anyone know if the pilot screw will be the right size? also i have the needle in the middle is that good to start with ?
30mm oko carb what jet size to start with?
- Thread starter blaster 0108
- Start date
I have a .5inch spacer with boyesen power reeds fmf pipe heavy bore with wiseco with the oko 30mm.Im running 45pilot and 158 main with needle in 2nd slot.So far mine is running pretty lean.Just ordered a 55 pilot and a 165 main.Float level is right at the gasket(19mm) and crimped the fuel float needle spring slightly to make it engage faster to make sure the bowl is getting sufficient fuel.Im about 800ft above see level in dry hot climate.Also seems like this carb is craving for more air.Stock airfilter box seems to be resticting things a little at the boot.This carb really sucks some air.
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Good start, Not sure what a heavy bore is, or the crimpped feul stop thing, But Im can say, That your float should be measured to 19mm. You should start with that before trying to jet or you will be chasing jetting.
The pilot either too lean or too rich is determined by the air screw measurement, If the air screw is 2 or more turns out, then your pilot is too rich (as you are letting more air in the further out the screw is turned.) If your air screw is less than 1 turn out you should increase your pilot by one size( as you are increasing the feul mix that the idle needs).
I think you may be very close to where you need to be, with the mods you have listed, which is basically stock motor, with a FMF pipe and boysen reeds. Boring the motor isn't really going to require a larger jet. Hell from a stock motor to a 240 kit most guys are only one jet size from each other.
Sounds like you need some fine tuning!
Needle, 2nd from the top or from the bottom? Bottom I hope.
Please explain how to crimp the fuel stop to make it engage faster, you lost me here!:-/
Some pretty weird thinking here, either you are a lot smarter than I think you are, you are bluffing, or you do not know what you are talking about or doing.
You are wise enough and old enough to be able to tune without performing a plug chop.
You bend the tab on the float assembly to make it fill quicker.
Smoke bears no relation to jetting and cannot be used as a tuning method.
If it sounds like it is lean when revving down, it possibly is lean.
No need for a hotter plug if you have the jetting correct.
If you take the air filter off, it dont starve for air, it starves for fuel and leans out, commonly known as bogging.
C'mon now, say something intelligent.8-|
Ok a few questions, The 1/2 in spacer is not going to make you need more or less fuel mix. You say it get hot where your at, But the hotter it gets the less jetting you need, as the air is less dense when it is hot, so less air get's in. So if you jet for say 60* when it hits 80-90* you will be on the rich side. If you jet it rich for 60* when it gets to 80-90* you will be way rich and actually wasting fuel and possibly fouling plugs.
Are you saying you opened up the petcock nipple (Made larger)? And what tabs are you referring to , If you are saying the float, then you will actually be dumping feul out the overflow if they are not adjusted properly again wasting feul.
Please give us some info on what your doing, as we are open minded, but have just about done everything there is to a blaster!
Then stuff me with the rough end of a pineapple.
I have had over 50 years with them and would never use the tuning methods you prescribe.
There is a right way, and a wrong way to do things,
Common sence does not come into the equasion these days.
Years ago (before the era of performance pipes) you could get away, by using common sence and jet by ear, but times have changed my friend, things are a little more technical now!
When I first heard about plug chopping, I said "silly idiots, how can you tell tuning by a smoke ring".
I have long since eaten my words, and now get top performance out of motors.
Man your methods are for the birds and they can keep them!8-|
Yeah.Ive tried different oils from yamalube to belray.I seen a kit thats made for the big bore on ebay hope this cures it.:-/
I can understand why you feel that I am picking on you, and maybe I am, but for good reason.
Some of your methods are unconventional, and some of them are very, very wrong, not only for 2 strokes, but for any motor.
I am concerned that someone with little knowledge will try some of your remedies with dire consequences.
A 2 stroke is a 2 stroke, old school or not, and with todays aftermarket strap ons, cannot, and I say again, cannot and should not be tuned by ear, or by the amount of smoke that it blows!
And as to respect, is is given in relation to your information that you post.
Some of your methods are unconventional, and some of them are very, very wrong, not only for 2 strokes, but for any motor.
I am concerned that someone with little knowledge will try some of your remedies with dire consequences.
