non-CV carb (VM?) pilot screw adjustment

[AOD]

application: 78/79 GS550 carb - non-CV type

i took apart my carbs last night and cleaned some things up. i noticed the pilot and air adjustable jets are marked from the factory with a slot in the carb and the slot in the screw. my question is regarding the pilot screws. i had VERY different settings for each of the screws in the stock position.

#1: 1 and 1/2 + 1/4 turns
#2: 1 and 1/4 turns
#3: 7/8 turns
#4: 7/8 turns

i am awaiting new main jets to rejet the bike, and o-rings for these pilot jets, but my question is, since i'm rejetting should i leave the pilots where they were, or adjust them all to a neutral spot? all at 1 and 1/2?

i am not aware of how Suzuki determines the original marking for these screws...my guess is they pump fluid through it at a certain rate with a vaccume on the engine side of the carb and measure flow rates. so would i be screwing things up a lot by adjusting them?

i haven't recorded the turns of the air adjustment screws on the outside yet. since i am only rejetting the main jet, i probably want to set the airs to 1 and 1/2 or a little richer to compensate for the pod air filters and 4-1 exhaust.

anyway thats another topic...any advice for my pilot jets?

thanks,

~Adam

[AOD]

ttt - anyone?

[KEITH KRAUSE]

The pilots are set at the factory and you cannot duplicate their settings. They are set differently to allow for differences in each cylinder,so this is not a problem. Since you now have the pod's and pipe, you will have to make changes. My advice would be to buy a Dynojet jet kit and follow their directions. If you don't buy the kit, you can go with Mikuni jets. For your pilot system, try turning the pilots underneath out 1/2 turn from where you had them.(out to richen) You may have to go another 1/2 turn after testing. The side air screws should not be turned in, this would only defeat the whole idea of pod's, which is to introduce more air and get more power. The air screws should be adjusted to achieve the highest idle and then re-set your idle knob if you need to. They will probably be around 2 to 2 1/2 turns out. If adjusting both pilots and air screws is not enough to get good performance/plug read, you may have to go up on your pilot jet size. Next, you WILL have to raise the jet-needle. I am not familiar with 550's but if similar to my '79 1000 you raise the needle by lowering the c-clip. Try 1 notch first and go from there. As for the mains, I would go up about 3 full sizes and go from there. Do what the plugs tell you. The pilots and air screws effect idle and have an overlap effect on the needle up to about 60 in top gear. So if you just cruise around town you will be using a combination of the pilot system and the needle setting. It takes about 5-10 miles to get a good plug read.The needle has the most effect at just under 1/4 throttle to 3/4 throttle. The main and needle also overlap each other, but the main has the most effect at 3/4 to full. Before testing, make sure your carbs are sinc'd and your ignition timing is good. Good luck. I'm on vacation until the 12th, so I hope you get help if you need it later. KK.

[AOD]

thanks Keith. so what you're saying (maybe someone else can clear this up) is that the the pilot screw is for the fuel mixture and the top/side screw on the carb is for the air mixture? or is it just idle air mixture?

i will reset the idle mixtures as you suggest. i believe the bike was running a bit lean on cylinders 1 and 4 prior to the pod filters. i will try adding 1/2 turn as a starting point for the pilot screws and maybe 1 and 1/2 to 2 turns for the air screws as a base.

main jets will be brought up to #95 (from 80) on the stock main jet.

~Adam

[KEITH KRAUSE]

thanks Keith. so what you're saying (maybe someone else can clear this up) is that the the pilot screw is for the fuel mixture and the top/side screw on the carb is for the air mixture? or is it just idle air mixture?

i will reset the idle mixtures as you suggest. i believe the bike was running a bit lean on cylinders 1 and 4 prior to the pod filters. i will try adding 1/2 turn as a starting point for the pilot screws and maybe 1 and 1/2 to 2 turns for the air screws as a base.

main jets will be brought up to #95 (from 80) on the stock main jet.

~Adam

In the pilot circuit, the pilot jet regulates the fuel flow into the main bore of the carb through 1 passage. But a second passage to the main bore is regulated by the pilot screw position, this is for 'fine tuning' and this screw has a lot of effect. This screw is underneath. Turn out to richen. NEVER seat these screws tightly, they can break off at the tip. The side air screw adjusts how much air comes through the air-jet. Turning it out allows more air which also helps atomize the final fuel mixture. By adjusting these 2 screws,you have a certain range of control. One allows fuel and one allows air, the combination is the mixture. To get you in the 'ballpark',an additional 1/2 to 1 turn out on the pilots and the air screws adjusted for highest rpm will be fair compensation for the pod's. But you will also have to raise your jet-needle or it will not run right. It will run lean and hot.

