plunger on carburetor - starting

[Johnyk]

I can't seem to start my 1988 yamaha 4-stroke 9.9 unless I push down on the plunger on the carburetor. I found this out after taking the carb off three times, cleaning out a bunch of gunk and soaking it with cleaner. Can someone tell me what the plunger does and what I might need to fix so I don't need to do this?

 

[rodbolt]

Re: plunger on carburetor - starting

its an odd system that uses intake vacum and a thermal valve to move the plunger, if the throttle is opened during start or the valve is bad or a hose misrouted it wont work, pushing the plunger down manually overides any enrichment.on a cold engine the plunger should be up, if not there is a problem'the manual overide has two positions, plunger locked in the up position is constant rich,down is constant lean.

 

[Johnyk]

Re: plunger on carburetor - starting

Thanks that helps, although it seems weird that it would need to be lean to start. Anyway, I'm thinking I may have re-installed the plunger wrong. I guess I'll need to find myself a manual and see what it should look like.