mix screws

[KEITH KRAUSE]

Your float levels should have a range. You can choose to get right to the minimum or maximum. You just have to be more precise with measuring.
I've read where some people say if it's lean adjust 1mm richer and vice-versa and they don't mention if this adjustment would put their float levels outside of the factory range. I personally haven't had to go under or over the factory range to allow for typical mod's.
I don't know if changing the float levels 1mm will help your mixture screws or not. But as I said earlier, if carb related, it has to be float level, pilot jet size, or a dirty pilot air jet passage that's causing a rich condition. I hope that changing the float level 1mm won't effect the rest of the performance though. I think you said you were happy with the bike except for the stutter?? Did you ever take any plug reads at 1/3 and wide open throttle? It really depends on where they are set at. Your floats should have a range of about 2mm. The CV carbs are a bit more complicated and have more things to fiddle with than the VM carbs. Personally, I don't think they lend themselves to re-jetting well. The primary air jets, the vacuum port enlarging, the diaphragm assembly spring rates (lighter/stronger), all add more things to think about.
I know you're a bit frustrated over this, and I'm trying to help you out.
One thing I've learned is to take care of all the basics, THEN re-jet. If something's wrong, I know I can blame the jetting. It's more work of course (basic maintenance) but can save you time and even money by allowing you to focus on the jetting and the parts you're trying to make work, instead of trouble shooting.
I read posts all the time that start off saying the carbs were cleaned, the floats are good, synch is good...and of course the guy's complaining. But as the post continues, you read that this and that WASN'T checked. The guy spends so much time back tracking and trouble shooting, he gets nowhere.
Any re-jet I've done completely by myself, with the owner not "helping", I've started with the basics, even if there's no reason to believe this or that needs checking or adjusting. That means a compression test if there's any doubt, fix any cause of oil burning, valves adjusted, ignition timing/spark, fresh plugs, intake leak checks, clean carbs with good o-rings/rubber parts, floats adjusted, mixture screws set, bench/vacuum synchs, filters clean/oiled, new exhaust gaskets...
Pay attention if the stutter gets worse as the motor reaches normal temp or gets better compared to cold. It should change either way. Ride the bike in a way that makes the stutter most noticable. Then pay attention to any difference from hot and cold. If the stutter gets worse under the same throttle position as the motor heats up, then it's a rich condition. If the stutter goes away a little bit, it's a lean condition. Also, with the bike idling on the centerstand, in neutral, does the stutter change at all compared to riding (under load)? Do the cold to hot riding test first, then the neutral test. After these tests, then see what partially bagging the pods does.
Let me know what happens with the float adjustments (if you decide everything else is good with the pilot circuit). Just be sure of the basics first. If there's something else I can come up with, I'll let you know. I'm working Saturday 'til about 4, so I'll check in with you if I can after that.

 

[Jethro]

Man, I appreciate all the help. You should get an award for all the help you've given us! It must be frustrating for you too...

First off, I can say with total assurance that the engine is healthy. That part I have gotten quite good at- valves are adjusted, compression has been checked, I don't burn any oil, fuel economy is quite good (further indicating a healthy engine), exhaust is sealed well- the only engine related item I worry about is the timing. I've heard that my 83 doesn't have timing adjustments, but I think that is false. I also worry about the advancer, becasue that was a problem on my 81, but overall I'm pretty sure things are good.

Over the winter I cleaned the carbs as well as I could with compressed air and carb cleaner. I really don't want to dip them, becasue I worry about the black paint on the carbs, so that is a bummer. I'm about 90% sure the carbs are totally clean.

I think you said you were happy with the bike except for the stutter??

It's taken a while, but I am finally super happy with everything else except the stutter. The bike pulls hard and smooth all the way to redline, I got rid of the nasty bucking by leaning up the needle jet. This could further indicate that my floats were too rich if I had to do that to compensate??

Did you ever take any plug reads at 1/3 and wide open throttle?

My plug reads at 3/4 and WFO are really good- FINALLY! I'm not looking forward to having to check them again after leaning the floats a little.

Pay attention if the stutter gets worse as the motor reaches normal temp or gets better compared to cold. It should change either way. Ride the bike in a way that makes the stutter most noticable. Then pay attention to any difference from hot and cold. If the stutter gets worse under the same throttle position as the motor heats up, then it's a rich condition.

