Pilot screw turns: the saga continues

[Gorminrider]

As far as gauging the fuel levels; where do you look on the outside of the carb to measure from? the line made by the top edge of the float bowl? or do you picture where the gasket surface is behind the bowl flange? Can you check the middle carbs, 2 and 3, on the bowls of 1 or 2 if the bike is level?

Carb bowls all have independent levels set by their floats. IF your needles and seats are good, the shop manual will guide you. Try to use a fullish tank of gas at roughly the same height as it is on the bike to "bench-test" all this. This will be a good test of your needles and seats, and thereby a good test of fuel levels.
ON the bike, agin with a "fullish" tank,
Carbs may not be level when the bike is sitting on wheels or especially the stand, which can angle them forward or maybe even back if the suspension has been changed... so judging fuel levels wiith a tube on the drain screw will often be an angle..the centre of that "angle line" across the bowl's seam =the center of the bowl's seam and that is where the level should be observed.

 

[Guest]

More thinking out loud:
If my idle circuit is too lean for three of my carbs then I can either increase the size of the pilot jet or decrease the air pilot jet. I believe the effect of either is not proportional from what I have read.
My thought is this. I'm curious if I could test changing the air pilot without having to buy new buy filling the hole in it and then drilling to a new smaller size? Less air being added to the pilot mix should richen up my idle. Whatever I used to fill the hole could be something easily removed like super glue or cheap epoxy so my alteration isn't permanent.
It's either that or drill out my pilots carefully. I have to find out how the air pilot influences other circuits...

a helpfull diagram I found on DO THE TON.com

 

[Guest]

Going back to the drawing board this weekend. I keep reading the tuning guides and they keep making me think maybe I'm not being thorough enough with my main jet selection. 124 right now seems like it's fantastic, but then again the 130 did too. I'm chasing my tail right now and I'm questioning why I can't tune idle at all. It just makes me think I haven't done my due diligence on steps one and two. If I'm doing microscopic adjustments now just to get a smidge closer to running under 1500rpms then how can I expect to tune any finer once I'm there? It just doesn't make any sense so I must need to start over again.
I won't be back until I have it figured out or need advice on something different. I know realize it's hard to diagnose someone's carburation without being there and I'm probably just wasting my time asking a million questions hoping to have an epiphany. I've always had success bouncing ideas off other people but that's just not happening with this one.

 

[Big T]

Your idle circuit is lean? Turn the mixture screws out 1/4 turn at a time to correct the mix
How many turns are they out now?

 

[Guest]

Big T, I just can’t find a sweet spot. I’m pretty sure it’s not there. I start at 2 turns. Going out from there does nothing good. turning just #3, which is my richer cylinder, half turn in is about the best i can get to lower idle to around 1600. From there i start turning screws in which actually raises the rpms some but when I adjust the curb idle speed it just stalls out. I have to keep turning it in as I lean. I think the problem is at that point the rpms are getting me out of the idle circuit range and it starts to go on the needle.

Does any of that make sense?

When I open the screws eventually I get blue exhaust and it starts fouling plugs.

 

[Guest]

I?ve had the floats at ranges above and below the baseline so I?m not getting anywhere with them either. I?m contemplating soldering my air jets shut and drilling them smaller and seeing what that does.

 

[Gorminrider]

the centre of that "angle line" across the bowl's seam =the center of the bowl's seam and that is where the level should be observed.

gee, I didn't say that right! I meant that the middle of that line is going to be the fuel level to double check against the manual's spec. But on the bench is the best.

...it's a pretty wild place you're goin, Edgecrusher...drilling out jets and all...It's a four cylinder bike and tuning the idlemix by ear is way hard compared to twins...but given that the manual's or steve's specs should run the bike at low rpm, rich though they might be, I have sneaking suspicion you're overthinking this. It's something simpler..ie: blowing through the idle passages, there's one you need block(being three outlets not two)...: the mixture needle's washer placement (a rubber one and a small metal one and the spring in correct order on each carb....the littlest things can send you off the path into the deep and dark woods

 

[Big T]

I agree

You need to go back into your carbs and find the issues.

