Consequently, if the jetting was on the money before the spacer was installed, the carb may need to have a size or two larger main jet to compensate. Other jets use random numbers to represent jet size, and in many instances multiple jets have the same jet size with a different taper. I'm not so concerned with the actual jet size as I just kept jetting up until power started to fall off. Main Jet has been removed and the needle is visible along with the pilot jet. therefor saving you not just a lot of Money, but also a lot of tinkering hours. This is usually the jet size in inches. is always open. All main jets are sold 2 per package Note: Jet hole sizes provided below are for reference only. Ask us a question using the form below. What's the formula for the Dells?. The size 80 jet is 13. We also cover vacuum and mechanical secondaries. In our case, the 650 Street HP used straioht boosters rather than the downleg style used in all the other carbs. All in stock for next working day delivery - Pilot Jets, same brand as OEM but a fraction of the price. Your engine's cubic inches Your expected maximum RPM (Redline). Our one Ultra-series carb was the 950. 30mm, so i am confused as to to what the actual siz e of the drill bits are in standard. CFM Calculator. You most likely will have to change the jets (as I did) from the stock 1406 jets to the 1405 jets and metering rods. [(DxR)/3456] x [(B/14. The Weber is. Running the correct ratio of fuel and air makes your dirt bike run optimally. It is on a 10. Probably comes jetted square like that because it has a power valve on the secondary while other carbs with a jet size bias, do not. CARB JETTING; CARB JETTING. The main jet. In those cases use drill bits to measure the hole, then convert the drill bit to decimal. Because the secondary side of the Qjet opens according to the airflow requirements of the engine, the same basic carburetor size can be used on a large range of engine sizes. THE CARBURETOR AND ALL PARTS ABOVE WILL BE COMPLETELY ASSEMBLED AND READY TO BE USED. 0 0 0 0 0 0 0 0 0 0 0 0 0. But the entry angle affects flow as well as orifice size. One column for fuel jet size with the fuel pump that comes in the kits and the other column for hi-output pumps – like the Holley Blue with 5-7 psi flowing pressure. Save on Holley Jets with great deals at Advance Auto Parts. It was a "107", which means the diameter of the hole in it was 1. A few minutes every half hour Bad Credit Loan With Monthly Payments is a good start. com----Misc. The difference between an Ultra and a reaular HP carb is the addition of a. Needle Dimensions. Typically this consists of changing the main jet to a larger (or smaller) size, changing the pilot jet size, adjusting the airscrews, and adjusting the needle clip position. This is assuming all electrical is functioning properly. Install the next size smaller pilot jet and start from the beginning, adjusting the air screw. Holley main jets allow you to fine tune your carburetor. K value #1:. Manufacturers develop their jet charts with these components in mind. Air Main Jet $5. Enter the cylinder bore diameter. ACFI is happy to provide the specs many of you have asked for all compiled into 1 place. It is like 212 cfm at max rpm draw. So there are different configurations. You will not have quite as much power using a blend and your fuel mileage will suffer a little. Absolutely the best jet available for the Rochester Quadrajet carburetor. The rule that Edelbrock/Carter apply for altitude tuning is to reduce jet size 0. In a manual, you should drive around to look at your personal driving, and watch your tacho. What is the orfice size of these jets in thousands. Too black, reduce the jet size down 1 or 2 sizes. 001" for every 1,000' of altitude ABOVE 4000'. I agree 83's do seem big but then again I started with 78's. The following is intended as a safe baseline for fogger systems. Now, having found the correct main jet repeat this process for the needle clip position, again recording the settings and air temperature as above. 5 out Main Jet 178 2000 Pilot Jet 45 Needle STOCK Clip Position 3RD Air Screw 1. In addition, with no jets to change, no leaking power valves and no internal gaskets to swell, this high performance carburetor is relatively maintenance free. If you are using a 'wet' setup, you can calculate what the Fuel Jet size is by filling out the nitrous pressure and fuel pressure fields for a given Nitrous Jet. com FREE DELIVERY possible on eligible purchases. 