DIY Carburetor Synchronize / Balance Tool

[@peterhiggs3862]

After 56 years of motorcycling, I finally got a twin cylinder bike... Looks like I need two plastic bottles now. Thanks for the video..

[@SevenSinsMC]

Hey Mike, Thanks for the info! I built mine using sauce jars and some $5 tube from Home Depot. She runs better than ever!! I will try to remember to post a pic later! THIS WORKS, PEOPLE!!!!!

[@Chris_KS5KY]

Mike, I thought I had an idea on syncing carbs before I watch your video...I had no clue. The way you explained it is flawless and well enough that anyone could do it and you took the fear out that I had that I would mess something up. Thank you. I can't wait to try it and see how well both my bikes run afterwards.

[@padrote2865]

The sync he is talking about @ 6:30 is a bench sync (you set the slides so they open at the same time so that each carburetor lets in the same amount of air into its chamber). The other sync is vacuum sync...that's where the plastic bottles are used.

[@ruikazane5123]

Bench sync first before vacuum. Bench sync is a good point to start first, and can be done without much tools. Vacuum sync needs balancing each carburetor in order to have the same air pressure(negative pressure) on each of the cylinders. Valve clearances are better to be set first before even thinking of syncing them, but, that is not the case.

[@gregorytimmons4777]

@@ruikazane5123 Yeah, not here on a 2 stroke.

[@justanothernoobe]

mate that was really helpful … and nice to see a home-made method that blows away all those claims that you need to spend hundred bucks on a special tool! Thanks for taking the time to share that :)

[@haazimkhalid8087]

Hey man...I know this is a very old video but I tried this and it worked!....I have a Honda CB125 super dream that I bored out to 250cc...it ripps !....but I had issues with the dialing in both the idle screws perfectly....I was looking at getting a carb sync meter but it's expensive!...and this worked perfect...my bike pers like a kitten....although I must point out that I failed at my first attempt using cheap plastic bottles...the bottles sucked in on themselves for the pressure...so I used small glass Jars that come with a metal cap...thanks man !

[@Scoutsixty]

That is the best damn tutorial I've seen yet! Great job! It is so simple yet so important. Again, great job!

[@Mikeandwendy74]

thanks, I appreciate that and try to pass the info along the best I can

[@wheelervilleoutlaw326]

Jonathan Williams

[@doricdave]

As someone else said, I used two water bottles and the vacuum suckes them in completely and drew water into the carbs!! Use firm plastic or glass bottles/jars!

[@smguser7110]

Very mechanically inclined, creative, and I really liked the explanations. The accent was awesome!! Thanks for a great video!

[@adamskinner5868]

Excellent, followed what u were saying and it all made sense and I learned something. Before I always thought balancing the carbs on my old Honda was beyond me, some tricky magic I'd have to get someone else to sort, so thanks a lot to you and youtube, well worth watching.

[@christopherjholland]

Cool Video. I need to attempt this for my 3 cylinder XT snowmobile. The slides are totally wrong, so your video really helped me to figure that out. Thanks

[@eckeldave]

Nice homemade manometer. FYI: If you bleed the air from that short transfer tube between the bottles, you'll be able to dial it in perfectly level across the bottles. Now I've got to add a third bottle to make it work for a triple!

[@TheHijglander]

Thanks for sharing this build! The one I made works great on a BMW R1200GS from 2009.

[@sped105]

Three and a half minutes in and I'm already giving it a like. Thanks for your time.

[@robertstovall7195]

I like your workbench with the round tool holders

[@BMJAUDI]

Those are beer holders

[@Michael-rh7ie]

Great easy to follow video ,love the milk crate vac bottle stand- nice and stable.

[@selwynprice2023]

This is a great idea, if I could suggest using strong bottles ( Glass) as my plastic bottle rig just collapsed. I have a 1000cc motor which obviously creates lots of vacuum.

[@le7decav]

That's very CLEVER . Congratulations. From France.

