Author Topic: Needle clip position - explained? (Read 25636 times)

Duanob · « **on:** July 12, 2011, 07:57:57 AM »

1976 CB550K 087A carbs

Does anybody have a good article or write-up that explains what needle clip position does? All 4 of my carbs are running rich which in a way is a good thing, they are all pretty consistant. I've gone through the carbs a few times but I've never touched the clip position and now I'm thinking they may need to be adjusted. The air filter is new, all o-rings are new, all floats have been checked and rechecked with a level tool (clear tube). Nothing blocking the air intake. I hear about raising and lowering the needle but what does that do?

And BTW my gas mileage is horrible. I hear guys getting 45 - 50 but mine on a good day gets about 35 MPGs. There are no leaks anywhere so all the fuel is going through the carbs.

the technological J · « **Reply #1 on:** July 12, 2011, 08:12:18 AM »

basically the wider open the throttle is the more vaccum pressure and the level at which you set your jets controls at what level of vaccum each hole in the jets are exposed...
35 unfortunatly is teh norm for the 550 mpg i dont really know why and ido know they like to run rich..... have you changed your air filter? i would start there before messing with consistant carbs

Duanob · « **Reply #2 on:** July 12, 2011, 08:13:54 AM »

Thanks. Airfilter is new.

So what happens when the clips are lowered vs raised?

Nortstudio · « **Reply #3 on:** July 12, 2011, 08:17:47 AM »

Don't mean to jack, but I just also posted a question about the needle clip. Duanob, can you tell me how to get TO the clip? I'd like to check mine as well, but have never been in there....

Silverback · « **Reply #4 on:** July 12, 2011, 08:41:21 AM »

For non-PD carbs: To get to the needles, you must pull the carbs, remove the carb brace(4 phillips screws on back don't forget the return spring), unscrew caps on carbs and unscrew the two small bolts holding the needle to the slide.

Lowering the needle (Raising clip position) leans out the mixture while raising it (lower clip position) will do the opposite. The main jet feeds the needle emulsion tube. As the slide is opened fuel makes its way past the taper of the needle. The lower the needle, the less fuel that gets buy at this point. When the throttle is opened even more, the needle is less influential and the main jet becomes the determining factor for the amount of fuel entering the motor.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** July 12, 2011, 09:09:53 AM »

Knowing that you've gone through your carbs I'd first ask 2 questions: Have they had a proper synchronizing AND do they have stock size jets? Then I'd ask if you have the needle clip in the correct stock position. IE make sure they are set up correctly before you start playing. You need the proper baseline to begin with then 1 change at a time. After the one change do a proper plug read in the different jet rpm areas and go from there.

willbird · « **Reply #6 on:** July 12, 2011, 09:11:41 AM »

Putting an object inside the emulsion tube to alter flow is a part of many carburetor systems. In some systems the needle is raised and lowered mechanically as more air is allowed in (with butterflies or slides) and in some systems it is raised and lowered by vacuum.

I know that is more info than you asked for :-).

In the Kehin carb the needle rises and falls with the air control device.

Somewhere on the site is a chart that shows what feature of the carb is having an influence on the mixture at a given throttle opening. But if you open your air box or take off the pods you can look in there as you open the throttle and see the needle rise and fall, and get an idea what throttle opening raises it completely out of the emulsion tube. Crud on the needle from leaving fuel in the carbs could richen the mixture too because it effectively makes the needle bigger, as can crud in the emulsion tubes or blocking some of the holes in the emulsion tubes.

I just recently cleaned a set of carbs I left set with fuel in them, the needles did have some buildup on them.

fmctm1sw · « **Reply #7 on:** July 12, 2011, 04:33:25 PM »

I think the Honda motorcycle carburetion manual may have what you are looking for. It's here somewhere...

Duanob · « **Reply #8 on:** July 13, 2011, 02:35:05 PM »

Quote from: fmctm1sw on July 12, 2011, 04:33:25 PM

I think the Honda motorcycle carburetion manual may have what you are looking for. It's here somewhere...

WOW! I think I just discovered fire! Or eternal youth! I can't believe I never saw that manual before but I downloaded it and have been reading it. I feel like I really understand how these carbs work for the first time since I bought my bike over a year ago. Everyone here should download it.....NOW what are you all waiting for?

http://forums.sohc4.net/index.php?topic=17788.0

the technological J · « **Reply #9 on:** July 13, 2011, 10:46:14 PM »

Almost a 1000 posts and ur just now getting a manual? I'm afraid to see what your other posts are about!

dave500 · « **Reply #10 on:** July 14, 2011, 12:32:37 AM »

you dont need to pull the carbs off the bike on non pd carbs,just take off the caps and they can be gotten at,i do it all the time,you need finesse and deft fingers,you will need to resync them though.

Duanob · « **Reply #11 on:** July 14, 2011, 08:23:17 AM »

Quote from: the technological J on July 13, 2011, 10:46:14 PM

Almost a 1000 posts and ur just now getting a manual? I'm afraid to see what your other posts are about!

Thanks for the confidence dude. I ask very few questions if you bothered to check my posts. I have every other manual I just didn't see the carby one. With all the carb quesions on this board, apparently I'm not the only one. Now that I've found it I steer other members with simple carb questions right to it.

Dave500 yeah I went out last night and had a look see. I think I can get to the needles without taking the carb rack off the bike.

willbird · « **Reply #12 on:** July 14, 2011, 08:57:42 AM »

Quote from: dave500 on July 14, 2011, 12:32:37 AM

you dont need to pull the carbs off the bike on non pd carbs,just take off the caps and they can be gotten at,i do it all the time,you need finesse and deft fingers,you will need to resync them though.