Your bike should idle easily. I'd be putting the carbs back on n the ultrasonic, air jet down after you pull the mix screws and the pilot jets.

 

[Steve]

I believe it has been said (possibly more than once), that you need to start with a stable baseline. That is your fuel level. Whether you use a setting on the floats (22.4mm ? 1.0mm) or a fuel level (5.0mm), you need to set that to the standard, THEN make all your jetting changes and adjustments.

One possible scenario: your fuel level is low (floats about 25mm), so you richen up the pilot screws enough to get it to idle so you can get down the road to do you other jetting checks. Now you find that you need to change your main jets, as well. By the time you get to fine-tuning the needle, you find that you need to raise it a bit, too. Instead of making three separate adjustments, with all the fine-tuning interim steps for each one, just raising the fuel level by setting the floats to within the proper range would have richened them all, allowing you to run stock jets.

There are also situations where an over-sized pilot jet will mask a lean condition on the needle, but a rich main will mask the other end of the needle range. Your bike will idle great and will run great at the drag strip, but will run like crap when cruising on the highway.

Please start with the proper fuel level.

Oh, and don't drill jets. You may end up with exactly what you need, but pity the poor slob who gets the bike when you sell it. He will read the size and make an adjustment based on that reading, not realizing that's not the actual size of the holes.

One last thing to consider: YOU might be that "poor slob". :-k
How do you know that the previous owner didn't drill out the jets? They might not be what you think they are, so when you change that 115 main jet (that is actually drilled out to about a 135) to a 125, thinking you are richening it up, you will be surprised to find that it's running leaner, instead.

Once again, start from a known baseline, with known-quality parts. When you make adjustments, change ONE thing at a time.

.

 

[Guest]

gee, I didn't say that right! I meant that the middle of that line is going to be the fuel level to double check against the manual's spec. But on the bench is the best.

...it's a pretty wild place you're goin, Edgecrusher...drilling out jets and all...It's a four cylinder bike and tuning the idlemix by ear is way hard compared to twins...but given that the manual's or steve's specs should run the bike at low rpm, rich though they might be, I have sneaking suspicion you're overthinking this. It's something simpler..ie: blowing through the idle passages, there's one you need block(being three outlets not two)...: the mixture needle's washer placement (a rubber one and a small metal one and the spring in correct order on each carb....the littlest things can send you off the path into the deep and dark woods

I agree with everything you just said. The unfortunate part is I feel like I've double checked everything that has been suggested or I can think of.
For certain I have done exactly what you said regarding the idle passages. Studying the diagrams I've found on CV's I've studied where they go and when the carb is completely torn down I grab my berrymans and spray from every side. I especially focus on going thru the airjet while holding my fingers over the screw hole and the pilot jet hole and look down the throat to make sure it's coming out the tiny holes with force both sides of the throttle plate. Even without covering the choke hole which is down where I can't get my finger there is a strong spray coming out the venturi holes where the mixture is delivered into the air stream. Doing this multiple times and each time confirming the result I should have clear passages correct??
The idle screw idea is a good point. I've thought about it and I believe I've checked to see proper order. O-ring first, then washer, spring and screw, right?
But despite starting to wonder about igniter issues or a loose can chain or something non-carb related causing this I'm still almost certain it has to be something I'm just doing wrong or over looking.

 

[Guest]

As far as baselines, I have set everything exactly per specs and had no luck. I'm about to start there again even using the stock 117.5 mains which I haven't done this year (I have been trying to tune this for several years). I'm not an idiot when it comes to machines but I will admit that sometimes I do get in a hurry and miss things.

