Is this the end?

[Neosophist]

Gotta start somewhere so primary check will be the checking the reservoir hose isn't kinked. The pressure in the system is obviously greater than the 1.1 bar that the rad cap spring seal can cope with.and is looking for the easieast way out, in this instance through the rad cap. When I did the rrear cyclinder rebuild I used a new gasket and torqued down as per manual so I'm hopeful that this hasn't blown. If it has would I not expect to find some evidence of coolant in the engine. If it means another tear down and new gasket so be it. At least I will have a better idea of what I need to do and could bypass all my previous errors. C'est la vie.

rad cap could also be not sealing / broken, you can pressure test them.. if its old as the hills, new ones arent super cheap but a worth while investmenmt, they will last 20 years.

run it with the rad cap off.. if you get a stream of bubbles straight away then that will be combustion gasses getting into teh coolant.. it will overpressurise and overheat and blow out coolant.

you dont always get oil in coolant or coolant in oil but you might get a lot of steam if water is getting into the cylinder.. could just be gasses getting past the gasket into cooalnt.

start with the easy stuff first.. no spare rad cap anywhere?

whats the engine time running at?

[dirty30-2008]

Stroke of luck. Coolant pipe was pinched by the heat guard . Once sorted got a few bubbles come through into the coolant reservior as the rad level was slightly below the neck on start up. Rad cap seals and she was taken for a tentative spin , about 10km. All seemed fine. Did a pressure test 120 on no 1 and 150 on 3. Not ideal but given the mileage I can only put this down to worn rings. Trouble is shes going to take a bit of a back seat as the deauville will be my daily commute. Gives me a chance to tidy the old girl up.

[VtypeV4]

Glad it lives fella, nice one..

[Neosophist]

Stroke of luck. Coolant pipe was pinched by the heat guard . Once sorted got a few bubbles come through into the coolant reservior as the rad level was slightly below the neck on start up. Rad cap seals and she was taken for a tentative spin , about 10km. All seemed fine. Did a pressure test 120 on no 1 and 150 on 3. Not ideal but given the mileage I can only put this down to worn rings. Trouble is shes going to take a bit of a back seat as the deauville will be my daily commute. Gives me a chance to tidy the old girl up.

yeah thats super down. did you try putting a spoon of oil in the cylinders and pressure testing it again?

[richyrd5]

Glad to hear she's living,albeit with low comp!!..well done

[dirty30-2008]

Thanks for the pat on the back. I sometimes doubt my own abilities but it was either write it off or hang in there. I probably could have done the rebuild in a day with the knowledge that I have learned from this but you guys have a wealth of experience that you are happy to put out there for us to feed off and for that I am grateful. Wouldn't hesitate to do it all again. Will try a little oil in the bore to see if the compression comes up, but certainly wont be in a hurry to replace rings if that is the case. I expected the drop in compression on No3 as the decoke was needed badly. Hopefully it will increase slightly as the top end beds in/ cokes up. With the bike now running I have the pleasant dilema of which do I ride today. Must say getting on the NC after the deauvilles armchair of a seat was an uncanny experience! Have done about 30km on her with the carb slides drilled and shimmed. Does seem a little crisper coupled with the de-coke but not taken her above 8 thousand rpm yet .will report back on this later.
Cheers Guys