[@CHIBA280CRV]

That is a excellent homemade tool and lesson . Thank you for sharing...

[@colinthomasson3948]

Great help, the narrower the bottles, the more sensitive the gauge response, I think

[@Alf-Garnish]

very informative, clearly explained, i now know the diff between Balancing & Synchronization.

[@deniscortes9200]

OH YES INDEED, IT WAS HELPFUL. WHAT A "SIMPLE" WAY TO FLOW BALANCE MULTIPLE NORMALLY ASPIRATED CARBURATORS. NOW MY HS-4 SUs ARE CONDEMNED TO BE IN BALANCE. THANKS.

[@allensnook7760]

This is what i was hoping to find,easy simple method of getting both carbs in unison,thanks ill be ready for snow.snooky pa.

[@gvrose1]

That's a very cool method to balance the carbs. Thanks for posting! PS,. Inexpensive as well!

[@vincehowell1956]

This is very good. Just advice on setting up the carbs before using the balancing tool was enough to get my guzzi behaving it's self . Thank you

[@dalemicallef9292]

Great idea and I'm sure it will work perfectly when I get some stronger bottles. The ones I used were fairly thin plastic and instantly collapsed as soon as I started the engine... DOH!

[@jake_break9185]

😆. had a Homer moment "Doh!". lol

[@dalemicallef9292]

@@jake_break9185 not kidding. Moment of panic as I watched the water being sucked into the carbs 😨. My Mk2 version used plastic beakers with rubber sealed clip on tops. Works a charm 👍🏻.

[@snuffelsuf]

love old school diy videos...this is tops!

[@islandrider91]

I am going to start building one of these set ups to have on hand for my sled! great video 👍👍

[@Born_Stellar]

While most of this is way different than my dual zenith carbs, I think that bottle sync tool will really help! Thanks!

[@bryans8193]

Could you also make a video on how you actually go about syncing the carb slides with the drill bits? That would be great!

[@allensnook7760]

Me too i got lost on that step,snooky.pa.

[@OutbackOntario]

great video! thank you, but the idle screws only lift the slider, as soon as you rev the engine its all up to the throttle cable slack.. so your just really fine tuning the idle balance, but this method works well for fine tuning the throttle cables

[@bobflyman]

Just made one of these, good idea. But the vacuum on my 1978 Honda CX500 sucked and collapsed the plastic bottles both sides. I'd been careful not to put too much water in but the collapse squeezed the contents, it got near the top of the bottle on one side and started to suck water into one cylinder. Use strong heavy plastic bottles.

[@jake_break9185]

Looks like he uses Gatorade bottles or poweraid should be the same 👍🏻

[@airric166]

Great job explaining in great detail to make it simple to understand.

[@dumpsterfire6351]

Gangster ! Saved me buying that $120 carb sync tool 🤜🤛

[@camgreer]

Very nice info. Thanks a lot. This will save me some money for sure.

[@forreststump11]

cool. I will have to try that sometime just to see how accurate it is, and then use vacum gauges to check.

[@mastershake156]

How did it go?

[@dilbone1]

Great little tool here. I have a manometer setup that I've used to sync carbs for quite a while and I use transmission fluid in it just in case it gets pulled into the carb so no harm would be done...but this idea is great. One thing though. You DO want the level of fluid in each bottle to be at the same height for the carbs to be perfectly sync'd. If one bottle has a level higher than the other then that carb is pulling more vacuum. It's not about stopping the levels from moving up or down, it's about the level of fluid being exactly the same in each bottle. If you have 1" of liquid in one bottle and 4" of liquid in the other when the levels finally stop rising/falling, then you are extremely out of balance.

[@ledbetter1226]

That's actually incorrect, the level of fluid is irrelevant. All that matters is that both Carbs are pulling the same vacuum, if both are pulling the same vacuum then no fluid will travel between the bottles because the vacuum from each carb is cancelling the other out. So regardless of the level of fluid, if the fluid isn't transferring to another bottle then the vacuum is the same and your carbs and synced.