The boggling thing is right after I replaced the valve seats and needles and set everything to baseline it started up and idled great for the first time. I should have left it alone and went out and rode it, however, I started fiddling with idle screws and suddenly it changed after 10 minutes of good idling. You'd think I'd be able to find that spot again when it idled but three days of trying and not even close. That's where I start to overthink and wonder if there is something kicking in when the engine starts getting really hot. I have a lift I work on and while I'm tuning I open the garage door and run a plain old box fan infront of the tire to try cooling the engine. It doesn't keep up and I end up quitting when the temp starts climbing and I keep burning my forearms on the valve covers. Fun stuff.

 

[Guest]

BTW I'm trying to break up some of these thoughts so you're not having to read a long post. lol

So a new development tonight. I went to start the engine and the choke wouldn't move. It appears that the rod wants to move but one or more of the carb plungers is binding or jamming.

I have to look into this further next time. Today I tried the air jet solder thing which did richen it up but the stalling was the same and screw situation was the same. The rest of the night I spent getting the bodywork remounted. It's all in pretty sad shape and hasn't been on the bike for a few years. I still had to finish up some wiring left from my harness restoration to get the headlight, brakes and new signals all working for test runs before I get pulled over by smokie.

I've been neglecting the wife and kids pretty bad this week so I don't know if I'll get back to it this weekend despite my inability to think about anything else. Possibly a break is just what I need.

Thank you all for taking time to give me some help today. I do appreciate it!

 

[Gorminrider]

I feel your pain, man....it can get boogerish. And, Sometimes, it's best to just go away from the bike for awhile....I try to do this when the "second time doing same thing without result" doesn't work. Just leave it al tidy on the bench and go fly a kite.

after all the puzzling and visual processing, Something Epiphanal will often bubble up from the depths given awhile to rest and digest.

 

[Guest]

It’s a labor of love. I spend more time working on bikes than riding. I think it’s because my dad died on a motorcycle when i was only eight months old. Before mom got rid of his Kawasaki KZ I spent my early years staring at it wondering how it worked. Then when I was a teenager I found a connection to the dad I never knew through bikes and using his old tools. Motorcycles have been an important part of my life. They have been whats made me who I am today. Without motorcycles I cannot exist.

 

[Guest]

Back at it.
Went back through the carbs. There was some strange buildup in #4 choke plunger that was stopping it from sliding. Not sure where it came from but cleaned it out and got the chokes sliding smooth again.
I was going through all my jet kits from my previous GSXRs and Katanas which luckily were all Mikuni and found a set of brand new 37.5 pilot jets. These were the perforated style. The bike had the solid style. So I swapped in these shiny new ones hoping for some improvement.
I set all the floats to 22.4mm baseline. Started with the mix screws at 2 turns. Cleaned the solder off the air jets which was very easy to do. Just heat it up and blow it out.
Bike runs like it has been. No improvements. Tired of doing the same thing and getting the same results I'm moving to road tuning.
Driving it hard for a bit today I find the idle circuit popping on decel crossing over into the midrange circuit. With the 124 mains in WOT feels close but I'm going to go back to the 130's and see the difference. After looking through my supply of jets I've collected I see I have a few sizes I may be able to try out to get closer. It's hard riding the bike at WOT and trying to observe what it is doing. When the powerband hits it's around 7-8K and there's not a lot of room after that before it's maxed out and I have to let off. Trying to to modulate during WOT doing 80+ on this old bike so I can see if it perks up for a second after getting off the throttle is a little sketchy on public highways. I don't want to get pulled over aand I definitely don't want to freak people out speeding up and slowing down.
I tried putting a little choke in while modulating WOT and it didn't seem to help so I'm not confident a bigger jet is the way to go but if it gets worse I know to go down.
I think I saw some 127's in my organizers so I'll those first and if I get improvement I'll go to 130. I know on 130's my needle was perfect at the 4th notch which is where it is now and is giving some popping and looking lean. Gotta stick to the plan and get the right main first though.
If I can nail the main and then the needle and I'm still having a problem getting it to idle without stalling then I'm going to have to look at more than just carbs.
I found an old igniter the other day and plugged that in just to see what it's deal was. Two cylinders weren't firing. The way the engine just falls out at anything south of 1600 rpms no matter what I do with the carbs still makes me suspect an ignition problem a little bit. The fact that the carbs are absolutely clean and I have baselines set and it just absolutely won't run to any degree under 1600 makes me suspect this. I also suspect a possible fuel delivery issue, like it's not flowing fuel fast enough to keep the carbs topped off. While riding there are moments at any throttle position where it acts like it just ran out of gas and wants to stall but then come's back right away. Observing the little clear filter I had inline I would say delivery wasn't the problem but it's not out of the question. My tank was pretty nasty before I started all this. Every time I pull the carbs apart I have sparkling clean bowls so I don't think there's any little bit's left in the tank, however maybe they're too big to get past the screen on the petcock and slowing flow. Next time I run the tank down I will have to pop it off and see. Unfortunately, I just topped the tank off today.

