Hi, I need some help please.

I have an NC35 that won't start. Its been standing for a few months and when I came to start it yesterday it fired up briefly for a few seconds then died and I've been unable to restart it. I've traced it back to what seems like no fuel reaching the carbs. I've checked the fuel tap works when a vacuum is put onto it (using a length of hose and sucking on it).
The problem seems to be no vacuum coming from the vacuum hose which is connected to the inlet manifold ?. The hose is in good condition with no splits or cracks. I can suck and blow into the hose, theres no restrictions.
When I crank the engine over I can bearly feel any vacuum being pulled. Any sugestions as to why I'm not getting a vacuum and what I need to do next.


Appriciate any help you can offer.


Jeremy

If you remove the tank and put an external fuel supply direct to the carbs what happens - plug the vac line first..

I removed the tank and added an external fuel supply - tried starting the bike again and it still wouldn't start. As I was cranking the engine over I was getting a small vacuum being pulled on the vacuum hose this time.
So the problem isn't the fuel supply from the tank or the vacuum valve not working. I also removed the two rear plugs, both were dry and looked ok.
I could easily blow air into the fuel line going into the carbs but when filled with fuel I had a lot of resistance - as expected.

pull the carbs

Did you have spark on the rear cylinder plugs?

I got the bike going - I removed the plugs again and gave them a good clean with a wire brush then checked each plug and lead was giving a good spark against the cylinder head - good spark seen. Refitted the plugs and the bike fired up almost straight away (using a bottle with fuel connected to the fuel line, kept it going for 10mins before stopping. I then refitted the tank and now no problems with it restarting now.