Shim CV Carb Needles?

[Nessism]

Going through the carbs on my GS550T and decided to try to shim the needles a smig to ward off that cold blooded nature a little. Pulled the C-clip (had to grind down my circlip plyers to get down at that bugger) and noticed that the needle is sitting on a spring pushing it upward against the bottom of that plastic plug in the slide. Normally, to shim the needle it's a matter of putting a washer under the needle to raise it up a little. On these carbs though I had to remove a plastic spacer on top the needle and replace it with a couple of washers that are thinner (thus, raising the needle). I know this is hard to visualize but those that have been inside these carbs may know what I'm talking about. I wound up raising the needle about 2mm or so which is a WAG (wild ass guess) in terms of what should work best.

Anyone ever attempt a mod like this? If so, please share your experiences.

[chef1366]

I put the washers under the c-clip which raises the needle. I kept the plastic piece where it was. I would start with one washer which is 1/2 notch on an adjustable needle and work from there.

[Road_Clam]

Going through the carbs on my GS550T and decided to try to shim the needles a smig to ward off that cold blooded nature a little. Pulled the C-clip (had to grind down my circlip plyers to get down at that bugger) and noticed that the needle is sitting on a spring pushing it upward against the bottom of that plastic plug in the slide. Normally, to shim the needle it's a matter of putting a washer under the needle to raise it up a little. On these carbs though I had to remove a plastic spacer on top the needle and replace it with a couple of washers that are thinner (thus, raising the needle). I know this is hard to visualize but those that have been inside these carbs may know what I'm talking about. I wound up raising the needle about 2mm or so which is a WAG (wild ass guess) in terms of what should work best.

Anyone ever attempt a mod like this? If so, please share your experiences.

When you say "cold blodded" exactly what's your engines behavior?? Shimming the needles affects acceleration (or lack of) from 1/3-3/4 throttle. You may want to investigate the pilot jets, and or your air screws first. It all depends on where in the rpm's your engine is incorrectly running. Heres one of my positive jetting expereinces:

http://www.thegsresources.com/_forum/showthread.php?t=91853&highlight=pilot

[Nerobro]

"cold blooded" is a pilot jet/pilot screw problem. not a needle problem. :-) Get those cleaned.

[Nessism]

I put the washers under the c-clip which raises the needle. I kept the plastic piece where it was. I would start with one washer which is 1/2 notch on an adjustable needle and work from there.

On my carbs there's a spring on the bottom of the needle that pushes it upward so the needle height is controled by the space on TOP the needle, not below it.

I removed a plastic spacer, maybe 4mm tall, and replaced it with a couple of washers, about 2mm tall, to my net effect it to raise the needle 2mm.

After what some of you other folks write I'm starting to wonder if I'm wasteing my time. My goal is to improve off idle throttle response, which I always thought the needle helped. Maybe not.

[Nerobro]

"off idle" is almost entirely the pilots jet and pilot screw. Needle is cruise and transiant responce.

Though you haven't described what you mean by cold blooded. Is it that when the motor is cold it doesn't respond well to throttle inputs? Your bike should only need choke for tens of secconds at most. ;-) If it's taking more than that, your pilot screws are dirty or really severely maladjusted.

I have the same carbs as you do on my GS550E.

For the reccord, I had almost no success adjusting the needles on my bike untill I got a dynojet kit. If your bike is stock, leave the needles stock.

[Nessism]

For the reccord, I had almost no success adjusting the needles on my bike untill I got a dynojet kit. If your bike is stock, leave the needles stock.

I'm a little embarrassed here but I don't have any drivability issues yet because I just bought this bike and haven't ridden it yet. I bought the bike with gunked up carbs and hauled it home.

I have a fair bit of experience with these old GS bikes though having owned a 450 and knowing friends that have owned them over the years as well. GS Suzuki’s are famous for their lean carburetion since these bikes are air cooled and were back in the early days of emission controls for motorcycles. My 450 would not accept throttle very well when cold; engine would bog and accelerate slowly until warm. This symptom was most noticeable when riding at lower engine speeds - maybe 1/4 or 1/3 throttle which I thought was "needle" territory.

Just wondering but what did you do to shim your stock needles? Did you change the spacer on top the needle or ? With the spring pushing upward on the needle shimming underneath will do nothing.

Considering I haven’t even ridden the bike yet, maybe I should just try the bike stock first and see what happens <insert sarcastic remark here>.

[Nerobro]

My 450 would not accept throttle very well when cold; engine would bog and accelerate slowly until warm. This symptom was most noticeable when riding at lower engine speeds - maybe 1/4 or 1/3 throttle which I thought was "needle" territory.

sounds like your 450 had gunked up pilot needles.

Just wondering but what did you do to shim your stock needles? Did you change the spacer on top the needle or ? With the spring pushing upward on the needle shimming underneath will do nothing.

Considering I haven’t even ridden the bike yet, maybe I should just try the bike stock first and see what happens <insert sarcastic remark here>.

You change the thickness of the spacer on top of the needle. That's it. :-)

And yes, return the bike to stock, work from there.

[relic-rider]

When I rebuilt the carbs on my 750, I couldn't get 3 of the 4 mixture screws out. It was quite doggy in acceleration and took a long time to warm up. I decided to wait until winter to attempt to get those buggers out. I wanted to RIDE and not be dinking around with the carbs. So I did a quick fix and swapped the plastic washer on the top with the metal washer on the bottom. I guess that is like 2 1/2 notches on a regular needle. All I can say was WOW on my acceleration. It helped the warm up time a little bit , but I still need to get my mixture screws loose to fix that problem. It has been running and starting fine all summer. I'll get it running properly later this year.