 

[Steve]

I set all the floats to 22.4mm baseline. Started with the mix screws at 2 turns. Cleaned the solder off the air jets which was very easy to do. Just heat it up and blow it out.

You mentioned something about breaking up the posts, but there's still too much for me to keep straight.

Try STOCK pilot jets (whatever they are), keep the 22.4 float baseline, turn the mixture screws out THREE full turns. That is three FULL 360? turns. I have to say that because I went to help a member many years ago who inssisted his screws were out three turns. I started by checking for myself and they stopped dead at 1 1/2 turns. He said "I counted three turns of the screwdriver." I turned the screws out three full turns, but bike started easily and ran reasonably well.

Yes, three turns is a bit too much, but the bike will run easier with a rich mixture than it will with a lean mixture.

Some bikes have what you describe as "perforated", others don't. I have not noticed the pattern to see which ones have them and which ones don't.

And, ... since I didn't read all that you posted, what's with the soldering of jets? It's bad enough that you can't get things right with known jet sizes, but when you install unknown variables, all bets are off.

Also, I have forgotten what bike you are working on. It's likely one of the bikes in your signature, but that yellow is impossible to read.

.

 

[Guest]

It’s my 83 gs750es, Steve.
i can understand your frustration and confusion with my situation. You don’t know my experience level and have to err on the side of caution. At first glance it would seem I don’t know what the he’ll I’m doing because I just can’t seem to accomplish something that’s so basic but I assure you I am not one of those ignoramices.
37.5 is the stock pilot and the new ones I have in now are genuine mikunis. I haven’t found anywhere that a remarkable difference is made using perforated pilots but I would imagine out of common sense that they help slightly with atomization. They didn’t make a difference in the end. When i compared my old to these the new did seem to be more open. Whether that’s because they are the different style or because they were so shiny I don’t know.
As far as my experiment with soldering the air jets I figured this was a low risk chance to take. Air jets are simple to access and replace. Brass accepts solder very easily and to remove the solder all you need to do is heat them back up and blow out the solder. It allowed me to drill a smaller hole and test the result without ordering new and waiting weeks to move on. In the end, they were returned to their original state. I didn’t drill into them- there is no damage that would keep me from returning to baseline. I have metric drill bits and a chart telling me what each size compares to in Mikuni jet sizes. As far as worrying about the next owner, this bike isn’t getting sold to anyone again and this process was just a way to see whether going a certain way with the jets would net a better result before buying new jets to put in. So I would really appreciate if you would get it out of your mind that I’m trying to bastardize these carbs.
Nonetheless, I appreciate your continued help and ideas. I have reasched a point where I think all the usual suspects have been addressed repeatedly and I’m just going to need to work my way through this problem myself until I stumble upon that thing that is holding me up.
Sometimes it seems like this old bike isn’t really worth all this effort but I’ve gone this far, i might as well keep trying.
i will try to ride it making one change at a time in hopes i get somewhere with it. I’m just hoping it’s a matter of having pods and the engine being ultra sensitive as a result. About ten years ago when I first put the pods on because my airbox had had it, everyone on the forums told me it would never run right without the air box. Perhaps they were right despite the fact there are many people who have had success. Seems like most bikes with pods are 1100’s not 750’s because of the definitive gains that can be acheived with 1100’s. Maybe 750’s just don’t flow as well making tuning difficult.

