Cleaning the carb today. There is a wee black circle above the hole for the main jet in the picture on the left. It is blocked, but maybe it is supposed to be. I have given it a gentle poke and it feels as if it should be there, but it could just be dirt jammed in. 

My finger is on the screw that leads to the black bit.

It is a PHBL26

 

The bike has a good spark but is harder to start than it should be.

Dirt or that is what it is supposed to be like?

 

thanks

https://www.dellorto.co.uk/product-category/dellorto-motorcycle-carburettors-parts/complete-carburettors-dellorto-motorcycle-carburettors-parts/phbl-20-to-26mm/

The info you need should be on the above website.

thanks, I now know that when looking from the bottom it is the pilot jet that leads to the black bit.

Will now have a dig on the link, ta

11 minutes ago, misterroy said:

thanks, I now know that when looking from the bottom it is the pilot jet that leads to the black bit.

Will now have a dig on the link, ta

The small hole on the engine side of the needle block is the pilot circuit there is another in the inlet venturi (body tube) to allow mixture into the engine when the slide is closed.

Best to use an airline and not poke anything in to parts of the carb.

Edited November 19, 20178 yr by trialsrfun

I had cut some nylon strands off the kitchen brush, so the poking was not very violent. 

What I have learned today is the Pilot hole in the carb does not go straight to the tube that sits in the reservoir, there is a wee dog leg.

My bonus learning is not to leave the jet hanging by a few turns when it is in the kitchen to take a picture. Somewhere between the front door and the shed it unscrewed. Spent longer looking for the jet than cleaning the carb.

On a Keihin the hole at the botton is microscopic and can be blocked by a bead of water. I have no idea about the Dellorto. You may be fooled by the size of the opening at the top into thinking the bore is the same all the way. If it is like the Keihin you can bung up the carb by opening it more. The problem with sticking anything mechanical through holes is if what you’re poking in there (wire) is harder than the oriface you can ream it out larger. Something soft like fishing line won’t damage the jet/passages but can peel off threads that you’ll never get out of the hole. 

Compressed air is the way to go making sure it has some place to come out. You want enough pressure and air flow to dislodge obstructions but not so much pressure it damages o-rings or seals in the carb.