Inside A Motorcycle Carburetor - Needle Height Tuning Adjustment | MC Garage

Do you know what part in your carburetor controls the majority of the fueling? What does raising or lowering the needle mean? Today on MC Garage we talk about the carburetor needle and how it keeps your bike running.
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This is it guys-the last installment of our how to tune a carburetor series. We’ve got four other videos that preface this video; if you haven’t watched them yet, make sure you jump back and check those out. Each builds on the knowledge of the one before. We’ve covered how to set your float height, how to tune the idle circuit, and how to jet for rich and lean on the main jet. Now we get into the piece that transitions the fueling from the pilot to the main jet: the needle jet and needle.
The needle jet-or nozzle as it’s sometimes called-is located in between the main jet and the carburetors venturi. Fuel comes through the main jet and into the needle jet. So the main jet does affect the needle, especially as the throttle opening increases.
The needle is attached to the slide and slides up and down within the needle jet. The needle is tapered, like a needle, and has a smaller diameter at the bottom than at the top. As the needle’s position changes within the jet up or down, the opening increases or decreases because of the diameter of the taper changes within the fixed diameter of the nozzle. This is how the fuel is metered.
So if the slide is all the way up at wide open, the smallest diameter is inside the needle jet making for the largest opening. Vice versa when the slide is all of the way down. Some needles have adjustable height positions while sitting in the slide. An E-clip sets the position, and that position is often referred to as “the clip.” Moving the clip up will lower the needle, making it leaner. When there are no clip positions on the needle, you can move the needle up by placing small washers (a move called shimming) in between the needle and slide. To lower the needle? You will need a longer needle.
When someone says drop or lower the needle, that means a leaner setting. Raise the needle for a richer mixture. This is fine-tuning your carburetion in the areas you ride the most often. Honestly, how often are you wide open? Just a fraction of the time, but how often are you at 70 percent throttle? Often.
As always, your manual will have the recommended clip position, but a good rule of thumb is to start in the middle position. Then just as you did with the main jet, feel the response. If it’s sluggish and sputtery, it’s rich. A bog means lean. Also hold the throttle at the midpoint; if the revs climb or run away and will not settle into an rpm, it’s lean. When the rpms dip or drop, it’s rich. Adjust the clip position accordingly.
For even further fine-tuning, try optional needles and nozzles with different tapers and diameters. These will help to get that last little bit of perfection into your jetting and tuning, but in reality you should be able to get 95 percent there with the needle you have. That last 5 percent is usually for the mechanics who are tuning for expert racers.
That’s the gist of the needle. Get the idle and wide-open-throttle jetting set first, then pay attention to the mid. Take it step by step; think about the effects each change will make before you do it. Test and repeat. In a short time you will have a crisp, properly jetted motorcycle.
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[@mathiasjerpseth8871]

The hardest thing about adjusting the carb is finding these videos in the correct order. Good videos tho 👍

[@ianowen4481]

That's true. I thought they said we could find links to the other videos in the description but they're not there. Great videos though.

[@davidvaneck4856]

That's what I'm trying to find atm.hummmm

[@MrMrsregor]

yea. this is the most important and confusing part. would be a great video or would be nice if it was included in the first video of this series

[@dallasdeckard6551]

Really easy to understand instructions! This whole series is awesome. Making a playlist in order would be wonderful.

[@spikekatsuki]

guys I think you need to put the series on a playlist or something

[@Dowent]

It has been for years, check their playlists section.

[@speltwrong9009]

@@Dowent it's 130+ videos it may as well not be in a play list. No one is going to scroll threw and find the right series within in the series. Also you can't just hit back in the video

[@allhailhailee]

Came here just to say this 4 years later.. 100+ videos to go through 😅

[@MrMrsregor]

YES ! seriously, I really like this mini series and like to reference back to it every time I do carb tuning, but fumbling around looking for the next show is ridiculously annoying

[@glennd864]

Thanks for the down to earth 🌎 explanation of what the needle jet does. I will use this info to dial in my four wheeler tomorrow, as it's been sputtering through the midrange after replacing the carburetor. 👍

[@Alien590]

Well explained without using more time than needed 👌👍

[@ourhouse8640]

Dude you are awesome. I have looked at ALOT of vids and yours explained things prefectly. Thank you for posting and hope to see alot more good stuff.

[@happyrv2061]

your video's on carbs has helped me greatly. I fought for 2 weeks straight trying to figure out the carbs on my 1994 Virago. "You are a Gentleman, A Scholar, and a Judge of Fine Women "

[@mathster]

Perfect and straight to the point great tutorial 👌 👍

[@meteormotorcycle4442]

Thanks for the carb tech! Great articles on diy carb care and tuning!

