FJ1100 carbs

FJ111200 · April 02, 2011, 06:10:47 AM

OK this is the problem i've got which led me to this site.
On the fourth carb, the one that is on the right as we sit on the bike, the pilot air screw does not screw in as far as the other three. I've checked that the rubber o ring and metal washer are not trapped down the hole and they are not. I've got another bank of 1100 carbs which are well worn, but the pilot air screw goes in all the way although it took a bit of force to get it seated all the way, and that's the same on the 3CV carbs i've got aswell. I don't want to ruin what is potentially a re good carb.
Could it be that the fourth carb on some 1100 models has a factory pre setting that means the p.a.s. cannot go in any further and so acts as a guidline for the other three?
Or is it just that the previous owner at some stage made a balls up and cross threaded the hole?
The brass on the p.a.s. is still in good condition and i'm scratching my head. I want to use these carbs but don't want the engine running weak/hot on that cylinder, leading to other potentially harmful head and piston problems.

andyb · April 02, 2011, 07:56:28 AM

Is the very tip of the screw tweaked a pinch, by chance? Alternately, if you take the spring out, does it screw in further?

FJ111200 · April 02, 2011, 08:26:12 AM

Thanks for the reply. No, the tip seems fine. I've just compared the spare ones i've got under a magnifying glass and they all look the same, but one of them seemed to screw in further than the others. It makes no difference whether the spring is in or out.
I have thought about trying to screw it in and out a bit further each time so that the screw cuts a new thread, but don't want to overdo it in case i make a mess of things.
I've cleaned the hole out to the nth degree and can't see any crud in there, unless there is a fine layer of some sort of superglue, used to hold the screw in because of a damaged thread.

weymouth399 · April 02, 2011, 08:56:14 AM

DO NOT I repeat DO NOT wind the fuel screw in tight, you will damage it or the carb body. Only lightly seated NOT TIGHT.
If the carbs are off, you should be able to see/feel the tip of the fuel screw in front of the slide.
(be very carefull not to damage the tip) That should tell you if the screw is in all the way or not.
Let us know what you find.

Bob W

SlowOldGuy · April 02, 2011, 04:51:35 PM

Quote from: FJ111200 on April 02, 2011, 08:26:12 AM
I have thought about trying to screw it in and out a bit further each time so that the screw cuts a new thread, but don't want to overdo it in case i make a mess of things.

The BRASS mixture screw will NOT cut new threads in Aluminum.

Remove the carbs and look back into the throat from the cylinder side. Is the tip of the mixture screw protruding into the throat? That's the only way to gauge whether it's the same as the others.

DavidR.

FJ111200 · April 03, 2011, 07:02:13 AM

Thanks for the replies.
The number 4 carb does not have the screw protruding into the carb throat like the other 3 do.
I'm well and truly stumped.
So it's not a factory pre-set position then?
My only reasoning now is to turn it as far as it goes and leave it. When the other 3 are backed off 2 turns they still protrude into the throat.
As i said before, my only concern is that it will run weak/hot on that cylinder.

Flynt · April 03, 2011, 10:16:26 AM

sounds like something is in the hole... maybe one of the little silver washers is jammed in there and won't let the needle through? Can you visually confirm it is clear?

Frank

FJ111200 · April 03, 2011, 10:31:20 AM

Quote from: Flynt on April 03, 2011, 10:16:26 AM
sounds like something is in the hole... maybe one of the little silver washers is jammed in there and won't let the needle through? Can you visually confirm it is clear?

Frank

I think that is the only possibility. Though when i've taken all four out and compared the holes and seats they all look the same, that is, just the way the carb bodies have been drilled with the stepped hole. Shining a torch down the hole and looking at it with a magnifying glass, and they are all looking the same.

Flynt · April 03, 2011, 10:34:13 AM

Try a light in the carb throat and looking in through the hole the needle goes into... you should see right through it.

Frank

FJ111200 · April 03, 2011, 10:38:58 AM

Yeah mate, done that, and i can see through the hole clear as day.

FJ111200 · April 04, 2011, 11:37:34 AM

Thanks to everyone for your input.
I've got the carbs sorted by putting on a spare carb that i had onto the bank. I know some of you might think why didn't i do that to start off with, but i was trying to save the offending one, and in the end had to give up. Whatever it is was not going to play ball, it really has been a S.O.B.
I've just pre-synced and bench tested them and they are fine. So my next step is to rig them up to one of my XS1100's.

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FJ1100 carbs

SlowOldGuy