The stutter does get worse when hot, definitely. When I first start the bike, the stutter is not noticable. Due to the fact that the smaller than stock pilot jet improved things slightly, I am going to lean the floats a little bit today. Hopefully this will help things.

Thanks again Keith, you rock.

 

[KEITH KRAUSE]

Hi. I'm off to work in a minute.
Just for the heck of it, shoot some carb cleaner spray into the pilot air jets/passages while you have the carbs off. They're at the filter side, near the side/bottom of carb intake. They're the jet that's not removable. The other hole is for the primary air jet. Clean 'em both out real good. Then rinse the cleaner out with gas immediately. Not much extra work, and might help.
Hopefully, re-setting the floats 1mm (?) will fix you up. But if the stutter is something else, it could be just one carb messing things up. So be thorough with each carb. But as I keep saying, when your mixture screws operate the way they should, you know things are right again.

 

[Jethro]

Well, I'll report on todays tinkering.

I took the carbs off and leaned up the floats. It seemed to make a slight difference in the stutter, but it's the same story with my mix screws. 1/32 of a turn out is the best setting. I made sure the passages you talked about were clear (they seemed to be, I sprayed carb cleaner in there and blew them out with air) and took her for a test ride. It was still missing a little at the take off. I decided to put the #45 pilots back in with my leaner float height, just to try it. Again no change with the mix screws- 1/32 of a turn out is the only setting that doesn't make the motor bog down. Power through the upper range is still great, so I'm not touching the needles. Any higher and I think it will start to buck at full throttle- however, maybe with my leaner float heights, it won't do that this time? I may try and raise the needles a notch, that's an easy job anyway. Some folks say that higher needles help thier stutter on the take off, but I'm still concerned that the mix screws don't affect anything. The stutter seems a little bit better, but not tons. I tried to get a new set of plugs for some new plug reads, but the shop only had 3 D8EA's left. I'll see if I can get some Monday and do some 3/4 and full throttle chops.

Checked synch again today, it's quite good. All less than a cm of each other.

After my test ride, I lubed up the advance unit. The bike was still warm after I did that, and just by playing with the throttle in the driveway, it seems quite a bit better. Maybe this was the casue of my stutter? It probably hasn't been serviced in years. Tomorrows ride will really tell the tale, but I think I may have made progress. I'll let you know!

 

[KEITH KRAUSE]

Hey! You just leave me hanging with that ray of hope at the end?
Well, an advance unit sticking or not operating correctly would certainly cause the stutter too. The advance kicks in right above 1,500 rpm's or so and generally fully advances about 2,500/3,000 rpm. This would be right about where your stutter is. Hope you found the fix. Like I said, basics.
I'm at a total loss about your mixture screws not having an effect as they should. All I can say is check out some jetting websites and you'll see what I say about them. I know you've tried hard to fix it. I'm guessing if the stutter goes away you'll probably just live with it. If the bike runs good...
Usually, actually always, when something is not working correctly, like your mixture screws, but the bike seems to run fine, then there's a second problem you're not aware of and the two problems compensate for each other. They tend to cancel each other out, but you know something's not "normal". In this case, you know your mixture screws are not responding the way they should.
Something's causing this condition, and the mixture screws are telling you somethings wrong. The screws should be about 1 1/2 to 2 turns out for the "sweet spot". I just can't say if the stutter is related to the mixture screws problem, or a seperate thing. Anyway, I hope the stutter goes away with the advancer being lubed. You still need to check that the advance marks line up at about 2,500/3,000 rpm's. Let me know how it goes.
PS: is there ANYTHING else you can think of that could cause these problems? Did you get the EXACT length and design of pilot jets? They must have identical amount of holes and be exactly the same length. Mikuni makes more than one length of pilot jet. Did you replace the mixture screws? If so, are they identical? You replaced the rubber plugs that cover the pilot jets? What air jets came with your jet kit? I haven't noticed you say anything about them. I have to say that according to a diagram of carbs similar to yours, the primary air jet shouldn't have an effect at closed/minimal throttle positions, that's the pilot air jets job, but I don't actually have your specific model carb diagram and so I'm just wondering out loud here, trying to come up with something.

 

[Jethro]

With correct float levels, 45 or 47.5 pilot jets, clean passages, this shouldn't be happening.

