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Pipe from carbs. Where should it go?

PostPosted: Wed Jul 11, 2018 10:57 pm
by rabbit
Hi there.

Fuel not getting through to the engine on my SR43A

Took the carbs off and found a pipe was disconnected but can't seem to see where it should go.

There is a t piece in between the carbs at the top on the airbox side.

Shown on this schematic as part number 50 :

https://images.cmsnl.com/img/partslists ... 1_70bd.gif


Anyhelp appreciated!

Many Thanks

David

Re: Pipe from carbs. Where should it go?

PostPosted: Thu Jul 12, 2018 6:56 am
by guru
This pipe coming from that T-piece is about 15-20 cm long and goes nowhere.. It is called "air vent hose" in the work shop manual and what it does is to let the carbs breath out the fuel gas...
Your problem must be somewhere else..

Re: Pipe from carbs. Where should it go?

PostPosted: Thu Jul 12, 2018 7:29 am
by BigBob
Indeed. I`ve even removed that length of pipe on all my Bigs as it serves no purpose at all.
Check your vacuum line is not perished or disconnected or there`s not a kink in a fuel line. Fuel filters can also become clogged over time.

Re: Pipe from carbs. Where should it go?

PostPosted: Tue Jul 31, 2018 11:09 am
by Hann
Another pipe hose connection question....

I`m working on a SR42A.

Where should the vacuum hose from the fuel pump attach?
At the moment it`s connected to the top of the r/h carb (on the diaphragm cover). I think this is incorrect and it should be connected to the l/h carb in the area at the rear of the choke plunger mechanism?

Which leaves the question what are the stubs on top of each carb - are they for balancing the carbs and should normally be capped off (one of the stubs has snapped off...)?
Do these carbs balance in the same method that any other motorcycle carbs are balanced ie: vacuum gauges? - i`ve never worked on a single with twin carbs before.

Thanks.

Re: Pipe from carbs. Where should it go?

PostPosted: Wed Aug 01, 2018 1:48 pm
by dave#22
Hi, you're correct, the vacuum pipe does not go to the carb top...on the SR41 it goes to the LH carb body (in the position you mention) and on the SR43 it goes to the same place on the RH carb body, not having an SR42, I presume it goes to the LH carb body.
I think the holes in the carb tops are to let the diaphragms breath, but not sure.
Hope it helps.
Dave.

Re: Pipe from carbs. Where should it go?

PostPosted: Wed Aug 01, 2018 2:25 pm
by BigBob
Yep, Dave is right. The hose goes to the top of the l/h carb body where the vacuum caused by the piston descending activates the fuel pump which is mechanical and has a diaphragm in it. On the SR43 the hose goes to the top of the r/h carb.
The carb bodies are the same as used on the GS500, GSX600/750/1100, and GSXR750/1100 Slingshots etc and the nozzles on the carb top were used for the 2nd air system as required in California and other tree hugging areas.
I guess Suzuki figured it wasn`t cost effective to build two types of carb.

Re: Pipe from carbs. Where should it go?

PostPosted: Wed Aug 01, 2018 10:13 pm
by Hann
Yep, cheers guys got it sorted now by attaching the hose to the l/h carb body - it idles like a champ now.
I only noticed that hose connection stub on the l/h carb by seeing a very faint wisp of fuel vapour exiting it after i stopped the engine one time. On closer inspection i found it to be pulling in air so obviously not correct for it to be vented to atmosphere like that.
It`s funny how the bike ran though with the pump hose connected to the r/h carb diaphragm cover because there`s no vacuum created at those little stubs at all - i took one off to inspect it and the carb body directly underneath is flat with no drillings or anything by the look of it.
I haven`t got the proper DR tank here so have a temporary fuel tank rigged up set high on the frame top tube, the fuel must of flowed past the fuel pump by gravity only?