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Discussion Starter · #1 ·
Well I'm back to work on the bike. I fired it up for the first time in a long while - started up pretty easy, but there are definite carb issues. It has an enrichener circuit, and when I pulled the lever to activate it the rpm's went too high. I can't be sure how high b/c I removed the tach and I haven't heard the engine in so long (I'm going to hook up the tach while I try to work out the carb issues).

The MAIN problem is that I know the pilot screws have been messed with, and they were pre-set by the factory; all service manual specs just say "PRE-SET" instead of giving a number of turns out after bottoming. They are supposed to be plugged, but I am the 3rd owner and there were no plugs. I have been to shops (and Suzuki has no tech support line), but nobody has any real answers for me other than that I'm in over my head. But I'm not ready to give up and pay someone to get this thing working right for me.

What I'm going to do next is remove and inspect the intake manifold boots for any cracks and replace the gaskets between manifolds and cylinder head. That's in the works, but half of the screw heads are already stripped out (any suggestions on how to make this easier would be appreciated). Then I will remove all of the jets from the carb and thoroughly clean them. I already cleaned the hell out of the circuits w/carb cleaner, but w/o removing the jets I can't be sure that the holes in the sides of the jets are clear. Then I'll put everything back together and see what happens.

The last thing is the idle adjustment screw (the one screw that hits the throttle plate linkage to hold the butterflies open just a bit). I have the spec for idle rpm's, but this would be affected by both the idle adjustment screw and the four pilot screws. The service manuals don't tell how many turns to move the screw, only idle rpm range.

This carb is a Mikuni BST33SS (49-state model), I.D. #44C10. My bike is a Suzuki Katana GSX600FL (year 1990). If anyone has some suggestions, I really would appreciate them.
 

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McBain said:
Well I'm back to work on the bike. I fired it up for the first time in a long while - started up pretty easy, but there are definite carb issues. It has an enrichener circuit, and when I pulled the lever to activate it the rpm's went too high.
I think you just answered your own question there buddy.. Ive never heard of an enricher circuit. hmm.. What lever did you pull to activate it? The choke? When you turn any choke on it richen's things right up.

I know when I start my bike up cold with the choke it runs fine at a decent idle till the engine warms up.. then it rev's to about 3 grand and hang's there pretty steady till I turn the choke off. Or if the motor isnt warmed up yet and I hit the gas with the choke on it rev's high then comes back down. Some bike's are different then others.. Ive seen some bikes rev high right from the get-go within a fiew seconds after start up. If thats the fact I wouldnt worry about it as long as you inspected everything and the carbs seem in order being clean and the gaskets are good..



Im gonna re-read your post again just to double check, make sure I read things correctly
 

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generally a good starting point for mixture screws is 2-2.5 turns from all the way in. just be easy setting the screws all the way in. it's easy to break the tip off the ends of the screws. just turn them in until they just seat, then back out 2-2.5 turns. most any jet kit will have you adjust the mixture screws, so someone has probably installed a jet kit.

also, while you have the carbs apart to clean them thorouly, look at the brass tube that the needle slides thru, make sure it's not ovaled out AT ALL. if in doubt, replace them. some of the older mikuni carbs had problems with the needles bouncing around and wearing the tubes the ride in.

for the stripped screws, see if you can get a pair of vise grips on them. once you get them broken loose, they should come out easily. just replace them with new ones after that.

as a starting point for the idle adjustment screw, back it out until the end of it just stops touching the plate, then watch the butterflys , and turn the screw in until the butterflies open just a bit. once you get it started, you can fine tune it from there.

make sure you sync the carbs too.

if you're running pod style filters, be prepared for a lot of fiddling with the carbs. those oil cooled suzuki motors are a lil picky about carb tuning with pod filters.

those motors are a lil cold-blooded at times too, it may take a few to let the motor warm up before it'll clear up and run smooth. that seems to be pretty normal with them.

if have any trouble along the way, post up, i know those motors all too well, i'll help with what i can.
 

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McBain said:
What I'm going to do next is remove and inspect the intake manifold boots for any cracks and replace the gaskets between manifolds and cylinder head. That's in the works, but half of the screw heads are already stripped out (any suggestions on how to make this easier would be appreciated). Then I will remove all of the jets from the carb and thoroughly clean them. I already cleaned the hell out of the circuits w/carb cleaner, but w/o removing the jets I can't be sure that the holes in the sides of the jets are clear. Then I'll put everything back together and see what happens.
The best and eastest way to check for leaks in the intake boots between the carbs and the head.. is start the bike and see if you can get it to run at a lower RPM or idle if you can. Once you've done that get a can of starting fluid and spray the boots, spray each boot one at a time. If you spray one boot and the bike rev's, you got an air leak. Sometimes theres pin holes you wont see with the naked eye. The vacume from the engine will suck the starter fluid right in and make it jump if theres a problem. BUT if you so have an air leak 90% of the time the bike will dog on you when you give it gas because it will suck more air. More throttle = More vacume or suction which would pull unwanted air into the carbs mixture.