I have 47.5's I havent tried yet. But we think this is a rich condition, so I don't know. I got another ride in, the hesitation is still there.

Did you replace the mixture screws? If so, are they identical?

I did, but they are all Identical. I was thinking of replacing them though anyway, maybe I will this week.

What air jets came with your jet kit?

I didn't install the jet kit, it come with the bike. It always had a little hesitation though. I have 160, 170 and 180 pilot air jets though, and have tried them all.

One thing I notice though Keith, my manual shows something other than you say in previous posts:

Just for the heck of it, shoot some carb cleaner spray into the pilot air jets/passages while you have the carbs off. They're at the filter side, near the side/bottom of carb intake. They're the jet that's not removable. The other hole is for the primary air jet.

My manual shows the removable air jet in the throat of the carb as being a part of the slow circuit. I wish I could scan the page, but I assure you, the manual shows that.

We'll see how the bike does tomorrow on a long ride, but the hesitiation is there, I am sure. All other carb actions are awesome, and work great. It's fast. Maybe I just am being to picky? I expect smooth, un-stuttering power right off the line with very little throttle. I might just need to live with the little cough off the line, and be the tough guy next to the Honda Accord can deal with it. I feel like an idiot when I have to blip the throttle a little.

Hey, is it the rich condition that causes the cylinder to load up with excess gas and stuff at the light? I don't know, should I buy a 135 pilot and see what that does? I'm thinking of trying the undrilled slides off my 81 carbs. Maybe that will work better with my pods and rich condition.

That's the wierd thing!!! I have pods, 4/2/1 performance pipe and I have a rich condition!!! With way smaller than stock pilot jets. Why is this happening???

 

[KEITH KRAUSE]

I don't know. But trying to find a problem that someone else created can be a PITA. Who knows what could have been done wrong?

 

[Jethro]

Another update:

Yesterdays ride went really well. I am so happy with the throttle response it's great. Off the line hesitation is definitely improved, so much that I can say I'm happy with it. It coughs a little bit but a hair more throttle and it's clean smooth power. I have no stutter or surge throughout the entire range of the throttle. Power is strong and hard everywhere. Great!!

The only issue is that it is definitely still too rich. I get puffs of dark smoke on hard acceleration and the folks behind me smell it. Strange, I get killer milage and awesome power. This machine is as fast I'd ever need right.

I tested the compression a few months ago, so I'm sure the smoke isn't coming from rings, but I will again tonight just to be sure.

Still too rich, but I don't really want to change anything. It's the best it's ever run right now.

 

[KEITH KRAUSE]

I'm not sure what you did, but I'm glad it's running better.
I know you said you might try different slides. That could certainly effect throttle response.
It's impossible to know what the PO could have done, if they did anything wrong. I was even thinking the piston springs could be changed, which changes throttle response and can also create a richer or leaner condition, depending on the spring tension. I read at a jetting website that some people install stage 7 springs that improve throttle response buy also richen the mixture. This mod' also "has adverse effects on lower throttle positions", according to the writer.
So I don't know what to say. Could be many things still.
You never said where the float levels are re-set though. You just leaned them some. If they were way rich, they could still use some leaning? I've never had to go over or under the factory min/max setting to make a bike run well, but you should measure if you want sometime and see where they're at. The float level definitely effects the pilot circuit and the mixture screws. You may still have some room to adjust.

 

[Jethro]

Yeah, I bent the tangs on the floats a lot, and measured off the gasket surface. They were rich, I may yet try and lean them up some more. With the way it's running, I kinda don't want to mess with it, but I don't want to be a smokey, stinky lead bike (which I always seem to be :lol: ).

 

[KEITH KRAUSE]

Dark exhaust could very well be the floats too rich. In light of everything you've tried, I would try leaning them again if you still have room for adjustment. Like I said, I've heard some people actually go beyong the factory min/max to get what they want, but I can't say I recommend doing that. I'm not sure what you're using to measure with or your exact procedure or your float valve spring conditions. You can always put them back if you don't like the results. I know you're getting tired of messing with it though.
I'm assuming you haven't kept a record of adjustments though. At least you don't say. Then you'd know what you can still do. I assume you have the factory min/max info? Records of each adjustment and the results will allow you to put things back to a known value/performance if you go too far and don't like the results.