[@spikeafrica]

Awesome video, helped me tune a lean spot out.

[@reddevil331]

Most understandable needle position video I've seen.

[@derekv275]

Yes simple and understandable info. Its what I been looking for lol

[@stiffcookie]

Him: How often are you wide open? Me: If you're a cop, you have to tell me, right?

[@arthurpendragon9079]

Since you have done so well with carbs, how about an article on another vanishing art... ignition points?

[@snackbags]

Hahaha!

[@RideWithTheWolf]

Good straight forward video.

[@ggjesus5667]

Thank you so much even know this video is 3 years old it is definitely helpful

[@marcusblickerify]

Man thank you for the video! Helped me a lot!!! Grip it and rip it brother!

[@aaronbaar2866]

Great video hands down

[@vivinvincent692]

Wow. This is great info.. even better.than the last host.. keep up the good work. Cheers.

[@brianb5779]

Video helped me out so thank you

[@josecruz-zd3iz]

How about a video on leak testing on a two stroke? You could feature the Motion Pro kit. Trying to get a vintage Yamaha scrambler running. Thanks!

[@jluis5188]

LOVE U BRO. lol thank you for all this info.

[@ozziejim8472]

Great stuff, thank you.🍻

[@billterri4889]

My KX125 carb was leaking when turned off so I did a rebuild. (I live at very low altitude & bike is stock except aftermarket exhaust and some porting) Other than that Bike was running pretty strong but was definitely due for a new top end which I did. (I was getting a good bit of spouge at the silencer which I always saw as normal for a 2 stroker but I am repacking the silencer as well.)The carb kit had all stock size components so I used those. The old main jet was a 400 but the stk one I used was a 420. The clip on the old needle was on the 2nd slot down The replacement needle is the exact same type but factory spec calls for clip in 3rd position. Since I already have the main going from 400 to 420 what do you recommend for the clip position as a starting point?

[@rodneybutler7939]

great job!!!!!! thank you!

[@shanemyers4142]

Love your vids brother. This bike I'm working on dies upon throttle unless i spray the carb with fuel, then it revs normally. I'm goin to try and shim my needles cause it's only thing I have not done to these carbs and it's so confusing why the bike isn't running properly still after all I've done to it.

[@AndrewBoundy]

I need to watch these 5 carb vids a few times with an old carb to hack-up on a bench. I figure once I've done that a time or two, I'll be set :-)

[@tommers1209]

I'd watched a ton of carburetor videos, both for cars and bikes, and while the engineer in me understood the principals, it wasn't until I took one apart to thoroughly clean and re-jet that I really felt comfortable with these contraptions.

[@MTRONO055]

Very informative 👍🏼

[@brianb5779]

Is there anyway to know which needle to use? Ill clarify, im working on neighbors honda 50 and got a bag of parts, there is a bronze thicker needle and a silver thin needle in the bag with other mismatched parts...

[@garyh2289]

I'm interested to know the setting you ended up on with the gas gas as they are a bit of a nightmare and I have one that I need to get right.

[@OlszkoolCustoms]

Thank you!

[@charanjeetsingh6137]

Bike with fresh work done with new cylinder kit ..is its carb require couple of settings after 500kms done or it can be tunned just one time when job completed in first attempt..

[@allenhale2316]

I have a little Suzuki gz250 that I recently cut the baffle off. I’ve read that can cause lean issues but I couldn’t imagine it’d be major as the bike ran great for an hour after. Should I do some type of adjustment on my carb somewhere to balance for the new straight pipe?

[@thysdejager8287]

I really liked this video.On xs1100 special yamahas mikuni carbs what does the R stands for as part of the jet ID or size.Thanks.

[@Lex-fd5dz]

Question: is it easier to start up a 1 cylinder bike as compared to a 2 cylinder bike? Maybe 2 cylinder need more electricity to start as compared to 1 cylinder

[@waya121]

i watched all the carb videos and this is still black magic

[@shenenfernando4164]

When you adjust the needle to do more on petrol should it go down or should it go up. presently my needle position is in the middlecut

[@billypat3256]

What would it tell you if the engine will run perfect without the airbox on, once it is added, it starts to bog. Then add the filter and airbox cover, it runs at 90%??? Been stumping me, and it's a brand new good aftermarket carb. Loved the vid, i'll try to apply some of the stuff to my problem!

