Hity carb, just replaced PD19J with PD18j, #34 pilot, #75 main. It is 1-1/4 +_ 1/8 (that 1/8 is like a fine tuner/turner). Redid the float hang, pried it slightly up - - the float is parallel. Throttle response and release, idle return is key on. It never felt this responsive, strong with dead on return to idle RPM. My setting, with your demo, brought my engine sound, crisp, like your baby. The instruction was dead on. I’m on a 50cc. Really cool! Thanks!
Thanks Matthew great instructional video, I’ll be watching. I try to do all my own work on my bike YZ250f, these types of videos are very helpful. I like how your to the point and give the viewer what they need, minimal chatter.
Hi Matthew, thank you for that tutorial with the fuel screen,I will try that with my Yamaha sr 125cc carburetor 1999,I've been having idling problems, my fuel screw "is" fully seated in,therefore, I need to turn it out 2 turns & listen to the rpms, hopefully, should become higher,thank you friend & your engine sounds Awesome, the way your power drops immediately after throttle is the works ,thanks again Matthew 🙂🙂🙂
Great information and well presented. I just got a used crf450x that smells like it runs rich and even runs like it runs rich and even when the engine is cold it starts better with the hot start lever pulled lol. I’ll be trying just what you did tomorrow. I’m guessing I may need to go to a smaller pilot as rich as it seems, but we’ll see.
Man I can't tell you how much you have helped me with my fcr39mm! Dude you are my fcr mx guru thanks for the information. I am doing a drz400 swap.....so much help again thanks!!
This is great man. So easy to follow. I've got a custom fuel screw on the way and now I'm quite confident in what's got to be done. Cheers bro thanx!! Jamie
MatthewMCRepair The screw is in place! Couldn't believe I had to dam near completely disassemble the whole bike to get the carb out though lol.. after rewatching this video I definitely have to adjust my screw though, to many people telling me my idle was too high but after hearing your bikes idle, I'm going to spead it up. I'm riding a 2008 crf450x
FYI you can fit the R&D Racing Flex Jet to the FCR39 even though they say it only fits the MX version. The flex jet is in a better position and easier to adjust. I just used a small rats tail file to remove a little material from the tunnel that the screw runs through, it’s very easy. Some people drill the hole wider, but the interference is not concentric so drilling isn’t required and is a little more risk.
I’m going to visit your website to see where you mentioned if popping or rumbling on deceleration , and or if a backfire snap after full throttle then let off snap, seems somewhat healthy or not? And side note how important is backpressure(a metal screen on end exhaust is just for dirt or really important)? U r a genius
Good job that was probably the best video on that only thing you could have done maybe is show how to use a volt meter for guys that don’t have RPM screens
I'm buying a used bike tomorrow and I don't know anything about maintanance on the dirt bike yet but it is a 125cc 4 stroke (Japanese brand). I would like some tips on what go adjust or change when I get it
I went to go se my 2004 kx250f & i pressure washed it super good - looks brand new !!! But,,, the damn thing started to run like dook..... (Pressure washer might have turned fuel screw) idk but ,,, it started running hot & melted the airbox & spit out coolant for the first time ive ever seem that happen since ive owned it new..... I could not figure it out - this video nailed it & my bike idles , revs down & runs like before.... Slight bog at initial throttle but managable
My carb from my 08 yz450 i turned it all the way in and the bike didnt died.. I cant really notice any Diference when ajusting the screw. And on 1/4 trottle She hesitates thanks 4 help
I have a 2014 yz450f with a rebuilt and and had a filled up to the top with antifreeze but for sum reason the bike gets imidietly hot but I haven’t been able to ride because I don’t have a back tire right now so I just leave it idleing
Thanks a lot matt, I appreciate it. I'm not to computer oriented and I just stumbled on your comment accidentally. I'm trying to get up to date here in 2017 haha
Excellent explanation, thank you! Ran out of daylight today. My fcr idles excellent but I have a hanging idle when i blip the throttle. When I turned AF screw all the way in the bike didn't die. Maybe a float or cable issue?
