Checking carburetor slide diaphragms for problems
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- เผยแพร่เมื่อ 7 พ.ค. 2013
- Got lucky on this set. The previous person installed the slides wrong. Luckily they didn't pinch them, This set is all ready to go back into the bike and fire it up!
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I'm new to the motorcycle building world and I'm finding great advice not only in your videos but also in the replies you're giving people on your videos, it's helping me a lot with this rebuild, thank you =D
Kieri Ogden
Excellent. Hopefully I'll be putting up quite a few more videos in the winter. I got bogged down with a ton of customer bikes this year :) If you have any questions don't hesitate to contact me at bruno@motorbikebrunos.com Good luck on the motorbike!
Man this video is gold within the first 2 minutes 10-year fuel injection master technician Automotive side European but damn I didn't even think about that I'm dealing with a single carb here and mine's falling like a lead brick too
Look for the holes or rips anywhere. Make sure you tug on it all around (lightly) as some won't show until they are stretched a bit. I've had some success on impossible to find parts with similar components to a pedal bike tube patch. I replaced the cement with fuel resistant flexible Liquid electrical tape.
Great job...clear and simple...thanks
Concise and informative. Thank you.
Not a problem. Glad it could help you!
thanks for sharing.
No problem, I hope it helps.
thanks bro
Hello, great vid and advice. How do you install the diaphragms the correct way?
John SwedishPride You have to make sure the slide diaphragm edge is in the groove. Some times I find it easier to hold the slide up slightly from the throat using my finger or back handle of a screw driver so there isn't tension on them. That way the diaphragm will stay in the groove. Otherwise, Honda Bond or yamabond will work if you let it dry slightly before you try to put the spring and cap back on.
im trying to find a vacuum sliders for a 03 750 katana can anybody help
Hey nice vid! Hope your still around it’s been awhile. How do you know if the slide goes down too fast or too slow? Mine takes 2 secs ( 2 Mississippi counts).
In case someone finds it useful, after replacing my spark plugs the bike runs smooth again, so the two Mississippi count was good on the time it takes the slide to come back down on this bike. It is a gradual slide back down not a fast one. Good luck to anyone working in this issue.
@@WordLogos Sorry I missed this question. Yes, each carb has a different time depending upon the spring's ability to push it down and the passages that allow it to come back down. Some have the small brass hole in one of the corners that needs to be cleared, and then it will come down at the correct rate (it's not often they get plugged, but I've seen them plugged before) Glad you got it running well!
Will a cracked diaphragm make it rapid misfire at say about 7000rpm when twisting the throttle quickly? If I back off a bit it revs on up...
Xs750 3cyl, 9000rpm redline, bored to 850 152 jets, needle in position 2, open shorty pipes, open mikuni carbs almost identical to yours. No matter what jets I put in or how I adjust the needles the same thing happens, I've been through the ignition system, fuel system, electrical system... Just fixed the diaphragm and gonna reinstall the carbs tomorrow probably.
When checking for holes I recommend folding the diaphragm down and inspecting the tops, crease tears will be more visible this way. That's how I found the pinhole/ tear in one of mine, couldn't see it from the bottom, it was a crack in the fold next to the slide.
Also, I understand that you are making a video, but when pulling slides you should push it out from the bottom instead of pulling it from the diaphragm for longevity.
Thanks
Sorry I missed this one a year ago...one thing I'd check with an odd misfire at 7000rpm is that you may have TOO much fuel going in at the top end. So your main jet may be too high but works well in the low and mid range. Another thing could be worn main jet holder (the long tube the slide needle sits in when the bike isn't running) Those can get out of round and oblong so they cause some weird issues like that since the needle can't close it off fully and lets too much out at higher revs in an odd pattern. Any holes in the diaphragm will show up as one slide not lifting as high as the others so the opposite could be true with respect to fuel for that cylinder. Usually you can catch that with a good synchronizing tool and check what the vacuum is doing on all 3 at low and then high rpm to see if there's an outlier. Did you ever find out what the problem was?