[@charliecalvert4831]

I have ac125 virago. The bike wont accelerate on full throttle. Itsxa new carb could the needle position be wrong or the main jet too small

[@bernardmcnamara]

Hi Justin. I own a 1998 Yamaha R1. That is hydrologic locking due to fuel seeping out of the carburettors. While parked over one or two nights. It's also ending up in the motor's engine oil. The last oil change I drained 5.2 litres of fluid from the engine. The engine only requires 2.9 litres of oil.

[@teacherpaco]

What about if the bike is running super lean at one and a half turns (air filter side)? What should i go for a bigger or smaller main jet?

[@rkprecisionproducts8575]

Hi, I use tm32 for my air cooled 250cc bike. The problem am facing is, the engine in off condition if we give the throttle means the engine gets richer and takes so many kicks to start. Kindly give me a solution...

[@georgebrandt541]

xr650r slow speed jet t 65 trying to avoid off idle bog 175 main 3rd clip down ...hard tune ..tips? Would the main jet setting affect the off idle bog ? Would the idle air needle compensate for this ? How about live computer metering ? ride safe G

[@johnalderson7997]

My 2501966 Ducati scrambler reves higher when it is lean over or on the kick stand .Is it the need jet (Dellorto UFB24BS cab)

[@db21637]

How about a vid on balancing/syncing multiple carb setups

[@markkaplan2133]

I replaced the needles in my carb. Is it possible that this will stop the engine from engaging if the starter is functioning?

[@frankjamison1239]

I jus broke the end part of my needle in my 49cc moped kinda worried about driving it will it be ok

[@Kevccordion]

How do I know if I need to do this, or adjust the screws?

[@troolllllinnnzaragoza3169]

What happens if your bike runs great but the clip positioning is at the very top. Therefore the lowest/leanest setting for my needle. Do I need to jet down? Or leave it if it’s running good?

[@jaystrappa]

My bike bogs if you gun it for a split second then runs perfect should I richen the needle one position?

[@joshpashia637]

Have a Kayo K6R "nibbi carb" that has a bog issue going from idle to heavy throttle is fine in every other position and scenario. Make it richer?

[@michaeldutremble1859]

My 2006 crf250r pops when laying off the throttle, idk what’s up with it . I re jetted it still can’t seem to figure out whats wrong with it

[@disguyygotyou3906]

I can't find info and desperate did a rebuild adjusted valve legitimately off the bike verifyd carb cleaner shot put of every port carbs syncd fine it idles fine wot it amazing now sounds way better I cruise and lose here holding rpms best way to describe it high gear low rpms holding throttle it runs fines keep holding throttle same spot but starts to sputter comes out of it wot right away this narrowed it down correct?

[@faisal_nisar]

What is difference between needle lean/rich adjustment and AFS lean/rich adjustment...my bike seems to ride fine for few meters and then when the carburettor oil starts to come down in the carb it starts to die for few minutes and then its fine.

[@patmclean1951]

This Is great! I’m going have to back up and watch the other carb instalments. My ZR750 has a flat spot about 6k rpms. This might be the issue.

[@paky66]

We have the same bike :)

[@patmclean1951]

1991 for me.

[@paky66]

@@patmclean1951 same as mine😝

[@Majorgaines]

So I have a 2001 ktm EXC (2 stroke) with a Keihin pwk (it oem) I finally have everything tuned in well but I need a leaner needle and can't find them anywhere or find out what needle I have now.

[@elsonjayvictorsaringan8776]

Whats the reason why gasoline comes out on the mouth of the carburetor when going full throttle? Can you please help me.

[@javierortiz2990]

Para una rieju mr 300 que agujas y posición del needle poner a 1,100 pies de altura?

[@kentrobbins7279]

Can you help me ? If i spray ether in carb it will run but it wont start if not sprayed

[@bofflombard8755]

Can someone please help me my bike dies when I'm full throttle can moving the needle cause it when you start in the middle and move it one down or not

[@allencrowell7518]

I have a 2003 arctic cat 300 4x4 and the exhaust keeps getting red hot. What should I do to it?

[@tosheshdaulta8899]

It would have been nice if you could have put up links to the preceding videos.

[@ProDigit80]

I'm just wondering if adjusting the clip will do something to the top 20% of the throttle?

[@nitromatt37gaming52]

Try syncing 4 carbs on a 81 Kawasaki kz650 csr h1 its a royal pain took me 4 days to finally get it right with only a screw driver

[@daveco1270]

According to the specs I'm supposed to set my jet needle clip on position 4. What they don't tell you is if 4 is the top notch or the 4th notch down on the needle. Does it go 1 - 4 from the top down or vise versa? Thanks.