[Nessism]

sounds like your 450 had gunked up pilot needles.


You change the thickness of the spacer on top of the needle. That's it. :-)

And yes, return the bike to stock, work from there.

The pilot jets in my 450 were clean, the problem is that the bike was jetted LEAN from new. Same with all the GS bikes.

I returned the needle back to stock but I'm still looking for feedback from some people that have tried raising them a little - relic-rider is reporting good results which is encouraging. I messed around with raising the needle on some of my others bikes over the years and seem to remember it helped improve drivability some but it's been a while so I was hoping to get some more feedback before messing around with the 550's carbs.

[Road_Clam]

I'm a little embarrassed here but I don't have any drivability issues yet because I just bought this bike and haven't ridden it yet. I bought the bike with gunked up carbs and hauled it home.

I have a fair bit of experience with these old GS bikes though having owned a 450 and knowing friends that have owned them over the years as well. GS Suzuki’s are famous for their lean carburetion since these bikes are air cooled and were back in the early days of emission controls for motorcycles. My 450 would not accept throttle very well when cold; engine would bog and accelerate slowly until warm. This symptom was most noticeable when riding at lower engine speeds - maybe 1/4 or 1/3 throttle which I thought was "needle" territory.

Just wondering but what did you do to shim your stock needles? Did you change the spacer on top the needle or ? With the spring pushing upward on the needle shimming underneath will do nothing.

Considering I haven’t even ridden the bike yet, maybe I should just try the bike stock first and see what happens <insert sarcastic remark here>.

Good train of thought. If your bike is stock, there will be NO need to re-jet. Bikes back in the early 80's were jetted pretty close to ideal running, unlike now, where EPA regulations are extremely tight, causing manufactures to jet the bikes so lean, they barely run .

[Nessism]

Bikes back in the early 80's were jetted pretty close to ideal running, unlike now, where EPA regulations are extremely tight, causing manufactures to jet the bikes so lean, they barely run .

I'm not so sure about this statement. These old GS bikes, particularly the 2-valve per pot varities, were jetted quite lean from the factory in order to meet the EPA requirements. More modern bikes have much better combustion chamber shapes which makes all the difference in emissions; because the combusion is cleaner the motor can be jetted richer to begin with.

Case in point is my other bike, a Kawasaki EX500. This bike likes choke to start but you can quickly turn it off unlike my old 450 which required choke for several miles before it will pull cleanly. ](*,)

[mafd2]

I have a 1981 550T and had a problem with hesitation and stumbling off idle and around the 1/4 throttle range. I had to run the bike for a good 10 minutes or so before it would start to clear up. After that, the problem was only sometimes barely noticeable. These bikes were set up lean from the factory. So then, how did I fix the problem? Well, those of you who think putting washers under the clip and leaving the plastic spacer on top will raise the needle is wrong. You are correct Nessism! Putting washers under the clip will not do anything! Instead, this will only compress the spring. The more washers you put under the clip will only compress the spring more and not raise the needle higher in the guide holder. The stock spacer on top of the clip keeps the needle in a fixed position. Sound confusing? The spring keeps tension on the needle and pushes the needle up into the guide holder. If you want the needle to go higher you have to remove from the top of the clip. Removing the stock spacer and using needle washers (like those in Dynojet kits) does the trick. Removing the stock spacer pushes the needle higher into the guide holder making it richer. I finally got my carbs dialed in by removing the stock spacer and using 1 washer above the clip. You have to leave the stock washer under the clip. The stock washer under the clip keeps the clip and needle from falling through the spring. My idle mixture screws are 2 1/2 turns out. No more hesitation, or stumbling of the carbs and any throttle position. Bike runs and idles perfect.

[Nessism]

I have a 1981 550T and had a problem with hesitation and stumbling off idle and around the 1/4 throttle range. I had to run the bike for a good 10 minutes or so before it would start to clear up. After that, the problem was only sometimes barely noticeable. These bikes were set up lean from the factory. So then, how did I fix the problem? Well, those of you who think putting washers under the clip and leaving the plastic spacer on top will raise the needle is wrong. You are correct Nessism! Putting washers under the clip will not do anything! Instead, this will only compress the spring. The more washers you put under the clip will only compress the spring more and not raise the needle higher in the guide holder. The stock spacer on top of the clip keeps the needle in a fixed position. Sound confusing? The spring keeps tension on the needle and pushes the needle up into the guide holder. If you want the needle to go higher you have to remove from the top of the clip. Removing the stock spacer and using needle washers (like those in Dynojet kits) does the trick. Removing the stock spacer pushes the needle higher into the guide holder making it richer. I finally got my carbs dialed in by removing the stock spacer and using 1 washer above the clip. You have to leave the stock washer under the clip. The stock washer under the clip keeps the clip and needle from falling through the spring. My idle mixture screws are 2 1/2 turns out. No more hesitation, or stumbling of the carbs and any throttle position. Bike runs and idles perfect.

Thanks for the insiteful post maf2d. Now I'm swinging back toward raising the needles again. Time to make a decision and stick to it...for now.

[Road_Clam]

Case in point is my other bike, a Kawasaki EX500. This bike likes choke to start but you can quickly turn it off unlike my old 450 which required choke for several miles before it will pull cleanly. ](*,)

All your 450 might need is a fuel screw tweak, or maybe a one size richer pilot. I am talking about the generall running at speed, not cold starting behavior.