A 2 stroke is a 2 stroke, old school or not, and with todays aftermarket strap ons, cannot, and I say again, cannot and should not be tuned by ear, or by the amount of smoke that it blows!
And as to respect, is is given in relation to your information that you post.
Ok I see.Read my post and tell me what is dire consequence.Or better yet read the manual and relate everything I have said and tell me how its wrong.If you have a question by all meens ask I will do my best to explain if its not making sence to you.I may be overkill on my set up but its not wrong. its a 2 stroke if any thing its not precise thats why they dont make them no more?There is nothing unconventional about it.I tune motercycles to air craft. air craft has a diafram thats the only difference.Blaster wont run upside down?You can call me a redneck and I will agree and so are most people that run a pit crew.Im just a little ahead of you like I said I can slow down and explain if you would like.(Pull the bowl off the carb with it still in the bike.PS TURN THE FUEL PETCOCK OFF?Now that its off push the float all the way up so it thinks its full and shuts the feul stop.Now turn on the fuel and release the float slow and let the gas drain until you see the secondary start dumping fuel.Now you understand why I adjusted this.I heard rumor that these carbs were known to run the bowl ouf of fuel this is why I did this.And it was leaning out after reveing(after throttle was closed it did not come back to idle dont know how to say it but like it was lean and it wanted to rev down slow.So thought float blowl maybe low hents why I did this adjustment.)But its more efficient no need to perform this Im just a precision freek as I just tune to where I know its going to last.With aircraft same thing just a whole bunch more variables with altitude temp aircraft orientation.And you cant just do it and ride you have to do it by memory.You dont get it I know but its not relevant to what jet size to start with any way.I said what jets to use if its wrong tell me.
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So this is the correct way to set the float level. Not in my book!
Do you now see why I am concerned!
I can see that you are set in your ways, and nothing I, or others say will convince you that tuning a 2 stroke today is now quite a fine art.
Carburetor Jetting
Before you begin your search for the perfect jetting, you need to be sure that there are no problems with your machine that will make it impossible to tune your carburetor . Take some time to go over the check list I've prepared. You'll save yourself some time and money in the long run .
1.Clean and oiled air filter
2.Good compression
3.Crankcase or vacuum leaks
4.Blown head gasket
5. Operating power valves
6.Cracked or broken reeds
7.Silencer packing oil soaked or blown
8.Clogged carb vent hoses
9.Weak spark
All of these problems can affect carburetor tuning
Basic two stroke carburetor tuning is a skill that should be mastered by anyone that has a two stroke bike or ATV. There are many informative articles on the net related to two stroke carb jetting and tuning. My method of two stroke carb jetting is aimed at training you to recognize when your two stroke carb needs to be adjusted and what changes you can make to accomplish the task. The best way to tackle a job or learn a new skill is not to cut corners , but to grab the bull by the horns and try to learn something. I can sit here and try to make this easy for you by giving you a list of jetting specs for your bike or I can get rich selling jet kits that I think will work, but the results will be the same , you will learn nothing. It's time to get fuel on your hands and use your head. When your done, you will know when your bike is lean or rich and you'll know what to do about it .
Basic Tools
You'll need some carb cleaner or even better, a dip tank. You can get the dip tank at any auto parts store. You can also use it to clean power valves and other small parts. Compressed air is a must! You'll also need a small flat-head and a #2 phillips head screwdriver. Main jets can be removed by a 6mm nut driver or a flat-head screwdriver.
Step by Step
The first step is to completely disassemble and clean your carburetor. Take care not to lose any of the small parts. Use the compressed air to clean all of the passages in the carburetor . Inspect and record the sizes of the main, pilot and needle jets. Compare the sizes to the stock factory sizes. If you bought your bike used, the jets may have been tampered with and jetting may be a long way off. You can find the stock specs in your service manual or you can call your local dealer. Take a look at the needle and seat. Check for wear. Wear will appear as a ring or depression on the needle. Replace as nessesary. Set the float height according to factory specs and reassemble. Reinstall. Your jetting should be fairly close and now you can begin to tune your carb. If you don't have the stock carb, you have no way of knowing what stock jetting is.
