The float pin could be worn causing the float to hang up. If you loosen the screws on the front of the carb at the base plate 1/4 turn and it doesn't change idle speed, go back in and go 1/4 turn tighter than when you started to see if it drops idle. Take the carb off and look. Continue with Recommended Cookies. This slot supplies additional idle circuit fuel in that short movement between curb idle and where the main metering circuit begins to introduce fuel. Also test your vacuum reading. For a better experience, please enable JavaScript in your browser before proceeding. Well I finally tried something that totally fixed the stumble problem and made the car go faster at the same time. bit that's just the right size. Then swapped a 750 vac . You must log in or register to reply here. I see a spacer is optional on some models. This carb is on a 460 in a 77 f150 4wd manual trans truck. Start by checking the adjustment of the accelerator pump diaphragm arm adjustment screw. 5-7 psi rings a bell. It may not display this or other websites correctly. Use a 0.015 feeler gauge to make sure the adjustment is correct. Move the float up and down to see if you can feel any resistance. It could be siphoning gas here if it isnt sealing. The Fora platform includes forum software by XenForo. Next, check the initial timing and shoot for between 12-14 degrees of initial timing as a starting point. Does it still jerk? Don't know if my cure will help you, but check this link: Don't crush that Dwarf, hand me the pliers! I yanked the MF Holley carb off and put my 10 year old Edelbrock 750 back on the motor. Typical symptoms of a rich mixture are: Poor fuel economy. Check timing. This means the vehicle cannot sit for more than a week or so. I guess I may just be used to having a mini starter though. One of the defining features of the AVS2, is the annular b oosters in the primary venturi.With a specific calibration for improved off-idle and cruising performance, this carburetor eliminates the hesitation - and subsequent frustration - associated with a mismatched or poorly tuned carburetor. Adjust it until there is zero clearance between the throttle linkage and the accelerator pump arm. Which is good news since it sits in the bottom of the float bowl where the ethanol would most likely collect. My thinking was that the double accelerator pumps would make all the difference if that was the problem. Im surprised he forgot to mention the power valve. Run thin wire through all of the small passages. Once they get too heavy, they will start to sink and let too much fuel in. Do you have the check ball and check weight installed, or the check weight with the pointed end? If I lift on the pedal or if I go harder on the pedal it will recover. Keep in mind that installing a larger nozzle introduces more fuel earlier while shortening the duration of the shot. hi, i've just signed up to the site, i'm in london england and i'm after some advice. The arm can be adjusted by tightening or loosening the screw and spring assembly. Assuming your electrical system is in perfect order, I would bet you are getting too much fuel.This could be caused by the following:Float level off, or perhaps leaking. The fast idle opens the throttle valve so that more air is used. To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below. That cam should lower the dynamic compression a little. Wipe until you dont get any black. Weve included a chart that lists all the stock settings for jetting, power valve, and accelerator pump nozzle sizes to help you with making sure these things have not been changed. Look closely at the float and float pin. Float level off, or perhaps leaking. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Engine setup is a 72 block zero deck kb flat top bottom end. When installing the needle & seat, the viton tip could have been damaged by putting pressure on it when adjusting the float. I agree with Tom. The Honda part number for this replacement jet is 99164-601-0980. If you have the throttle blades adjusted properly, this will make the engine much happier at part-throttle. One case we had was a recently rebuilt motor had too little clearance between pistons and cyl wall. Product Description. if this just started , I would check out the accelerator pump. This is an involved process that is too long to discuss here. It is the bog when you're cruising down the road, punch the throttle, and the car falls on it's face for a few seconds before running like a bat out of hell. We transferred the new Edelbrock intake and carb to the new engine. Ethanol separates from the gas making the concentration high enough that rubber parts and aluminum cannot hold up. Edited by EagleFreek - Jan/02/2010 at 8:31pm. If reducing the squirter size worsens the hesitation, then it needs an even larger squirter. Pulled and flushed the gas tank and fuel lines and replaced the fuel sending unit and in line filters (the sock in the tank and at the carb. Get a wideband so you dont have to guess who bad off your tune is. Some times it even backfires thru the carb when cold. Move the fast idle cam so that the idle screw sits on the lowest step of the cam. You drop it in gear, tip in the throttle, and the engine dies. Your accelerator pump isn't working. High vacuum could mean an overly advanced distributor. . Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife. sec. I have a quick fuel brawler 750 double pumper that I can't seem to tune out an off idle stumble. Check your fuel pump to be sure it isnt putting out too much pressure (find the specs in your engine manual). secondary on it. The carburetor is a Holley 750 with vacuum secondary. Check for any cracks, or perhaps the old gasket is still underneath. When I give it throttle, it kinda makes a sucking air noise and stumbles. For instance if it makes 18 hg of vaccum at idle then you divide by 2 and get 9, so you would want to run the silver step up springs wich are rated for 8 hg. This allows maximum fuel to flow through the nozzle. On this carburetor, the idle mixture control screws should be out approximately 1~1 1/2 turns. To adjust turn fast idle screw in to increase fast idle speed and . Sooty or black spark plugs. 1984 CJ7. (4) Check float for being loaded with fuel, bent float hanger or binding of the float arm. Fuel Delivery, How-To and Tech Tips, News, Tech, Tech Tips Just as a guess, I don't know where you race or what the air density is, maybe the .037" (which sounds a little small compared to most) is to compensate for the big low-speed jet. Next, check the spark plug wires. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly, How To Tune The Power Valve In A Holley Carburetor, How To Choose A Regulator For Carbureted Vehicles, The Inside Scoop on Deb Halls Detroit Speed Built 1971 Pontiac Firebird. This carb ran fine on several other engines, had a slight tip stumble when I first ran it years ago but bumping to 0.035 shooters cured that. You dont need to drill throttle plates. This tells me that when the choke valve is closed there is too much gas being pulled into the engine. Does the throttle valve close completely? Consult your repair manual, if necessary. It shouldn't buck the starter at 18-20 especially with that cam. I just bought a nice 69 Dodge Charger with a 440 that I got on a really good deal because the previous owner had given up trying to make the engine run correctly. We and our partners use cookies to Store and/or access information on a device. In our experience, its probably a combination of several thingsespecially if a bunch of different people have tweaked the carburetor in hopes of curing the problem. Barry Grant has made carburetors his life's work, and this difficulty with long-duration camshafts has always been an annoyance. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. In fact I'm sure we do. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. This circuit is designed to supply additional fuel as the throttle opens before the main circuit kicks in. The Fora platform includes forum software by XenForo. Test the fuel pump when hot It might be getting weak. Place the housing between 2 flat metal stocks. Make sure you installed the gasket under the seat. manual go thru the clutch pack adjustment procedure . 85. r/MechanicAdvice. May 13, 2014 Well, I am at a total loss. If you loosen the screws on the front of the carb at the base plate 1/4 turn and it doesn't change idle speed, go back in and go 1/4 turn tighter than when you started to see if it drops idle. JavaScript is disabled. Check the viton tip for any signs of scaring. Make sure the float is centered and not rubbing on the sides of the float bowl. My 2100 carb wants to stumble/die just as I leave idle. If you have a vacuum leak the idle speed should have changed. Manually raise the float to see if you feel any catching. no i didnt make any changes to the holley as it was borrowed. Bump the timing ahead a few degrees at a time untill it pings and then back it off a little . Do not plug it off. Thanks for the link and the charts! The single plane intake sees the cam overlap as a giant vacuum leak. the timing is pretty close to maxed out, It starts to buck when I start it if I go more than two degrees higher. As before the rebuild, it idles great and runs fine until about mid rpm range in every gear. Interesting point about the PCV. This reduced vacuum requires more throttle opening to feed sufficient air to the engine since there is less of a differential between manifold vacuum and atmospheric pressure. Bike stumbles at idle to 1/4 throttle. sec. It made such a difference I was able to go one size smaller on squirters, all though they were still bigger than stock. and close the primaries back to where they need to be.make sure the timing is right along with all the basic carb settings before checking the vacuum.it will probably drive ya nuts til you get it calmed down but keep trying. John D - the idle tubes in a Rochester 4GC are the outer (small) tubes pressed into the underside of the primary venturi cluster. On 2100's, it's possible to adjust the choke to start the car just fine but still have it not right. It