I made a Carb Cleaning Video that's fun? 1979 Honda CB750F DOHC
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- čas přidán 29. 06. 2024
- We're kicking off a new project by starting with one of the most annoying projects - CARBS! They are for a 1979 Honda CB750F Supersport that we've nicknamed 'The SportBobCruiser' It's missing a lot of parts, but to start, we want to hear the motor run before going any further on this project. That means cleaning carbs that haven't been apart in years.
Thing is, few people want to watch carbs getting rebuilt, not even the guy doing the work, so we try and make this video interesting. It is meant to show some of the trickier parts of the process and should be used with the PDF linked below.
Super Detailed How-To PDF HERE: www.cb750c.com/publicdocs/Sea...
Want to see more of the Custom BMW R90/6 Project? Check out the playlist here:
• BMW R90/6 Custom build
I'm on Instagram @roodlum / roodlum - Auta a dopravní prostředky
Sooo what's going on with the bike now?
So this was a buddies' bike - he eventually traded it for a different one. ¯\_(ツ)_/¯ It wasn't the first dohc cb750 to come through my workshop and it won't be the last, though
@@roodlum ok cool cool, very well made video! I was looking forward to the next bit. I'm getting an 81 cb750f up and running right now myself
Thanks! If you'd like some inspiration, I just put up some photos on instagram of the last dohc cb I did, back in 2019. instagram.com/p/CofPSPZjJQ5/
You’re cool. I’d be your friend 🖖🏼.
Help my 750 cb carbs had a small washer and rubber under on of the jets in the inside
Thanks so much for making this. Ive cleaned so many carbs in my life but have lost motivation for 4 cylinders and you brought it back. I have a 1979 CB750K that has everything it came off the showroom floor with. Cleaning the carbs right now and trying to get it running by the end of this month for the Woodward Dream Cruise here in the motor city
A good video and an excellent PDF, as it contains the correct way to do all the things that most people get wrong. (Like getting the mixture screw O ring and washer the wrong way round for one).
The detail on how to get choke mechanism assembled and that annoying choke spring in correctly is another point that's very clearly written.
The only thing I would say is that it's a good idea to grind or file the tips of the choke flap retaining screws off before removing the screws. I've seen many of these carbs where one or more of the screws has been peened over excessively at the factory, and would almost certainly strip the thread in the mounting bar if removal was attempted without grinding the tip off. In the past I've had to fit M3 helicoils to these and it's a 'fiddle' one can do without.
I've just built a set of these for a 1981 750KZ from the original carbs which had been partly buggered up by someone who didn't know what he was doing, and a secondhand set my customer purchased. Why there are so many differences between carbs beats me. The original carbs had adjustable floats and fixed pilot jets, and the used set had fixed floats and removable pilot jets. I used the adjustable floats in the new bodies with the removable pilot jets. Worked like a charm.
All the best.
This helped me alot.
Quick enough to not loose focus and instructive enough for me to reassembly all the springs and orings
Thanks for the vid
Bought a 1979 Honda CB 750K two years ago. Running not too well but enough to get it home. Seven degrees Celcius. Poor idle but good acceleration. Took the carbs off, cleaned them out as best I could without disassembling them all. Put them back on, bike ran like crap. Took the carbs off again and cleaned them again, put them back on, bike ran like crap. Cleaned out the gas tank and cleaned the carbs one more time, WITHOUT REMOVING THEM FROM THE BIKE. Replaced the ignition wires and spark plugs. Now she pulls 9500 RPM, and idles at 900 or lower. The carbs can actually be cleaned quite thoroughly without removing them from the machine. Did it, was successful and have owned 12 motorcycles over 51 years
I'm happy to hear that! I have them off the bike but I don't really want to rebuild them fully because I'm new to all this. Just want to clean them enough for the bike to run smoothly. One of the cylinders isn't working but compression and spark is fine so I believe the culprit lies in the carb #2.
Thanks for the PDF file, & the clear images on it. My small choke spring jumped off of the carburetor 1-2 rod & I didn't see where it was attached. So I put 1/2 & 3/4 carburetors back together & rewound the small spring after all was said & done.
Nice video! You make it look so easy! Thanks for the step-by-step instructions!😎👍
Just discovered your channel. For this genre, you are the best, hands down.
