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question on shimming the needle

  • Thread starter Thread starter oldgsfan
  • Start date Start date
O

oldgsfan

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I'm trying to shim the needles on my carbs - I just want to make sure I'm replacing the correct washer. I'm guessing I'm supposed to be replacing the plastic one at the top of the needle, not that flat metal washer beneath the little clip. Is that right?
photobucket-38106-1340580605414.jpg



I'm doing this, by the way, because I just installed a V&H 4 in 1 - I re-jetted, bumping up my main jets to 120 from the stock 115's.

The bike is running pretty good but not fantastic - it has plenty of pep and lots of power when I'm accelerating. There's no popping on decel.

The only issue is some weakness when I'm cruising freeway speed. From what I read, shimming the needle may help.

This is going on my '80 850G
 
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Replace the plastic washer with a couple of thin steel washers about 1/2 the height of that plastic washer. You can even sand down the plastic washer with a piece of sandpaper placed on a flat surface. Just make sure all the spacers are the same thickness when you are done.
 
Send me a buck and your address and I'll send you 20 shims.
16 to use and 4 to lose.

Eric
 
What I really need is a decent set of circlip pliers..man, those things are a pain to get out and even harder to get back in!

I got one done but I've given up for the night and will buy a decent set of pliers tomorrow - something that can reach into the tube where the needle sits.

Picked up the washers at a radio shack and, as someone else mentioned, the kid didn't know what I was talking about but I found them with their hardware. last pack in the drawer.
 
I just cut down a cheapie pair or circlip pliers to get them to fit down into the slides.
I used a cutting disc on a die grinder, zipped the flairs off the pliers where they were joined, and made the pins in the end smaller to fit into the holes at each end in the circlips.
I also ground out between the pins as the pliers wouldn't close far enough to remove the clips.
I got the pliers free as they were left in my garage when I got the place, so all in all, my new CV carb circlip pliers were free.


Tank
 
You don't need to put the circlips back in when you are done. And I don't understand the idea of sanding the plastic washer. The idea is to raise the needle so to do that you would add a few small washers under the existing plastic washer. Just make sure that the needle when placed in the slide has no vertical play when the plastic spring seat is positiioned in the slide. You don't need to replace the circlips because the spring bears down on the seat which retains the needle.
 
1980GS1000E said:
You don't need to put the circlips back in when you are done. And I don't understand the idea of sanding the plastic washer. The idea is to raise the needle so to do that you would add a few small washers under the existing plastic washer. Just make sure that the needle when placed in the slide has no vertical play when the plastic spring seat is positiioned in the slide. You don't need to replace the circlips because the spring bears down on the seat which retains the needle.
Click to expand...


Obviously there is some confusion here.

The needle height is controlled by the height of the orange plastic washer above the small circlip on the needle, because a spring pushes up on the needle from underneath. Make the washer/spacer thinner and the needle height will increase.

The circlip being mentioned by others is the one in the slide that holds the plastic plug piece in place. That circlip is critical otherwise the needle will just fall out.

Needle.jpg
 
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These are rough measurements as a micrometer will tell slightly different measurements:

The plastic stock spacer measures 2.50 mm's.
The 3 mm flat washers measure .50 mm's.
So, if you replace the plastic spacer with (4) 3 mm flat washers, you have raised the needle .50 mm.
Etc.


Eric
 
Ok so thinner washer equals raising the needle. Right?
My plastic washer did measure 2.50
The little metal washers were just over. 50 each
I wasn't sure how high to raise the needle. I was going to replace the plastic washer with two metal washers. Now I'm thinking that might raise the needle more than i need.
 
@Nessism- I forgot that when I raised my needles I took out the small springs. I then stacked a bunch of washers, some above and some below, around the fixed lug on the needle. When I reassembled, since there was no small spring pushing up on the plastic seat, I just omitted the circlips. My old 900 Ninja used the same principle to hold the needles in. It works fine. Perhaps the plastic plug is different on the 850, but on mine, the diaphragm spring bears against it and that holds the needle in place.
 
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1980GS1000E said:
@Nessism- I forgot that when I raised my needles I took out the small springs. I then stacked a bunch of washers, some above and some below, around the fixed lug on the needle. When I reassembled, since there was no small spring pushing up on the plastic seat, I just omitted the circlips. My old 900 Ninja used the same principle to hold the needles in. It works fine.
Click to expand...

:confused:
Doesn't that add a ton of weight and make it much harder for the slide to rise?


Eric
 
1980GS1000E said:
@Nessism- I forgot that when I raised my needles I took out the small springs. I then stacked a bunch of washers, some above and some below, around the fixed lug on the needle. When I reassembled, since there was no small spring pushing up on the plastic seat, I just omitted the circlips. My old 900 Ninja used the same principle to hold the needles in. It works fine. Perhaps the plastic plug is different on the 850, but on mine, the diaphragm spring bears against it and that holds the needle in place.
Click to expand...
I guess this would work, but I'd be concerned about anything that "locks" the needle in place. I believe the purpose of the spring is to press the needle to the top - setting the needle height - while letting the needle "float" so it centers in the bore of the main jet. This float prevents any binding that could cause the slide to hang up and keeps the needle from rubbing too hard on the walls of the main jet, wearing out the soft brass.
 
Craftsman needle nose pliers # 45664 work for me {black & gold}. I pull the needle down from the bottom against the little spring and grab it with vice grips then put the circlip in with the pliers which fit the holes perfect. I dont know about leaving the circlip out, youre on your own there
 
Katarat said:
Craftsman needle nose pliers # 45664 work for me {black & gold}. I pull the needle down from the bottom against the little spring and grab it with vice grips then put the circlip in with the pliers which fit the holes perfect. I dont know about leaving the circlip out, youre on your own there
Click to expand...

Sears didn't have those pliers in stock..so I filed down a pair of needle nose pliers I had until they fit into the circlip holes. Your vice grip tip was a big help. Don't know why I didn't think of that on my own, but it made installing the rest of the clips much easier.

The carbs are back together. I'll button up the bike tomorrow and see how it rides. Thanks for all the tips and advice.
 
@7981GS- Weight?!? No.
@AJ- The key is proper fitment. It doesn't bind, is free to rotate, just not go up and down, and when you consider the environment the needle is in with the intake air and engine vibration, that needle is shaking a bit.
 
1980GS1000E said:
@AJ- The key is proper fitment. It doesn't bind, is free to rotate, just not go up and down, and when you consider the environment the needle is in with the intake air and engine vibration, that needle is shaking a bit.
Click to expand...
In mechanical design, it's very common to "float" a part when you have multiple alignments with some parts held rigidly. In this case, you have the main jet fixed and the slide moving in a precision bore. Floating the needle lets the needle self-align to the jet. Note that the needle itself only goes through a small hole in the slide and it's a loose fit, rather than trying to rigidly lock it to the slide.

That said, the main purpose for the spring is to set the height of the needle relative to some reference (the height of the retainer clip), but I wouldn't discount the self-aligning feature of the spring arrangement. I've seen jets worn oval by needles even with them spring loaded. YMMV. ;)
 
I agree on the principle of floating the needle. The method I outline allows that. Even more so than having the small spring preloading it.
 
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