Some Guidelines
Perfect fuel air ratio is 12.5/1. Any more air and we term the mixture lean - Any more fuel, and we term the mixture rich. A rich mixture makes a very distinct sound and smokes excessively. Start your bike and bring it to operating temperature. Next, engage the choke. Hear the difference? This is what a rich mixture sounds like. A rich air fuel ratio won't hurt much. Not that this means it's a good thing , but it doesn't have the same piston melting power as a lean mixture. Lean is heat and excissive heat destroies engines! Therefore, we have to be careful not to let our engine run lean for any length of time. Lean engines will be slow to respond and at times will pop and backfire.
Carb School
We've established our baseline jets and I'm going to assume that your bike is running fair. NOW WE'RE GOING TO SCREW IT ALL UP!!!! When I first started tuning carburetors , I would talk to other racers, call service shops, ask my friends, I even let my dad help one time ( one time!!!! ) All of this effort got me one thing ......FRUSTRATED!!! I began to realize that you can't explain how a carb sounds or feels. I also realized that most of the people I was asking were as clueless as I was. Hence the screw it all up method of carb tuning was born. This is how it works. Remember those sizes that we recorded--the main, pilot and needle jet. We are going to buy a series of jets in both directions of the standard jets and your going to keep changing jets until you find the perfect combination for your riding style and riding conditions .
What to buy
Buy six main jets- three larger and three smaller than the stock number. Buy six pilots- three larger and three smaller than the stock jet size. Buy two needles- one leaner and one richer. These jets will cost you between $30. - $70. depending on where you get them. It may seem like a waste of money, but you need jets to jet your bike. If you need jets and can't find them, give me a call and I can help.
The Main Jet
Start with the air screw out 1.5 turns and the needle with the clip in the center position. Turning the air screw in will make the mixture rich at, and just after idle . Turning the screw out will make it leaner . The clip on the needle can also be moved to calibrate the jetting. If you move the clip up, you lean out the mid circuit. Down makes it richer. The main jet is most felt in the 3/4 to full throttle range. Change main jets in large steps at first to get a feel for what it does to the power of your bike. Listen to the way the engine sound changes. Look for changes in exhaust smoke. A word of caution here . As the part number of the main jet gets larger, the jet is richer, smaller and the jetting gets leaner. Remember not to make the main jet so lean that you create excessive heat and damage the engine .
Needle Clip Position
Needle position is most felt at 1/4 - 3/4 throttle position. Try the clip in other positions and try the other needles. Feel what it does to the bike. Do the same thing with the pilot. The pilot will be most felt from idle to 1/8 throttle.
Some Hints
Temperature, humidity and altitude are the most important variables to take into consideration when jetting your carb. You may have your jetting perfect for a given condition but, as soon as any of the variables change, so should your jetting. Here's an example. If you live in New England and start riding your bike in April. The engine is responsive at all throttle settings and makes tons of power. The temperature is a cool 50 - 60 degrees and the reative humidity is about 65%. Perfect riding weather. Now ride the same bike with the same jets in August when the weather is 98 degrees and the humidity is close to 100% . The bike smokes more than normal and is'nt as responsive as it was in April. Why? As I said previously, the perfect air fuel ratio is12.5-1. When the humidity goes up, the air thins out. If you have less air , you need less fuel. Lean the carb. Some bikes are more sensitive than others to these changes. The same thing goes for altitude. If you live or ride in the mountains, you need to go leaner. An important thing to remember is if the weather starts to get cooler and the humidity drops, you need to go back to the richer settings or your running the risk of a blown engine. Another thing to remember is the stock jetting is a little on the rich side.
Ken, You Can't Be Serious!!!
This system of jetting may seem a little seat of the pants to some of you, but it works if your trying to learn how to tune your carb. You can pick up any service manual and get all the long explanations and principles of carburation if you think that's what it will take. The scope of this page is not to tell you, it's to try to teach you. It's been my experience that most of us learn more by our own mistakes and hands on experience than by reading formulas and theories. Remember, propper jetting is the cheapest power you can buy.
Before you begin your search for the perfect jetting, you need to be sure that there are no problems with your machine that will make it impossible to tune your carburetor . Take some time to go over the check list I've prepared. You'll save yourself some time and money in the long run .