I love the videos they are very informative. I have a smooth running idle but when I blip the throttle it seems like it hangs rather than going down to idle. And suggestions?
@@vogs2 I had to keep choke pulled out even when engine was warm, and didn't start easily. Also backfiring. Opening the fuel screw a bit for richer mix solved all these problems.
Matt I got problem with my 07 rmz250 got to idle but as soon you touch the gas shuts off was a pain to start but now got it to idle has 270 kit stage 3 procircuit kit from cams to titanium valves n exhaust ported n polished whole works like it’s starving for gas carburetor been rebuilt any points on it thanks
My 05 Kx250f has been backfiring like crazy when letting off the gas or decelerating the least little bit. Any ideas? It was revving and returning to idle perfectly and then bam, all of a sudden.
what about the idle screw? my knew pit bike 125cc 4t only starts when the choke is open even when it's hot, I've been testing the screws and I think I've messed up the mixture, it runs fine anyway, it doesn't die at half throttle and it doesn't lock up at full throttle but I have to have the choke open.
What of i have the hanging revs coming back to idle but can allso turn fs on all the way and it doesmt die? Also have a bog on snap throttle while on stand
I recently bought a 2004 KX250F and I bought it as a project and it needed a new cylinder head and all new valves so I replaced all that and it starts after like 40 kicks maybe with the choke and I cleaned out the carb and jets and the valves are in spec. It’s also has stage 2 hot cams in it so idk if that makes a difference on what the fuel mixture screw should be set at but it’s hard to start and has trouble running nicely so any other idea on what it may be besides the fuel mixture screw cause I’m stuck
MatthewMCRepair yeah I adjusted it to 2 turns out and it did start but after warming up for a little I turned off the choke and died a couple seconds later. Now would you need different jetting to accommodate for aftermarket cams or can you use the stock jetting?
Thanks for your video.....can you tell me what would cause one, after adjusting to hang the idle then by itself start stumbling a really low idle then again, change to a hanging fast idle without touching the screw? Hopefully I explained good enough....it just seems to have a mind of its own...lol. thanks in advance.
@HTMR I did...Originally it had a cracked intake boot so I purchased a new one. When spraying the intake boot now with carb cleaner, nothing changes like it did on the cracked intake boot. I think the o-ring on the pilot jet is probably shot allowing it to suck air through a bad o-ring? I just don't know what else would cause it to change so drastically without touching anything.
Im having a problem with my 07 ktm xcf250. It runns on the choke but without the choke it will die when i use the throttle. Jets are clean and accelerator diafram is good. And idea what it mite be. Thank you.
How can you tell it's seated when you turn it it? Is there resistance? I don't want to turn my in too much as damage the thin tip needle? Thanks for the video -helps understand how to tune and more importantly which direction to turn for rich/lean.
I have a kxf250 and the idle screw the black plastic one won't turn. I can move it a tiny bit and it just bounces back. Do these jam for any reason? I ask because I need to adjust it as my bike won't stay running when ticking over :(
Hey my 04 crf450r doesn’t wanna idle when I set the carb to it’s settings (2 an a half turns out on idle screw an fuel mixture an 2 turns out it’ll rev to the sky but it starts very easy but when I get the idle to be low but I have to give it gas so it won’t die it’ll be very hard to start
So this is good info but what keeps that screw from falling out? Cause mine is loose and rattled out and gone forever , almost prefer factory one so that it doesn’t fall out, or was mine old and warm out?
Hi all, I have a yz250f, note I'm very new to bikes, so when I pull out chock I can start it so naturally the revs are higher but after 3 min of idol when i go to put back choke the bike stalls is it the same problem than this, hopefully it is because I just wanna ride the thing 😢
I’ve got an 06 wr450. It has a problem with choke. Cold starts are easier with the choke off as for with it on, the bike just dies. warm starts are fine. In general, it just seems like it could run smoother. Looking for any advise before i get around to setting the fuel screw
Idk what’s going on w my crf 450 the screw fell off while I was rideing and now I put a new one and it won’t turn on now just back fires only turns on by push
Very helpful video but you said in the video that turning the fuel idle adjustment counter clockwise lowers it however the manual says different, wad that a typo or is the manual wrong?