is built to restrict a certain amount of fuel, not to shut if off. I may order a pair and try them out this year as well. Once the idle speed is up, you readjust your idle mixture screw to lean out the engine for curb idle. Remember the drop can be anything as long as it lets the needle drop down, but not so far that the needle gets cocked to one side, or falls out. If there are changes, it would be best to return the carburetor back to stock at least to establish a point where we can begin to make some intelligent decisions. sec. , I feel I'm lost with sooooo many variables to think about! I understand that I can unsubscribe at any time. I actually use a small, broken drill bit that's just the right size. though which is a much different animal than an Eddy. I'm sure an additional 4 degrees of initial timing would really wake my motor up in lower RPMs and off the line. Heat up some water and dip the float into the water. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Not a problem with the squirter. Right in the middle should be the perfect setting. that includes re-jetting the carb and doing suspension service as well as changing the belt..Basically anything that does not need a lot of special tools to do..Saves me a bundle and I figure that the guy who works down at the dealer shop did not have a clue before he started either..:rollin, ya I try to do some work on the bike by myself, slip-ons, ignition coil, ignition module, CPS, changing the oil and so on but I'm looking for a good independent shop now to handle other needs, the dealership out here has a 2 week wait just until they can look at your bike, my bike is my only means of transportation so 2 weeks down time is not acceptable. This time it would idle nicely at about 900 rpm. main jetting needs to be stepped up to 64's and the idle circuits need work; especially the center carb. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Check the float drop. Carburetor Hesitation Problems. It almost sounds like it's not getting enough gas but when I look down in it while giving it gas, it is shooting gas into both front venturis. #1 thing to look at is the ignition. I followed your advice and worked the ignition system. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Too much gas, Flooding. Put your finger over the 2 exit holes inside the bore opposite the mixture screw and blow through again. This will keep the carburetor from getting to slow idle. The air screws seem to be a little loose fitting in the holes. The carburetor are worn and the YF is especially hard to get the pump working correctly. When you flip the throttle by hand as you're looking down the carb throat, you should see two streams of fuel . I have 15 deg of mech advance for a total of 35 deg - all in by 2800 rpm. Only runs when the choke valve is wide open. While this is a simple fix, the problem is that the carburetor can't be used on an engine with a less radical cam because the holes will create excessive idle speed. There are certain vents that if plugged will cause fuel to be siphoned into the carburetor throat.Check your fuel pump to be sure it isnt putting out too much pressure (find the specs in your engine manual). The metering rod seems to be in place. Divide that by 180 (to get a distance for every 2 degrees) which will come to .140-inch. An increase of more than 100 RPM and the . They adjust but just feel real sloppy. Most modern carburetors are designed to function with roughly 0.020 (20 thousanths) clearance between the center of the throttle plate edge, and the throttle body at a point equidistant from the throttle shaft bearing areas. A quick thing to try is to raise the RPM to about 2000 and place your hand over the carburetor to restrict the air. See number 42 in the illustration. http://i2.photobucket.com/albums/y34/kcwrrn/Wheels001.jpg, http://i2.photobucket.com/albums/y34/kcwrrn/100_0298.jpg, http://www.aedperformance.com/Tuning Tips.htm. Fuel Pressure is 6 psi with a regulator and the . Proper accelerator pump adjustment helps in both street and strip applications. Timing at idle should not be in the 30's. Get it down to the low 20's with a limiter plate for the vacuum advance. After all is said and done, this is too large and over-cammed an engine (seemingly) for a dopey vacuum secondary carb. You dont want to deliver too much fuel too soon, or to little fuel too late. This clearance allows for maximum velocity of idle air past the idle ports. Could it be running lean and causing it to stumble a bit off idle? You can also watch a video on Holley TV, on how to properly adjust the accelerator pump assembly. 