I thought I had changed the clip position on my K2 carbs on the bike, but memory can play tricks after 20 years. I did it in a buddies back yard 40 miles from home and I simply could not fathom that I pulled the rack off and all apart to do it.

dave500 · « **Reply #13 on:** July 14, 2011, 12:39:59 PM »

take off the cap,the remove the bolt holding the lift arm to the shaft,the remove the top nut at the other end and swing the arm up and lift the slide out,ive managed to pop that slide end ball out and back in by taking up the tension of the spring,its ok but if the little steel thrust jigger that lives inside the nut dislodges youll have to remove the nut to square it back again anyway,use 1/4 drive sockets and dont rush,one or two of the phillips screws on the caps are awkward to get to under the spine of the frame,i always replace those with allens anyway which makes it easier.

Nortstudio · « **Reply #14 on:** July 14, 2011, 01:21:04 PM »

I finlly got a close look at the needles for the first time. they all were uniform, and in the right position.

Dave, good call on the Allen head replacement. Do you know offhand the size required?

The only thing I'd add, pre allen head, would be that a magnetic screw driver is a must, if you don't want to remove the "plunger.". Sorta obvious I guess.

Duanob · « **Reply #15 on:** July 16, 2011, 04:37:00 PM »

It worked! I decided to dig into my carbs today and ended up taking the whole rack off the bike. I got to the needles and there was some corroded kind of crud on the upper part. I cleaned them up good and dropped them two notches. Rechecked the floats again and found a couple 1 mm high. Reset them. Cleaned out all carb body orifaces with canned air. Put the carbs back on the bike. Got it started but it ran like crap. Someone mentioned I would have to resync the carbs and they were right. They were all way off. Synced it up good and she ran better than ever. No hesistation and lots of pulling at 1/4 throttle which is a big change. In the end I'm pretty happy. And best part....it didn't cost me a dime!

Nortstudio · « **Reply #16 on:** July 16, 2011, 05:52:16 PM »

Congratulations!!!

Quick question: is there a setting for the idle screw to start off at - for when carbs have been totally rebuilt? Also, a base setting for the screw that hits the throttle? These carbs are totally new to me - so I have no idea of their previous setup. If the shape they were in is any indication, they are surely set wrong.

Thanks

willbird · « **Reply #17 on:** July 16, 2011, 08:24:50 PM »

I guess I would confirm the needle position by doing some plug chops, my bike was lean at 50-60 mph , the plugs were white, and raising the needles one notch cleared that up.

Bill

dave500 · « **Reply #18 on:** July 16, 2011, 08:34:46 PM »

with the type one carbs,assemble the rack then back the idle screw all the way out,then adjust the sync screws looking thru the carbs untill the light goes out,then adjust the idle screw up untill the light just shines(some people may have to bend over naked for this to happen),i rarely bother with a bench sync,(that is my bench sync)just start it up and adjust the idle as you sync them properly,you should be able to stall the engine by winding the idle screw out going slower and slower till it stalls,some people have the adjustment screws wrong before they start and end up with an idle they cant lower to that point.

Nortstudio · « **Reply #19 on:** July 16, 2011, 08:42:54 PM »

Thaks Dave,

I have the 087a carbs. Not sure if that changes things. I got the sync screws adjusted so that the light was barely shining through, but knew that the idle screw should be somewhere specific. Ill back it out tomorrow and start over with the sync screws.

Appreciate the help. Hopefully I get this baby running as sweet as Duanob's bike is now.

dave500 · « **Reply #20 on:** July 16, 2011, 09:30:46 PM »

do yours look like this nortstudio?type ones,all four carbs have an individual sync adjuster,,the pds look different and #2 is not adjustable,either way if you set the primary sync this way you should be alright.

Nortstudio · « **Reply #21 on:** July 16, 2011, 10:00:22 PM »

Yep, they look like that. Supposed to be same as the 022a, which Im guessing are all "type one." they definitely are not PD carbs. I have individual sync screws for all 4 carbs, and will be making sure they are now set with the light coming through, but with the idle screw out.

I also did some research between this post and last and realized my shop manual is missing the first page or so of the carb setup, which is why I was looking and looking and never found anything.

Looks like I should be all set....famous last words

dave500 · « **Reply #22 on:** July 17, 2011, 12:12:54 AM »

i like to use the solid air screw,the ones with the hole must be some kind of smog limiter type,so even if its fully home itll only go so rich at idle and most likely be leaner than you want anyway,you can solder them up if your handy and have solid ones if you cant source them.

Nortstudio · « **Reply #23 on:** July 17, 2011, 04:50:50 AM »

I definitely have the ones with the hole. Right now I'm running way too rich, but we will see where I'm at with these fresh carbs. Thanks for the tip.

Deltarider · « **Reply #24 on:** July 17, 2011, 05:00:30 AM »

Quote

i like to use the solid air screw,the ones with the hole must be some kind of smog limiter type,so even if its fully home itll only go so rich at idle and most likely be leaner than you want anyway,you can solder them up if your handy and have solid ones if you cant source them.

Could you explain some more, Dave? On my 500 I have the standard airscrews (with a hole and crossdrilled) and I guarantee you that by turning them in I can make it idle so stinking rich, that fuel almost exits the exhausts as a fluid.

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Author Topic: Needle clip position - explained? (Read 25636 times)