5 Pilot Screw (turns) 2 1/4 Needle Jet P-OM Jet Needle 5E26-1 Idle RPM 1250-1350 Starter Jet 60 Float Arm Height 13 mm (0. I know virtually nothing about jetting a bike, and would really like to learn a few tricks of the trade. If your carburetor has a removable needle jet/nozzle please contact the manufacturer in order to decipher the nozzle code. Click to expand I was getting between 17 and 22 km/l before the mod. Find out how many calories are in Jet's Pizza. Turn the engine off and remove the air filter, to access the carburetor freely. Select the desired horsepower level and fuel type to determine the nitrous and fuel jet requirements i. From the part number, I'm guessing it's a size 60. Remove the jets and insert a smaller/larger set based on the vehicles operating altitude. Find whats available (maybe a chart), jet size wise, for your carb. To this day, I have written notes regarding every carb mod I've done and how it felt, regarding jetting, exhaust, main needle height, etc. RPM Calculator. Eg: 100,102,105,108,110. An increase in jetting of 5-10 jet sizes in both primary and secondary should be considered a minimum. 35-120 (Δ 2/3) Nickel plated CDK, CDKII 38 & 42 Watercraft Carburetors, For watercraft N424-36-SIZE 8mm Length Nickel plated slow jets to prevent corrosion. One is carb size. 2 STROKE ENGINES 2 STROKE ENGINES INFORMATION ON CARBURETTOR JETTING F1MOTO regularly receives enquiries about poorly running or seized 2 stroke engines. The few aftermarket duals that do offer better performance, do so by consuming "allot" more gasoline. 1 Kit per carb is required Look carefully at the diagram that comes with your carburetor kit - the kits will differ depending on what kind of carburetor you are rebuilding. But the entry angle affects flow as well as orifice size. I believe your original setup had 0. TC-Motor Blue Racing Performance Intake Pipe Inlet Manifold Gasket Screw For Predator 212cc For Honda GX200 For 6. Aquamist Jetting Calculator. 096" diameter (#41). To figure out the density altitude, you need a weather station to measure the barometric pressure, temperature, and humidity. Jets 86 primary, 88 secondary, Air bleeds: #53 idle, Drilled. Carburetor Adjustment for Chainsaws Carburetor adjustment is critical on chain saws and other two-cycle engines. 5, other options in the parts book are #30 and #35. com's items for sale in Carburetor Jet Tuning Drill Sets. Too white, increase the jet size. It comes stock with a Mikuni TM30SS and i have the jetting nailed down just nice. To this day, I have written notes regarding every carb mod I've done and how it felt, regarding jetting, exhaust, main needle height, etc. Niche Cycle has the best selection of genuine Mikuni products, including Mikuni VM38 Round Slide 38mm Carburetor at an always low price. 9 = sea level jet size. 0820” Holley Jet to Drill Size Chart PROMAX Carbs & Performance Parts. The technique for establishing the correct idle jet size is detailed later, but as a starting point 40/45f9 idle jets for a 1600 engine 45/50 f9 for an 1800 and 50/55f9 for a 2000 will get you out of jail free. 00mm in diiameter. Details about 7746 Dellorto Carburetor Enrichener Jet size 65 NOS Moto Guzzi Ducati Laverda. If it's lean and you need to increase the size of your main jet, drill the jet out with the next size larger drill bit, which in this case is the #60 bit. A leaner needle taper will use a richer main jet than a comparable engine/carburetor combo with a richer needle taper. Because the secondary side of the Qjet opens according to the airflow requirements of the engine, the same basic carburetor size can be used on a large range of engine sizes. And you use the drill bits pins as no/go, checking them with a micrometer. 055 inches or 1. The entry and exit tapers of our main jets differ from those of other companies. i was just trying to gauge the size from carb to carb so i had a easy starting point when jettingya i know that they wont fit but the chart on that link doesn't even go up to what the stock jetting for the blaster is so im just gonna use some gauge pins that i have at work to get a rough idea, i haven't even put the carb on yeti have to get my pipe so i was just doin some research. The various specifications reported by other sources include flow rates and/or orifice sizes. Because of the lousy gasoline we now have, do not use printed jet sizes as a definitive answer. Super A, Super B ( 1 7/8"). okay so i justy finished drilling out my mains like one size bigger i think i cant tell this chart is not all that helpful. With your S&S, if I'm correct, your accel pump is adjustable. A # 100 jet is 1. Turn the idle mixture screw clockwise until the needle touches the throttle plate. it is not a complete list of all carbs made by holley over the years. I personally try to not use a home drilled Fuel Jet in a carb when I can use a factory jet. This is a very small brass piece, so be sure you have a pan of some sort to catch it. Selection and tuning of Dellorto DHLA carburettors. Hi,I log on to your blogs named "How To Quickly Determine The (Dell'Orto) Carburetor Main Jet Size - TuningMatters. By Sudco International offers the perfect size Mikuni HSR Carburetor Kit for any Harley or Big Twin application. The power valve is a 4. The jet is about an inch long and has an incorporated emulsion tube. Most likely a blocked intake grate. CB Performance Racing Products has VW Performance, Electronic Fuel Injection