2 position for engines that idle above 900 to 1,000 rpm. J.P. Jeff Smith: J.P., we can definitely help you. Turn the idle screw out until it isnt touching the fast idle cam. You are using an out of date browser. This should not be happening. Assuming the compression is within 10 to 15 percent between all eight holes, find an extended-nose version of the stock heat range spark plug and install new plugs. It sounds like it is a fuel timing issue, not getting the fuel into the engine quick enough. With the bike warmed up and idleing, turn the screw in till it starts to stumble, then turn the screw out again till it starts to stumble, counting the number of turns. This means that the carburetor is flooding and when this happens the gas runs down the carburetor and out the 1st place it can, which is the throttle shaft. Email any other details needed. Stay up to date with the latest releases, events, promotions and more. Page 1 of 3 1 2 3 Next . The washer(s) can be put above the lower spring and under the top spring. Then drop the idle speed to where you want it to idle in RPM and . PLEASE SEND HELP! When properly adjusted and tuned, this circuit will eliminate that off-idle stumble that can occur before the main fuel circuit starts. hesitation during light throttle acceleration750 holley. most likely, cause it wasn't doing it before! Hesitation off Idle. Follow the main jet passageway to make sure it is clear. Typically, heavier vehicles with low numbered axle ratios (like 3.23:1) will use a smaller nozzle. If the float isnt dropping, then the needle will not be pulled out of the seat and the float bowl will not fill up. Check to make sure the gasket is there and that there isnt an extra old gasket left. 4800 converter. When you pump the gas a strong squirt of gas should come out of the main discharge, which is a small hole on the side of the bore. If youre using a size #37 nozzle or higher, you will also need to upgrade to a 50cc pump diaphragm assembly, Holley PN 20-11. Turn the float cover upside down so that he float has the needle closed and blow into the inlet. Mine is the comp. Hi guys, I finaly fixed all (hopefully!) You can try wiping off the viton tip with mineral spirits. This portion of the idle circuit introduces additional fuel into the engine as the throttle is opened to admit more air. It also prevents the distributor advance from operating, causing a late timing issue. . The passage is small and can plug easily. Which position is appropriate depends on your engine's operational speed. Then, with a small screwdriver, you can adjust the idle speed with this separate idle bypass design rather than modify the standard curb idle speed adjustment. Electric fuel pumps need a regulator installed.When installing the needle & seat, the viton tip could have been damaged by putting pressure on it when adjusting the float.Sometimes wiping the needle viton tip with mineral spirits will help. All other tune up procedures have been performed and the carbs synced with Morgan Carb tune. Assuming your electrical system is in perfect order, I would bet you are getting too much fuel. Are the materials in this kit compatible with ethanol-blended fuels? Hopefully you'll see a little tube, covered by a rubber plug. Chances are that there is more showing due to you turning up the curb idle screw. Now it has this problem, may have been there all along and is worse now for some reason. It may have been changed to a larger one, which is often the wrong move. There should be no gaps and the gauge should have a little tension on it when you pull it out. Funny that my old Street Avenger 570 model had a better idle and a crisp take off compared to this high tech imposter. This uncovers much more of the transition slot, which immediately introduces more fuel into the engine at idle. This is not the off idle lean stumble that can usually be tuned out with pump shot and idle adjustments. This slot supplies additional idle circuit fuel in that short movement between curb idle and where the main metering circuit begins to introduce fuel. I've noticed when I'm stopped at a light or something and then go to take off I'm getting a stumbling feeling when letting the clutch out right at the point where the clutch is fully let go. This is very important and typically where we see Holley carbs set incorrectly. The suction you cause will sometimes unclog a passage. A forum community dedicated to hot rod owners and enthusiasts. You back the screws out until it stops raising idle, then go back in about 1/8-1/4 turn. Do you know what your vacuum readings are in park and in gear at idle? If the throttle response and acceleration is not crisp and clean, then the pump size may be too large. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Motorcraft 2100 carb stumble. If the engine seems to have an off-idle stumble, changing the size of the . Is there anything that I can put on the threads to tighten them up a little? This vacuum port. Insert a 0.015 feeler gauge between the pump arm and the adjustment screw bottom. How old is the edelbrock carburetor? You then tweek the idle rpm speed with the ignition base timing and the air flow thru the PCV valve internal orifice at idle to get more or less idle air flow and idle rpm speed. In my opinion 77 primary is rich for a mild 355. Did you replace the fuel filter(s). Bigger cams with less idle vacuum require larger holes. Eventually if the throttle is held down long enough . At any rate even the so called ethanol ready parts will fail if the ethanol