Suzuki GN 250 Cafe Racer Build - Part 13: Carburetor Basics

In Part 13 of our Suzuki GN 250 Cafe Racer Build, we talk carburetor basics: like how to clean and re-jet for top performance.
SUBSCRIBE FOR MORE! bit.ly/2ywbdhZ
Suzuki GN250 Manual: bit.ly/2uAuktw
Great article on how a carb works: bit.ly/2D7rC1L
#### WHAT I USED ##########
K&N Filter: amzn.to/2BhNKFy
Here at House of David MC, we celebrate the process that is building custom scooters and motorcycles. We know that all moto-builds are different and each one presents its own set of challenges and obstacles. So let’s learn something today, and maybe build a motorcycle while we’re at it!
One Motor, One Revelation at a Time.
+++INSTAGRAM: / houseofdavidmc
+++FACEBOOK: / houseofdavidmc
+++WEBSITE: www.houseofdavi...
+++MERCH: teespring.com/...
:::: Music ::::
Anozira- 3D Blast (BONUS)
bit.ly/2CJaWOD
/ anoziramusic
Desembra - Hit 'Em [NCS Release]
bit.ly/1JlLKvB
Desembra
• / officialdesembra
• / desembramusic
• / desembramusic
• / desembra. .

[@thomasgormly3264]

This is a really helpful video. I just wanted to point out that at 3:00, you say that the needle is connected to the throttle. In case this confuses people, it should be noted that this is a constant velocity carb. So the throttle is connected to a throttle plate, not to the needle. The needle moves up and down with the slide due to vacuum pressure on the top diaphragm. Vacuum pressure is created partly by the piston intake stroke and regulated by the throttle plate. The slide and needle move up together when the throttle plate opens, because increased airflow through the carb leads to negative pressure after the venturi (+ intake stroke vacuum) and this negative pressure is carried to the top side of the diaphragm. This lifts the slide and needle together, allowing increased fuel through the needle jet.

[@SAKOadventures]

Thomas I need help! You seem to know how these work how do I get that needle to move up and down as the throttle opens the butterfly? My carb stays closed with the needle but the butterfly opens and it won't rev up? Please help🙏

[@tufftrails]

That was really good and it's helping someone 5 years after you posted it...thank you so much.

[@iRidetas]

Most clear cut carby instructional ive seen on the tubes mate! Cheers great job! Could never ghet my xs650 when I had it to run right with a pod filter due to the blocking of holes and swirling air!

[@HouseofDavidMC]

iRidetas thabks, bro! I'll have a bit more tweaking to do once she's running- it's always seems to be different from one bike to another 😁

[@jamesmealing5753]

I just seen this was an old video but it is great

[@HyralProductions]

There is always more air in the mixture than fuel,more exactly for every liter of fuel vapor you need aprox 14liters of air.the correct ratio is 14:1 air fuel ratio,so if you are bellow 14:1 the mixture is rich and if you are above 14:1 it is lean.

[@harrybrown4815]

6:45 wrong! main jet is last. This is why, idle circuit works through out the whole throttle range so at idle or at flat out it is still allowing a metered amount of fuel through the carb. As the idle circuit works the first quarter of your throttle its jet has to be set correctly and can give you up to half of your rev range, so it is working a lot of the time. [poor idling or stalling engine because of gummed up or blocked idle jets including the air inlet of the idle circuit. rev passes cause lean conditions on the rest of the fuel cir The Jet needle and needle jet come next but usually these will be already set to work within a good tolerance band that will work with the idle circuit. If you need to enrichen this part of the circuit you raise the needle and if you want to lean you lower the needle once you reach the limit of in either direction within this mid to higher part of the rev range its time to look at going larger or smaller with the main jet. Now it is just figuring out which main jet to install for balls to the wall WOT flat out top end but you've already probably figured this out by now because of the previous step. you will need a vacuum gauge to accurately set the idle circuit and on multi carb bikes set the balance. before doing any of this you will need to check the float height is correct as this effects the lean/rich state throughout the whole carburation range.

[@zscott453]

Superb detail and simple enough for beginners to follow! Great video

[@HouseofDavidMC]

zscott453 thanks!

[@UnhingedHarry]

Thanks mate. Very helpful.

[@bramskahoon4072]

Might be good idea use torque wrench to tight up them screws to even out the new seal

[@sergioandino1278]

now this got me more interested. thanks for the education bro

[@montymccune201]

sergio andino awesome!

[@isaacgonzalez4661]

Hello, good night friend, first of all I wanted to thank you for your videos, they are very good. I wanted to know if you have any videos of how to carburize the motorcycle, turn it on and carbure it by adjusting the air and gasoline sprain.