[@dilbone1]

@@ledbetter1226 With all due respect, then I'm not sure you know how a manometer works. Different levels precisely means there are different pressures involved. That is exactly what a manometer does. Now, does a slightly different liquid level mean there is very much difference in pressure? No, but none the less, there is a pressure difference if the levels aren't the same. The one with the higher liquid level has less pressure, thus the liquid is "pulled" up to a higher potential plane...or rather pushed up by the higher pressure on the other side. I would say that "perfectly" tuned means equal levels. "Close enough" is levels not continuing to move.

[@bobnewton6377]

Hi @@dilbone1 this system is not acting like a manometer, and so the principles are different. Manometers have a single liquid mass in a uniform U-shape tube with one end closed. They are initially calibrated for a specific purpose and then relative measurements are taken. External pressure verses the internal pressure of the sealed end of the system changes the height of the liquid in the tube. The system in this video has two separated liqid masses connected by a tube, where by the height of the liquid in one vessel has no impact on the height of the liquid in the other. A pressure difference will initiate a transfer of liquid, as both ends of the liquid transfer tube are at the same height, i.e. the bottom of the bottle. They only variator in this system is air pressure above the liquid surfaces in the bottles, as generated by the engines twin cylinders. That being said, I think I agree with one of the above comments, that this will only balance the carbs for idle only. As soon as you twist the throttle the slack is taken up in the throttle cable, you are off idle and the idle screw position plays no further roll in regulating the balance of the system. So the best you can hope for is maybe better slow traffic. Close to and coming off idle improvements in smoother very low speed running.

[@dilbone1]

​@bobnewton6377 I'm not calling his set up a manometer. What I use is a manometer. Syncing the carbs at idle means they have the same start point. Since they are linked mechanically I'm not sure why you're saying they would unsync off idle. However, one could certainly check balance at off idle RPM if so desired. I don't think I'd trust this set up for syncing carbs myself. I don't see it being sensitive enough

[@bobnewton6377]

Hi. Thanks for your reply. If you read carefully I did not say they would unsinc, just that the noticeable improvement would only show at, or just coming off, idle. I hope that makes sense. 😊

[@TimHaunFishing]

Excellent video man, I really appreciate it. On a side note though, that poor pool table xD

[@danielblanton7920]

Eventually all pool tables in your basement become work benches; not sorry.

[@michiel1362]

Well at least put a insert plate / board on the felt?

[@Lucas-vk8fz]

Awesome explanation..gonna try this tonight..thanks

[@MrNightpwner]

This video is gold. So the point is to have fluid level equal at idle?

[@Mikeandwendy74]

correct if thats what your after, I have many vehicles some with twin carbs, some with 4, my 4 carb bike wants to be synced at 3500 rpm due to engine vibration, but most vehicles, motorcycles, snowmobiles definitely want to be synced at idle.

[@minibikedude04]

Mike OD always check the service manual for your engine. My 1981 Honda CM400C says to perform the carb sync at 1200 (+/- 100) RPM. The guys who built your engine knew what they were doing!

[@Rustbox306]

MrNightpwner No, not the fluid level, the fluid level change rate null so neither bottle sucks from the other : level does not matter.

[@johnpeterson7245]

MrNightpwner @d

[@BillMiller43]

Good explaination, I'll build one. Have always done at night comparing exhaust port flames. On my motorcycles. Drill bits on boat carbs or where I didn't want to remove exhause.

[@jake_break9185]

you would fire engine up without exhaust manifold attached to head? 😮

[@calvinmientke3539]

I built one with four inputs for my 650 Maxim and it worked great. THEN I left it in my Wisconsin garage over winter. Froze, broke, start over. Hint...empty the jars! Don't freeze!