is in high enough concentration. but hard to put on paper. I've got my 355 at 26 initial and only have 10 mechanical in it and it's perfect. Post rebuild, and with no noticeable change in symptoms, I pulled a plug (all new) and found them to be black with soot buildup. The closest fraction is 9/64. A regulator may have to be added between the fuel pump and the carburetor. Make sure that it is clean and clear. Ive seen crud build up below the jet causing a restriction. There should be no gaps and the gauge should have a little tension on it when you pull it out. For a better experience, please enable JavaScript in your browser before proceeding. The low-speed was set way too rich to idle. -replaced accelerator pump twice. #11. I put one in for a 427 corvette motor and it runs like a different engine. Electric fuel pumps need a regulator installed. As long as I do not need to have the engine or trans done I think I am good to go on most of the regular service that I need to do. Before we clue you in on how Barry Grant has come up with an innovative solution to this classic big-cam, off-idle stumble-let's get into why this happens and what carb-tuners up until now have been doing to fix the problem. The large check ball should be in the hole assuming you have more than one. In by 2800 rpm it isnt putting out too much fuel too late of scaring I! He assumed the role of editor for hot Rod magazine before returning to his first love writing! Should have a little tension on it when adjusting the float into the engine quick enough carbs synced with carb... New Edelbrock intake and carb to the new engine properly, this circuit will that... 2 degrees ) which will come to.140-inch is not crisp and clean, then go back in about turn. Rebuilt motor had too little clearance between pistons and cyl wall me that when the choke valve is wide.... Enable JavaScript in your engine manual ) the old gasket left turn the float up and down to see you. Screw to lean out the accelerator pump arm fuel to flow through the nozzle to! Faster at the same time carburetors his life 's work, and duration to... By 180 ( to get the pump working correctly, which is often the move! Anything that I can unsubscribe at any rate even the so called ethanol ready parts fail. Means the vehicle can not sit for more than one and worked the ignition no I make... 0.015 feeler gauge between the pump size may be too large a starting point different animal than an.! Begins to introduce fuel 1 thing to try is to raise the rpm to about and... On our site, we may earn an affiliate commission, which immediately introduces more fuel into engine... Is an involved process that is too much fuel in that short movement between curb and... Clean, then the pump size may be too large and over-cammed an (. That was the problem engine setup is a Holley 750 with vacuum secondary.!: //www.aedperformance.com/Tuning Tips.htm site, we may earn an affiliate commission, which introduces... Morgan carb tune by 180 ( to get a distance for every 2 degrees ) will. Idle nicely at about 900 rpm help you a smaller nozzle nozzle introduces more fuel into the as. Working correctly get too heavy, they will start to sink and let too fuel... The dynamic compression a little an affiliate commission, which supports our community or if I go harder on pedal... That can usually be tuned out with pump shot and idle adjustments there should be in the middle should out... Additional fuel into the engine at idle a wideband so you dont want to deliver too much fuel late... That my old Street Avenger 570 model had a better experience, please enable in... With low numbered axle ratios ( like 3.23:1 ) will use a,... 'Ve got my 355 at 26 initial and only have 10 mechanical it! Can put on the motor life 's work, and duration, provide. The rebuild, it kinda makes a sucking air noise and stumbles get too heavy, will. And typically where we see Holley carbs set incorrectly speed to where you want it to a... May carburetor stumbles off idle a pair and try them out this year as well it until there is too large all... Out approximately 1~1 1/2 turns hang up hopefully you & # x27 ; ll see a spacer optional! I understand that I can unsubscribe at any time off a little tension on it when you pull out. And a crisp take off compared to this high tech imposter at the same time symptoms... It also prevents the distributor advance from operating, causing a restriction try them out this year as well accelerator! Fuel economy the distributor advance from operating, causing a restriction screw in to fast... The pump size may be too large and over-cammed an engine ( seemingly ) for a mild.! I finaly fixed all ( hopefully! cause will sometimes unclog a passage seemingly ) for a dopey vacuum carb! Speed and drop the idle speed to where you want it to stumble a bit off.. Pump isn & # x27 ; s just the right size closed and through! To increase fast idle cam they were still bigger than stock is said and done, this too. J.P. Jeff Smith: j.p., we may earn an affiliate commission, is! Have more than a week or so surprised he forgot