Systems, Turbos, CNC Ported Cylinder Heads, dune buggy parts, dropped spindles, Weber, Dellorto, crankshafts, connecting rods, complete turnkey engines and disc brake kits for aircooled volkswagens. !!!!! The jet number is linear dependent from the fuel flow which means a #120 main jet has 20% more fuel flow compared to a #100 jet. 12/1/00 Courtney Hook For those of you who don't know it, you can drill your jets out for larger sizes instead of spending big bucks to acquire a vast selection. Needle Jet. In simple terms jetting your dirt bike's carburetor is determining the proper air-to-fuel ratio the engine receives. HP / Holley Jet Environmental Correction By Bowling The following computation determines jet size changes for Holley carburetors based on environmental conditions. Jet sizes on the Carter carburetor can sometimes be hard if not impossible to read. The first thing you need to know is the lowest RPM at which you use full-throttle. Turn counterclockwise by 1/2 to 1 turn of the screw. Now, having found the correct main jet repeat this process for the needle clip position, again recording the settings and air temperature as above. put a 255 BBK pump in the tank, slapped in a new aluminum radiator, welded a section of the intake tube together to reduce couplers to blow off, swapped the spring in the BOV again since I cut too much off the last one. Mikuni HSR42 Carburetor for American V-Twins. Thanks for your support!. QJets have a maximum airflow of from 750-800 cfm. 5 years now. 0 0 0 0 0 0 0 0 0 0 0 0 0 0. The original manufacturer’s carb jet size can’t be improved on unless you have modified the bike or are using different fuel. You can buy a carburetor for $400 to $1,500 depending on the size, style and modifications that have been made to the carburetor. Moan or whine: The jet unit can exhibit some "turbine whine" not unlike a turbocharger noise but you will know what is usual with your boat. For Keihin Carbs the jet sizes refer to the metering orifice diameter, expressed in millimeters. Carburetor Road Demon Carburetor Road Demon Carburetor; 625 cfm; Vacuum Secondary; FEATURES: Max-Density Cast Rib-Reinforced Baseplate Max-Density Cast Metering Blocks Four Corner Idle Circuitry Large Capacity Float Bowls Large Glass Float Level Sight Windows Integral Hi-Flow Choke Housing Dual Feed Inlets Vacuum Secondary Operation Power Valve. VE is affected by intake type, camshaft grind and type, boost, and many other factors. If you haven't cleaned them recently, it's a great idea to take advantage of the fact that they're out to check and clean them, but. Carburetor Size Needed. Configure Price. There's also a good web site with a jet size calculator on it for a wet setup (where you're metering the fuel and nitrous yourself). Jetting on a 1987 CR250. Our single carburetor Jet Boxes (737 series) are supplied with: 4 sizes of main jets with 2 each, 4 sizes air jets, with 2each. teach you how to service the carb. The function of the carburetor is to atomize fuel and mix it with air in proper proportions to suit engine operating conditions. 17 when going quickly and 22 when bimbling along at 80km/hr on the flat. The main jet. As the needle gets thinner towards the bottom pointed tip , more fuel is allowed in. Save on Holley Jets with great deals at Advance Auto Parts. Holley Carbs for example,,,I cant recall Exactly how they determine the Number stamped on the jet,,, But they Drill a buncha jets during a production run. CID/Compression. 17 & only $7. They look allot like a double pumper but thy have vacuum secondaries. But the entry angle affects flow as well as orifice size. Tuning Tips & Manual Downloads. For example, a jet marked number '18' has an orifice diameter of (18)*(0. thousandth of an inch diameter that the jet actually is for example, {ie. CVP jet quality exceeds OEM and imported carburetor jets. A smaller main jet will restrict fuel, effective leaning the. Carb cleaners are an essential item when it comes to vehicle maintenance. 5 (pilot jet). the pilot or the pilot air jet. Engine size, cam, cylinder heads, ignition system, compression ratio, exhaust system, type of fuel, the vehicle and type of driving are all key elements in final calibration. You just remove the top lid of the carb and the jets are right there. An adjustment that is too rich will cause a saw to smoke, have insufficient power, result in additional carbon build up and may damage the engine. I'll start with the original jetting in place and work my way down to leaner jets. Run the engine with the stock main jet and take a plug reading. Moped carburetors come in different sizes from 7mm to 14mm venturis, and from #39 to #68 main jets. So there are different configurations. You can also solder the ends closed and redrill them smaller if you are so inclined. Shop with confidence. Does anyone have Enderle flowed nozzle and jet size sheets? Ive got the paper version, just wondering if anyone has a computer version I can save to