Hi all I’m rebuilding my st1100 1992 , have ultrasonic cleaned the carbs and fitted a kit , the bike runs very well , but the choke kind of hisses when on and the bike will stutter and cut out if too much choke is applied , the hissing seems to be coming from the holes in the pic , if I block them with my fingers the hissing lessens so I’m pretty confident the noise is from there , anyone had this before ? Any help would be appreciated before I pull it apart again thanks
Choke / carburettor issue
- Thread starter PaulCovy
- Start date
I tried it with and with the filter housing on you can still hear the noise and the revs don’t pick up with the choke , it’s starts fine , but with the other bikes I have they all need a little choke in the morning , but this is my first experience with a Pan? So I’ve nothing to compare it with really thanks
I've never heard the hiss, so can't help there. I cannot recall there actually being an auxiliary air flow, just the trumpets.
The ST usually/always needs choke to start, it will then rev happily on the choke/enricher and can usually be pushed off very quickly in normal temps.
Upt.
The ST usually/always needs choke to start, it will then rev happily on the choke/enricher and can usually be pushed off very quickly in normal temps.
Upt.
That’s what I’d have thought , but even a little bit of choke the hiss like an air leak , with the choke off no hiss and it idles and revs fine , does sound like an air leak , but from the circled parks in the pic, it’s very odd , it’s all that’s stopping me from putting it all back together and taking it round the block
Don't start riding until you need no choke.
ST1100Y
Site Supporter
We don't know what exactly you'd done to the carbs...
No filter plus no lid leans the mix tremendously...
No choke required for starting would indicate a rich idle mix setting...
No filter plus no lid leans the mix tremendously...
No choke required for starting would indicate a rich idle mix setting...
The bike had been sat , I’ve removed the carbs to find blocked jets , before the bike would only just run with the coke on full and then only just , any throttle it would die straight away , stripped out all the floats jets ect ultra sonic cleaned the body’s , cleaned the jets set the float heights with new needle valves , set the pilot screws to 2 turns out from seated. The bike runs and idles now , but the choke doesn’t seem to pick the revs up like I’d expect from cold start , just kills the engine
Did you replace the four inlet boots? If these are original and hardened....or cracked....they will suck air. Also....did you balance the carbs after they were reinstalled?
Yes all synced , and 4 new tour max boots fitted , it only makes the hissy sucking noise when the choke is operating, if the choke is off it’s fine , it’s very odd
I may be wrong, but I think those holes go to the needle diaphragms to let them equalize. If those are hissing then there is a tear in the diaphragm or it isn't seated/sealed properly. And if it's only during choke, there could be something sticking in that assy.
Again, I'm not a carb expert, but that's where it seems to be pointing.
Again, I'm not a carb expert, but that's where it seems to be pointing.
New video by Martin Blower
photos.app.goo.gl
ST1100Y
Site Supporter
Well, the thing only runs properly with filter installed and air-box closed...
M2C: if a cold engine fires without choke, and/or stalls when choke is applied I'd estimate an already too rich mix... check spark plug picture to confirm...
I only very briefly tested the `91 I'd recently worked on without filter & lid, and didn't notice any hissing sounds... but I didn't play around much, cause it runs like crap with lid off... it fired, yay!, filter and lid on, test again, choke works, runs fine, OK, let it warm up, check for leaks, non found, throw Tupperware back on...
maybe I’ll bung it back together and run it round the block , the plugs were black and they are brand new , but then I have been messing around with the choke a fair bit , so I’ve wound the screws back 1/2 a turn each , I’ll clean the plugs and see what happens
Slydynbye
Will ride for Pie
One WAG, Are the choke plungers moving the same on all 4 carbs? If you separated the carbs it could be tricky to get them right. I had to slightly bend the rod connecting the 2 side to get them right. Also make sure they are all fully off when the choke is turned off, maybe loosen the cable a bit to make sure of that.
I never split them , they are all moving and are free , they do go back all the way too
You can put some miles on it without putting all the body work back on. It's much hotter without the bodywork but still fine for sorting it all out.
Slydynbye
Will ride for Pie
If you do ride without any body panels make sure you have secured the little "Nut clips" they can fall off easily and are about $5 each to replace with STock. I have yet to find a correct replacement other than OEM for the little ones.