Why would I be getting gas into the diaphragm area where you take the cover off? I have a 95 Yamaha Virago XV SG 535
Just rebuilt all 4 carbs fuel including cut off diaphragms, needle and seats, the slide diaphragms looked good. Floats set to 16.5mm, synced carbs, all to cure off idle sneezing on 98 Vmax. STILL SNEEZING! New plugs, COPS, stock jetting, stock exhaust. Could the slides/diaphragms be the problem? Should I replace them anyway? By off idle, I mean low rpm under load, as in when you're just pulling away from a stop. It does it the worst when on a dirt road, 1st gear, going 5 mph or less....don't ask. :-)
OK, if the slides aren't torn or have a hole in them, they are unlikely to be your culprit. Slides don't become part of the equation until about 1/4 throttle when you switch over to the main jet from the pilots. What are your mixture screws set at? They have a brass or silver cover over them if you have not dealt with them before. (or the previous mechanic) so look that up on the forums for that procedure. If stock is 2.5 turns. Try 2.75/3 turns out from LIGHTLY SEATED... DO NOT TIGHTEN THEM DOWN YOU WILL BREAK THE TIP!! I can't stress that enough. Also, have you checked the valves or done a compression test? Bikes like the yours people rarely take the time to do the valve adjustment and pass that on to the next rider... Many times I find it's never been done at over 30k + miles. All of these can cause low end stumbles.
Thanks a bunch for taking the time to reply. I have adjusted the jets from their 3.5 stock turns out to more a little at a time.... no luck. I did a valve lash adjustment at 2000 miles to quiet a noisey valve train using shims...that was 42000 miles ago. Valve noise is still not present. Not saying it's not valves but you get the idea. No vacuum leaks detected either. I'll keep looking.. . thanks again!!
@@jh5881 I'd double check your compression then (didn't see if you said you did that recently). What spot exactly is the stumble? And did you sync the carbs while running, or just on the bench?
I have a 1996 Yamaha VMAX. The two spark plugs on the right are running rich. The two spark plugs on the left are normal. What would cause something like this?
Mark Jurik sounds like sticking floats. Usually happens when it's left on the side stand and the fuel dries out. I'd clean out the float valve seat with some brasso or toothpaste if you don't have brasso. It could also be float heights incorrect.
helli sir my 2000 r6 i lift up the tank and rev it and the 2 middle ones does not move at all, any idea whats wrong? pls help
Sounds like the slides are stuck in place by old fuel. It varnishes and holds the slide needles in the main jet holders. You'll want some carb cleaner spray up the main jet after you pull the float bowls off. You may need to remove the main jet to spray up there. Spray a little, wait a minute and spray again. If you do that a few times it softens up the old fuel and then you can pull up on the slide to free it.
HOW DO YOU PUT IT TOGETHER AND HAVE THE DIAPHRAM ALL LINE UP. I CANT GET THE RUBBER TO SIT FLAT THEN GET THE TOP ON AND HAVE THE DIAPHRAM STAY FLAT
Trav, really sorry for the late reply. I'm sure you got it sorted. But just in case...some of the slide rubber will swell, making it rather difficult to re-install. Those need to dry out and usually they will go back to normal size and be easy to install again. Otherwise, one trick is to hold the slide up from the throat of the carb so that it's sticking half an inch or so above the mating surface. That allows you to put the edge in facing DOWNWARD instead of how you normally do it, you still have to install the spring and it's a little bit of fussing about if you haven't done it before, but you'll get the hang of it. Otherwise, I have a really thick grease I use sometimes on the stubborn ones. I'll line the track with grease, put the edge of the slide into it and then it will hold MOST of the diaphragm if not all of it. Makes it a bit easier if needed.
could a bad or incorrectly seated diaphragm cause sputtering? single carb by the way
Repdan1
Yes, but define your sputtering for me. The vacuum draws the slide up to allow more fuel into the throat. With a torn diaphragm, your boot MAY rise slightly but not enough, or not at all. Float height could cause your sputtering, bad spark plug/poor spark and if it's a 2stroke could even be time for new piston rings etc. What machine?
