4:00 Correction! I mis-spoke here in regards to Humidity the chart is right but I said it in reverse. High humidity=less dense, Low humidity=more dense. This was brought to my attention by @Shadowdog500 Thanks man!
14.7:1 is stochiometric ratio, not optimal, but idealistic (calculated by chemical formulae), to actually burn 100% of oxygen you need ~13.2:1 and to burn 100% of fuel you need ~16.5:1 AFR.
I just had a soft seize on a husquavarna chainsaw that went into a lean condition. It appears that the fuel line hose to the carb was slightly ill fitting and started to suck air and less fuel. Now the rebuild consists of piston, cylinder and ring inspection and take it from there. As most people who experiece the lean condition and then a seize will say...."It was running great until it stopped".
Funny, I just learned about what a motorcycle rectifier is. And he used the base word in the video. 00:22 Rectify means to make things right/ to fix mistakes. A motorcycle rectifier takes the 'bad' A/C and turns it to D/C of the correct voltage. Basically.
BEST CARB SETTINGS VIDEO I HAVE EVER SEEN!!!! Everything so well explained!! My bike is spitter/coughing at high revs and I dont know why, lol Tomorrow this video will make wonders when I come to solve the issue :D
I recently tried a 24mm carb on a 81cc engine, the carb is set up for a 120cc engine, I'm guessing it needs much larger jets because it wouldn't run above half throttle and sputtered from about 1/4 on throttle, the 81 cc is modified, free-flowing exhaust, high revving cam , and ported head, with in shrouded valves, with a redline around 9500-11000 rpm, I'm about to go to a bigger bore, 90cc with a better head, larger valves, and about 0.5:1 more compression, I'm hoping for a minimum of around 12 hp at the wheel, I just wonder if this carb is going to work, it's a CV carb, the largest factory type carb available is a 20mm, I have a modified aftermarket intake port matched to the head, I have tiny drill bits to drill the 105 jet to about 120-125 +/-, in about 2 size steps, I have it at about 108-110 now and going to try it, I'm thinking about drilling the slow jet slightly to hopefully get a better idle, and just off idle, and I have washers to space the needle if needed, I have been wondering if modify the spring would help throttle response any? Maybe shorten the spring to lower the tension, so the throttle can open faster and easier, I had lost the stock springs and had to use a random spring, I only had half throttle, unless I had speed and let off, and went to full throttle really fast, then it went close to full throttle, luckily I found the stock spring! I was thinking if it's just long enough to close the throttle, maybe it will give throttle response like or close to the same as a slide carb, CV carbs suck with a variator I guess I may as well keep it, if I had a real transmission, I think I'd convert to a slide, any suggestions? Should I go with a 20mm carb and be happy with what it offers??
My issue was unknown modifications made to the carbs. Foind out the carb slide springs were trimmed and slides drilled out. Bought a used carb that was unmolested. Went with factory jetting settings. 190m 35 P. 2nd notch from the bottom on the needle jet clip. Slow roll pulls like a champ wot through the gears. But highway speed 70mph and twist to wide open throttle, i hit like a wall, and slightly roll back off the throttle, it comes back alive. Full bowl height is at factory spec. Carbs are synced. New air filter fuel filter. , coil, coil packs, plugs. New fuel pump and relay. Im wondering gas cap vent or peacock valve
i just got a brand new apollo rfz 125 open and went out to the trails today and after the exhaust pipe was all purple/blue for the first 5 inches of the pipe. so hopefully i didnt cause any damage? the bike performed really well tho.
That is going to be normal to have metal discoloration from heat. They don't use high quality materials for the exhaust. I would not worry as long as it is not glowing red.
When my vstar is cold and hasn't run in a few hours it cannot and will not start without starter fluid. After I fire it up I have to stand there opening and closing the throttle until its hot. After that it starts as if there was never a problem to begin with. This occurs regardless of whether or not the choke is on
It is probably some debris in the fuel system, that is the most common culprit and the first thing to check before proceeding. Clean the tank, fuel shut off, and dismantle the entire (both) carburetors and ensure every passage and jet is clear. Then re-set (or check) that the carburetor settings are set to the factory positions. You will need a manual for this information. Read up on this site and it will also help you get familiar with all the parts that affect the mixture while the carburetor is operating in different positions. www.thejunkmanadv.com/motorcycle-carburetor-jetting.html
Thanks for sharing your knowledge junkman. I'm trying to figure out why my ,82 Goldwing isn't running well after removing the engine for a starter clutch repair this past spring. I might have a vacuum leak among other issues since I can see the spark plugs are white on at least three of the cylinders.
