt material(under the cap) then under thast theres a small plastic white bit with 2 holes in,i made them bigger and now seems ok.
if this didnt work i was going to drill a hole and put a breather pipein or just buy a used tank off ebay with breather lines
 
Hi j450n &hyper 78. Thanx for the rplys. J should I put the return valve also at the bottom of the tank. Hyper should I make the holes under the cap in the white plastic bit bigger instead of making a larger hole n the cap.?
 
YES, I TRIED MAKING THE HOLE BIGGER IN the cap with no joy, so i made the holes slightly bigger in the white plastic.not too much bigger.after youve done,try blowing into the wholw thing and see hoe easy it is to blow through.
the petrol comes out the tank,into the tube and to the bottom of carb,then returns from top of carb back to tank.
 
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