Its a 1990 dr250s, bike is like flooding itself. cleaned the carb, put new gaskets in because it was leaking drove it for about 3 weeks and it was fine but i found out i had an air leak because the cap was cracked but i replaced the cap and diaphragm and then the sputtering started happening but i went back to the old cap but it was still sputtering but i never went back to the old diaphragm so wondering could that cause it. Its like when im trying to cruise in any gear when i get to like 20 percent throttle it starts sputtering any ideas? Ive been through the carb and so has my mechanic and he said it seems fine but he might not have known about the diaphragm also replaced the ignition coil
Repdan1
If you pull the carburetor out again, you should be able to tell if it's working. Lift up on the slide, and it should come down with a look of suction. If it just FALLS down quickly, you've got a problem. Either ripped boot or installed incorrectly. You thought the boot wasn't ripped, so the round diaphragm lip may have slipped inside the top part slightly so it's not sealing as it should. Otherwise, you may have set the float height incorrectly. Verify that first. Float height can be a part of the problem you describe as well. So it drove well for 3 weeks even with the cracked/air leak? Interesting. Might be too hard to diagnose over the computer :(
Motorbike Bruno's Garage Inc. Yeah obviously im not gonna ask you loads of questions because we would just be here forever, theres no tears anyway but im gonna throw the old diaphragm back in just to see because there was nothing wrong with it i just thought id get a new one i'll try that out and see how i get on, just 1 thing i forgot which way is it i bend the tang to lean the float height? Waiting on a clamp for my new silencer so ill let ya know in a couple of days but thanks for the info!
Repdan1
shoot me an email Bruno@motorbikebrunos.com we'll get you sorted out. I can send pictures that way to help out :)
Motorbike Bruno's Garage Inc. Well when i say fine i mean it wasnt sputtering but engine was surging had to mess with idle adjuster when i got to lights and it was real hard to start. Im in ireland so ill take the carb off later and send some pics to your email and you can just get back to whenever you have time , thanks a lot :)
Got a question, I have a 83 Kawasaki 750kz with 4 carbs on it. It will start with the choke on then start rising in rpm’s forcing me to shut it off. But when I turn the choke off it was just die. Could it be one of the slides sticking? I don’t even know at this point
Hello Cade! Sounds like a few different things to look for.
#1 air leaks. The carb manifold boots that attach the carburetor rack to the engine can fail over time. Some have O-rings that dry and crack when they shrink causing massive leaks. Runaway engine RPM can be attributed to this quite often, likely 50% of the time or more. If you have the cash, get some new ones. Z1 enterprises usually has them on hand. If not, or not sure if you want to sink money into it yet, take the old boots off, and use a good engine gasket sealer to put a thin film on them so you get a good seal. If possible, wait a full day before installing the rack of carbs again.
#2 Throttle sticking, throttle plates really far off on sync. So make sure your idle adjustment is bottomed out so that the throttle butterflies close fully. Make sure your throttle cables have slack so when you install them, they aren't holding the butterflies open such that you are basically holding the throttle open by the tightness of the cables. When they are all fully closed, check to see that there's not one butterfly that is being held open by a botched carb job etc.
#3 check your mixture screws. Make sure they are set to roughly the proper setting. If you have open exhaust (loud) or open air filter (more free flowing than stock) then you'll need to go .5 to 1.5 turns more rich than stock setting. Look this type of thing up on the KZrider forum for your bike.
#4 Your choke is working fine and you just have plugged pilot jets. Those bikes on choke can rev to 6000rpm Typically between 4-6k. If you choke it and it revs up that high, lower the choke slightly so it sits at 3-4k. But, if you take it off choke like you say and then it doesn't run...your pilot jets are plugged most likely.