[@nicmiller8662]

Excellent video. I have one question do you think it would work if instead of using 1/4 inch fuel line to the carbs then converting them to fit the primer, if i just used primer lines all the way from the carbs to the bottles would it still work? I think it’d be easier than converting a 1/4 line to the primer

[@lttanguay]

Dude, you are a genius!

[@allensnook7760]

That was so easy to comprehend others make it seem complicated.thanks.snookie pa.

[@IamDaytrader]

I built 4 carb setup 20 years ago simple balance vacuum hose on a flat board using motor oil as the gauge. Never sucked anything the gauge is 4 feet tall with another 6 feet of vacuum hose

[@sheldonkary8374]

This seems to me to do nothing to balance the carbs through throttle range. Yes, they will be balanced at idle, but as soon as throttle is moved they will be back to where they were when they were synced using the cable adjustment.

[@daleerickson520]

lol, so I made one with plastic bottles as it shows in this video. The vacuum from my engine crushed them!!! FYI, USE GLASS BOTTLES!!! My ver 2.0 worked fine :)

[@seancashin3210]

WELL DONE! I have a corvair with dual rochesters. Ive seen the $45.00 tool that you set on top of the carbs after removing the air filters for balancing them. Would I need to make something to sit on top of these carbs?...no, because that would choke off the air right?...where do I hook up the tubes on my carbs?

[@CrackedHeadsMusic]

I didn't know Robert De'Niro made instructional videos.

[@danw5157]

LOL You talking to me???? I;m the only one here.... You talking to me????

[@Royalbigness]

Sounds nothing like him bro

[@rkaraidos]

Nice

[@youronlytruth]

Ha I was thinking this too!

[@ktmgsxr1]

That funny! Your so right! Lol

[@pauloisidoro2]

Thanks for the tutorial I will try this with my twin su carbs (MGB)

[@Mikeandwendy74]

use glass bottles snapple bottles they hold up alot better with rubber stoppers for the caps, they will work o n all engines

[@NickLiftsNude]

This is a great video , thanks for the help. This is been the part that been scaring me about rebuilding my mikuni 38mm yamaha triple carb. getting everything balanced and synched seems to be what everyone has the most trouble with. In this video you explained how the sync the "low" or idle screws. do you imagine doing the same thing with the "high" or open throttle screws?

[@bryans8193]

Thanks for the info and great video by the way!

[@Mikeandwendy74]

Your welcome and thanks

[@patrickjordan5619]

Thanks sir for your video. Really helpful!

[@George-ie1si]

Great work bench you have.

[@davidanderson1763]

I like your explanation of how to adjust your carbs. I have an XLT triple. how would I build it (balancer) for a 3 cylinder?

[@Mikeandwendy74]

I would hook up # 1 and # 2, balance them, then remove #1 and hook it to # 3, then balance # 3 to # 2 without adjusting number 2, only make adjustment to # 3 carb. Thats exactly how I balance my 4 motorcycle carbs, 3 is just as easy as 2

[@davidanderson1763]

I was kind of thinking the same way. Thank you.

[@underdogontheappalachiantr9646]

On my 3 cylinder mercury. I was thinking to hook up 2 and 3 and synchronize 2 with 3. Then hooking up 1 and 2 and sychronizing 1 to 2. Since if you mess with three it affects both one and two.. would this be correct

[@ArcticJeff]

Very helpful, thank you for posting this video.

[@georgemooyman7155]

Great work bench.

[@twoeightythreez]

You can add 2 more bottles inline with the hoses to carbs which will ensure you cant suck water into the engine

[@weeverob]

i used Gatorade plastic bottles for syncing my xs650. the vacuum coming off the carbs crushed the bottles like King Kong was sucking on the hoses. will remake this manometer using glass bottles.

[@michael_vl]

Very nice tutorial! Is there a way that ican use this when my carbs dont have a vacuum?