McBain said:
The last thing is the idle adjustment screw (the one screw that hits the throttle plate linkage to hold the butterflies open just a bit). I have the spec for idle rpm's, but this would be affected by both the idle adjustment screw and the four pilot screws. The service manuals don't tell how many turns to move the screw, only idle rpm range.
Do each of the 4 screw's your talking about go into the carbs? Or go to the linkage? Usually theres 1 air fuel mixture screw near or around the float bowl on each carb, and 1 idle screw that moves the throttle linkage for the idle.. that is set with the RPM's



McBain said:
The MAIN problem is that I know the pilot screws have been messed with, and they were pre-set by the factory; all service manual specs just say "PRE-SET" instead of giving a number of turns out after bottoming. They are supposed to be plugged, but I am the 3rd owner and there were no plugs. I have been to shops (and Suzuki has no tech support line), but nobody has any real answers for me other than that I'm in over my head. But I'm not ready to give up and pay someone to get this thing working right for me.
Im a yamaha man so it could be different with Suzuki's. But from what Ive always known is that all carbs usually starts with the air/fuel mixture screw's turned out (I think) 2 turn's from closed (but not tight, closed is closed)
 

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skr00zloose said:
also, while you have the carbs apart to clean them thorouly, look at the brass tube that the needle slides thru, make sure it's not ovaled out AT ALL. if in doubt, replace them. some of the older mikuni carbs had problems with the needles bouncing around and wearing the tubes the ride in.

Get ahold of FactoryPro, they make the best emulsion tubes for these carbs. There a little pricey but there nickel plated and dont wear for shit. Ive been tryin to get a set myself, my emulsion tubes are shot.



skr00zloose said:
as a starting point for the idle adjustment screw, back it out until the end of it just stops touching the plate, then watch the butterflys , and turn the screw in until the butterflies open just a bit. once you get it started, you can fine tune it from there.

make sure you sync the carbs too.

if you're running pod style filters, be prepared for a lot of fiddling with the carbs. those oil cooled suzuki motors are a lil picky about carb tuning with pod filters.

those motors are a lil cold-blooded at times too, it may take a few to let the motor warm up before it'll clear up and run smooth. that seems to be pretty normal with them.

if have any trouble along the way, post up, i know those motors all too well, i'll help with what i can.
:Stupid:
 

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Discussion Starter · #7 ·
An enrichener circuit is pretty much the same thing as a choke; the difference is that it opens up a circuit that adds a rich air-fuel mix instead of moving a plate that further blocks the venturi to create higher vacuum and a richer mix through the pilot and needle circuits. The reason I was worried about the higher rpm's with it on is that they seemed excessive; I won't really know until I hook up the tach - it's just been a long time since I had this engine running, so on this point I was probably just worrying over nothing.
 

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Discussion Starter · #8 ·
spyder said:
The best and eastest way to check for leaks in the intake boots between the carbs and the head.. is start the bike and see if you can get it to run at a lower RPM or idle if you can. Once you've done that get a can of starting fluid and spray the boots, spray each boot one at a time. If you spray one boot and the bike rev's, you got an air leak. Sometimes theres pin holes you wont see with the naked eye. The vacume from the engine will suck the starter fluid right in and make it jump if theres a problem. BUT if you so have an air leak 90% of the time the bike will dog on you when you give it gas because it will suck more air. More throttle = More vacume or suction which would pull unwanted air into the carbs mixture.

That's the plan after I get it all back together, except for the starter fluid. Some told me to use contact cleaner and other stuff, but I like the starter fluid idea, as this would create an easily noticeable difference. The engine didn't dog on me when I gave it more throttle though, so maybe the problem is dirty jets or the incorrectly adjusted pilot screws. Like an idiot I forgot to mention the main symptom that is a problem: when I gave it throttle the rpm's increased as they should, but they didn't drop when I let off - it took way too long. I know the throttle didn't stick; it snapped right back to closed position.




Do each of the 4 screw's your talking about go into the carbs? Or go to the linkage? Usually theres 1 air fuel mixture screw near or around the float bowl on each carb, and 1 idle screw that moves the throttle linkage for the idle.. that is set with the RPM's

Each of the four screws goes to the carbs, and the one idle screw does move the linkage.