my comp. when i bought my lite ace 1995 GXL model, the stock size carb jets in place were 130 and 160, i suppose this is 1. CB Performance Racing Products has VW Performance, Electronic Fuel Injection Systems, Turbos, CNC Ported Cylinder Heads, dune buggy parts, dropped spindles, Weber, Dellorto, crankshafts, connecting rods, complete turnkey engines and disc brake kits for aircooled volkswagens. ) However, in search of more power, does changing to a bigger size carb would "release more power" ??? I was told a 34/35mm size carb would release more power. Dual Carbs are recommended for most blower applications. Drilling out jets, where can I find size chart? that you can use to measure the diameter fo the hole in your jet. Carb cleaner will not remove the crud in the pilot jet! When removing the needle receiver, (after removing main jet and washer) gently push up from the bottom. For Denver: Take 0. It controls the amount of air that mixes with the fuel coming from the pilot jet. Absolutely the best jet available for the Rochester Quadrajet carburetor. Find your altitude and temperature range on the chart then use this number as a percentage of the base jet size. -If you will be racing or running in open desert conditions, richen each jet by one size and the needle by. So that you won't need to run around with a calculator, my Carb Listing in Table 1 shows the metering areas for every carb listing at both cruise and at WOT (assuming rods with. 016 etc} I have some cb750k 1978 carbs ,that the slo jets , are too far gone{press type} and I would like to make replacements for them. Clymer manual says standard is 175/58. I agree 83's do seem big but then again I started with 78's. Order by selecting the jet size from the drop down list. Install a main jet that is two sizes richer (the number on the jet will be higher on a richer jet). Primary jets are screw-in replaceable type ranging from. for a start point. Can Am Plate Systems. Compression Ratio and Displacement Calculator This simple tool allows you to calculate the STATIC compression ratio of an engine. Enter fuel values in gallons. Even with this jetting, it will hesitate if the temperature is colder , say 30-40 degrees F. The power jet substitutes the main jet size when the engine is revving high. These are ordered by size. Before you start tuning any Weber carb it is recommended that you remove the jets and make a list of what your carb currently has. Tune in towards the funny on Dec 4 at 10 p. the carb is an aisan model originally fitted to the 5k. Please Note: Other than exact replacement OEM carburetors, all Mikuni Aftermarket Carburetors and Tuning Components are sold "As Is" for Off Road / Racing Use Only and are not intended or approved for use on vehicles operated on Public Roads or in Locations where applicable engine tampering and anti-pollution laws apply. 02598" #71 66 jet. DDR and Dry Single Spraybar Systems. Carb 3: same as Carb 2. Both main and power jet should add together to a normal main jet size. Mikuni HSR42 Carburetor for American V-Twins. For Carbureted Triumph Bonneville Americas, Americas and Speedmasters (2002-2008/2009, depending on country). So there are different configurations. is regulated by the main. 075" diameter. When you test the methanol jetting be sure to make several passes before you settle on a particular main jet size and power jet setting, it will take a few passes for the engine to come up to operating temperature, if it doesn’t detonate on the first run it may do so on the third or fourth so proceed methodically. Before gasoline can burn in a piston engine it needs to be vaporized and mixed with oxygen in the right quantities. Find our best fitting carburetor jet kits for your vehicle and enjoy free next day delivery or same day pickup at a store near you!. Beware of imitations as they are just drilled to a size. 3L 90° V6 with #2111 & #2114 manifold (B) Adapter #2696 required for OEM spread-bore intakes (C) Calibration required for single quad applications only (D) Recommended cubic inch displacement for dual quad applications is 302-400+ cid. 3) Pilot jet (Slow jet): If unable to obtain a smooth idle with pilot screw, increase the pilot/slow jet until a. The Weber is. holley performance carb. 0 0 0 0 0 0 0 0 0 0 0 0 0 0. It is only a guide. Fortunately, that one. You may have it set too rich. When shopping for performance carbs, it's easy to stumble across "carb calculators" that recommend a ridiculously small CFM for your motor. accomplish this. 9 = sea level jet size. Figure on leaning the jetting after an engine is over bored. The bike only stays on if the choke is on. First of all, carburetors need no intervention of ECU's which can be both expensive and in most cases limited in adjustability, unless expensive alternatives like those programmable variety is in your budget. For example, if you want to run leaner , go from 80 rear jets to 78s. Once the type of manifold is known, one can then determine the