![7 Common 4 Stroke Dirt Bike Jetting ISSUES [FCR Carb on 4 Stroke MX Bikes]](http://i.ytimg.com/vi/kdVuB0Y98QU/mqdefault.jpg)
![7 Common 4 Stroke Dirt Bike Jetting ISSUES [FCR Carb on 4 Stroke MX Bikes]](/img/tr.png)
Hity carb, just replaced PD19J with PD18j, #34 pilot, #75 main. It is 1-1/4 +_ 1/8 (that 1/8 is like a fine tuner/turner). Redid the float hang, pried it slightly up - - the float is parallel. Throttle response and release, idle return is key on. It never felt this responsive, strong with dead on return to idle RPM. My setting, with your demo, brought my engine sound, crisp, like your baby. The instruction was dead on. I’m on a 50cc. Really cool! Thanks!
Thanks so much man, my bike would run to hot and never want to start. Now I turned it to 2 and it’s less hot has more power and starts up
Thanks Matthew great instructional video, I’ll be watching. I try to do all my own work on my bike YZ250f, these types of videos are very helpful. I like how your to the point and give the viewer what they need, minimal chatter.
Did it work after u adjusted the screw ?
Best explanation to this 4 stroke carb tuning. Great video thank you.
Thanks, Exactly what I needed to solve my throttle hanging up on my freshly rebuild 250F
Same
did u just turn the fuel screw and it fixed it ?
@@rileyduff6604 yes. I bought an aftermarket fuel screw, installed it and followed his instructions. problem solved and I learned something.
Brian Rose cheers bro yeah i fixed mine but i still have stock fuel screw was so hard but i got it
Hi Matthew, thank you for that tutorial with the fuel screen,I will try that with my Yamaha sr 125cc carburetor 1999,I've been having idling problems, my fuel screw "is" fully seated in,therefore, I need to turn it out 2 turns & listen to the rpms, hopefully, should become higher,thank you friend & your engine sounds Awesome, the way your power drops immediately after throttle is the works ,thanks again Matthew 🙂🙂🙂
Great video just bought a bike an it wouldn’t start , did this and she fired right up easy an to the point 🤟
Great information and well presented. I just got a used crf450x that smells like it runs rich and even runs like it runs rich and even when the engine is cold it starts better with the hot start lever pulled lol. I’ll be trying just what you did tomorrow. I’m guessing I may need to go to a smaller pilot as rich as it seems, but we’ll see.
I'm gonna try it when i get home today...hopefully it will help with the bike not wanting to idle
Man I can't tell you how much you have helped me with my fcr39mm! Dude you are my fcr mx guru thanks for the information. I am doing a drz400 swap.....so much help again thanks!!
Dude my kx250f runs perfect now thanks the fuel screws was all the way up
This is great man. So easy to follow. I've got a custom fuel screw on the way and now I'm quite confident in what's got to be done.
Cheers bro thanx!!
Jamie
Cool. Keep me posted on outcome.
MatthewMCRepair The screw is in place! Couldn't believe I had to dam near completely disassemble the whole bike to get the carb out though lol.. after rewatching this video I definitely have to adjust my screw though, to many people telling me my idle was too high but after hearing your bikes idle, I'm going to spead it up. I'm riding a 2008 crf450x
Yeah, it takes some effort to get to these carbs.
Awesome and to the point, thanks! I found out my hot start was corroded in the open position and causing a similar popping..
What is a hot start? My rmz 250 pops a little But when i start it the pipe gets red
FYI you can fit the R&D Racing Flex Jet to the FCR39 even though they say it only fits the MX version. The flex jet is in a better position and easier to adjust. I just used a small rats tail file to remove a little material from the tunnel that the screw runs through, it’s very easy. Some people drill the hole wider, but the interference is not concentric so drilling isn’t required and is a little more risk.
I’m going to visit your website to see where you mentioned if popping or rumbling on deceleration , and or if a backfire snap after full throttle then let off snap, seems somewhat healthy or not?
And side note how important is backpressure(a metal screen on end exhaust is just for dirt or really important)?