Great video! Exactly what I was looking for, especially that little washer on the fuel screw! Getting ready to tackle the re-linking
Best video I've seen on cleaning these carbs. Thanks!
nice video right to the point with details great job
I literally bought for me -80 cb750 3 days a go, and today opened carbs first time! Thanks for vid, (instant sub) and I will stay tuned for more vids to come:)
Welcome aboard! Glad you found it useful!
Thank you! Very helpful and easy to follow
Your video is excellent. But the detailed PDF is out of this world. Thanks so much for sharing this content. 👌🏻👌🏻
I'm rebuilding a set of carbs for an 82 CB750 that unfortunately arrived to me already 100% disassembled.
Trying to figure out all the throttle/choke shafts and linkage between the middle 2 carbs has been a spring loaded nightmare.
Just a few screen shots from this vid totally solved the one part I couldn't figure out because it appears my tabs were bent out of position.
Months later this gem is still helping folks, thanks again!!!
ah haha happy to be of service!
dude, this video saved me and my project. you easily earned the sub
You're chill as hell.
Excellent I have a 1979, and an 81 DOHC CB 750 - originals - not chopped - I have rebuilt carbs and will enjoy your vid - thanks for making it !
Great work!
This video is awesome! So detailed and informative, thanks for making this.
Glad it helped :)
you really did make it easy, thank you!
I am going to clean the carbs for my 77 CB750F SS. I think i will also take smart photo's of everything when disassembling just as a backup. It looks like it can get kinda complicated.
That was very cool.
I picked up a 1982 nighthawk cb750sc with the same carbs as the bike in this video. It had been "sitting in storage for 10 years" but only has 13,680 miles on the odometer. I spent so much time meticulously tearing down, cleaning, and reassembling these carbs. Put the rack back on the bike and synced the carbs. Took the bike for a ride around the block, parked in the driveway, shut it off, and all 4 carbs immediately start flooding. My joy turned immediately to frustration. 4 new floats, needles, and pins are ordered but I'm not looking forward to pulling the carbs, replacing the parts, and syncing them again. I've had more trouble with these carbs than any other set I've ever worked on and I've had trouble finding parts for them but after this everything inside the carbs (except the slides) will be new
Great video man!!! thank you so much !! subscribed !!
Gracias . Logre armarlo por tu video.😄👍👍👍👍
This is an awesome video man! Thank god you have this pdf as well. I couldn't find an super detailed manuals. This def saved me! Where did you get the carb rebuild kit from?
Awesome T-shirt design 👍
Thanks! Made it myself :)
Great video this helped me out a lot with my old CB.
Btw- at 10:23 I believe you inserted the choke link into the wrong spot on the return lever 😅 I had it all together before I realized the choke plate would not return..
..unless the '80 cb750c is different!
Great Video, where did you get the carb kit ? I need one for my CB900F
great video, just one question: are the mixture screws air or fuel screws? does turning them out make the carb richer or leaner? thanks a lot
hey man great video! do you know where to get floats for these carbs? mine are cracked
My 1981 Cb900c has issues. It has the same carbs and I cleaned them decoupled them and all that. I don’t think I have vacuum leaks in any of the boots but it seems to have one near the crank case breather hoses if that’s possible. Either way I ride it for a minute, it gets all warmed up then when I pull In the clutch it’s revving at 5,000rpm 😑if I rev it a couple times it SLOWLY goes down to around 1,500rpm. I am just lost, I put in a new starter clutch bearing and the timing advance all looked mint and the spring functioned well. It only happens when the clutch is pulled in or in neutral. I have adjusted the idle as I go and it still happens.
Nice video and amazing pdf ty 🙏🏼 where did u get the rebuild kit want to get a quality kit
Rebuild kitrs are all over the internet. If you want a "quality" one they are VERY expensive. If you want a sufficent one, not very expensive. eBay, Amazon, etc. All over.
Hi, nice video. What is the liquid in the ultrasonic and the spray you used? Going to give this a shot. Wish me luck. Will be on my first bike, never touched one ever besides msf training. But if I can build a Wiped film evaporator I’m sure I can do this 😅
Hey thanks! The ultrasonic just uses water with a little degreaser in it. I use something called 'Purple Power' as it doesn't react to the aluminum of the carburetors. Simple Green will oxidize the metal if left in too long. The aerosol can is called carburetor cleaner, which you can pick up at pretty much any auto parts store. You got this!
Do you know where to get a carb rebuild kit? I’ve ordered two now and they’ve both been wrong. A link would be super helpful!
