Carb flooding?

WEM

WEM

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I put the fuel tank on my 1974 850 MkII today for the first time this year. The left carb drain plug had a weep. Tightened the drain plug. The leak persisted. I tried several new washers. The left drain plug leaked each time. I could see the fibre washer become saturated and it looked like the fuel was weeping through the washer. I swapped the left drain plug and washer with the right drain plug and washer. The left side still had a weep. I decided to try to start the bike to see if it would run. Tickled the right carb. It took about 5 or 6 seconds for right carb to flood. Tickled left carb. Left carb flooded immediately. It seemed to already be flooded. Bike started on first kick but was running really poorly. Occasional backfires on left side. Pulled the spark plugs. Left spark plug was soaking wet. Ordinarily, I would suspect the spark plug might be the problem but because of the issue with the left carb I suspect that something is going on with the left carb causing it to flood. I had the carbs apart this winter to check float bowl heights. Float bowl heights were fine. Everything was cleaned and reassembled correctly. (I thought). The carbs are five year old Premiers. Hoping to get time tomorrow to pull the carbs off to have a look. Removing the carbs is always a nuisance mainly because of the inside Allen screws and the rubber boots. Any suggestions regarding what else might cause the symptoms I have before I remove the carbs, or what I should be looking for after the carbs are removed. Thanks.
 
WEM said:
I put the fuel tank on my 1974 850 MkII today for the first time this year. The left carb drain plug had a weep. Tightened the drain plug. The leak persisted. I tried several new washers. The left drain plug leaked each time. I could see the fibre washer become saturated and it looked like the fuel was weeping through the washer. I swapped the left drain plug and washer with the right drain plug and washer. The left side still had a weep. I decided to try to start the bike to see if it would run. Tickled the right carb. It took about 5 or 6 seconds for right carb to flood. Tickled left carb. Left carb flooded immediately. It seemed to already be flooded. Bike started on first kick but was running really poorly. Occasional backfires on left side. Pulled the spark plugs. Left spark plug was soaking wet. Ordinarily, I would suspect the spark plug might be the problem but because of the issue with the left carb I suspect that something is going on with the left carb causing it to flood. I had the carbs apart this winter to check float bowl heights. Float bowl heights were fine. Everything was cleaned and reassembled correctly. (I thought). The carbs are five year old Premiers. Hoping to get time tomorrow to pull the carbs off to have a look. Removing the carbs is always a nuisance mainly because of the inside Allen screws and the rubber boots. Any suggestions regarding what else might cause the symptoms I have before I remove the carbs, or what I should be looking for after the carbs are removed. Thanks.
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Were there any issues PRIOR to you taking the carbs apart to fix them?
 
CanukNortonNut said:
why not just take the float bowl off the problem carb and have a good look. Have a look at the drain plug area for any radial cracks or lines as a leak path.
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I had a look for any possible hairline cracks and couldn’t see any. I’ll look more closely tomorrow. I will pull the float bowl off first. Thanks.
 
Could be a stuck float and the float needle not seating right, hope you turn your fuel tap off when parked up as once I forgot to turn the fuel tap off and next morning when I started the bike up a fuel and oil mixture blew out of my breather hose and filled up my catch bottle with oil/fuel, the float/float needle stuck open and filled my crank full of fuel overnight, has only done that once in 49+ years of ownership, found out was a bit of crud stuck under the float needle to cause it to flood my motor and forgetting to turn off my fuel tap the last time I rode it, worst part the motor fired up fist kick, filled up the catch bottle and spewed on the floor, shut down the motor real quick, the bike was parked on the side stand and was the left carb that had stuck float.
Amals don't have a overflow hose like most other carbs, my old PWK carbs one carb use to have a sticking float and would piss out fuel from the overflow regularly, didn't do it all the time but I could never get it right so went back to my old Amals after about 10 years of trying to fix the problem, didn't do it all the time but enough to piss me off with fuel coming out of the overflow hose when stopped.
 
WEM said:
I put the fuel tank on my 1974 850 MkII today for the first time this year. The left carb drain plug had a weep. Tightened the drain plug. The leak persisted. I tried several new washers. The left drain plug leaked each time. I could see the fibre washer become saturated and it looked like the fuel was weeping through the washer. I swapped the left drain plug and washer with the right drain plug and washer. The left side still had a weep. I decided to try to start the bike to see if it would run. Tickled the right carb. It took about 5 or 6 seconds for right carb to flood. Tickled left carb. Left carb flooded immediately. It seemed to already be flooded. Bike started on first kick but was running really poorly. Occasional backfires on left side. Pulled the spark plugs. Left spark plug was soaking wet. Ordinarily, I would suspect the spark plug might be the problem but because of the issue with the left carb I suspect that something is going on with the left carb causing it to flood. I had the carbs apart this winter to check float bowl heights. Float bowl heights were fine. Everything was cleaned and reassembled correctly. (I thought). The carbs are five year old Premiers. Hoping to get time tomorrow to pull the carbs off to have a look. Removing the carbs is always a nuisance mainly because of the inside Allen screws and the rubber boots. Any suggestions regarding what else might cause the symptoms I have before I remove the carbs, or what I should be looking for after the carbs are removed. Thanks.
Click to expand...
Later premier carbs they come with thin fiber washers (not sure about yours). Try two washers, or a stat-o-seal (Dowty washer), or an O-ring. If they are aluminum Premier's then the drain plug sealing surface of the bowl is machined. If zinc, then not machined and careful flattening will probably work. If thick washers, you've probably over tightened and cracked it.

