SOHC.co.uk Forums > CB350/400

Carbs off bike - Total disassembly or not?

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Mikep328:
Thanks Ted!

I ended up separating the carbs.  All sliders are free and all linkages are OK.  The chokes tend to close a bit on their own because the detent is not strong enough to hold firmly against the choke butterfly springs.  I disassembled the detent mechanism - not much to be done there though cleaning out the detent itself, where the ball engages, helped - there was a lot of crud in there which kept the ball from seating as deeply as it should.  It's better now though still not as positive as I'd like.  I thought about drilling the detent "depression" deeper but I don't like modifying something that obviously worked fine when new.   But it does seem that those choke butterfly springs are much stronger than they need to be AS is the throttle return spring...Now that's a SERIOUS spring!  I'd be happy to find/install one that is a bit less aggressive.  :)

Oddjob:
Find a stainless steel split ring (like the ring on a key ring), I found a pack of 10mm ones I use to have for sea fishing rigs, remove the spring from it's pin at the bottom of the carbs, I threaded the pin through the ring as the carbs were apart when I did this but you could thread it onto the pin like you thread a key onto the ring etc. When it's on clip the spring onto the ring

I tested this method to see if it actually made a difference and by using a fishing spring weight I can 100% say it does, the poundage needed to open the throttle decreased from around 14lbs to around 10lbs, I have the figures somewhere.

Mikep328:
Good idea, I have some split rings laying around...

With the very generous help of Multiman, who came by the house/dropped off a section of tubing for the between-carb vents and a dollop of red rubber grease, I am reassembling the carbs with the intent of reinstalling them tomorrow.

I seem to recall reading in a post (of course now I can't find it) that the carbs could be installed with the airbox already mounted to them.  Of course it is quite possible that either I misread the post or that I mis-remember the post.  If that's possible it seems it would be a bit easier.   No idea if a new original airbox back in the day was somewhat flexible/rubbery or more hard/plasticy.  My airbox is quite pliable, maybe it's a replacement though its not listed on any of the numerous parts receipts that came with the bike.

McCabe-Thiele (Ted):
The trouble with the airbox is it is so pliable that when you try to fit it to all four inlets one always seems to pull partly off.

Only time mine fitted as it should was when there was no rear wheel, mudguard or battery box in place. It was easier to build backwards.

Multiman:
I haven't tried fitting the airbox to the carbs before fitting the assembly to the engine so won't comment on that.

To help get the airbox onto each carb I shove the two centre fittings by pushing from through the air filter housing with my fingers or any other prodding device I have a to hand.

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