U r a genius
Good job that was probably the best video on that only thing you could have done maybe is show how to use a volt meter for guys that don’t have RPM screens
Just tune by ear then.
Nice! Most of the recent carbs, especially the ones with a plug over the set screw, come set too lean for emissions reasons.
Thanks this will help I hope. If not I have another problem.
Great video, could you do a Honda Navi is a 4 stroke engine too!
I'm buying a used bike tomorrow and I don't know anything about maintanance on the dirt bike yet but it is a 125cc 4 stroke (Japanese brand). I would like some tips on what go adjust or change when I get it
125cc what? Best thing to do is get a service manual and read the maintenance section. It will explain what you need to do.
Thanks for the vid, One question, if the screw Is all screw in, (leaning) the bike must stop?
I went to go se my 2004 kx250f & i pressure washed it super good - looks brand new !!! But,,, the damn thing started to run like dook..... (Pressure washer might have turned fuel screw) idk but ,,, it started running hot & melted the airbox & spit out coolant for the first time ive ever seem that happen since ive owned it new..... I could not figure it out - this video nailed it & my bike idles , revs down & runs like before.... Slight bog at initial throttle but managable
I have vids to clear the bog.
If in doubt rule it out.
Runs better but still popping on decel.
I care not as the power is smooth.
Great info, thanks !
My carb from my 08 yz450 i turned it all the way in and the bike didnt died.. I cant really notice any Diference when ajusting the screw. And on 1/4 trottle She hesitates thanks 4 help
I have a 2014 yz450f with a rebuilt and and had a filled up to the top with antifreeze but for sum reason the bike gets imidietly hot but I haven’t been able to ride because I don’t have a back tire right now so I just leave it idleing
So if my rpm drops slowly it's rich?
great video, helped me a lot. regrats from brazil
After a blip of throttle yes.
@@HTMR 1:35 but you said if rpms hang you gotta richen it up. So is it rich or lean if the rpms hang?
@@dantsy6397 hanging rpm is lean
Thanks a lot matt, I appreciate it. I'm not to computer oriented and I just stumbled on your comment accidentally. I'm trying to get up to date here in 2017 haha
You are the man !! Very well explained thanks
Excellent explanation, thank you! Ran out of daylight today. My fcr idles excellent but I have a hanging idle when i blip the throttle. When I turned AF screw all the way in the bike didn't die. Maybe a float or cable issue?
Year make model? Stock pilot jet? Any mods?
@@HTMR 2006 yfz450 (ATV) bill balance edition 48 pilot jet, 165 main jet, K&N filter, EHS lid, heads P/P, FCR is bored. cam mod , AC pump mod (zip)
wow that is snappy and beautiful!!!
My 2004 honda crf250x with a fcr carburetor has a 155 pilot and 42 main jet and the fuel screw and needle clip in position #5
I will try this out on my crf, good video
I love the videos they are very informative. I have a smooth running idle but when I blip the throttle it seems like it hangs rather than going down to idle. And suggestions?
You have a lean hanging idle. Adjust fuel screw richer.
is the carburetor Same as pz30b carburetor with acceleration pump and slide
great tutorial, thank you!
Your welcome.
My quad seemed to get hot really fast after new exhaust and better filter im guessing it’s funning to lean ? To much air not enough gas ?
On my '05 WR 450 i have it running perfect but alot of popping on Decel, what can I adjust.. Ty..
My xr650l runs good at about 3 turns out... Is that ok
Yes
@@HTMR thanks bro... I did go ahead and order a 55 pilot jet
Great clip huge help . Detailed and clear thanks
what if it want ideal and cuts out when you push choke in and it back fireing lots
I'm having this same problem with my bike right now and can't figure it out"
@@vogs2 I had to keep choke pulled out even when engine was warm, and didn't start easily. Also backfiring. Opening the fuel screw a bit for richer mix solved all these problems.
Mein, this is the perfect explanation. Best ever 💥💥💥💥💥💥💥💥
Is it the same for the twin air
How about the air idle mix how many turns min. And max?
Thanks for the help brother from Sacramento, Ca.