#5 Float height. If you have low float levels, you run lean, when you run lean, you get high idle conditions and hanging idle conditions. Verify this via the forum as well.
You keep saying that the diaphrams were installed correctly but you never say how they were incorrect or what the right way is. I'm guessing that the upper edge just needs to be seated in the channel around the top perimeter.
Would a dirty/gummed up needle prevent the slide from dropping down completely?
+SoulDaddy33 I said they were pinched from the previous owner and not seated correctly. If someone is going this far into their carburetors, I assumed they read the manual or have a general understanding of how they work. This was just to point out what can happen if they are seated incorrectly. To answer your question, Yes, the upper edge needs to be seated in the channel around the top. Not all channels look the same, some will have a deep groove, where others have a notch to keep the slide pointed the proper way, and others are more "flat" in appearance. The main thing is that it be seated all the way around in such a way that it can become a "sealed" surface. Any holes in the diaphragm or in the sealing surface will not allow the vacuum to pull the slide up, or it will fall much more quickly than it should and throw off the balance of the fuel mixture to the other carbs. A gummed up needle usually doesn't hold it from going down, it will more likely HOLD it in place! Typically that's what happens. There's not a ton of fuel that sits in the main jet holder from the few hundred carbs I've worked on. Not saying it's not possible, Ethanol is nasty stuff these days!
Hi Motorbike Bruno,
I have a 200cc bike (pulsar 200NS) bike was giving jerks all time slow fast starting. When I got carburetor checked they say the slide is rubbed at one part. Do need to replace it for fixing this problem. That slide doesn't have tears or holes but one side seems to be rubbing which removed the coat of that slide. What should I do?
It depends on how bad it is rubbed off. I find that the material gets slowly scratched when the slide needle is bent too far in one direction so the slide isn't going up and down in the center. It's being pushed one direction due to the bent needle. Sometimes the slide needle itself isn't bent, but installed incorrectly so it leans too far and has the same effect. If the rubbing was really bad, you should replace the slide. Also verify there isn't a sharp edge or metal burr that is causing the rubbing of the slide.
Also, it could be mixture setting on the carburetor, or if it's a clogged fuel vent in the gas tank you could have fuel starving.
Thanks a lot for the reply!
I'll check it for sure.
Dude, I need some advice...I need to add gas directly into the carburetor in my car to get it started everyday...after that it will start and run fine....then after a few hours i gotta pour gas in the carb to get it started again....every now n then I also hear it make like a hissing sound or exhaling sound when I try to start it again. Also, after I slow down after high speeds it shuts off and i gotta pour gas in again to get it started. The fuel pump is fine. What could be the issue?
jorge pluas
I'm assuming you got this figured out, sorry I didn't see your reply until today! I know much less about cars than motorcycles, but carburetors are all about the same. Sounds like your slow jets (pilot jets) are plugged up, or if you have a mixture screw, it's plugged up or incorrectly set. If the fuel pump is fine, it sounds like you just aren't getting enough fuel into the bowls, or into the throat. Do you have an accelerator pump on your carbs? Let us know if you figured it out.
What the hell balancing carburetors before they're even on the bike.!!! Yes it is possible and easy to do.!!!!
You can add a bout a 18in piece of tubing and suck on it to see if the slides are going up and down smoothly you can also suck them up clamp the tubing and see if they leak back down.???? I also clean the slide and the needle and spray them with high heat silicone lubricant and the boar to.!!!
Rick Simpson sure thing. This is just a video of an odd problem due to pinching the slide diaphragm. It's not a video on cleaning carbs.
Oh and I don't use any of the lubricant on the slides or bores. It just gives dirt something to stick too. May not hurt anything, but they had no lubricant from the factory.
Motorbike Bruno's Garage Inc. that is a good point but the spray high heat silicone lubricant that I use evaporates and leaves no sticky residue.!?! Some that I've worked on are old Warren and rattle around probably ain't necessary on good ones.!!!!!
