Crankcase pressure G3LS

John Baldwin. · Post by **John Baldwin.** » Thu Nov 06, 2003 5:27 pm

I would be grateful for any help/views on two issues with my 1953 G3LS

1.I have had a problem for 18 months with excessive oil coming out of the pressure release valve . There is a constant oil mist blown out of the pipe which quickly marks the road if you are standing still. It does not just occurr when you start so seems not be caused by wet sumping. I have checked the valve and replaced the diaphragm

I have now taken the head off to try and find an explanation. There is an old quite deep score in the barrel ( I guess about 15 thou deep and 3/4 inch long). Is it possible that this is allowing pressure to escape into the crankcase and causing my problem. Any other thoughts

2. I am fed up with the Monobloc carb intermittently running too rich and am thinking of buying a concentric on the grounds it is more reliable (so I read) Is this a good idea (accepting that purists would not approve- but then my existing monobloc is not authentic either)and if so what jet sizes etc do I need to ask for

Thanks

John

Tolly · Post by **Tolly** » Thu Nov 06, 2003 10:20 pm

John,
One of the most common causes of crank case pressure build up is compression blowing by the piston, if you have a score down the bore this could be the cause of the problem but check the bore ovality as well as the bore wear.
As for the carb problem are you sure that it is sometimes running too rich? When the slide wears on these they usually run weak due to the air pulling past the slide.

Hope this helps.

Regards Mike

silverarrow · Post by **silverarrow** » Fri Nov 07, 2003 4:15 pm

B4 changing the carb due to intermittant rich running, I would look into the possibility of the float stickin and/or sinking or set too high effective 'flooding the carb on a more or less permanent basis. A worn needle valve could also be the trouble. I have used the same MK1 carb on my 18S for 31 years and it works well, that is if the unleaded does not gum it up.

Les Smith (silverarrow397) [:o)]

lawrence · Post by **lawrence** » Fri Nov 07, 2003 8:31 pm

Surrey Cycles are extremely helpful on carb queries. They have a website for which i don't have the address. A search should soon turn it up.

Lawrence[}:)]