The flooding is most likely a stuck float needle, stuck float, or a misadjusted float.
 
Because it is the lowest point, sometimes what appears to be leak from drain plug is actually coming from somewhere else ( banjo, bowl gasket, tickler).
Also, some version of the stay-up float had interference from the metal part that caused flooding. The fix is filing the edge off a bit.
 
If you have those new(ish) red fiber washers they are a PITA. They are tough to get a good seal with. The other option seems to be the green or black "paper" washers, they work perfect. Unfortunately they seem to be a one use item.
 
I took the left float bowl off this AM. Everything looked good, was in the correct location and seemed to be working correctly when the float tang was manually depressed. I decided to pop the right float bowl off even though the problem was with the left carb so I could do a side by side comparison. The tang on the float on the left carb was bent down very slightly more than the tang on the float on the right carb. Made a very minor adjustment to the tang on the left float so both looked to be as close to the same as I could get them. The adjustment was no more than 1 or 2 mm. Reassembled the carbs, turned on the petcocks and no leak! Both carbs tickle the same now. There doesn’t seem to be any flooding in the left carb. I guess the float needle in the left carb wasn’t sealing properly before and with the minor adjustment to the tang it is now working properly. Amazing what a difference in operation that minor adjustment in the float tang made. I started the bike and it is running much better. I hope to get a test ride in tomorrow. Thanks to everyone for their suggestions.
 
Such a minor/simple adjustment/fix, always pay to take a bit more attention when doing carbs or any other things on our bikes, anyway good you found the problem and easy fix.
 
I get to start other owners Nortons regularly and In the past have tired myself out at times with fruitless kicking . This year no such problems. I have ensured that carbs drip fuel . And if the fuel is brown sticky and smelly , a lot of fuel . Tickling the carbs often does not result in any drips at all. But holding the tickler down and giving the carbs a whack invairiably gets the fuel flowing . sticky float needles !. There has been many first kick starts ,even with HC 750 ,s , And i am now soon to be 80 years old. And only 12 stone.
 
It only takes a small rust particle from the tank to cause a float needle to weep fuel.
These particles are smaller than the fuel filter, so I've taken to putting small magnets on the underside of the tank adjacent to the petcocks if it's had previous evidence of rust.
 
I taped a magnet to the fuel line on our little Hondas racer, and it was definitely catching the crud from the tank, so I'll stick with it.
 
Don’t want to say too much in case the gremlins are listening, but first ride of the season was a joy. Fifty year old bike and a seventy year old rider, doesn’t get much better. Thanks again to everyone who offered advice.

Carb flooding?
 
Mart UK said:
Annoyingly, rust isn't magnetic.
Click to expand...
Returning to this - my Ducati restoration.
I'll continue taping magnets to my fuel lines post-rebuild, since they're definitely catching something coming out of my de-scaled tank, even if they do miss those non-magnetic rust particles ;)
 

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WEM said:
Don’t want to say too much in case the gremlins are listening, but first ride of the season was a joy. Fifty year old bike and a seventy year old rider, doesn’t get much better. Thanks again to everyone who offered advice.

View attachment 120091
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Nice motorcycle! I always liked the 3-color version of what the factory offered.Mine came that way but switched to the Interstate tank and side covers.
Mike
 
YING said:
Nice motorcycle! I always liked the 3-color version of what the factory offered.Mine came that way but switched to the Interstate tank and side covers.
Mike
Click to expand...
My bike has had several colour schemes over the years but I returned to the original look 5 or 6 years ago. I always liked the red, white and blue scheme. The bike gets lots of comments when I’m out and about. The paint was applied in my shed and is hardware store rattle can paint. My son says the bike is a good 10-footer (ie. looks good from 10 feet away). Any closer and you start to see the warts and blemishes. 😂.
 
I'm also a fan of the 3 colour JPN scheme (might not be the correct description, but I'm sticking with it).
My 920 work-in-progress.
Once the Ducati stops distracting me I'll carry on with it.
 

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