What happens if there are holes in the membrane?
This will cause an unbalanced carb. Depending upon the severity of the hole, it will raise or lower the diaphragm too quickly and will typically not lift up during low vacuum (idle, cruising) causing a lean cylinder as the slide needle isn't being moved up and out of the main jet holder to allow that fuel into the cylinder. If you snap the throttle or go wide open the slide can work "enough" and then when throttle is let off, it drops to the bottom immediately and causes the same lean condition with backfiring etc possible. In short, do not try to ride the bike like this.
How do you put the diaphragms in correctly?
Shoot me an email at Bruno@motorbikebrunos.com I'd be willing to help you with your issue.
The main thing is to get the lip of the diaphragm in the groove without it moving out of place. Many of the diaphragms have a little "bump" that fits into a specific spot on the top of the carb. You can use a little bit of Yamabond or Hondabond to help with this. Another trick is to hold the slide up a little (through the carb throat) while you are putting the cap on. I'll see about doing a video about that in the spring here.
Ohhh ok thank you
Could a torn or punctured diaphram cause a cylinder to not get fuel?
Yes and no. The short answer is no. It would still get fuel at idle and through the choke circuit. So if you are asking if it will cause the bike to not start, then no it has no influence on that. However, if you are talking about fuelling while you are riding, yes. If it rises part way then you aren't getting enough fuel to that cylinder when you are on the throttle. It also completely throws the sync off. That carb slide is going to go up and down at the wrong rates. No good.
@@RSVbruno Thanks for the reply, the bike runs and idle fine but will not run on one of the cylinders and I wondered if it was because of the diaphram. If a carb is getting fuel to the bowl and has spark why would it not idle on that cylinder.
@@noah2016999 what's the compression? Timing? Valve clearances?
is it possible that after replacing the diaphragm , friction is still present because of the carburetor walls are damaged due to friction.
RkD TourCam usually the walls don't get damaged, unless there is dirt or debris in there. The slides will wear down all little bit, but that's normal. Double check for burrs or anything that might be hanging it up. I use an engineered steel wool substitute, or scotch pad. Make sure you clean the slides well too. Any varnish or gasoline traces can stick too.
Motorbike Bruno's Garage Inc. I recently changed my bike carb diaphragm and still the bike is not revving on higher rpm and i still feels lags.
RkD TourCam if the slide moves up and down with a slight resistance, it's fine. Are you running stock exhaust pipes and air intake? If you Change either of those, you have to add more fuel by changing your jets.
Motorbike Bruno's Garage Inc. Yes everything is stock, but bike feels jerky and cant revv up higher on 6th gear
RkD TourCam could be clogged air vent, not allowing fuel to enter carbs to fill fast enough. Or low compression, valve clearance issues possible too. Sticking slides show up moreso on the low end with hanging idle and out of sync feelings.
What does the diaphragm do exactly?
Robert I didn't see this 7 years ago.. But just in case anyone else needs the info: The slide blocks air from getting to the engine, allowing the small pilot jet to get enough fuel to the engine to start it. Then as throttle is applied, the engine vacuum draws the slide upwards to allow more air into the engine. While it's doing that, the slide needle (tapered needle that goes down into the main jet holder) slides up and away from the main jet holder. The taper angle and length changes the amount of fuel able to get pulled out of the main jet holder nozzle and into the throat of the carburetor. It's why you see different shaped needles in jet kits. They allow more fuel up and out faster than the stock one to help produce more power with the added air/exhaust changes you do.
@@RSVbruno My diaphragm seems to be worn out and the slide occasionally gets stuck in the up or halfway up position. I've been chasing a rich issue on a Ducati and was wondering if this could be the culprit? The symptoms are fouled plugs, jerking, stalling, heavy backfiring, and horribly rough idle.