Great video, brother, helped a lot! Could you tell me where that sneaky spring ejects from? You mentioned to watch for it but i’ve since forgotten where they “spring” off of lol
If you mean the ones that are in between the carbs, they get sandwiched between the throttle plates (where the adjustment screws are) I assume they help keep the throttles synchronized. Hope that helps!
@@roodlum perfect thank you!!
i just got a 89 fzr600 from my friend and one of the float seats in one of the carburetors is broken, i have no idea where to get a new one, and i have looked online for about an hour, are you able to put more modern floats in a carb or does it have to be that specific model
two questions -thanks; !- at 1:19 and that you are holding in 1:22 - where the fuel hose connects to the carb assembly the overflow occurs when parked. And my engine seems to behave if running on 3 cylinders or running on less gas ( similar to going to reserve on the highway) and then full power returns intermittently. I added Gumout. 2- the Black hose from below where does it connect to as seeing in many pictures it connects back to the assembly but not sure where. - thanks !
Looking forward to seeing what you do with the foot controls. I have a UK 81 750k which has the same setup and I'm pretty sure there isn't anything off the shelf that fits to sort the rear brake pivot as it pivots off the aluminium part which you'd want to get rid of
Thanks! I do believe our plan is to machine a new aluminum block to replace the oem peg mounts
@@roodlum interesting! As a budget option, I was thinking of moving the peg locations, adjusting the foot pedal and trimming them down to look nice. You'll probably cross that bridge before I have to do mine so I'll use you for inspiration 😂👍
So.. this video helped me soooo much , thank you. I was curious though, where does the vent tube plug in to? When I took mine out, it was tracking back over my airbox but went under the frame and now I'm scratching my head as to where it went. The tube that comes out the center of the 4 carbs after the T. Please give me some insight.
That tube just runs to open air, but there's a clip on the top airbox mount to hold it in place, if I recall correctly.
@@roodlum perfect! Thank you soo much, I got it locked into that lil j hook and it's tucked behind the snorkel. Good?
I rebuilt my carbs 2 years ago using this video. When I first rebuilt, the bike would start immediately when warm. Now it struggles a little bit. I’m thinking reset the idle mixture. I don’t remember how many turns out. Any suggestions
I must be strange because I love cleaning & rebuilding carbies 😂
I honestly think the worst part is getting the carbs back into place on the bike! Otherwise it's pretty satisfying seeing the parts get nice and clean again
Thanks for the video! have you had any discrepancy with float level? Manual says 15.5mm but mine are around 26mm and won't come close to 15....
I'd check to see if the float is on upside down with that much of a discrepancy. 15.5mm should be the correct height.
Could you suggest a good place to buy a rebuild kit ?
I have these carbs and 1 keeps leaking out of the float bowl. I have taken them apart replaced the float needle it worked ok for 2 rides now the same one is leaking again. I added a fuel filter to. Is it common for the plastic floats to go bad on these?
Do you have any more vids for this cb750 build? Other than @andymechanic your last video was VERY thorough. No one does it like you 2. Keep it going!
Unfortunately my buddy who owns this bike decided to go a different direction! Thanks for the kind words.
@@roodlum damn that sucks, what did he do with it? Sell it? And what solution did you put in the ultrasonic cleaner?
I have a set of carburetors that are VB 52BXXX designated, that I'm trying to rebuild, from a late 70's early 80's CB 750 machine. I think I'm OK with sourcing the repair kits for them, but I have a broken float bowl which needs replacing. I believe they are the same as the 42 A carb' bowls, but don't know for sure. Can you shed any light on my issue and confirm if the 42 and 52 bowls are interchangeable ? Much appreciated if you can get back to me. Will definitely be using your video and detailed Pdf as my rebuild guide.
That's a good question, I think you're correct, but I'm not completely certain. I know the float bowl gasket is the same for all 79-82 models but the float itself changed after 79. The part number for the float bowls do appear to be the same across the different models of 79-82 CB750 F, K and C
Quick question. Where does the random little spring go when you seperated the carbs go? Thanks
Sorry for the late reply - but those go between the throttle linkages.
Can you tell me what you soaked the little rubber parts In to recondition them?
It's called wintergreen oil, a small bottle will go a long way. (don't touch it with bare skin)
Should have watched this first. No other carb disassembly video I've watched shows how to seperate each individual carb via the choke plate
How many gallons is that ultrasonic cleaner? I'm looking to clean my carbs in an ultrasonic cleaner, but I'm not sure if I should go with big cleaners.