High altitude air is more dense and low humidity right? so what should we do when the carb getting miss fire? do we need to rich or lean the air screw? thanks
The mixture screw is only for adjusting the mixture at idle speed though. In general higher altitude means less fuel required as the air is less dense because of the lower barometric pressure. You need to change the overall jetting, not just the mixture screw.
Could be that the spark plug is too cold of a heat range, but that would be a guess. I would correct the leak first. I have info on my site about this.
I’ve fixed the leak but now the threads in the head are stripped, lol. I have high compression in my cylinders. Are colder range plugs not preferred with high compression?
It really depends on the engine design. All the heat range means is the ability of the spark plug to dissipate heat. Use this link to determine that. From reading this it may be too hot of a heat range. www.ngkntk.in/ngk-technology/importance-of-heat-range/
I am not sure what you mean by air/fuel mix passage? You mean the throat of the carburetor, that is the only area that the air and fuel really mix for the first time.
How in the world did old bikes ever get such a reliability / bullet proof reputation when it seems like nowadays jinking with carb. bikes are a constant hassle. I don't see how the dealerships would have ever made money unless it was from the constant servicing and adjusting of carbs. Maybe it was normal procedure back then and fuel injection has just spoiled us.
humidity has more fuel? i thought the h20 takes up space making it leaner...? i'm gonna have to look into this one because i think you got it wrong on this one
Thanks 😊 🙏 that was helpful 😀 Plugs are still sooty could it be the mixture I'm doing wrong From the bonnie Highlands of Scotland America 🇺🇸 💙 god bless
Recently I installed a new carburetor in my car. The bigger main jet that it came with was of size 180. With 180 jet, the acceleration was jerky from half to full throttle, but it accelerated pretty quickly. I swapped the larger main jet from 180 to 135. Now with 135, the car bogs down under wide open throttle (especially when the pedal is quickly depressed), and then picks up after around 2 seconds. I've also noticed that the acceleration isn't as good with jet 135 as it was with 180. It idles perfectly fine and acceleration is smooth and crisp for half pedal; only problem is that with WOT, it bogs down and isn't accelerating as it should. Should I go for larger jet size of 150?
Why did you decide to make such a massive main jet change? Try the 150, see if it splits the difference and try to hone in on the range you need to tune around. Your seasonal adjustments should be one or two sizes max.
Well I don't take projects, but watch my Barn Fresh Series and learn some tips and tricks to help restore it yourself. Feel free to comment and ask questions
I just bought a new dr650 and it feels very sluggish. I know it’s not a sports bike and it cuts out when I first start even when the bike is warm. Stalls out sometimes from a stop (I know how to work a clutch) and 5th gear is pretty much useless. Do you guys think the carb needs to be tuned? Is this normal for a brand new bike?
A question my bike runs good low and mid power but at full power it feels very weak and have to short shift! Could this be lean on the main jet? Just installed a full exhaust ony 2 stroke gilera mxr 125 , ran fine before the exhaust change! Extremely appreciated a reply
I want my scooter fly so should I be setting up my carburetor for high altitude I don't understand I'm not cool like you no I'm just giving you a hard time video helped me a lot thank you
hello, my son has an 2004 cbr125r from Honda, he has n aftermarket exhaust an pops on dethtrottle/deacceleration. Guess its running lean. have u suggestion what to go up to from the 118 stock main? Do he need yo go up on pilot to?
Hello, and thank you for the videos. I have a question, Why at lean mixture for two stroke the engine tends to increase a little bit the speed of engine: Thank you in advance.