Im a yamaha man so it could be different with Suzuki's. But from what Ive always known is that all carbs usually starts with the air/fuel mixture screw's turned out (I think) 2 turn's from closed (but not tight, closed is closed)
The problem with Suzuki is that they have NO tech support line; their customer service reps know even less than I do. And the service manuals (factory & Clymer) say nothing about the number of turns, just the rpm range. I'll try two turns out.
 

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Discussion Starter · #9 ·
skr00zloose said:
generally a good starting point for mixture screws is 2-2.5 turns from all the way in. just be easy setting the screws all the way in. it's easy to break the tip off the ends of the screws. just turn them in until they just seat, then back out 2-2.5 turns. most any jet kit will have you adjust the mixture screws, so someone has probably installed a jet kit.

also, while you have the carbs apart to clean them thorouly, look at the brass tube that the needle slides thru, make sure it's not ovaled out AT ALL. if in doubt, replace them. some of the older mikuni carbs had problems with the needles bouncing around and wearing the tubes the ride in.

for the stripped screws, see if you can get a pair of vise grips on them. once you get them broken loose, they should come out easily. just replace them with new ones after that.

as a starting point for the idle adjustment screw, back it out until the end of it just stops touching the plate, then watch the butterflys , and turn the screw in until the butterflies open just a bit. once you get it started, you can fine tune it from there.

make sure you sync the carbs too.

if you're running pod style filters, be prepared for a lot of fiddling with the carbs. those oil cooled suzuki motors are a lil picky about carb tuning with pod filters.

those motors are a lil cold-blooded at times too, it may take a few to let the motor warm up before it'll clear up and run smooth. that seems to be pretty normal with them.

if have any trouble along the way, post up, i know those motors all too well, i'll help with what i can.
I got the bike with aftermarket pipes, so it probably has been jetted. I'll readjust the screws to 2-2.5 turns. I'll also check the tubes and replace if ovaled out at all. And I'll try the vise grips; I'll let penetrating fluid soak in for a while before I do (and then clean the heads with contact cleaner before applying grips). I will adjust the idle screw before putting on the airbox, but I'm not sure what pod filters are; are they small filters used individually for each carb? If so, I don't have them - I use a single K&N with the stock airbox. I know what you mean about these engines being cold-blooded - I remember it taking a while for the engine to warm up before I took the bike apart. I forgot to mention the main symptom, which is that when I had the engine running and gave it throttle the rpm's raised but took a while to drop to previous level. I know the throttle didn't stick - it snapped right back. Maybe the problem is dirty jets and/or improperly adjusted pilot screws? Could this symptom be caused by a vacuum leak? Thanks for your help - I'll keep posting, but it will take me a while to do all of this, esp. b/c I'm waiting on someone to weld shut the drain hole on one of the float bowls. I had noticed a fuel leak from one of the carbs around the drain, so I screwed in the drain screw a bit - the metal around it cracked. I figure that it will be ok to just plug up one out of four drain holes - hopefully I won't have to drain the fuel from the carbs that often.
 

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Discussion Starter · #10 ·
skr00zloose said:
generally a good starting point for mixture screws is 2-2.5 turns from all the way in. just be easy setting the screws all the way in. it's easy to break the tip off the ends of the screws. just turn them in until they just seat, then back out 2-2.5 turns. most any jet kit will have you adjust the mixture screws, so someone has probably installed a jet kit.

also, while you have the carbs apart to clean them thorouly, look at the brass tube that the needle slides thru, make sure it's not ovaled out AT ALL. if in doubt, replace them. some of the older mikuni carbs had problems with the needles bouncing around and wearing the tubes the ride in.

for the stripped screws, see if you can get a pair of vise grips on them. once you get them broken loose, they should come out easily. just replace them with new ones after that.

as a starting point for the idle adjustment screw, back it out until the end of it just stops touching the plate, then watch the butterflys , and turn the screw in until the butterflies open just a bit. once you get it started, you can fine tune it from there.

make sure you sync the carbs too.

if you're running pod style filters, be prepared for a lot of fiddling with the carbs. those oil cooled suzuki motors are a lil picky about carb tuning with pod filters.

those motors are a lil cold-blooded at times too, it may take a few to let the motor warm up before it'll clear up and run smooth. that seems to be pretty normal with them.

if have any trouble along the way, post up, i know those motors all too well, i'll help with what i can.
I forgot to add that I will sinc the carbs - I bought a carb sinc tool a while ago. I was planning to do this last - this is right, yes? Also, one of my cylinders, when I checked it a long time ago, had compression way below spec. I had done the valve adjustment myself, and it was the first time I had done one. But I may not have had the engine properly warmed up and since then I had a friend who is a mechanic help me with the valve adjustment, so hopefully when I check it again it will be better. If it is still out of spec, could this possibly be a big problem when I try to sinc the carbs? The bitch of it is that before I messed with the bike the engine performed pretty well, aside from a bad oil leak from the cylinder head which I fixed. I do remember some trouble syncing the carbs, even with the help of the teacher of the motorcycle maintenance class I took, but it still ran well on the road.
 