[AOD]

hmmn...i've never looked at the needle stuff. i have the main jets out now...how do i go about adjusting the main needle?

i hoped that with the bigger main jet and the tweaking of the pilot screw i wouldn't have to mess with the needle a lot.

i have the carbs on the table here...just not sure how to do the adjustment you suggest.

~Adam

[KEITH KRAUSE]

hmmn...i've never looked at the needle stuff. i have the main jets out now...how do i go about adjusting the main needle?

i hoped that with the bigger main jet and the tweaking of the pilot screw i wouldn't have to mess with the needle a lot.

i have the carbs on the table here...just not sure how to do the adjustment you suggest.

~Adam

My '79 GS1000E carbs are Mikuni VM26SS. I THINK you're carbs are similar. If you don't have experience,you really should get a manual. To adjust the jet needle is the most work in jetting. It is also the most important because the engine is running on the needle most of the time.(normal cruising and up to 3/4 throttle) After adjusting the needle you should also sinc the carbs. Every time the needle is moved the carbs should be re-sinc'd. It's work, but it is necessary for the bike to run right. Raising the needle up a notch may not be enough. You may have to go a notch and a half(using jetting spacers) or 2 notches. If I just took a guess, trying to get it right the first time, I would try a notch and a half. So you will need to get some jetting spacers. If you try 2 notches you will not need them. The spacers are used for 1/2 notch changes. Most shops should have them. Most shops would probably charge 1-1 1/2 hours to do this change, at about $60 an hour? You can change the needles with basic hand tools, but you will need a carb sinc tool to sinc the carbs properly. Again, a shop will probably charge 1 hour to sinc? If your carbs are similar to mine,you have to remove the throttle spring, take off the tops, remove the 4 hex bolts holding the throttle valve arms, remove the hex bolt holding the throttle cable pulley to the throttle shaft, remove the stopper plate that holds the shaft, take out the rubber side plugs and push the shaft out. Pull out the slides. Looking down inside the valve there are 2 phillips screws. Completely loosen them, carefull not to strip, but don't take them out by themselves. Lift up the valve arm and the screws and a small plate should come up with it. (Out of space, will continue next post).

[KEITH KRAUSE]

This plate has a dimple on it and a hole. If the plate is dropped by mistake, make sure it goes back right side up. Now you can push up the needle from underneath. Leave the small spring in the valve. The needle has a thicker plastic spacer on top the needle clip and a thinner one under the clip. Make sure they go back the same way. Remove these spacers. Note which notch the clip is in and remove it with needle nose pliers and replace it 1 notch further down or 2. Carefull pushing the clip back on, don't bend the needle. This raises the needle. If you use a spacer to get a 1 and 1/2 notch change, then note the clip position and lower the clip 2 notches AND put the jetting spacer on top of the clip. Put the plastic spacers back on and put the needle back through the spring. From underneath, pull the needle down enough(don't let the plastic spacers pop off) to allow you to replace the valve arm with the 2 screws and plate. Make sure the hole in the lower part of valve arm aligns with the hole in the plate. Tighten the screws and slip the slides back into carbs being carefull not to hit the needle tips too hard going back into their needle jets. Grease and put the shaft back through the valve arms and the throttle pulley.Finger tighten all 5 bolts. Replace the stopper plate and tighten firmly. Now tighten the throttle pulley bolt first, about 4 ft/lbs. Move the slides up and down a couple of times to help them settle. Now torque the 4 bolts to about 4 ft/lbs. Replace rubber plugs. Now adjust the fully closed position of the valves. This is basic sincing and if done right, the bike will run 'OK' but sincing with a tool is much better. Run the throttle stop screw out to make a good clearance from the throttle pulley. At the top of the valve arm, loosen the nuts that hold the adjusting screws. Turn these screws slowly to bottom out each valve. If bottomed properly, they will all be fairly uniform. Now tighten firmly the nut while NOT allowing the screw to move. Now adjust the fully open throttle position. Push the slides up completely and hold them... ( I hope your carbs are like mine and I am not wasting our time. I also hope I am not offending you by this 'step by step' thing. I don't know how much you know. I hope to continue this later so I can get some sleep).I will be packing for vacation but I will try to finish this . I need to get the manual from the garage , it's kind of difficult to describe the fully open throttle adjustment, which is the last thing you have to do. KK.