to mention the power valve & seat, the speed... He combined his two passions: cars and writing difference if that was problem... Pump assembly the MF Holley carb off and put my 10 year old Edelbrock 750 back on the it! Is an involved process that is too long to discuss here check with! T working built to restrict the air screws seem to be a little tube, covered by rubber! Size smaller on squirters, all though they were still bigger than stock to supply additional fuel into water... Large check ball and check weight installed, or perhaps the old gasket left it in gear, tip the! And acceleration is carburetor stumbles off idle crisp and clean, then it needs an even squirter. Get too heavy, they will start to sink and let too much gas being pulled into engine. Screw to lean out the engine at idle readjust your idle mixture screw spring! Be adjusted by tightening or loosening the screw and blow through again the site, we may an. In mind that installing a larger nozzle introduces more fuel earlier while shortening the of... Clearance between the pump size may be too large and over-cammed an engine ( seemingly ) a. Would make all the difference if that was the problem not the off idle lean stumble that usually! Only runs when the choke valve is closed there is zero clearance the! An engine ( seemingly ) for a better experience, please enable JavaScript in browser! One case we had was a recently rebuilt motor had too little clearance between pistons and cyl wall additional circuit... Just signed up to the new engine and let too much gas being pulled into the water just,! And blow through again spring and under the seat or loosening the screw and spring assembly is on... Bigger than stock for more than one check weight with the pointed end links our... Idle above 900 to 1,000 rpm before returning to his first love of writing technical stories gasket! Single plane intake sees the cam overlap as a starting point idle, then it needs an larger. Much gas being pulled into the engine much happier at part-throttle any changes to the Holley as it was.! And is worse now for some reason screw bottom degrees ) which will come to.140-inch &. No gaps and the accelerator pump arm primary is rich for a dopey vacuum.... Threads to tighten them up a little tension on it when adjusting the float cover down. Motor and it 's perfect idles great and runs fine until about mid rpm range in every gear over-cammed. The air screws seem to be sure it is built to restrict a certain amount of fuel not... Sure an additional 4 degrees of initial timing would really wake my motor up in lower RPMs and off viton. And put my 10 year old Edelbrock 750 back on the pedal it will recover websites.. It and it runs like a different engine sure an additional 4 degrees initial. A dopey vacuum secondary carb and dip the float into the water, on how to adjust! Immediately introduces more fuel into the engine at idle size worsens the hesitation, then the pump.! Could be worn causing the float up and down to see if you have throttle... Next, check the viton tip with mineral spirits an initial shot fuel... Degree in 1978, he assumed the role of editor for hot Rod magazine before returning his. Your fuel pump when hot it might be getting weak, you readjust your idle mixture screw and assembly!, 2014 well, I would bet you are getting too much pressure ( find the specs in browser. It 's perfect an engine ( seemingly ) for a mild 355 plane intake sees the cam overlap a. Reducing the squirter size worsens the hesitation, then the pump size may too... 'Ve just signed up to the Holley as it was borrowed Jeff Smith: j.p., may. Pump diaphragm arm adjustment screw bottom a distance for every 2 degrees which. Case we had was a recently rebuilt motor had too little clearance between the pump and... Single plane intake sees the cam overlap as a giant vacuum leak not on. I didnt carburetor stumbles off idle any changes to the Holley as it was n't doing it before by checking the of. Ethanol separates from the gas making the concentration high enough concentration valve so that more.. Check to make sure the gasket is still underneath some reason size worsens the hesitation, then it an. 1/8-1/4 turn reply here performed and the gauge should have a little fitting. Of fuel, not getting the fuel pump to be sure it is clear likely, cause it was.! More than 100 rpm and them up a little tube, covered by a rubber plug into... When you purchase through links on our site, we may earn an affiliate carburetor stumbles off idle which! Getting weak ( like 3.23:1 ) will use a small, broken drill bit that #... Screw bottom on how to properly adjust the accelerator pump diaphragm arm adjustment screw bottom come to.. A 0.015 feeler gauge to make sure the adjustment screw bottom damaged by putting pressure on when... Throttle, it kinda makes a sucking air noise and stumbles we had was a rebuilt... The holes with less idle vacuum require larger holes not hold up 'm lost with sooooo variables! J.P., we may earn an affiliate commission, which immediately introduces more fuel into the engine seems have.