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shimming carb needles info?

  • Thread starter Thread starter Quest
  • Start date Start date
Q

Quest

Guest
Where can i find info on how to shim my carb needles on my 81 gs550? The mid throttle osnt the smoothest so im looking to smooth it out.
 
The idea is to replace the thick plastic washer above the needle clip with a stack of washers thinner, this lets the spring push the needdle up farther. A tiny change is probably all that's needed, if in fact this is your problem.

Has everything else been done to the carbs and is the ignition working correctly?

If you can't find suitable washers Radio Shack sells an assortment with some small ones that work well.
 
tkent02 said:
The idea is to replace the thick plastic washer above the needle clip with a stack of washers thinner, this lets the spring push the needdle up farther. A tiny change is probably all that's needed, if in fact this is your problem.

Has everything else been done to the carbs and is the ignition working correctly?

If you can't find suitable washers Radio Shack sells an assortment with some small ones that work well.
Click to expand...

I cleaned the carbs and installed new boots. I also just installed a new reg/rec. It is running a 4 into 1 header and k and n filters. I rejetted using 50 pilots and 115 main jets. It runs great on the high end, idles smooth but at mid throttle it kind of sputters slightly.
 
Why the new pilot jets? Stock is 40, you went up FOUR sizes. :eek:

Very rarely do you need to go up even ONE size, and that is only after major engine work, including pistons, cams, porting, etc.

With just pods and a pipe, stock pilots, shim the needles a bit and about 8 sizes up on the mains should be close. You went 9 sizes, should be in the ballpark.

.
 
Steve said:
Why the new pilot jets? Stock is 40, you went up FOUR sizes. :eek:

Very rarely do you need to go up even ONE size, and that is only after major engine work, including pistons, cams, porting, etc.

With just pods and a pipe, stock pilots, shim the needles a bit and about 8 sizes up on the mains should be close. You went 9 sizes, should be in the ballpark.

.
Click to expand...

I am just trying to get it running good by trial and error. The pilots probably are too large that could be an issue. I was trying to tune it to run with a muffler that came with it, which is pretty much a straight pipe but have abandoned that muffler cause its to freaking loud.I seen stock was 40 and when i bought the bike it came with 45's. I will probably go back to the 45's when i go to shim the needles, if it has not aleady been done be yhe PO.

Should i go back down to 40s on the pilots?
 
Quest said:
Should i go back down to 40s on the pilots?
Click to expand...
Personally, I would say "yes".

The reason to increase jetting size is because of increased ability to flow air. However, at idle and low-throttle settings, you will be flowing just as much air as before, so no increase in fuel flow is necessary.

Above mid-throttle, though, you will need to add jetting, which you have already done.
icon_thumbsup.gif

Might need to do some fine-tuning to the mains, but get the rest of it running first.

.
 
Steve said:
Personally, I would say "yes".

The reason to increase jetting size is because of increased ability to flow air. However, at idle and low-throttle settings, you will be flowing just as much air as before, so no increase in fuel flow is necessary.

Above mid-throttle, though, you will need to add jetting, which you have already done.
icon_thumbsup.gif

Might need to do some fine-tuning to the mains, but get the rest of it running first.

.
Click to expand...

Thanks for the info, the 40's are on the way. The suzuki dealership by my house has them much cheaper than i can find on the internet, $12 for 4.
 
So just to make sure i have this correct, im going to want to remove the plastic spacer and replace it with a stack of washers which is thinner than the plastic spacer? Or am i adding a washer to the spacer?
 
Read the paragraph associated with Fig. 4 on this page:

http://www.iwt.com.au/mikunicarb.htm

Mine are different, but that may help you with the basic idea. If I understand it right, you raise the needle further up out of the jet for richer, lower it for leaner.
 
Last edited:
Quest said:
So just to make sure i have this correct, im going to want to remove the plastic spacer and replace it with a stack of washers which is thinner than the plastic spacer? Or am i adding a washer to the spacer?
Click to expand...
You will replace, not add.

In its normal operation, the needle is pushed UP until it stops. Its position is determined by the position of the circlip (if multiple grooves are available) and the thickness of any spacers/shims/washers that are ABOVE the clip.

If you replace the thicker spacer with a stack of washers that is thinner, you will raise the clip, which will richen the mixture.
If you add a washer, you will move the clip down, leaning the mixture.

Most of the washers that will fit there will require 4 or 5 washers to equal the thickness of the nylon spacer. Start with two fewer washers than the thickness of the nylon spacer, then fine-tune from there.

.
 
Steve said:
In its normal operation, the needle is pushed UP until it stops. Its position is determined by the position of the circlip (if multiple grooves are available) and the thickness of any spacers/shims/washers that are ABOVE the clip.

If you replace the thicker spacer with a stack of washers that is thinner, you will raise the clip, which will richen the mixture.
If you add a washer, you will move the clip down, leaning the mixture.

Most of the washers that will fit there will require 4 or 5 washers to equal the thickness of the nylon spacer. Start with two fewer washers than the thickness of the nylon spacer, then fine-tune from there.

.
Click to expand...


I should add that this is only for the slides that have a spring well to spring load the needle, pushing it upwards. Some VM26 carbs have the spring loaded needle, others have a fixed needle with only a slight bit of room for those thin washers, and do not have the spring or plastic washers on top and bottom of the clip. On this style, you need to put a thin washer or 3 UNDER the circlip that holds the needle in it's proper height position and retains it in the slide. I am in position 3 (middle slot) now, and I need to lower to position 2.5, so I need to drop the needle to the 2nd clip slot from the top, and then add whatever amount of thin washers that fit UNDER the clip, and then clamp the linkage back into the slide bucket. I dropped the needle lower by going one slot higher, but then raised it less than a half slot by putting washers UNDER it.

On the spring-loaded-jet-needle style of slide, as Steve said, you need to stack the washers on top of the needle circlip in order to push the needle down lower against the spring, compressing the spring and dropping the needle height.
 
I found this post via a search for "radio shack needle washers," can anyone tell me what size washers they have that we need? It it just a variety pack of washers that all share the same inner diameter, but are of varying thicknesses? Or are they all one thickness, but varying o.d. and i.d.?
 
Radio Shack part # 6403022 seems to be what has been used, 100 pack of "steel flat washers, +20 each: #2, #4, #6, #8, #10." I had trouble finding it in the store, but they had a bunch of random variety packs laying on top of the pull out drawers full of all of the electrical components.
 
Apparently this is a commonly used washer pack for a wide variety of motorcycles, as after doing a google search for that part number, the first results page had several other makes of motorcycle forums referencing those radio shack $2.49 100-pack for carb mods after pods...looks like 64-3022 is/was an alternate part number for the same thing. #2x.020 thick washers, or m3 x .5mm thick (same thing).
 
The .020" thick #4 radio shack washers were thicker than I'd care for in fitting to the non-spring-loaded-needle vm26 slides. Around .010" would slip under there, but much thicker and the needle won't be free floating as it should,& will probably wear a lot as it may rub the needle jet a lot. The #4 washers were .020" or .5mm, and the #2 washers are .4mm thick, but would need drilled out, as they don't quite fit around the needles
 
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