[AOD]

Keith, thanks for the reply again and the detailed steps to go about raising the needle. My carbs are simliar to yours, VM-something, with slides - so you're speil wasn't a waste. i do actually have two manuals for the bike. one is a Clymers i bought last year, and i got an original Suzuki manual with the 79 bike. i haven't gone through it much because everything i've done so far i did last summer on the 78 GS550. that bike had pod filters and the 4-1 exhaust (which is moved to the 79 GS550 now) when i got it, so i didn't mess with jets or anything - and the bike ran really rich. not to digress, but i did everything to clean them, no tuning, and no syncing and the bike ran pretty good, and still does.

as for raising the clips now...we might have run into a problem. i can only do the 'static' carb sync because i dont have a sync tool...and i'm not gonna pay a dealer for it.

i think what i'd like to try is jetting the main, adjusting the pilot filters to 1/2 turn more then the factory setting, adjusting the air screw to 2 turns out, and then run the bike. ride it, check plugs, adjust pilot screw if needed, and see how good i can get it. if it comes to the point where its not working out right, i'll have to go the needle adjustment and sync then.

that sound good?

enjoy your vacation too. 8)

[KEITH KRAUSE]

The jetting adjustments you say you want to do will help and of course I can't twist your arm over the needle thing. But trust me, ANY and EVERY stock motor with stock jetted carbs that has now got a pipe and pod's, will run very lean. This causes more heat, a surging effect can be felt while riding,you can damage the plugs and burn a hole in the pistons. The list goes on and on. To get it right you have to DO it right. If you feel because you can only manually sinc the carbs that the whole needle thing is a waste of time, it is not. Many people just manually sinc and their bikes run fine. Anyway, I'll finish about adjusting the fully open throttle. Lift up the slides and hold them there. Look into the rear of carbs and look up at the bottom of the throttle valve. The bottom of the valve should be between 0.5 to 1.0 mm above the carb throat chamber.(about 1/32''.) If it is not, then you turn the throttle stop screw in to reduce the distance or screw it out to increase it. You usually only need about 1/2 a turn or so. It is mounted with a spring on the bracket that holds the bank of carbs. When you push up the slides, you will see the throttle pulley stop against it. That's it. Put the tops on and mount the carbs. I don't like to keep hammering on this but do yourself and the bike a favor: AT LEAST raise the needle 1 notch, even if you don't plan to touch it again. 1 notch may be enough. If you spend the time now to do this right, you will be rewarded with years of more enjoyable riding. If you don't, you can cause major damage, especially if you get the motor hot on longer rides. KK.
PS: Tell you what,I don't know where you're at but if your carbs needles are the same, if you send them to me I'll change your needle settings. Just tell me where you want them set. I know this would take time and shipping $. But it's better than overheating your motor. I don't mind at all. Some of the good 550 pod people here can give advice as to the best needle setting to make. We might get it right the first time but even 1 notch will really help. Let me know by tonight since I'm leaving on Monday AM and will be away until the 12th. By the time they get here I'll probably be back.

[AOD]

i'll see what i can do with them Keith, i trust your experience on this matter and i definitly want this bike to run its best. since i dont have the sync tools i'm a little leary to start ripping out the parts in there, but you are adamant that its best i do it, so i'll go down the learning route again.

i'll grab my Suzuki manual tomorrow, and take a look at it during tests at work - and re-read everything you said about adjusting the needles. if its not too hard i can handle it. its just scary tearing it apart the first time, ya know?

the more i think about it though, i should have just switched the carbs on my 550's when i had them next to each other...the 78 ran really rich would could have been tuned out i'm thinking. oh well, live and learn.

enjoy the vacation, i'll let you know how things are coming along when you get back. i wont be able to work on the bike the weekend of the 12 and 13th, so i'm gonna try and get most done this week if parts come in.

~Adam

[KEITH KRAUSE]

Hi. Were leaving in a minute. Just thought I'd check in. You can do it, take your time. But if you get in a jam, like I said,as long as there's nothing mechanically wrong with them that would screw me up, just send them to me and I'll adjust the needles and manually sinc them. Let me know and I'll give you my address. Good luck! Keith.

[AOD]

this is definitely a thread to bookmark.

thanks a ton Keith, i sat down tonight, with a beer, and started to take the tops off the carbs. raising the needle by lowering the clip was a piece of cake. i just printed out this page, and went through it step by step. i had the whole thing done in about a half hour.

my main jets shipped, and my o-rings should be in this week. i SO can't wait to get the bike running again!

[KEITH KRAUSE]

Well, I'm back. Glad to hear you did the job with no trouble. You sure did them faster than I do. I hope you were carefull with the manual sincing. I assume you raised the needle 1 notch? This will certainly help it run better than if you did nothing at all. As I said earlier, you may need to make more adjustments to get it right. It all depends on how much time you're willing to take. Jetting can be a lot of trial and error. But if you test ride and it feels good AND your plugs reads look OK, then that's it. Let us know how it goes and if you need any more help. KK.

[AOD]

yeah Keith i raised them 1 notch. there was 5 total notches and the original setting was in the middle, so i have one more notce of play left...though i'm not sure the spacer part for the needle will stay on if you raise the needle again. thanks again for your help.

i had a little oring pains...but i think i got most of that squared away. i'm waiting for some carb kits to come in the mail, or from another GS'er, the fuel pilot screw. i ended up breaking the tip off one of them.

hope to get them done monday, time the new Dyna S statically, and run the bike!

~Adam