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No Vacuum on Carb#1

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element137:
Hi all - been a lurker on here for a while- this is great resource -many thanks to all for the info - its a massive help - currently restoring 76 400F and have hit a problem with trying to sync the carbs as I cant get a vacuum on Carb#1 - background so far - apologies for long post -
Bike was a non runner when I got it late last year - got it running but very rough running, wouldn't idle -
Stripped carbs completely , very badly gunked up - ultrasonic clean and vapour blast - reassembly - ( have used aftermarket brass except for float valve where I used the original OEM valve ) - first attempt with aftermarket float valves resulted in leaks on all carbs -
So this week tried to sync carbs using vacuum gauges - carbs 2/3/4 all pretty much spot on from bench sync - but no vacuum on Carb 1 - can move the gauge if I suck/blow on the line - so not the gauge -
I have sprayed Carb Cleaner around all the inlet rubbers and carb tops whilst its running which has had no effect - no rise in revs or stall - so I don't think there is a leak at the inlet / carb tops
Header on cylinder one just warm to the touch where others are hot from running - so I guess its not running on cylinder 1 - couldn't get the spark plug out yesterday so have not checked if its getting a spark - but my question is -
is there anything I could have screwed up so badly rebuilding the carbs that would cause vacuum loss on one carb ? - also noted that is starts from cold without choke - so assuming its too rich, also idle screw is turned out so far its no longer in contact with the bar at all - I am hoping I have messed up the carbs/bench sync rather than it being a bigger problem - but could that cause no vacuum on one carb in isolation ?

Johnwebley:
Have you checked the valves have  clearance and are opening and closing properly?

Use another plug to check the electrics work. Lay it on the head, see if it sparks.

Undo the carb drain to make sure fuel is in the carb

Sent from my SM-A750FN using Tapatalk

element137:
Thanks - the valve/spark check is my plan for Friday this week when I have a day to spend on it - I'll open the drain to see if there is fuel - so hopefully can start to eliminate some of the variables - as I have had the carbs apart its likely I might have messed up - I was hoping that someone might recognise this issue -   and point at the fact I might have done something dumb and obvious on the carb rebuild/bench sync - its clearly running very rich ( no choke needed  ) and the idle screw position means that in effect, its redundant now - so I am thinking I have messed up the rebuild of the carbs -

ka-ja:
The most obvious thing after valve clearances, is to check out the "non-removable" spark plug, I have had a faulty (brand new) spark plug before giving those exact same symptoms.

MrDavo:
I've tried to do the valve clearances on the wrong stroke before, so there's that to check.

The plug that won't come out is worrying. It could be cross threaded - I've read about plug thread helicoils being done in situ, with something to catch or remove swarf from the combustion chamber without dismantling, but I've never tried it.

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