Matt I got problem with my 07 rmz250 got to idle but as soon you touch the gas shuts off was a pain to start but now got it to idle has 270 kit stage 3 procircuit kit from cams to titanium valves n exhaust ported n polished whole works like it’s starving for gas carburetor been rebuilt any points on it thanks
Sweeeet video!! Thanks very helpful 👍🏾
so when ur talking abt the fuel screw is out from something, r u talking abt out from all the way in?
My 05 Kx250f has been backfiring like crazy when letting off the gas or decelerating the least little bit. Any ideas? It was revving and returning to idle perfectly and then bam, all of a sudden.
what about the idle screw? my knew pit bike 125cc 4t only starts when the choke is open even when it's hot, I've been testing the screws and I think I've messed up the mixture, it runs fine anyway, it doesn't die at half throttle and it doesn't lock up at full throttle but I have to have the choke open.
2021 Rmz 450 revs too high during cold start when choked?
What of i have the hanging revs coming back to idle but can allso turn fs on all the way and it doesmt die? Also have a bog on snap throttle while on stand
i was adjusting the fuel screw thinking it was the idle air valve hahah,thank you for the info
On which carb must i start if have 2 carbs? Suzuki intruder vs 800 1994
Need help, I think I
have a 49cc 4 stroke Motor. How do I connect and idle the carburator?
got a kawa 2011 250f there comming fuel to the karburator but not feeding it to the engine whys that?
I recently bought a 2004 KX250F and I bought it as a project and it needed a new cylinder head and all new valves so I replaced all that and it starts after like 40 kicks maybe with the choke and I cleaned out the carb and jets and the valves are in spec. It’s also has stage 2 hot cams in it so idk if that makes a difference on what the fuel mixture screw should be set at but it’s hard to start and has trouble running nicely so any other idea on what it may be besides the fuel mixture screw cause I’m stuck
I feel it’s most likely a carb issue but u really don’t want to spend anymore money on a new carb
@@kevinriess Did you adjust the fuel screw per this video?
MatthewMCRepair yeah I adjusted it to 2 turns out and it did start but after warming up for a little I turned off the choke and died a couple seconds later. Now would you need different jetting to accommodate for aftermarket cams or can you use the stock jetting?
@@kevinriess You need to adjust it while running. Engine warm choke off. What pilot jet size are you running?
MatthewMCRepair I just took the jets out and I running a 42 pilot and 175 main. Is that ok?
Can this cause ticking noise ? Other then valve or tensioner
Do you do it with choke in or out?
Just did a carb rebuild
hey man, my bike will bump start but not kick start. any suggestions? 04 kx250f
Thanks for your video.....can you tell me what would cause one, after adjusting to hang the idle then by itself start stumbling a really low idle then again, change to a hanging fast idle without touching the screw? Hopefully I explained good enough....it just seems to have a mind of its own...lol. thanks in advance.
Did you check for vacuum leaks?
@HTMR I did...Originally it had a cracked intake boot so I purchased a new one. When spraying the intake boot now with carb cleaner, nothing changes like it did on the cracked intake boot. I think the o-ring on the pilot jet is probably shot allowing it to suck air through a bad o-ring? I just don't know what else would cause it to change so drastically without touching anything.
@@dgmenace73 Year make model? What is stock and current pilot jet size? Fuel screw setting?
@HTMR I ordered a stock pilot jet and its running like a charm now. Thanks
Im having a problem with my 07 ktm xcf250. It runns on the choke but without the choke it will die when i use the throttle. Jets are clean and accelerator diafram is good. And idea what it mite be.
Thank you.
When I come to a stop and haul in my clutch if I don’t keep twisting the throttle she will shut off but she drive on her own w clutch in
BOA noite meu ktm sxf450 quando está mais quente fica a afogar tem alguma ideia da solução ?
How do I tune the bike when it doesn't start to begin with
Would this fix a bike that feels like it’s sputtering and backfiring?
when i turn my screw fully in the bike doesnt die, what could this mean?
And you called both of the screws idle screws how can that work
How can you tell it's seated when you turn it it? Is there resistance? I don't want to turn my in too much as damage the thin tip needle? Thanks for the video -helps understand how to tune and more importantly which direction to turn for rich/lean.
