Odd carb idle issue

Hi,
I noticed the other day that when I pull up to a set of lights the engine starts rumbling instead of idling smoothly.

Here are the symptoms of the idle issue.
- at idle #4 isn't firing up
- spark is present
- turn on the fuel enrichment circuit (choke) and it fires
- open the butterflys and it fires

My diagnosis was pilot jet or circuit is blocked so I pulled the carbs and got the ole carbie cleaner out and sprayed it through the pilot jet and circuit and it is clear.

checked the jet and circuit flow on number #3 to see the flow of the cleaner in comparison and it seemed the same.

Sprayed through the fuel enrichment and every other hole I could see in the bowl and base of the carbies and figured that even though I couldn't see or didn't find an obvious block and the carbies are nice and clean well I musta fixed it!

Put the carbs back in and... same problem lol.

So before I pull them off and basically strip #4 and clean everything from top to bottom this time I thought I'd ask you guys what you think?

Thanks!

 

Check your bowl fuel levels.

Gary

 

Check for a vacuum leak on the intake boots. Mine developed the same symptoms and it turned out to be a bad intake gasket. I had to have my pilot screw out to about 5 to get it to fire at idle, but opening the enrichment or giving in throttle and it fired every time.

 

Hi,
Thanks for those suggestions.
Excellent!

I'll let you know how I go.

 

If problem persists after the above suggestions, you might try ultra-sonic heated bath in carb cleaner.

I'm getting close to fixing mine and it seems the ultra sonic has made the most improvement.

Good luck.

 

Aha!
Checked the float levels via wet method - all good
Checked around the carbs for vacuum leak with a butane torch - none found

Didn't even THINK to check the mixtures but backed the mix screw out by 1/2 - 3/4 of a turn and #4 kicked in bringing back the smooth idle.

For some reason I didn't even think to recheck the mixtures since I just did them... only 2 years ago, sheesh!

Yes I will be doing a balance and colourtune later.

Thanks again for the help.

PS: (I rang 'The Bikedoctor' over here in Perth about doing an ultrasonic clean of the carbs not long ago and either the kid I spoke to was 'challenged' or they really don't want to mess around with carbs so much that the policy is to 'get rid' of people who ask about ultrasonic carb cleaning. Oh well at least they know how to fit tyres.)

 

Polish the enrichment tube plunger tip and seat....