Soft seize is when an engine overheats and the parts swell enough to prevent engine rotation, but when the engine fully cooled down to ambient temperature it will spin again. Even in this case the rings or cylinder may be glazed and piston ring seal is compromised. A hard seize is when the rings or bearings are stuck and scored and the engine is locked up even after cool down. Commonly know as a "blown engine" even though no parts actually broke. (eg. connecting rod or piston)
![กี่หมื่นฟ้า | Your Sky Series EP.1 [1/4]](http://i.ytimg.com/vi/vLGjxFL6U_I/mqdefault.jpg)
4:00 Correction! I mis-spoke here in regards to Humidity the chart is right but I said it in reverse. High humidity=less dense, Low humidity=more dense. This was brought to my attention by @Shadowdog500 Thanks man!
i realize it is kind of off topic but do anybody know of a good site to watch new series online ?
So, then you CAN'T really explain it to me = )
14.7:1 is stochiometric ratio, not optimal, but idealistic (calculated by chemical formulae), to actually burn 100% of oxygen you need ~13.2:1 and to burn 100% of fuel you need ~16.5:1 AFR.
didnt help me solve the issue but definetly added to my knowledge of theory and jetting concepts
I just had a soft seize on a husquavarna chainsaw that went into a lean condition. It appears that the fuel line hose to the carb was slightly ill fitting and started to suck air and less fuel. Now the rebuild consists of piston, cylinder and ring inspection and take it from there. As most people who experiece the lean condition and then a seize will say...."It was running great until it stopped".
Funny, I just learned about what a motorcycle rectifier is. And he used the base word in the video. 00:22 Rectify means to make things right/ to fix mistakes. A motorcycle rectifier takes the 'bad' A/C and turns it to D/C of the correct voltage. Basically.
Jetting and reading the spark plugs goes together right!?
Yes.
Very informative and to the point. Now don't fret - you look good and you speak well! Don't let it get to you. Thank you for all the info!
BEST CARB SETTINGS VIDEO I HAVE EVER SEEN!!!!
Everything so well explained!! My bike is spitter/coughing at high revs and I dont know why, lol
Tomorrow this video will make wonders when I come to solve the issue :D
You’re very bright, I like your approach. Thank you sir.
I recently tried a 24mm carb on a 81cc engine, the carb is set up for a 120cc engine, I'm guessing it needs much larger jets because it wouldn't run above half throttle and sputtered from about 1/4 on throttle, the 81 cc is modified, free-flowing exhaust, high revving cam , and ported head, with in shrouded valves, with a redline around 9500-11000 rpm, I'm about to go to a bigger bore, 90cc with a better head, larger valves, and about 0.5:1 more compression, I'm hoping for a minimum of around 12 hp at the wheel, I just wonder if this carb is going to work, it's a CV carb, the largest factory type carb available is a 20mm, I have a modified aftermarket intake port matched to the head, I have tiny drill bits to drill the 105 jet to about 120-125 +/-, in about 2 size steps, I have it at about 108-110 now and going to try it, I'm thinking about drilling the slow jet slightly to hopefully get a better idle, and just off idle, and I have washers to space the needle if needed, I have been wondering if modify the spring would help throttle response any? Maybe shorten the spring to lower the tension, so the throttle can open faster and easier, I had lost the stock springs and had to use a random spring, I only had half throttle, unless I had speed and let off, and went to full throttle really fast, then it went close to full throttle, luckily I found the stock spring! I was thinking if it's just long enough to close the throttle, maybe it will give throttle response like or close to the same as a slide carb, CV carbs suck with a variator I guess I may as well keep it, if I had a real transmission, I think I'd convert to a slide, any suggestions? Should I go with a 20mm carb and be happy with what it offers??
If this video helped you considering giving "THANKS" ❤ it goes to help making more videos like this.
These videos are useful, thank you for making them!
My issue was unknown modifications made to the carbs. Foind out the carb slide springs were trimmed and slides drilled out. Bought a used carb that was unmolested. Went with factory jetting settings. 190m 35 P. 2nd notch from the bottom on the needle jet clip. Slow roll pulls like a champ wot through the gears. But highway speed 70mph and twist to wide open throttle, i hit like a wall, and slightly roll back off the throttle, it comes back alive. Full bowl height is at factory spec. Carbs are synced. New air filter fuel filter. , coil, coil packs, plugs. New fuel pump and relay. Im wondering gas cap vent or peacock valve
Very informative. Thank you. I just ordered the jet slide chart. Keep up the good work.
i just got a brand new apollo rfz 125 open and went out to the trails today and after the exhaust pipe was all purple/blue for the first 5 inches of the pipe. so hopefully i didnt cause any damage? the bike performed really well tho.