[@jasonkimmel3061]

Great video! I wish I knew this forever ago

[@christianlebreton9857]

HI..i have 93 jaz Z...there no..primer plug, just the manual choke..where do I plug the hose to have the same result...tks

[@NickLiftsNude]

this is what I have my in mikuni triple. I have not done this yet however the primer kits are sold to take out the butterfly for the choke u can use those holes

[@josipbroz5434]

Great tutorial. Thank you

[@resodziadzu]

If the hose connecting the two bottles is filled with water, the two levels in the bottles should eventually equalize (without the device connected to an engine)

[@paulb4777]

Brilliant video - thank you for sharing

[@danielbelanger8444]

I'm converting my Triumph TR6 2.5L 6cyl to Mikuni HSR 45's. I love your video and assume this same technique will work the same way. Right?

[@jameshurdle2046]

So what would happen if one of the hoses that connected to the vacuume port of the front intake sucked water into the engine not alot but some

[@CreatorCade]

I may have to try this myself when I put dual carbs on my car.

[@MBTUE]

Very good video, thanks. I was wondering about the primer nipple. On my sled, for some reason there is a lever style choke ( like yours) it's a Polaris and the lever was stock and the previous owner put a primer on. I removed the primer and the lines going to the primer nipples on the carbs. What should I do with the open primer nipple? Should I plug it? Or connect the two nipples with a hose? I'm not really sure. Any ideas ? Mark

[@DeseretRider]

I agree with the principle here----He has gone to great pains to avoid sucking liquid into the carbs----but at the sacrifice of an awful lot of precision in setting the sync. This would not work well on syncing motorcycle carbs or injectors---which are synced to reduced engine vibration which 'puts your hands to sleep' Just using a plain old manometer would work better and produce a more accurate sync

[@yveskc1]

Thanks for sharing, helpfull tips.

[@FourthWayRanch]

I tried it, either it didn't work or my carbs were already synced. Can you get good enough vac from the oil injection fittings?

[@LACARRINDANGA]

Hi Mike. Thanks for your excellent explanation. Would this method be usefull for a yamaha rd 400 ? it has 2 mikuni`s 29. I wonder if i can use the lubrication nipple (where the oil tank from premix is connected to the carb), because it doesnt have a primer nipple. thanks

[@haxto1]

No! DON'T do it. These bikes are ruined at this point. BUT! Good news, I will gladly purchase that old RD from you to that you don't waste any more of your time on it. Contact me to make arrangements to get rid of that Yamaha RD 400!

[@bradleymoyer5236]

My bike has 4 carbs. Can I just add 2 more bottles to the operation I assume? I dont feel like spending 1t0 dollars for a tool

[@wecksell]

I think that would work, if you connect them correctly.

[@MrHanowski]

Suggest defining SYNC vs BALANCE at the start, then stay consistent with the terminology. Otherwise it's confusing. What is the purpose of meticulously syncing both barbs first, then readjusting (during balance phase) with idle screws? I assume you pick the idle RPM you want by adjusting both idle screws until vacuum is balanced and you get the RPM you want? So when done, vacuum is balanced and carbs are no longer physically in sync?

[@gorillaau]

What about if you have more than two cylinders? Three cylinder engines seems tricky.

[@gorillaau]

From other videos, you can have the bottom tubes connected, 1 to 2, 2 to 3, finally 3 to 1. Just add more bottles for extra cylinders.

[@tammybatdorff9201]

so lets say after carbs are synced iam fat at take off? turn both screws leaner or drop my pin

[@Mikeandwendy74]

the air mixture screws only affect idle and 1/8 throttle, if you crank the throttle and your running rich, raise the clip on your needle, effectively dropping the needle into the main jet deeper.

[@tammybatdorff9201]

Thanks. I will try that.

[@trondwell13]

WHILST KEEPING AN EYE on the state of your plugs - as if they run hotter (leaner) you can burn though pistons....keep checking the colour and try to get it right on pilot jets first before going to the needles.......also bear in mind needles affect 1/2 throttle to full throttle

[@bryans8193]

I have a 1989 ski doo with the mikuni vm34 carbs. The carbs have two vent tubes one on each side that hang down plus the nipple for the primer. As far as balancing with the bottle setup do I still hook them up to the primer nipple??