Use light finger torque and seat it until it stops. Use very little force and you will be OK.
My kx450f 07 won’t start there’s Fuel in and the choke is on can you please fix this adjustment
I have a kxf250 and the idle screw the black plastic one won't turn. I can move it a tiny bit and it just bounces back. Do these jam for any reason? I ask because I need to adjust it as my bike won't stay running when ticking over :(
Do you have to have idle low when u start to mess with screw
It helps with the procedure.
What does it mean when i blip my throttle and my bike dies? Great video by the way!
Bogging out or a misfire
This was very useful thank you 😁
AWESOME video... I'm an old guy, and new to this.... Mine has #'s 1-4 on it, so one "whole turn" is 1 ALL THE WAY AROUND back to 1 correct? Thank you!
Yes that is considered one turn
@@HTMR damn 5year old video, STILL helping others. Appreciate it. Have a good one.
Thank you so much this fixed my hot start issue
Great job on the video.
What does he mean when he says seed it
What if I went all the way against the hand of the clock and the engine didn't stop?
Your idle screw is the fuel screw what you on about? How can you have an idle screw and a fuel screw? You have an idle/fuel screw and an air screw
Bro it's mostly air. Not to sure. Offcores it's ok u have set it already if it was a gas screw. It would flood. Air mixture screw.
hello, new to riding. would this help with bogging?
Yes somewhat. You want to tune the AP timing and reduce the leak jet size; howtomotorcyclerepair.com/fcraptiming/
Two turn 180 or 360 degree?
Hey my 04 crf450r doesn’t wanna idle when I set the carb to it’s settings (2 an a half turns out on idle screw an fuel mixture an 2 turns out it’ll rev to the sky but it starts very easy but when I get the idle to be low but I have to give it gas so it won’t die it’ll be very hard to start
Andy idea what it is?
Thanks for the help
My fuel screw is good. Why am I getting low throttle baugg? Between low throttle and mid throttle.
Great vid bro, thanks!
Kawasaki/Suzuki/Yamaha/KTM/Husqvarna. My Suzuki RMZ 2005 was built in Japan. That's good. I had no clue. Thought hondoo was only on
Japanese.
So this is good info but what keeps that screw from falling out? Cause mine is loose and rattled out and gone forever , almost prefer factory one so that it doesn’t fall out, or was mine old and warm out?
There is a spring to keep tension on threads.
Hi I have a trx 450er hinson race parts when I start on choke idle the header glows red is that normal or would this idea help the situation thanks
Your videos are very helpful! I’m doing a FCR on my LTZ400 would the adjustments be the same for my quad? Fcr is from a yfz450 .
Yes, this applies for all FCR carbs.
The black knob with the ridges right above the fuel crew that sticks out the side what is that
Idle speed
if your bike won't start and you think the fuel screw is the problem should I start at 2 turns
Hi all, I have a yz250f, note I'm very new to bikes, so when I pull out chock I can start it so naturally the revs are higher but after 3 min of idol when i go to put back choke the bike stalls is it the same problem than this, hopefully it is because I just wanna ride the thing 😢
Nice video. How many turns does the pilot jet get?
So then what do you do if you put the screw in all the way and it still runs????
Pilot jet too rich or pulling fuel from elsewhere.
I’ve got an 06 wr450. It has a problem with choke. Cold starts are easier with the choke off as for with it on, the bike just dies. warm starts are fine. In general, it just seems like it could run smoother. Looking for any advise before i get around to setting the fuel screw
That happens when fuel screw and/or pilot jet is too rich.
Matt, great video. how would I go about draining the fuel on my 06 kx250f?
Why drain it?? Loosen the 17mm bowl nut.
Idk what’s going on w my crf 450 the screw fell off while I was rideing and now I put a new one and it won’t turn on now just back fires only turns on by push
Very helpful video but you said in the video that turning the fuel idle adjustment counter clockwise lowers it however the manual says different, wad that a typo or is the manual wrong?
Remember the fuel screw is upside down. Lefty loosey is richer.