That is going to be normal to have metal discoloration from heat. They don't use high quality materials for the exhaust. I would not worry as long as it is not glowing red.
@@thejunkman Thanks for the reply!
I love that shirt.
It is cute how he keeps pulling his shirt down.
When my vstar is cold and hasn't run in a few hours it cannot and will not start without starter fluid. After I fire it up I have to stand there opening and closing the throttle until its hot. After that it starts as if there was never a problem to begin with. This occurs regardless of whether or not the choke is on
It is probably some debris in the fuel system, that is the most common culprit and the first thing to check before proceeding. Clean the tank, fuel shut off, and dismantle the entire (both) carburetors and ensure every passage and jet is clear. Then re-set (or check) that the carburetor settings are set to the factory positions. You will need a manual for this information. Read up on this site and it will also help you get familiar with all the parts that affect the mixture while the carburetor is operating in different positions. www.thejunkmanadv.com/motorcycle-carburetor-jetting.html
New subscriber! Thanks for taking the time to share your knowledge!
Great video. Well done.
Thank you.
Thanks, share it around
Thank you!
Well we know what rich and poor is, now this!
Good video thanks
I did not learn one thing about adjusting the fuel screw on my 4 cycle.
You are on the wrong video. I have one all about it.
Thanks for sharing your knowledge junkman. I'm trying to figure out why my ,82 Goldwing isn't running well after removing the engine for a starter clutch repair this past spring. I might have a vacuum leak among other issues since I can see the spark plugs are white on at least three of the cylinders.
I woyld investigate the carbs on those cylinders. 1982, the rubber parts are probably shot. Might be the diaphragms in those carbs.
Excellent video ! Thank you.
Didnt mention rich or lean how to determine which one affects your machine
High altitude air is more dense and low humidity right? so what should we do when the carb getting miss fire? do we need to rich or lean the air screw? thanks
The mixture screw is only for adjusting the mixture at idle speed though. In general higher altitude means less fuel required as the air is less dense because of the lower barometric pressure. You need to change the overall jetting, not just the mixture screw.
@@thejunkman Got it, thank you so much :)
Any idea why my spark plug would be black (rich) when I had a vacuum leak at the intake? Idle jet passage is clean and clear.
And also the air/fuel mix passage is clean and clear.
Could be that the spark plug is too cold of a heat range, but that would be a guess. I would correct the leak first. I have info on my site about this.
I’ve fixed the leak but now the threads in the head are stripped, lol.
I have high compression in my cylinders. Are colder range plugs not preferred with high compression?
It really depends on the engine design. All the heat range means is the ability of the spark plug to dissipate heat. Use this link to determine that. From reading this it may be too hot of a heat range. www.ngkntk.in/ngk-technology/importance-of-heat-range/
I am not sure what you mean by air/fuel mix passage? You mean the throat of the carburetor, that is the only area that the air and fuel really mix for the first time.
How in the world did old bikes ever get such a reliability / bullet proof reputation when it seems like nowadays jinking with carb. bikes are a constant hassle. I don't see how the dealerships would have ever made money unless it was from the constant servicing and adjusting of carbs. Maybe it was normal procedure back then and fuel injection has just spoiled us.
Hi I have rev hang for a couple of seconds...could that be due to a vacuum leak or lean mixture?
Both. The lean mixture could be caused by the vacuum leak.
very helpful, thank you
Thank you.
humidity has more fuel? i thought the h20 takes up space making it leaner...? i'm gonna have to look into this one because i think you got it wrong on this one
You are welcome to. This is a collaborative effort.