It's 2.5 liters. It's juuust big enough to do one carb at a time. Since I made this video I've upgraded to a 22l unit that can handle four carbs at once, but for occasional use a small one like in the video is just fine.
My carburetors had a rubber and washer under one of the jets ??can't remember where
Hey Rich, hope you see this - I’m cleaning some CB carbs right now and I would really appreciate an answer to 2 quick questions - i don’t want to mess them up.
what frequency does your ultrasonic cleaner run at?
What cleaning solution do you use?
I tested it on a non critical part, and I’m seeing aluminum oxide on it a day later.
I've since replaced that harbor freight unit with a larger 22L cleaner, that one operates at 40Khz. I found that simple green will cause oxidation like what you've found, but water with a little Purple Power seems to work well. I always make sure to rinse the parts off after the bath, and to blow them out with compressed air.
@@roodlum ah! I’ll add purple power to the list. I have some purple simple green, and air craft simple green as well. Plus a “carb safe ultrasonic cleaner” - doing a little testing. So far the air craft simple green (would make sense it’s safe for aluminum) works, just hasn’t gotten as much off as I’d hope.
Using distilled water too for a truly Ph neutral mixture.
What’s your mixture with water? 50/50?
@@roodlum one other question - the carb “slides” have that plastic bit at the top, opposite the needle. Is that ok in the cleaner?
…Actually, it did clean well, just needed a higher concentration of cleaning fluid. I’m at about a 1:8 ratio cleaner:water
The square peg in the accelerator pump cap fell out as well as a tiny spring and a ball bearing. Do they all go in the cap or are the spring and ball bearing unrelated?
The square peg is not supposed to come out... There is a spring yes, it goes between the cap and the diaphragm. There isn't supposed to be a ball bearing in there, but it could have been under the square peg.
@@roodlum thank you for confirming the spring haha from what I’ve read so far the ball covers the hole like a valve, the spring keeps it in place, and the square peg keeps all that in place. I could be wrong but it fit together so well I couldn’t think of a different way. I guess I’ll find out when I try to run the bike next!
Hi in Spring 2021 I rebuilt my CB750 Carbs. Today I almost added a fuel filter. I write to ask if you have done this and successfully -
This morning I deferred on the Universal Motorbike fuel Filter, that when delivered from AMNZ, look like it applied to a lawn mower. Its diameter and the internal diameter of its replacement rubber tubes where about half the size of what connects the petcock to the accelerator pump. I figured the Engine would starve for gas if used.
Then I saw a video of fuel filters leaking - OMG - they leak ? . . . . could you imagine having a leaky filter dripping top done on top of your hot engine?
Anyways, I got hit with a lot of gunk when putting Seafoam into the tank, ( Carb 4 float caused over flow 7 Carb 1 Idle Jet causing Backfire ) which I remedied as described below, but would like to find a proven CB750 Fuel Filter solution -
Thanks -
Remedy: As all is installed and had been operating okay since recent restoration, objective was to correct carb issues with out having to remove teardown, clean and restore once more -
Solution: Turn off the Petcock. Drain the fuel bowl in question - using the drain tube, insert long red nozzle from Carb and parts cleaner. Seal so back pressure cannot escape. Open the fuel bowl drain once more, and give it a few friendly squirts of the carb cleaner.
You are talking Engine Tank Gunk that needs to be dissolved -
Close Fuel Bowl Drain.
remove long red nozzle from fuel bowl drain tube -
Open Petcock.
Start Engine - it could require more treatments. My Carb 4 Over flow issue was corrected with one treatment. My Carb 1 back fire at Idle is almost extinguished with two -
What cleaning solution do you use in the ultra sonic cleaner?
Mostly water, with a little degreaser like simple green or purple power. Just have to rinse the parts afterwards as the cleaner will leave a residue.
At 3:01 you mention the vent tube, on my carb coming off of my 1981 CB650C it's a T connector? I've looked at diagrams and it has it on there too, but yours doesn't, I'm just curious as to if it needs to have the T joint to the tank or not between carbs 1/2 and 3/4?
There are slight differences between years and models (that's Honda for ya!) but I would say if you're keeping the tank, to keep the tubing factory as well. CV carbs behave badly when you start messing with their vacuum.