1.Clean and oiled air filter
2.Good compression
3.Crankcase or vacuum leaks
4.Blown head gasket
5. Operating power valves
6.Cracked or broken reeds
7.Silencer packing oil soaked or blown
8.Clogged carb vent hoses
9.Weak spark
All of these problems can affect carburetor tuning
Basic two stroke carburetor tuning is a skill that should be mastered by anyone that has a two stroke bike or ATV. There are many informative articles on the net related to two stroke carb jetting and tuning. My method of two stroke carb jetting is aimed at training you to recognize when your two stroke carb needs to be adjusted and what changes you can make to accomplish the task. The best way to tackle a job or learn a new skill is not to cut corners , but to grab the bull by the horns and try to learn something. I can sit here and try to make this easy for you by giving you a list of jetting specs for your bike or I can get rich selling jet kits that I think will work, but the results will be the same , you will learn nothing. It's time to get fuel on your hands and use your head. When your done, you will know when your bike is lean or rich and you'll know what to do about it .
Basic Tools
You'll need some carb cleaner or even better, a dip tank. You can get the dip tank at any auto parts store. You can also use it to clean power valves and other small parts. Compressed air is a must! You'll also need a small flat-head and a #2 phillips head screwdriver. Main jets can be removed by a 6mm nut driver or a flat-head screwdriver.
Step by Step
The first step is to completely disassemble and clean your carburetor. Take care not to lose any of the small parts. Use the compressed air to clean all of the passages in the carburetor . Inspect and record the sizes of the main, pilot and needle jets. Compare the sizes to the stock factory sizes. If you bought your bike used, the jets may have been tampered with and jetting may be a long way off. You can find the stock specs in your service manual or you can call your local dealer. Take a look at the needle and seat. Check for wear. Wear will appear as a ring or depression on the needle. Replace as nessesary. Set the float height according to factory specs and reassemble. Reinstall. Your jetting should be fairly close and now you can begin to tune your carb. If you don't have the stock carb, you have no way of knowing what stock jetting is.
Some Guidelines
Perfect fuel air ratio is 12.5/1. Any more air and we term the mixture lean - Any more fuel, and we term the mixture rich. A rich mixture makes a very distinct sound and smokes excessively. Start your bike and bring it to operating temperature. Next, engage the choke. Hear the difference? This is what a rich mixture sounds like. A rich air fuel ratio won't hurt much. Not that this means it's a good thing , but it doesn't have the same piston melting power as a lean mixture. Lean is heat and excissive heat destroies engines! Therefore, we have to be careful not to let our engine run lean for any length of time. Lean engines will be slow to respond and at times will pop and backfire.
Carb School
We've established our baseline jets and I'm going to assume that your bike is running fair. NOW WE'RE GOING TO SCREW IT ALL UP!!!! When I first started tuning carburetors , I would talk to other racers, call service shops, ask my friends, I even let my dad help one time ( one time!!!! ) All of this effort got me one thing ......FRUSTRATED!!! I began to realize that you can't explain how a carb sounds or feels. I also realized that most of the people I was asking were as clueless as I was. Hence the screw it all up method of carb tuning was born. This is how it works. Remember those sizes that we recorded--the main, pilot and needle jet. We are going to buy a series of jets in both directions of the standard jets and your going to keep changing jets until you find the perfect combination for your riding style and riding conditions .
What to buy
Buy six main jets- three larger and three smaller than the stock number. Buy six pilots- three larger and three smaller than the stock jet size. Buy two needles- one leaner and one richer. These jets will cost you between $30. - $70. depending on where you get them. It may seem like a waste of money, but you need jets to jet your bike. If you need jets and can't find them, give me a call and I can help.
The Main Jet
Start with the air screw out 1.5 turns and the needle with the clip in the center position. Turning the air screw in will make the mixture rich at, and just after idle . Turning the screw out will make it leaner . The clip on the needle can also be moved to calibrate the jetting. If you move the clip up, you lean out the mid circuit. Down makes it richer. The main jet is most felt in the 3/4 to full throttle range. Change main jets in large steps at first to get a feel for what it does to the power of your bike. Listen to the way the engine sound changes. Look for changes in exhaust smoke. A word of caution here . As the part number of the main jet gets larger, the jet is richer, smaller and the jetting gets leaner. Remember not to make the main jet so lean that you create excessive heat and damage the engine .
Needle Clip Position
Needle position is most felt at 1/4 - 3/4 throttle position. Try the clip in other positions and try the other needles. Feel what it does to the bike. Do the same thing with the pilot. The pilot will be most felt from idle to 1/8 throttle.
