shimming carb needles info?

[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.

[tkent02]

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.

[Quest]

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.

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.

[Steve]

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

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.

.

[Quest]

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

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.

.

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?

[blowerbike]

no air box= st.3 jet kit needed.
do you have an air box installed?

[Quest]

no air box= st.3 jet kit needed.
do you have an air box installed?

No i have the dual k and n filters.

[Steve]

Should i go back down to 40s on the pilots?

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

.

[Quest]

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

.

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.

[blowerbike]

the problem is the shape of the needles.
the main part of a jet kit is the new needles.

[Quest]

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?

[JMHJ]

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.

[Steve]

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?

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.

.

[Chuck78]

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.

.

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.

[Chuck78]

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.?