Honda CB750 K2 Carb removal & cleanup
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- Опубликовано: 8 сен 2024
- Starting up the engine in readiness to complete a carb balance it soon became clear there was a problem, a major one, causing 2 of the 4 cylinders not to be firing. Eliminating it been an ignition fault (was hoping not given the new electronic system I installed!) it soon became clear we had a carburation issue....
So, carb balance delayed it's time to finally pull off those carbs & take a look inside!
Oh, we also get a surprise video call too...
Enjoy
Andy
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Thanks for all your support, until next time...
Andy
I recently bought a 1973 CB750 for $750 C. Other than the exhaust being rusted in half, it's in good condition. It hadn't been started since 1988. I cleaned the gas tank, put some light oil down the cylinders, replaced the battery and it started. It was alternately running on three or two cylinders. New plugs, same. Finally removed the carbs and cleaned the jets and passages. Voila! She's running on all four, and with a new header sounds terrific! I took her out this evening for a little test run in the neighborhood. So nice.
A great find & well done getting it up & running. They are a relatively simple bike to work on & have very reliable engines. An excellent project bike & they fetch good money these days once they are sorted.
Cheers Andy
Andy, it's better to use the back of your hand if checking for hot metal. Their are less nerves than on the front. That is one of the first unspoken rules of life in a ship's engine room. This was a topic mentioned several times as well when I was in marine firefighting certification school. In the engine room, no one can hear you scream. Cheers Andy.
I was battling issues on my 1980 CB750C and my 1980 CB900C, (generation after the k2)
Rebuilt the carbs on both, but with the older tank, even the slightest bit of debris jams up the CV carbs and creates headaches.
I switched over to the dual VM34 set-up from Murray's and been running pretty well since. At least until I laid down the 750C in the flood waters earlier this week 🤦🏼♂️
Oh bugger...hope you are okay? Yep...fuel filters are definitely a must...
Cheers Andy
Andy is starting to look like the Samurai Mechanic 🥋
Lol.....
You remind me of me 😂😂😂 love it great explanation on repairing easy to follow 👍
Ace work, Andy! 👌🏻
Carbs.... ya love em OR...... 😈
Currently finishing up with a v4 setup and they're about going back in today-ish.
There may be a video.....
It is the law to have to clean carbs . But really satisfying when It works out . Many times on many bikes I've thought , why have I got a four cylinder water cooled faired bike? my last single cylinder air cooled naked thumper was fine ! ..
Peace and love brother 👍🏻☮❤
that airbox is much easier then my Suzuki
The first thing you are going to do that is unnecessary is remove the carbs. I had all the same issues. You DO NOT need to remove the carbs. Cylinders 2 and 4 are fired from one coil. Cylinders 1 and 3 are fired with the other coil. You can remove all float bowls including the third carb that has an accelerator pump WITHOUT removing the carbs. I owned a 1980 Honda CB 750F and I currently own a 1979 Honda CB 750K that i bought in 2021. Without removing the carbs, I was able to clean them well enought to achieve proper idle speed of about 900 RPM right through to 9500 RPM (Red Line) with full powerful acceleration. What the issue turned out to be was the spark plugs and ignition wires. Replacement of these components completely solved the irratic running issue. Many people (like me) overlooked the ignition wires. They do wear out after 40+ years !
Thank you for your comment. Could I suggest you watch the previous videos in this series. All the best. Andy
spray bottle w h2o spray on header pipes no burnt hands
Hi Andy when i did my GL1000 carbs,I found 9% vinegar in the ultrasonic cleaner makes carbs look really clean .
Ah cool. I'll give that a try next time around. Thanks for the tip. All the best. Andy
Andy, you wanted us to remind you to nip up the emultion tube to the main jet on the first carb you clean.
Well did you?
Haha! Yes, Thank You, appreciate the reminder... Have a great day. Andy
I think mine had four port boot rubbers on the air breather box. I had a few bikes so don’t hold me to it. You may try some rubber grommets, if you can’t find a new parts
Plain and simple Andy thx for that..can you clean in-situ if necessary. ?
🇬🇧
In theory you can, but in practice, everything is upside down and very crammed. Just getting the slow jets out (which as mentioned in the vid, is what most often causes issues) is tough because you can't really fit a screwdriver under there. I do it with a teeny sideways socket wrench, but not much fun.
Mmmm.. air box hoses are gonna be fun. Your mastic idea might stress-fail as the hoses are pushed onto the carbs from the rear, maybe some heath robinson clamp can be rigged up so the hoses are held against the inside of the airbox while you're 'easing' them onto the carbs?
Yes, unfortunately they have gone hard & pretty beaten up so I have ordered a new set together with all new clamps too. Better to be safe than sorry...
Cheers Andy
Mine was the electronic ignition…..
I'm kinda OCD when it comes to my 1975 CB750 carbs. I've got the little tiny brushes, some high E guitar strings and 0000 steel wool to make the brass parts shine inside and out.
Good job Dave. I could certainly spend a lot more time cleaning these up but... I just don't have the time. Getting them in a serviceable condition is my goal at this stage...
The owner may decide at a later date to give them a full overhaul & clean...they certainly could do with one!
Cheers for now
Andy
Sent my carbs to a pro for a complete rebuild . Best 580$ I've ever spent . Sometimes you gotta leave the carb stuff to the pros . I'm not one .
I agree, I'm certainly not a pro rebuilder of carbs, I know that. Have advised owner to get them fully overhauled. My brief was to get the bike running & to start on the button. It starts amazingly well now with the electronic ignition system & runs pretty well, certainly acceptable, but I'm not happy knowing the condition of the carbs - could be much better.
Cheers Andy
@@AndyMechanic I'm kinda looking for another project but enjoying the 78 cb750f i just finished . Fork seals and new tubes are all that's left . I've got a front set of tubes and dual discs but 1 bent of course . 100$ for tubes . Thanks for the videos .
@@AndyMechanic carb rebuilds are for the winter time ... ✌️
Ahh l see from ebay photos they have 'lips' to supposedly hold them tight in the airbox orifices. They're are genuine Honda and pattern available on ebay, not too expensive either
Never seen a man get so excited over a clean idle jet, excellent work an vids, just one question, is that cam chain rattle , it does sound well balanced on the carbs, but that rattle would worry me, just my thoughts...
It's an internal issue with these engines, not camchain but from the clutch as I understand it. Honda issued a fix where one of the clutch plates was replaced to eliminate the rattle. This bike had not had the fix done when the video was made.
Cheers Andy
Well you learn something every day...
Garys practical workshop
IGNITION WIRES !
Not this time, already replaced & new coils too...
Can you tell me the order of my mikuni vm 32ss needle slide clips on katana sz 100 UK please 😢
Looks like a radiator overflow tank from a bike or ATV.
How long should the breatherhoses from top of carbs be . 2 of .?
It should make no difference but usually run down to just below the rear swing arm pivot bolt
@@AndyMechanic .thanks andy . It's been suggested to go over the top past the battery .sorry to disturb your night . Cheers.
@jamiestanley8774 all good matey, just watching TV tonight, been a long week already... all the best. Andy
looks like fuel tank off a tanaka strimmer
I think you are correct good Sir! Well spotted. Cheers Andy
its the strimmer tank
Sure is, worked out great :-)
Weed eater fuel tank a riaobe
.
Correct! Well spotted! Cheers Andy
Chainsaw
So close Lewis, good effort. Cheers Andy
Weed eater
Strimmer we call it in England...
Yes, you are correct. Great job :-)
Nice piece of recycling for the remote fuel feed
Cheers :-)