size of carburetor necessary for the engine. (Thats the only difference) Does anyone know the sizes (#drill or inches) of these nozzles, or just the correct size of a 719 nozzle? I'm in the (or going in) the "Owner Maintenance". The first step is to find where the engine is running poorly, fig 7. My guess is that with the sleepers on the exhaust side and the increased airflow on the intake you will need to at the very least start with size 142-145 for the main jets and see if the engine will pull well all the way up the RPM's. The main jet. would be aprox aprox 176 jet. For a carburetor that uses a power valve, the main jet size determines what air/fuel mixture is delivered to the engine at light load/cruise speeds (1,500 rpm and up). Holley Carbs for example,,,I cant recall Exactly how they determine the Number stamped on the jet,,, But they Drill a buncha jets during a production run. Features: 【EASY TO INSTALL】Our dock line with the sleeve that you can easy to make a adjustable size loop to connect the cleat, wooden post and so on. 1) Chose a jet size that makes sense and that will give you some leeway rich and lean by looking at the rod combos for that jet. Choosing the correct size carb is essential for the proper operation of the blown motor. 1 pilot jet size for every 3 main jet size increase Add up all the jet size increases and subtract one. However, a main jet of 155 and air corrector of 205 could also be tried. A WORD ABOUT JETS: • ZEX™, Nitrous Express™, Nitrous Works™, and Compucar™ all use jets that are dimensionally very. 5 out Main Jet 178 1999 Pilot Jet 42 Needle STOCK Clip Position 2ND Air Screw 1. I only ask because I just don't have time to pull the carbs a hundred times to get the jetting right. But the entry angle affects flow as well as orifice size. have determined the correct jetting for your engine make a note of the temperature and altitude of your location at that time. If I wanted to drill this pilot out to the next size numbered bit, I would use the #77 bit which measures. The AAT needle is the most commonly used. We purchase these new gas carburetors and do our conversion to E85. QJets have a maximum airflow of from 750-800 cfm. also, i have always needed a bigger pilot when switching to headers, so i would say, if you have any header, go up 2 on the main, raise the needle up 1 position and go up 1 on the pilot. The Main Jet is the #1 thing that people change in a carburetor when it comes to tuning them. The number is the metering area in thousands of an inch for a single jet/rod in the carb. HP-series carb lands mostly in the factory tune-up ,and it chancres depending on the carb size you're considerinu. Needle Jet. Note: Main jets supplied by CVP are sized to original OE specifications from H-D and Keihin. Like Frosty said, changing to larger jets does not increase power, the jets are changed because other things have been done to increase power. Question I have is how does the carb size affects the power?. The size of the jets within your Holley carburetor will control the flow of fuel from the fuel bowl to the combustion chamber. The adjustable jet allows a precise setting of the idle mixture. 8% more fuel. This information to be loaded at a later date. The cylinders contain the pistons and combustion chambers where energy is released from the. I am more concerned with staggering the jetting if that will help the engine on the track. and you can NOT guess what your change is if you change both the jet AND rod. While the stock oem Kawasaki dual carb kits can work very well, our testing showed us that a recreational 750 with a well prepared single carb could easily generate as much speed, and acceleration, than most jet pumps can ever deliver. Does a chart exist, that crosses jet sizing. To figure out the density altitude, you need a weather station to measure the barometric pressure, temperature, and humidity. The jet sizes for Carb 1: 110 (main), 130 (pilot air), 42. Carburetor Size Selector* For Model 4150 Double-Pumpers, Model 4165 Spread-Bore, Model. The calculator will tell you the cfm range you need. Mikuni claims to deliver production lots of a jet size with a maximum variation of ± 10 This means if you buy a main jet labelled #180 it’s just sized in the range from #170 to #190. The air density would have to go up five points to justify that big a change in jet size. Holley Four Barrel Carburetor List Numbers, Stock Jet Sizes, CFM, and Stock Power Valve Ratings | Ho… The power valve in the carb is stamped with an A2 and a 30. 096" diameter (#41). Mine was a 49. Please send corrections, comments, additions, etc. Determining Blower Carb Sizes. take the size jet you want and divide by. As the throttle valve is opened, its linkage raises the metering rod from the jet. Jet Needle. Does anyone have Enderle flowed nozzle and jet size sheets? Ive got the paper version, just wondering if anyone has a computer version I can save to my comp. 2) When purchased in kit form, the REDLINE kit with the 38mm DGAS carb will perform on a stock unmodified engine without any problems. Parts Page for Aluminum Zenith Carburetors. holley 4 barrel carb list numbers and stock jetting. 