[@thebaker7]

1 is the top setting with the top of the needle furthest down closet to the clip. Count from top down, so when you have the clip on the bottom groove and more of the needle sticking up above the clip, thats position 3 or 4.

[@Cody-ix4kt]

can anyone help can the needle cause bogging when under load if its not in the correct position

[@doctorthee]

In a 4 carb setup, where the 2 middle carbs have a larger size jet than the outside 2 (due to higher heat), do they also have different needle hight settings?

[@redtobertshateshandles]

No. They run a little richer right through the range.

[@chrisvillarreal2752]

I feel like I’m so close everything runs near perfect except for immediately cracking the throttle open fast, initial bog or drops on its face like it wants to die but only if twisted fast smooth throttle roll and everything runs great just really need that initial crack to be there especially in the off road turns… man once that bog hits you’re heart just breaks…

[@TheRealKalEll]

Curious... what makes a mini bike backfire on acceleration? Timing appears to be on the marks exactly, new carb but new oversized chrome air filter instead of the OEM tin can. Honda Trail Mini ct70. Serial number on block says it's a z50 but head says 72.cc. Runs ok but has no real power like a friends ct70 and when hot it sputters and pops on acceleration. Any help would be appreciated. Thanx4sharing, thanx4caring!!

[@dmo848]

Leak in air system

[@boimsenju5481]

I never get easy cold start with my 2 stroke, and have setting air mix many time. But when it start i am good to go and get hard again when the engine is stop even for just 30 minute

[@lonewoodsman00]

How about telling me how to hold the needle back in place? There's a little spring that sit on the barrel somehow... I just dont know how it sits or clips in

[@suzukils6505]

Question: 2001 Suzuki ls650 stock At 4,000 rpm (out of 6500) the motorcycle feeling like a pulsing surge. Is that a rich or lean condition?

[@redtobertshateshandles]

What he says. At part throttle does it rev up smoothly or does it hesitate then rev up wildly. You will feel it riding. Hesitation, then revs suddenly but with weak power. Common with vacuum carbs as they're jetted for fuel economy and environmental b.s.

[@yashpalchudasama501]

Sir i own a Suzuki gs 150r...please guide me how to tune carburetor for maximum mileage and good performance..thanks

[@Media4Mental]

We want Ari back! ;-))

[@andriustulusis8759]

50cc we always on the max capabilities, my street legal supermoto goes 49 mph, gonna put a sport exhaust and a sport air filter and hope for better results, closer to 60 i hope

[@colinchilds]

How do you move the clip?

[@bryanmiller5074]

Does carb need 2 be off 2 do this ?

[@MaassDefect]

i tried to clean my carburetor and when i put back on now it runs on three cylinders The fourth cylinder only fires when i start her up and then it stops working, Does anyone have any idea shy it does that?

[@darellrafial5717]

Please talk about straight exhaust pipe and stock exhaust

[@JT-mq1jk]

SO FOR HOTTER WEATHER DO I EED IT MORE LEAN OR MORE RICH? LOWER OR RAISE THE NEEDLE THINGY?? ANYONE ON THIS? PLEASE HELP, THANK YOU

[@redtobertshateshandles]

Standard jetting should but may not be in the middle, then it's fairly close for hot or cold weather. Fuel amount in the tank or altitude will have more effect. In hot weather try keeping a full tank, at high altitude half full.

[@Ald007]

I'm Brazilian and we don't have much information about needles, do you know if their adjustment influences the bike's height?

[@atifliaqat8159]

Never. Its just fuel adjustment.

[@sydyya991]

brother, I have a problem, I have a big idle, the gas at the end doesn't work, the last 2 centimeters doesn't react, help. MIKUNI BDS26

[@ivanm2225]

1:07 boy you about to poke yourself with that thing

[@augustusphilip3975]

Well explained bruh...nice work I have a doubt regarding the kill switch. What if i accidentally turn off the kill switch at 60 mph?🤔

[@Shoukath_Ali]

Nothing much happens..... The engine shuts down and you better grab the clutch

[@dmo848]

When I first started riding, my jerk friends would hit that kill button on me. 😂 took me forever to realize it. I felt dumb n they laughed hard. Things u don't know as a new rider😂 Cheers to ya. Thought my bike was dead

[@rodmaiquez726]

Guys I have a question, I have a 115cc scooter which I upgraded the bore to 160cc, I still use a stock 25mm cv carb, would it help if I put the needle on the richest or 2nd to the last richest, since if I full on open throttle it kinda feels like it cant keep up with the full throttle. Haven't touched the main and pilot jet.