@@drderplogic kind of depends. First thing to do is to clean the slide body really well. Clean inside the carb body where the slide goes as well. Is your diaphragm split? Or cut in any way? If the slide sticks upwards, that would cause a rich condition as the slide needle would be raised out of the main jet holder. However, float height, sticking float needle or mixture screws set too rich can do that too. Another thing to note is that your choke could be sticking.
@@RSVbruno I appreciate the quick response! Good video, too. They seem to be intact but I was struggling to get them to sit properly in the cutout, they were kinda stretched. I've already purchased a rebuild kit, as well as some new diaphragms (will take like a month, as they're coming from China 🙄) so I'll see if that helps. Carbs are no fun. I also didnt think to check the choke... thanks again for the input!
@@drderplogic if you recently cleaned them, the diaphragms can balloon up and if you wait a day they shrink back to normal. I use thick grease in the track where the diaphragm sits to keep her in place.
My diaphragm is getting stuck when it goes up any suggestions
Make sure you didn't forget the spring that pushes it back down. The other possibilities are dirt on the slide or in the carb body, or the track if it's like the sportbike round/flatslides. Another possibility is slide needle is pushing too hard to one side due to wrong installation of slide needle. It must be relatively centered and usually has some give in all directions. Not a ton, but some see if the needle is hanging up. Another thing depends on the angle of the carbs. You may find that if you put it straight up and down, gravity will pull it down easily, but when installed sideways it does not. Usually running the bike for a little bit will settle it back in place. Run without the airbox so you can see how it's reacting if you can't find dirt or any other issues you missed.
Motorbike Bruno I don't know if you have a video on how to balance carbs on the bench before installing them.??¿Make a video on this if you don't have one. You have probably done this or seen someone else do this.!!!? Hard to explain please bear with me.!! On your primary carb use a gauge wire or a small numerical drill bit to adjust your throttle blade angle or butterfly. Where this gauge slides in and out smoothly then go to your next carburetor the spring loaded adjustment screws that attaches one carb to the next adjust this screw to wear that butterfly is set where this gauge slides in and out smoothly continue on Down the Line fine tuning go back to the beginning and adjust and fine-tune again. This will help you balance them when they're on the bike and most times they're so close you don't have to balance them you may be able to get closer at idle but they'll be off at a higher RPM or you might be able to get them closer at a high RPM but they'll be off at idle.!!! I've had extremely good luck at doing it this way.!!!!
Rick Simpson I could make one, but there's quite a few good examples out there on it. Bench synchronizing will get you up and running well enough. But I always do a proper gauge sync (manometer) to get them all exactly where they should be for the given engine.
Motorbike Bruno's Garage Inc. you're 100% right thank you.I've been working on bikes for over 40 years I enjoy showing and helping people out like you do. I'm new to TH-cam videos I look at them and say shit I was doing that 30 years ago. But I still pick up some new tricks everyday. Do you have any videos on doing fuel injection bikes remapping or flashing the brains . Patch cables and programs.????
kz1100 spectre carbs?
Unfortunately this was so long ago I can't remember. Some of the KZ's had the chromed bowls on the outside like this set, but I just honestly can't remember :)
im trying to find a vacuum sliders for a 03 750 katana can anybody help
im trying to find a vacuum sliders for a 03 750 katana can anybody help
tony mims just go on ebay. If you only need one, just type in 2003 Suzuki Katana carb slide. $50 each usually (they gouge you) but they also make single rubber diaphragms you can install too. Those are around $28 each, but they aren't the whole slide. Another possibility is to talk to a seller and buy a whole rack of carbs. Make sure they say that the slides are ok! Good luck!
tony mims just go on ebay. If you only need one, just type in 2003 Suzuki Katana carb slide. $50 each usually (they gouge you) but they also make single rubber diaphragms you can install too. Those are around $28 each, but they aren't the whole slide. Another possibility is to talk to a seller and buy a whole rack of carbs. Make sure they say that the slides are ok! Good luck!
thank bro