 

[Nessism]

Is the fuel tank clean? If there is rust and varnish inside it will flow downstream and plug up the carbs.

Does this bike have pods and if so did you install a Dynojet kit or similar? You will have a very hard time getting the bike to run properly using the stock needles along with pods. And what kind of pods? Some of the cheapies block air passages on the carb inlet.

And how about vacuum sync? The bike won't idle properly until all the carbs are drawing the same level of vacuum.

I'd be sure to use pilots that match the originals (no holes.) And make sure you have the rubber plugs in place over them.

A couple of other things to do is remove the spark plug caps and measure the resistance. They should be about 5k ohms. The caps unscrew from the wires in case you didn't know. Before reinstalling the caps snip off 1/4" of wire so you get good contact.

 

[TxGSrider]

It’s my 83 gs750es, Steve.
i can understand your frustration and confusion with my situation. You don’t know my experience level and have to err on the side of caution. At first glance it would seem I don’t know what the he’ll I’m doing because I just can’t seem to accomplish something that’s so basic but I assure you I am not one of those ignoramices.
37.5 is the stock pilot and the new ones I have in now are genuine mikunis. I haven’t found anywhere that a remarkable difference is made using perforated pilots but I would imagine out of common sense that they help slightly with atomization. They didn’t make a difference in the end. When i compared my old to these the new did seem to be more open. Whether that’s because they are the different style or because they were so shiny I don’t know.
As far as my experiment with soldering the air jets I figured this was a low risk chance to take. Air jets are simple to access and replace. Brass accepts solder very easily and to remove the solder all you need to do is heat them back up and blow out the solder. It allowed me to drill a smaller hole and test the result without ordering new and waiting weeks to move on. In the end, they were returned to their original state. I didn’t drill into them- there is no damage that would keep me from returning to baseline. I have metric drill bits and a chart telling me what each size compares to in Mikuni jet sizes. As far as worrying about the next owner, this bike isn’t getting sold to anyone again and this process was just a way to see whether going a certain way with the jets would net a better result before buying new jets to put in. So I would really appreciate if you would get it out of your mind that I’m trying to bastardize these carbs.
Nonetheless, I appreciate your continued help and ideas. I have reasched a point where I think all the usual suspects have been addressed repeatedly and I’m just going to need to work my way through this problem myself until I stumble upon that thing that is holding me up.
Sometimes it seems like this old bike isn’t really worth all this effort but I’ve gone this far, i might as well keep trying.
i will try to ride it making one change at a time in hopes i get somewhere with it. I’m just hoping it’s a matter of having pods and the engine being ultra sensitive as a result. About ten years ago when I first put the pods on because my airbox had had it, everyone on the forums told me it would never run right without the air box. Perhaps they were right despite the fact there are many people who have had success. Seems like most bikes with pods are 1100’s not 750’s because of the definitive gains that can be acheived with 1100’s. Maybe 750’s just don’t flow as well making tuning difficult.

Someone may have pointed this out, that you can use the perforated (bleed style) pilot jets in the non-bleed pilot carbs, BUT they require a different size as the hole in the bottom of the jets are sized differently. You can search around the internet and figure out what size you need... Or just buy new non-bleeds in the correct size.

 

[Guest]

I have come to the dynojet vs mikuni jet equivalency issue. Lol

i have a mix. Had a dyno 124 and wanted to go up slightly on main. Ended up putting a mikuni 127.5 in. Comparing them by eye the dyno124 did appear smaller than the mik 127.5. However I’ve heard you need a dyno ten higher to compare to mikuni.
Just test rode the mikuni 127.5 and it idled slightly better at 1600 and pretty steady for the most part but still lean and stalling once in awhile. Gonna try to go higher and stay with mikuni jets.