carb fuel starvation - downhill & starting

A couple of questions related to XJ550 hitachi carbs, knowing that the spring clean is coming. Should I pull the choke plungers and needle assemblies out in the spring carb clean? I know that one of my 3 secas in the autumn was flat out refusing to start, turned over 100 times, but dry Spark plugs when i pulled to check, float levels were fine but as Rick says the pilot tubes get blocked with rust often, cleaned and blew them out but still no joy. Would not fire or even backfire. Is there anything in the top end of carb that can get gummed up on all 4 carbs? Vacuums are all good, and good fuel flow and I synced the carbs with a vacuum cleaner (actually a really good way on the bench, with a home made manometer). By the way dont buy the vacuum gauge from Canadian tire to sync with the Yics tool, it is nowhere near accurate enough. wasted lots of time building YICS tool, when a Dyson Rocks.
Also on other seca I have odd behaviour when i am going down hill , the bike becomes what seems like fuel starved - almost like only firing on 3 cyls. then on the flat - whoof off again fine, I am thinking float levels?

 

Did you check the choke passage in the bottom of the float bowl? It can be difficult to clean. In the past I've heated up the bowl and given the passage a blast of compressed air which did the trick.
I would think the down hill problem is 1 of 4 carbs not quite right. Good luck finding which one.

 

Simona ...

I think the 550 has Mikuni Carbs.

Sounds like you have to set your Float Levels if you are losing Power goind downhill.

 

Rick your right - its my big screen TV thats Hitachi, they are Mikunis... Whats the verdict on pulling out those choke plungers ? Cant hurt to clean there too right? Also David when you say heat up, d'you mean take a torch to them for a few secs inside?? removing all gasoline of course to avoid a Michael Jackson hair moment in the garage

 

Don't apply heat to the Mikuni "Chokes". They have Rubber "Stoppers" on the end rather than being like Hi-Tot and just having a tapered brass fitting.

Remove the whole Enrichment Valve and chuck it into the drill. Rotate them and clean them with 1500 Finishing Paper and then Brass Polish them before putting them back together.

Don't take the Rubber ends off. Use a Q-Tip and wipe them off with ArmorAll.
Clean the Bore they are in with ScotchBrite Pad and Flush with Carb Cleaner.

While the Valve is out ... Push Carb Cleaner into the Brass Siphon Tube at the Botton-end and flush-out the passage.