[@dmo848]

Need to mess with the air fuel screw my friend to get more power

[@rodmaiquez726]

@@dmo848 just bought a new bike with injection saved me the hassle 🤣

[@dmo848]

@@rodmaiquez726 I'm looking to get another but I'm jus still not won over by these high prices on everything. Kinda pisses me off. Folks want over a grand for stuff not even running. Smh

[@rodmaiquez726]

@@dmo848 yeah, here in my place even used bikes from '11-'15 costs 11-15k usd

[@jamesa6272]

What gets me is they say get the main jet jetting 2nd before the needle. Well how are you going to get to wot if your mid range is wonky.

[@AdamHuman-ei9oz]

how do you adjust a carb on a roadstar if it runs rich

[@eugendanciu9789]

Yamaha wr 450 2004 needle position?

[@carlostench3040]

Wat happens if I put my clip one more up from the normal position? Will it change the spped of my motorcycle or decrease the speed?

[@tomgarrett687]

It will run leaner. If it coughs out the carb, its too lean

[@fazimabdool6437]

@@tomgarrett687 a quick question bro...I have a Honda storm 125 cc and it has a CV carb ...the bike runs awesome but whenever I start it and try turning the throttle its sputtery for a few seconds and then smooth out and as the bike warms the throttle response is ok , my question is, is that normal for cv carbs ( because of vacuum) or is there anything I can do to fix this ? Thanks

[@triumphrider9796]

Learned a lot of this by necessity when changing the exhaust on my vintage bike, finally got it right and then unfortunately got rear-ended and destroyed that exhaust (pushed it forward about six inches or so, kinked one of the header pipes, fortunately I got away with, under the circumstances, minor injuries). Luckily I still had the older pipes and the different main and needle jet combo they required so I went back to those. Now I have an odd issue with my Bonnie ('02), until it's fully up to temp it occasionally spits and flashes back through the carb; it's even kicked the carb right off the manifold a few times (yes, the clamps were tight, replaced them anyway). Replacing the boots helped some but it still does it, goes away when it's fully up to temp, otherwise runs fine, valves adjusted not too long ago (made no difference). Any ideas?

[@connorjackson5050]

Ignition timing

[@triumphrider9796]

Thanks anyway but no, that's electronic and wouldn't vary with engine temp, seems related to choke somehow.

[@joeshiesty4216]

I full throttle and it won’t rev at full throttle idk where to put the needle

[@ChaosExplained]

My fucking hero

[@timsgaragefixflips2175]

Amazong video

[@aggieforlife13]

will the engine run if the needle jet is clogged?

[@tomgarrett687]

NO

[@albertngala5739]

Can u fix 100cc carburettor to a bigger bike 150cc

[@hrsey71]

the question remains.. when it says "set the needle clip in the x position FROM TOP/BOTTOM" is the "top" the furthest point from the tip of the needle? and the "bottom" the closest point to the tip of the needle? I've always been confused about that and haven't seen any clarification on this

[@4x4Mudmaster]

The top end is always where the clip goes.

[@hrsey71]

@@4x4Mudmaster you completely missed the question haha. if i were to tell you "3rd position from top", what end would you say is the "top"? the pointed end of the needle, or the blunt end?

[@billmastrippolito7132]

@@hrsey71 The end of the needle where the clip goes is the "top" of the needle, the groove closest to the "top" of the needle is position one, 3rd position is the 3rd groove from the top (more towards the pointy end)

[@hrsey71]

@@billmastrippolito7132 thanks!

[@joebartoszek1835]

ive searched everywhere and i need help. i recently bought a carb rebuild kit but i have a small handfull of parts from the kit i really cant figure out where they go. if they are meant for my carb then perhaps the previous owner messed things up. this is a new bike to me. anyone what to help a brother out? i which i could post a photo here....

[@billterri4889]

what brand carb kit?

[@biggussniffus5537]

2:05 sir you would be wrong lol

[@blakeneale6413]

so i cleaned my carb and mistakes my fuel mix as a jet and now it only starts with choke ogg

[@fatalcapsaicin5157]

Only starts with choke on or off?

[@muhamadmounawar3281]

Seen i put mikuni 32 mm on my bike everytime my spark plug become black why and then my bike doesnt start💔

[@tomgarrett687]

way to rich man...And it would be helpful if you mention the engine size. Example: 250 cc, 500 cc, or 750 cc. Clean your spark plug with sand paper and go down a size on the main jet....Still black plug, go down another size...

[@criticalthinkers3787]

So stutter is raise the needle and bog lower.... oke thanks was trying to figuren out why it keeps stuttering on 75%+ throttle with perfect mixture..