 

[Jethro]

Dark exhaust could very well be the floats too rich and that fits the mixture screw thing, and all 3 jetting circuits would be effected.

Barely, my tangs on the floats are bent at about a 20 degree angle already to get the factory settings. I am going to try and set them a little leaner.

I use a caliper to measure the 22.4mm float height best I can. But I wouldn't doubt that my float jet springs are bad. I need to replace them.

I'll let you know what happens with my float settings.

I'm also gonna try undrilled slides and stock piston springs (for the slide, right?)

It's a shame to change things, with it running this good, but I don't want it running rich.

 

[KEITH KRAUSE]

Yes, the diaphragm/piston assembly springs.
I'm not doing the work, but I think I'd try the float adjustments first. If you have the room for adjustment.
Float problems are the most common, that's why I suggest that first. Could be the slides or springs, but I'd go with the floats.
I know the temptation to do several things at once because you're tired of taking things apart.
It doesn't help much, but know that you're not alone. :roll:

 

[Jethro]

I know the temptation to do several things at once because you're tired of taking things apart.

Right. I have a habit of doing that. I'll just try the floats for now.

Is the fact that changing my float levels (by quite a bit) had no negative affect on my mixture a good indication that I need to lean them further? Just wondering.

Also, which circuit is more sensitive to float heights- pilot, needle or main? Or are they all equally affected by float heights?

 

[KEITH KRAUSE]

I know the temptation to do several things at once because you're tired of taking things apart.

Right. I have a habit of doing that. I'll just try the floats for now.

Is the fact that changing my float levels (by quite a bit) had no negative affect on my mixture a good indication that I need to lean them further? Just wondering.

Also, which circuit is more sensitive to float heights- pilot, needle or main? Or are they all equally affected by float heights?

Well, as for a good indication I don't really know how far you've moved the floats and at what measurement you started. You're saying they are at 22.4 mm now, correct? They couldn't have been too far off from the beginning if the bike ran as well as you say, but I suppose it's possible. If the bike still runs good, then we haven't caused a problem. You did say it's improved actually, but not much I think.
In my opinion, you should stay within the factory min/max range. I believe most others have that have re-jetted.
As for which circuit may be the most sensitive to float adjustments, I can't say for sure, but I believe it's the pilot circuit. The pilot circuit uses much smaller holes to keep the motor running correctly, so I think an incorrect fuel level would effect the pilot circuit easier.
Lastly, (I gotta get to work) you ARE measuring the float at the correct point? You have the odd shaped floats I believe? You measure at the top of the float, not the arm part of the float. If you measured at the arm part, you would actually be very rich. Talk to you later.

 

[Jethro]

I measure to the top of the bulb, as that was what it looks like in the manual. Is that what you mean by the arm? Have I been measuring my float height wrong? Should I measure from the flat part closest to the pivot itself? That would make my carbs way rich! Jezuz, don't tell me this, I've been messing with GS carbs for the past 10 years!

I swear, the manual shows the gauge at the bulb, not the flat part close to the pivot... I just checked it again...

 

[Anonymous]

I just got myself a set of K&Ns and in the instructions for adjusting the Idle Mixture and Pilot Jet they state:

Adjust for hightest idle speed. If less than 3/4 turn out is required, change to a richer (larger) pilot jet. If two (2) turns out or more are required, go leaner (smaller) in jet size.

this shed any light?

good luck brutha, I'm going through the same stuff.

M.

 

[KEITH KRAUSE]

Jethro, maybe you missread my last post. Maybe I worded it funny?
Yes, you measure to the top of the float. Some people make a mistake and measure at the very top, the ARM that holds the floats, and that would actually result in a rich setting. If you measured to the top of the float itself, the rounded "bulb" as you say, then you're good. But because of others making this mistake, I thought I'd mention it.
If there's ANY doubt, post a pic'. I would, but don't know how. But it sounds like you've been doing it right.

 

[KEITH KRAUSE]

Too early in the morning to think :lol: and I gotta go to work, but I'll continue this later.

 

[inquisitive]

Jethro,

Yeah, I bent the tangs on the floats a lot, and measured off the gasket surface.

Do different carbs have different methods of measuring float height? I think my 79 GS850 manual says measure from the carb body. Not sure how big a difference that would make.