[@thenoddy7]

Super helpful! I have a GN250 that keeps fouling spark plugs (which results in it conking out and it won't start). Have had some recommendations relating to the carburetor but as I'm a newbie it's all jibberish to me.. Still at a loss at what to do but this sort of content is pointing me in the right direction lol. If you see this, any advice would be appreciated.

[@thenoddy7]

@@nobody78578 ended up re-boring it, getting a larger piston, rejecting the carb, new battery, seems to be running ok now but this has only all happened in the last week so we'll see how she goes 😂

[@samobrien3947]

Great Video! Did you have to tune the Carby with adding the pod filter? And did the pod filter increase or decrease performance? I have the same bike... I like the look of the pod filter. Considering doing it. Have heard mixed feedback.

[@stevetownsend9991]

Did you end up keeping the 132.5 jet? I have a GN250 with the same pod filter, and I'm currently going through tuning at the moment. I've also heard that the needle can be moved up one position if the airbox has been removed.

[@maxv77]

When I use the throttle to rev tge engine. It seems to take a long time for the revs to drop back down.ive lubricated the throttle cable. Could it be that the diaphragm or needle jet is sticking slightly? I did just clean the whole thing out and it was OK before I did the cleaning. Should the needle jet slider that you can see need any oil on it to help it go up and down smoothly? Thank you

[@Hector.9T]

I have the same problem with my GN 250 motorcycle, it takes a long time to lower the revolutions, in fact when I hold the clutch down the motorcycle accelerates, were you able to solve it?

[@gregnovak0070]

Would you have the details on re jetting the carb for a pod filter?

[@peleymele2]

Does it run well with the 132.5 main jet and the pod filter? Im planning on doing the same thing, but with stock exhaust

[@conaboot]

So no video on tuning the carb (lean or rich)?

[@yamancansaraclar679]

Hi! Would you recommend a Mikuni TM28 carb upgrade for a 152cc Chinese bike? (CR152) Will it affect performance? Is it bolt-on? Will it harm the engine life? Many thanks!

[@miguelmadariaga2721]

buenas companero tengo una duda ...el filtro de aire pequeno si le trabaja bien .....yo le coloque a mi gn uno un poco mas grande y no trabaja mecanicamente bien pierde la fuerza y suena feo y me toco volverle a colocar el original

[@montymccune201]

Miguel Madariaga has cambiado el silenciador? Cada vez que quita el filtro de aire original, cambia la relación aire / combustible en el carburador. Si desea utilizar un filtro de vaina, comience aumentando el tamaño del chorro grande en el carburador, un tamaño a la vez, hasta que se maneje bien en el extremo superior. luego comience a ajustar lentamente el chorro pequeño

[@asumanisaac2463]

I ride tu250 Suzuki volty but I don't what is wrong with carb werever am trying to increase speed to more than 80 it reduces it's becomes funny like air is to mch than fuels what do I have to do to put back ma bike to normal as it used to bi before.

[@JP-or1my]

Can you link to that POD filter ? Cheers

[@HouseofDavidMC]

added to the description :)

[@JP-or1my]

Legend, thanks dude

[@sirbow2]

I just went through the hell of adjusting the fuel level on 4 carbs for my kawasaki. If it's not right, it'll cause all sorts of issues. In my case the level was so far off on some carbs that the idle jets weren't getting any fuel and the bike wouldn't start. Stick some clear tube on your bowl drain and use that to see the actual fuel level in the bowl. The service manual should give some sort of fuel level line. Like this: ww2-secure.justanswer.com/uploads/jpolicky/2011-03-14_032414_2009-07-19_032627_fuel_level_adjustment.jpeg

[@HouseofDavidMC]

Jordan Liske awesome info. I'll give it a look 😉

[@revivemotorcycles]

The gn250 carb has no screw to bleed access to overflow, just a dump screw

[@CalbardLog]

please what size is stock carb for gn 250

[@JORGE0204]

que filtro de aire le pusiste ?

[@leonardogoulandris1676]

Hi again, when you installed the new air filter, what did you do with the hose for the engine fumes that was going to the old air filter?

[@HouseofDavidMC]

i just left it off. Please forgive me, Mother Nature :)

[@suttlesid1639]

put a crank case filter on it it will make sure that if any air comes back through it will be clean

[@aaishameen7439]

Is the gn 125 very different from the 250

[@HouseofDavidMC]

Aaish Ameen the carb will be smaller on the GN125

[@periklis1994ify]

what numbers are your jets?

[@HouseofDavidMC]

I added a link in the description to the owners manual. Check it out for all the carb info! I only changed the Main jet to 132.5

[@josequins9099]

I get the names of parts wrong all the time. Often it's just the "thingee".

[@kaleelurrahaman1882]

Very annoying and unnecessary music