Some Hints
Temperature, humidity and altitude are the most important variables to take into consideration when jetting your carb. You may have your jetting perfect for a given condition but, as soon as any of the variables change, so should your jetting. Here's an example. If you live in New England and start riding your bike in April. The engine is responsive at all throttle settings and makes tons of power. The temperature is a cool 50 - 60 degrees and the reative humidity is about 65%. Perfect riding weather. Now ride the same bike with the same jets in August when the weather is 98 degrees and the humidity is close to 100% . The bike smokes more than normal and is'nt as responsive as it was in April. Why? As I said previously, the perfect air fuel ratio is12.5-1. When the humidity goes up, the air thins out. If you have less air , you need less fuel. Lean the carb. Some bikes are more sensitive than others to these changes. The same thing goes for altitude. If you live or ride in the mountains, you need to go leaner. An important thing to remember is if the weather starts to get cooler and the humidity drops, you need to go back to the richer settings or your running the risk of a blown engine. Another thing to remember is the stock jetting is a little on the rich side.
Ken, You Can't Be Serious!!!
This system of jetting may seem a little seat of the pants to some of you, but it works if your trying to learn how to tune your carb. You can pick up any service manual and get all the long explanations and principles of carburation if you think that's what it will take. The scope of this page is not to tell you, it's to try to teach you. It's been my experience that most of us learn more by our own mistakes and hands on experience than by reading formulas and theories. Remember, propper jetting is the cheapest power you can buy.
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the correct way to set the fuel level is to open the fuel over flow valve and with a clear tube hold it against the carb the level should be right at the gasket.but this carb is on the cheasy side and does not have the screw to open the valve. the 19mm measurement is right.
Im not set in my ways i never said you were wrong just waiting for you to prove me wrong.im just not getting how i am wrong my bikes been running good for the past 10 years with out a rebuild runs rich and i run a hotter plug.you tune for performance then richen in a notch.its all feel and experience its something learned and cant be explained in txt.
yes it is a fine art.takes a lot of trial and error and experience.does not matter these are old school basic mods all you are doing is increasing flow torgue and rpm.all this requires more fuel/air mixture.even just by adding a spacer.and beond that you need to make sure you have adequate fuel to deliver.have you found anything to prove me wrong yet.im not saying your wrong i never did.you should really do a read on carberation and tunning here is something i copied of ken oconer take a read.i:i
Im not set in my ways i never said you were wrong just waiting for you to prove me wrong.im just not getting how i am wrong my bikes been running good for the past 10 years with out a rebuild runs rich and i run a hotter plug.you tune for performance then richen in a notch.its all feel and experience its something learned and cant be explained in txt.
yes it is a fine art.takes a lot of trial and error and experience.does not matter these are old school basic mods all you are doing is increasing flow torgue and rpm.all this requires more fuel/air mixture.even just by adding a spacer.and beond that you need to make sure you have adequate fuel to deliver.have you found anything to prove me wrong yet.im not saying your wrong i never did.you should really do a read on carberation and tunning here is something i copied of ken oconer take a read.i:i
THIS HAS NOTHING TO DO WITH SETTING FLOAT LEVEL.ITS HOW FAST IT FILLS THE BOWL.FLOAT IS SET TO 19MM.WITH ALL DO RESPECT THERE IS A SECONDARY VALVE THAT FILLS THE BOWL WITH FUEL WHEN THE (FEUL VALVE STOP) OPENS FAR ENOUPH.The float opens and closes this valve?Your going to drive me nuts if you dont get it done explaining it lol.B)
I need to clarify this... What i was trying to say is a Ported/piped stock cylinder with a Keihin 35mm carb, and a ported 240 motor, guys here awere only one jet size larger than i was running on my stock modified motor!
Sorry guys I was hurring at work when i typed this!
I've ran the Driveline performance HD 240 Kit with a heavily ported blaster motor, No slippage at all one of the best clutch kits IMO!
I see you read my book, but I forgot to finish the last sentence.
Remember, propper jetting is the cheapest power you can buy, and should be confirmed by a plug chop.
Remember, propper jetting is the cheapest power you can buy, and should be confirmed by a plug chop.
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