Diaphragm/Piston - should it look like this?
- Thread starter WillemVanKatwijk
- Start date
Uncle Phil
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Just a note - if you separate the fours carbs from each other, you will probably lose your mind trying to get them back together correctly. 
I've never had that part off a carb so I have no idea.
I've never had that part off a carb so I have no idea.
Why do you have the carbs out? Was the bike running poor or perhaps the water hoses needed replacing? If there are no tears in the Diaphragms they might be OK.
ST1100Y
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Looks indeed like their slightly swollen due that darn ethanol additive... (confirms my aversion against E10 and preference for premium E5 fuel...)
As long as they're not torn or show punctures I'd leave them alone and only see of the sliders move easily...
And I'm with @Uncle Phil, swollen diaphragms will be a real PITA to put back together again...
ST carbs rarely need a full rebuild; pop the float bowls off, clean/replace idle and main jets as well as the float needles & seats (which I clean them with a Q-tip and little Autosol Chrome polish), see if the floats move easily, if the carb needles are corroded, worn or bend (likely not) and install new bowl gaskets when putting all back together...
Even the air cut-off valves are rarely damaged/in need of replacement...
New carb boots (isolators) are kinda mandatory, as they grow hard and kinda "vulcanize" themself on the stubs due the heat... I do them every 2~3 years to maintain an easy removal of the carb assy...
As long as they're not torn or show punctures I'd leave them alone and only see of the sliders move easily...
And I'm with @Uncle Phil, swollen diaphragms will be a real PITA to put back together again...
ST carbs rarely need a full rebuild; pop the float bowls off, clean/replace idle and main jets as well as the float needles & seats (which I clean them with a Q-tip and little Autosol Chrome polish), see if the floats move easily, if the carb needles are corroded, worn or bend (likely not) and install new bowl gaskets when putting all back together...
Even the air cut-off valves are rarely damaged/in need of replacement...
New carb boots (isolators) are kinda mandatory, as they grow hard and kinda "vulcanize" themself on the stubs due the heat... I do them every 2~3 years to maintain an easy removal of the carb assy...
The diaphragm is indeed misshapen, but hardly surprising if its been laid up for a long while with stale fuel and ethanol vapours doing their worst. Plus it's down to age and miles too. There's a danger they will be quite likely to split if messed with too much, but it wouldn't hurt to check they're no worse than that.
Upt.
Upt.
OP
OP
Bike doesn't start and was in the garage for a couple of years now. Only fuel used since the owner has this bike was 95/e10. This fuel is not the best for older bikes I understand. So, I persuaded the owner to use only 98/E5 as that is the only available alternative over here in The Netherlands.
ST1100Y
Site Supporter
Again, start at the business-end of the carbs: the jets hiding behind float bowls... that E10 crap is prone to leave debris and corrosion there...
Then the fuel supply... does the pump even run and deliver?
Next is ignition system... got spark?
Maybe the kill-switch is corroded (early models will actually crank with this in OFF)...
possible the connector shells behind the head-stock suffered corrosion...
possible the feed on the coils have bad contacts...
possible the ignition lock switch-plate has issues...
possible the starter relay (behind LH side panel, forward of battery) has a melted connector (unplug the red socket to inspect)...
Your diaphragm looks normal like mine.
I remove my carbs few mths ago to chase an issue with high fuel consumption and too rich condition after a shop major service(timing belt, water pump, idler bearings, all water hoses and elbows,carb boots) and clean up the pilot/main jets without splitting the x4 carbs.
Clean and check the diaphragms was not torn and all nooks and crevices that I can reach. Only took out the aircut valve that I can reach and they looked good.
Like Martin mentioned, most carb parts should be good, maybe only the carb bowl gaskets might be a concern, I reuse mine without any problems.
I remove my carbs few mths ago to chase an issue with high fuel consumption and too rich condition after a shop major service(timing belt, water pump, idler bearings, all water hoses and elbows,carb boots) and clean up the pilot/main jets without splitting the x4 carbs.
Clean and check the diaphragms was not torn and all nooks and crevices that I can reach. Only took out the aircut valve that I can reach and they looked good.
Like Martin mentioned, most carb parts should be good, maybe only the carb bowl gaskets might be a concern, I reuse mine without any problems.
Attachments
Your diaphragm's are stretched out badly. If you could find inexpensive replacements, I'd replace them.
As it is now, I can possibly see a delay in throttle response in the midrange, or potentially not being able to obtain full throttle rpm's from being so stretched out, not allowing the slides to be fully raised. Under load, you should be able to hit the rev limiter at 8500 rpm's.
As it is now, I can possibly see a delay in throttle response in the midrange, or potentially not being able to obtain full throttle rpm's from being so stretched out, not allowing the slides to be fully raised. Under load, you should be able to hit the rev limiter at 8500 rpm's.
NRP motorcycle carburettor repair specialist
NRP specialise in carburettor diaphragms, air cut-off valves [or coaster enrichment valves] carburettor overhaul kits and spares for all Japanese carbs.
www.nrp-carbs.co.uk
Sorry to hijack the thread.
Adam, I’d like to thank you personally from all your in depth posting and replies for the carb setup that helped me resolve my rich running/high fuel consumption that plagued me for over a yr.
Long story short, suspect shop did something to my carbs after service, prior to work mileage was ~15-17kml, after -12-14kml, low gear roll on bogs down with no power, high gear is fine. Mileage very bad during stop and go traffic, highway ride is ok. Range per tank dropped by -50km. Exhaust smells really gas rich, followed your various posts advise to check/setup carbs.
Found the courage to tackle carbs, Pilot screws was found to be adj -2-3/4, clean carbs, setup to -1-7/8(guesstimation for my tropical climate with 40/125 factory jets, no idle drop done) and synch. Bike sounds much better post sync , purrs during lower gears and smooth like butter.
Mostly importantly the mileage is back to normal for my location. Appreciate all your expertise and posts/replies in this forum.
ReSTored
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st-riders has a very comprehensive carb rebuild post with dozens of great photos.
Above is an image of the part in question.
Above is an image of the part in question.