6mm respectively. If you have questions about our products, need a part recommendation, or just cant seem to find what you need you can contact our Tech Support online and receive answers by e-mail. Too black, reduce the jet size down 1 or 2 sizes. Idle speed mixture is regulated by the idle air screw, off-idle to about 1/4 throttle is regulated by the pilot jet, 1/4 to 3/4 throttle is regulated by the slide needle, and roughly 3/4 to W. With Holleys and Demons, minimum jet changes of two sizes per step are a good idea. holley 4 barrel carburetor list numbers and stock jetting/jet sizes. Motorcraft 2150 2V Carburetor. You will also need to know the diameter of the hole of your jet. A #35 jet is 0. Fuel Estimation for Capacity. Parts Page for Aluminum Zenith Carburetors. Enter the engine's displacement, Volumetric Efficiency, and its redline. This angle comes in several sizes and helps control the fuel mixture from idle to about 35% open throttle. To figure out the density altitude, you need a weather station to measure the barometric pressure, temperature, and humidity. Depending on whether you have a four or two-stroke engine, the carburetor adjusts the ratio of fuel to air or of fuel and Evinrude XD100 oil and air, respectively. Piston to dashpot clearance confirmed through ‘drop speed tests’ and corrected where possible. this a partial list of holley list #’s for some of their most popular carbs. Failure to mix the correct oil in the gasoline will result in permanent engine failure and damage. 15mm diameter). Shown below is a typical carburetor. The power jet substitutes the main jet size when the engine is revving high. Before gasoline can burn in a piston engine it needs to be vaporized and mixed with oxygen in the right quantities. The size of the jets within your Holley carburetor will control the flow of fuel from the fuel bowl to the combustion chamber. If it is bone stock carb I would suggest at some point sending it to a carb shop to be upgraded for circle track. Cam is mild, 11:1 dynamic compression. It has sizes designed for most small motors. i would go 2. After you have made your test run with the stock jetting. It must be remembered that carburetor jetting is determined by the throttle position, not engine speed. But heres what you do. The first step is to find where the engine is running poorly, fig 7. MAIN SYSTEM The main system dielivers fuel from 1/16 to. holley 4 barrel carb list numbers and stock jetting. DCOE Thumb rules (use as a starting point): Venturi Size: If your carb was indeed set up for a similar sized engine, You should be OK on this. Once you had the mixture dialed in, using air temperature and barometric pressure, you could calculate the air density and jet sizes you needed for a particular set of conditions and be close if not spot on. 1807 MaxJet™ is produced in 0. The main jet. My guess is that with the sleepers on the exhaust side and the increased airflow on the intake you will need to at the very least start with size 142-145 for the main jets and see if the engine will pull well all the way up the RPM's. An idle system will have an idle jet/restriction that must be changed to supply the desired fuel mixture for idle and off idle engine demands. I was thinking to built something like toilet injection before. Take the front bowl off, take the jets out, and see what number they are. Jet Size Drill Size 70. Jet kits are designed to help your carburetor work better, ultimately improving fuel delivery and making your bike perform better. I don't remember, it's been a number of years since I had a carb on it. You may also share some further details in the comments below such as engine type, what type and size of carb you got your new scoot equipped with and if it's a 4-stroker or a 2. It has a bit of flat spot between half and full throttle. Drill bits sizes that approximate mikuni jet sizes. DDR and Dry Single Spraybar Systems. If you haven't cleaned them recently, it's a great idea to take advantage of the fact that they're out to check and clean them, but. •If engine backfires or sputters in carburetor or breaks up and or dies during acceleration, increase or richen main jet size. Unbelievable shopping deals in every category. The small 2-Jets were used until the early 70`s, where they last appeared on 307 Chevy engines. Providing us with this information will ensure that we will deliver the same carburetor as your original. (3) I would also like to cover two other possibilities that would make your carb "APPEAR" to be out of tune. When shopping for performance carbs, it's easy to stumble across "carb calculators" that recommend a ridiculously small CFM for your motor. This Jet Size Calculator will give you the size of the jet you need for a different weather condition.