Hi  Hi guys i am having trouble getting my restored ct3 to tick over. it revs really nice but wont idle it just dies i presume its something to do with the primary circuit being blocked or something. do the float valves wear out and need replacing this could be sticking shut i suppose, also what would be the consequences of this small hole in the picture being blocked, i dont know much about the black art of carburation . any ideas would be great. thanks. Jez..

That is the cold start (choke) hole. If it is blocked, and the rest of the carb is set up correctly, then the bike might not start at all.

I test mine by spraying a little carb cleaner down the top hole. If it doesn't appear through the hole at the bottom, then I've managed to clear all blockages with a piece of 0.4mm copper wire.

Sounds like you have a constipated pilot [i'll try not to think about that]. Have you had the pilot jet out as it's always a bugger to crack free & is a very small hole in the jet. I still use old acupuncture needles from 30 years ago but a small wire brush strand could do it. Have you had the needle jet out of the carb [emulsion tube up the middle the slide needle runs in]. & that little Oring the extension is super important to seal into the bowl base but for the opposite reason to what you're describing as would go rich.

Yep everything GR8UNCLEAL said. & 'if' that choke jet is blocked then with the choke in action it'll only be adding air & making a bad situation worse. So when warmed up just be sure the choke is 'off' when trying to idle it.

The throttle slide has number 2.5  on it ? .where should the needle position be. I have replaced all jets ??

Have you downloaded a Service Manual from the Tech Library on the forum?

On page 82 of the combined AT and CT manual, carb details are as follows:-

Main Jet - #230.
Needle - 4J13, with clip on second setting down from the top.
Pilot jet - #25.
Starter jet - #40.
Throttle valve cutaway - 2.0 (sounds like yours has the 2.5 from the AT bikes).
Carb stamp - 314.

Did you replace the jets with original Mikuni (good) or from an aftermarket kit (not so good)?

Aftermarket jets are a common source of issues. 

Make sure pilot jet circuit is clean... 

Prudent to check which carb and jetting revisons you have...  several revisions on CT model...  at least 2 on CT3.  Latest revision would be 314E2 if I remember correctly.  Not uncommon to find a 316 or other model carb has been installed by someone.  Carb number should be stamped on upper edge of mounting flange or sometimes on choke boss...  flange is best bet.

You also said "restored"...  there are many levels of "restoration" and it could also be that you have an air leak or something else creating an issue with the idle.  Most likely pilot circuit though.

thanks for all that tech info guys.i used after market jets needle is on the right setting everything is spotless clean etc.i have done a complete nut and bolt restoration on the bike. managed to get it to tick over by adjusting the cable slack at the throttle twist grip and carb top now it is running fine .many thanks for all your help. i have downloaded the manual now and will use it !!

Is the idle speed screw mising as that lifts or drops the slide. Be careful relying on cable adjuster to set the idle as things 'can' change when you turn the bars lock to lock.

Hi Guys, you were right the solution was tempary and the problem persists.i have replace all the jets and the o ring all looks clean . what about a sonic clean ??