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Discussion Starter · #11 ·
spyder said:
Get ahold of FactoryPro, they make the best emulsion tubes for these carbs. There a little pricey but there nickel plated and dont wear for shit. Ive been tryin to get a set myself, my emulsion tubes are shot.

:Stupid:
I live just a few miles from FactoryPro and I kind of know the owner, Marc (he did some work for me on another bike). I should have thought to ask those guys, but it's hard to get Marc on the phone and he's always real busy. I might head up there soon, so if you let me know exactly what you're looking for I can ask about it. Thanks for your help - I'll keep posting about how it's going.
 

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Bush pilot
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Yeah try 2 turns, if your in too far you'll notice the bike will "hang-up" momentarily before returning to idle after blipping the throttle. If it takes more than 2.5 turns I'd say the bikes likely not jetted and that could be part of the trouble....

Marc will deffinitely be the one to help you.
 

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Discussion Starter · #13 ·
g-style street-fighter said:
Yeah try 2 turns, if your in too far you'll notice the bike will "hang-up" momentarily before returning to idle after blipping the throttle. If it takes more than 2.5 turns I'd say the bikes likely not jetted and that could be part of the trouble....

Marc will deffinitely be the one to help you.
Did you mean 2 turns for the 4 pilot screws or for the idle adjustment screw?
 

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McBain said:
Did you mean 2 turns for the 4 pilot screws or for the idle adjustment screw?

pilot's

McBain said:
I live just a few miles from FactoryPro and I kind of know the owner, Marc (he did some work for me on another bike). I should have thought to ask those guys, but it's hard to get Marc on the phone and he's always real busy. I might head up there soon, so if you let me know exactly what you're looking for I can ask about it. Thanks for your help - I'll keep posting about how it's going.

I need a set of 4, emulsion tubes for an '89 Yamaha FZR 600. I think Factory Pro's are $100... Lemme know
 

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GURU
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Did you get the screws out? If you can get a dremel and cut a slot in it or cut and X for the philips head. I found cutting a slot in a stripped screw works most of the time
 

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Discussion Starter · #16 ·
Dudad said:
Did you get the screws out? If you can get a dremel and cut a slot in it or cut and X for the philips head. I found cutting a slot in a stripped screw works most of the time
That's exactly what I did; got a great new Dremel kit for X-mas. Came with an extension that let me get in there on the right angle. Screw came out easy once I cut the slots and used an impact driver. And yeah, I have a Kan-a-tuna; got it b/c I wanted to learn how to work on a bike w/o messing up something really nice. After this project I plan to get a more recent model GSX-R and fighter it. But I think the Kat will look pretty good when I'm done. Still, I know it's funny. Later . . .
 

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Eff Tee Pee
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hey thats the right way to do things. i started working on bikes with an old bone 1972 cl 350 that i dont plan on riding anyway. first motor i ever did.
 

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Discussion Starter · #18 ·
spyder said:
pilot's




I need a set of 4, emulsion tubes for an '89 Yamaha FZR 600. I think Factory Pro's are $100... Lemme know
I'm going up there tomorrow morning - I'll see if I can get you a deal. I have a jet kit I bought from Factory a while ago but don't need, so I may be able to get you a good discount. I don't know how you feel about giving out info online, so you'll have to tell me how I or Factory can get them to you. But first I'll find out about a discount and let you know. Later
 

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Discussion Starter · #19 ·
929_adam said:
hey thats the right way to do things. i started working on bikes with an old bone 1972 cl 350 that i dont plan on riding anyway. first motor i ever did.
That old metal is hard to work with (whole lotta stripped screws), but at least I have learned some ways to deal with it. I'll go into the engine later, as I know I have low compression in at least one cylinder (don't think the valve adjustment will have taken care of it). For now I want to get this thing on the road, but I am looking forward to tearing that engine apart.
 

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Discussion Starter · #20 ·
spyder said:
pilot's




I need a set of 4, emulsion tubes for an '89 Yamaha FZR 600. I think Factory Pro's are $100... Lemme know
SPYDER - I talked to Marc today and I will be able to get you a discount. Not sure how much; I didn't go up today b/c when I talked to Marc he was on his way out for the weekend, but I'm going up Monday b/c he said he would be around all day. If you want, I could try to set it up so that you can just call in to Factory and give them your info; ID yourself also by your CustomFighters screen name so they know who you are & can give you the discounted price. Later
 
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