@@roodlum okay noted, so my tank say has rusted through, thought I could save it but I can literally flex half the tankby hand 😥 so hoping to get the same year tank but for a standard CB650 not the Custom or a CB900C tank, hoping they should bolt on with minor changes if any. Any ideas on that front? As a standard CB650C tank will cost me nearly £200 and STILL have a big dent and rust
Hey rich do you have 1973 Honda Cb 750 carb cleaning pdf manual thanks
Hola tengo problemas con el bendix. Se puede poner de otra moto?. Es caro el original acá.
Where did you get new choke butterfly screws?
They’re typical metric screws (m3 I think) so most hardware stores should carry them. Get plated or stainless ones so yours don’t rust.
I've got overflow tube leaks from carbs 2 & 3 after reassembly. I've polished the float valve seat but I also noticed that when I fully block the it, the fuel flows out of one of the two upper vent holes in the main carb body (not the bowl). So far only tested this in one of the carbs. Is this to be expected? Hopefully I didn't miss a step from your video.
That… doesn’t sound right. When the float valve closes, it should stop fuel flow. Are you sure it’s coming out of the vents and not the connections between carbs for the fuel rail?
@@roodlum That was (and still is!) my hope! I've got some video. Would love your opinion on what I'm actually looking at. Ok to link to it?
Here’s what it looks like with the bowl removed:
czcams.com/video/fyKSfDwUEYw/video.html
It’s hard to tell from that angle but I’m wondering if you might be missing an o-ring on the fuel rail tubes between carbs
@@roodlum Problem solved! I had my fuel connected to the vent T instead of the fuel T! Ouch! Thanks!
Nice videos what happened to the 79 CB
Thanks. It's currently torn down. We ended up 3d scanning the frame - interesting things ahead.
At 2:59 and 3:33 a spring pops out from between carbs 3-4 and 1-2... where the hell does that spring come from??
Those go in between the throttle linkages of the two carbs. See page 8 of the PDF linked in the video description.
Is this the same for the 80s cb750c?
It should be pretty similar for all the DOHC CB750 bikes, with a few small differences like some years having press fit jets.
I've had all the honda bikes 73 to 83
These carbs are a bitch to get running right I've got a 81 750k took carbs off cleaned them out set air fuel 2 1/2 turns out and its running hot only runs on choke and worse than it did.
What's my problem???
PS where are you from and what is the cost of doing the carbs like in video
I have a 82 Honda nighthawk would you be interested in buying it for 600 thank you
Winter green what!?
8:46 - 'find yourself some...' - what? I listened back a few times, can't catch it.
Thanks!
wintergreen oil. Sorry for mumbling!
@@roodlum thanks. I'd never heard of it, so I googled it. All I got was results for 'aromatherapy' and 'essential oils'. Is that the stuff??
Yes, same stuff though it might be diluted when packaged for that use. It's also called methyl salicylate, searching for that might be cheaper.
I have a 82 Honda Cb 900f super sport I need help I can let it sit started up runs fine Rev's fine and after a while it seems like it only burns on two or three cylinders like it's not getting enough fuel turn it off for a little bit turn it back on it runs and Rev's fine then acts like it runs out of gas or a miss what could be the problem it have gas come out the peacock carbs was clean beginning of Summer time
Shit fuck, maybe you can answer this for me. My car does not.. have the main jet but it does have the idle. The main looks to be a simple pressed it fitting that sits a half in to an inch down in the tube.. what can that be? There are also no threads to put the main even if I wanted to.
Some years did have press fit jets unfortunately. You can buy replacement press-fit jets, including larger/smaller ones for tuning, but I haven't actually done it myself. I do have a CB750 in the shop with these jets that needs tuning and I'm considering swapping the carbs to avoid headaches.
Subbed 🤌🤌
Not as detailed as I thought you do ie plastic floats have a tendency to be buckled which doesn’t leave the right height for cut off what was the height required , the felt on the choke bar to stop crap getting in. How to reseat the fuel valve to ensure good seal and many more details would have been good
This vid is really just meant to accompany the already exhaustive rebuild document I link in the description. I'm just showing off a couple of procedures that are tricky to explain in words and photo, particularly installing the various springs correctly.
This video is too fast slow it down so I can actually tell what's going on
I’m sorry to hear that, Mr. Turtle. You can try slowing down the playback speed option in the lower right hand corner of the video.
There was nothing fun about that video...carb cleaning has traumatised me as i know what’s ahead of splitting 4 of these babies right up to sync...worst part is trying to get rid of the spills...nightmare technology.🪓 Even when you get them running you wonder how long will they work for.