Thanks 😊 🙏 that was helpful 😀
Plugs are still sooty could it be the mixture I'm doing wrong
From the bonnie Highlands of Scotland America 🇺🇸 💙 god bless
Recently I installed a new carburetor in my car. The bigger main jet that it came with was of size 180. With 180 jet, the acceleration was jerky from half to full throttle, but it accelerated pretty quickly. I swapped the larger main jet from 180 to 135. Now with 135, the car bogs down under wide open throttle (especially when the pedal is quickly depressed), and then picks up after around 2 seconds. I've also noticed that the acceleration isn't as good with jet 135 as it was with 180. It idles perfectly fine and acceleration is smooth and crisp for half pedal; only problem is that with WOT, it bogs down and isn't accelerating as it should. Should I go for larger jet size of 150?
Why did you decide to make such a massive main jet change?
Try the 150, see if it splits the difference and try to hone in on the range you need to tune around. Your seasonal adjustments should be one or two sizes max.
I would like to submit a short video to you of my Yamaha AT3 restore! I’m hearing a noise that I’m concerned about. Thanks in advance!
Well I don't take projects, but watch my Barn Fresh Series and learn some tips and tricks to help restore it yourself. Feel free to comment and ask questions
I only wanted a Free “non binding opinion “. I think I remember this noise. Sorry to bother you.
Oh, I see. Well post me a link over on my website and I will take a look.
TH-cam.com Search Yamaha at3 noise. Thanks!!
You Rock!
Sorry can someone explain why a leaner mix causes overheating? All I can think I'm my head is that the fuel somehow cools the air slightly?
Pretty much correct. It cools the combustion chamber and keeps that temperature in the normal range since fuel is very dense.
@@thejunkman mate thanks for the quick reply you're a legend, your videos have taught me so much
I just bought a new dr650 and it feels very sluggish. I know it’s not a sports bike and it cuts out when I first start even when the bike is warm. Stalls out sometimes from a stop (I know how to work a clutch) and 5th gear is pretty much useless. Do you guys think the carb needs to be tuned? Is this normal for a brand new bike?
A question my bike runs good low and mid power but at full power it feels very weak and have to short shift! Could this be lean on the main jet? Just installed a full exhaust ony 2 stroke gilera mxr 125 , ran fine before the exhaust change!
Extremely appreciated a reply
Yes it probably is.
I want my scooter fly so should I be setting up my carburetor for high altitude I don't understand I'm not cool like you no I'm just giving you a hard time video helped me a lot thank you
Wow, that grammar. Thanks man
How to tune 2 stroke mikuni carburettor. I have indian Yamaha RX 135.
I have a question , what is the main jet ring or spigot purpose and its function ??
It holds the main jet in place.
hello, my son has an 2004 cbr125r from Honda, he has n aftermarket exhaust an pops on dethtrottle/deacceleration. Guess its running lean. have u suggestion what to go up to from the 118 stock main? Do he need yo go up on pilot to?
Just have to try and see. Jets are cheap.
@@thejunkman thanx, do you know what jets I need to order, think it has an keihin carb
No. You will have to open it up and see which style of Kehin, there are different types. Go to JetsRus and match them up if you don't know.
Need a chart where can a get one. Playing mad scientist
OOOOOOOOO
MYYYYYYYYY
GAAAAAAAAWD
👉💥😳
Where can I find a pocket tuner? :/ can't seem to find any, dunno if in looking for it correctly
On Amazon for about $8. I have had this one since the 90s.
Hello, and thank you for the videos. I have a question, Why at lean mixture for two stroke the engine tends to increase a little bit the speed of engine: Thank you in advance.
Junkman review the Lectron carb!
Send me one and I'll consider it.
@@thejunkman Brilliant reply!
what a soft seized engine I know hard seized engine because I couldn't barely kick it over
Soft seize is when an engine overheats and the parts swell enough to prevent engine rotation, but when the engine fully cooled down to ambient temperature it will spin again. Even in this case the rings or cylinder may be glazed and piston ring seal is compromised. A hard seize is when the rings or bearings are stuck and scored and the engine is locked up even after cool down. Commonly know as a "blown engine" even though no parts actually broke. (eg. connecting rod or piston)
@@thejunkman thank you
I could make a video about it going more in-depth. Would that be something you and others might want to see?
@@thejunkman I don't think you can get more in-depth than that man
Wondering does this have anything to do with oil pressure in the engine how does it affect oil pressure
Steicometric point.
Stoichiometric
Credentials?