[@Mikeandwendy74]

the vent tubes are overflow tubes in case your float needle sticks open and allows too much gas to enter the fuel bowl. On the mikuni vm34's I would absolutely use the primer nipple to balance the carbs. The primer nipple gives you straight engine vacuum.

[@billhershkowitz5759]

Should this work on a Corvair with a dual-carburetor engine? Many Corvair owners use a "Uni-Syn" device which seems to accomplish the same thing as this tool.

[@ryanbachynski9115]

When you are balancing them what RPM are you looking for on the TAC? Because you could balance them but be idling too high or too low, correct? So you want to balance them at the proper RPMs, right?

[@madsthomsen9844]

Really great video! :)

[@georgemccaulley1648]

great videos thanks for the info.

[@felixstith1319]

what is that green hose attached to that jet on the left hand side of the carb for?

[@EitriBrokkr]

Primer

[@thegreekguyviva-greece5881]

dual carbs on car engine, common sense says use the always has vacuum port, do you think this will work on a car with this size bottles? I gotta try this shit today! !!!

[@johnchristensen3030]

has to be more accurate than gauges. BTW, 320 grit sand paper will clean up those callouses on your wrench fingers

[@omnirogue1]

awesome vid THX for making it

[@wtbofnc7880]

thanks so much for doing this video

[@128Farghal]

you are brilliant man!

[@andrewfritz5123]

What about for a 3 cylinder?

[@Rickengle300]

Just do two, sync em up.. then take one hose off one of the already synced carbs and move it to the one that you haven’t done yet.. now balance the third carb by adjusting only the 3rd carb to match the already synced carb

[@LiviuXSA]

but doesnt it make sense to balance them at cruising rpm like 4k or 5k revs, so you dont get vibration when riding on the road at speed, instead if you balance them at idle it'll idle great but there will be big vibration at high rpm

[@gregwlotzka120]

Thanks for the tutorial

[@samanpriyantha1763]

Excellent video.Thanks for your explanation.My bike Yamaha FZR 250. i cleaned my mikuni carburator (4) and cleaned main jet,pilot jet and adjust air mixture screw 2.5 turns out from the closing point.My problem is 3 times failed my eco (smoke) test and result show more petrol consumption.but last years without cleaning my carburator, easily pass the eco test.My problem is need to reduce petrol.I need lean mixture.If i synchronizing my 4 carburators,what will happened?How can i adjust?please help.Thanks

[@killer2600]

Depends on how far out of sync they are. It'll definitely make the bike run smoother to have them them in perfect sync. The mixture screws have more of an impact on fuel mixture but dialing in the mixture depends on a properly functioning bike and carbs which includes synchronized carbs.

[@trondwell13]

do a compression test as you may be passing oil past the rings etc......AND go for a one hour drive before going in for the test......nothing on the carbs will affect MPG - the only thing that will is attached to your right wrist

[@kenmontgomery287]

Big help. Thank you!

[@weeverob]

i used the plastic gator-aid bottles and the vacuum off the bike collapsed the 2 bottles like they were nothing. replaced the bottles with glass.

[@joshballard7431]

I have a 1400 motorcycle with two carbs I just rebuilt should this tutorial work for me?

[@wilmersegarra1574]

I'll imagine, that you will need to add the same exact amount of liquid in each bottle to be able to use this as intended right?

[@SaneAsylum]

Nope. The tube that goes into both bottles will equalize the level when the carbs are playing nicely and sharing.

[@tonylou1234]

Ingenious! Thanks.

[@NoOne-pj9hw]

How do u do a 3 carb set up with the bottles

[@michaelcorona1418]

How is this the most useful video to sync carbs in 2021