Refreshing Carburetors For My SOHC Honda CB750 Cafe Racer Project Bike | 23
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- เผยแพร่เมื่อ 3 ก.ย. 2023
- Refreshing Carburetors For My SOHC Honda CB750 Cafe Racer Project Bike | 23
In this video I refresh the carburettors of my CB750 SOHC Cafe Racer project bike. Overall the carburettors look in quite good condition. It appears that they have been refurbished, but then left for 5 or more years, so that there is some corrosion, especially on the steel parts.
Carb Cleaner: ebay.us/cPSpym
JIS Screwdrivers: ebay.us/l84kPe
I know that they did work to start the bike, as I have had it running for a short time. But as I found that I needed to strip the engine because of an oil leak, which led on to a full top end rebuild they haven’t been used for a while.
I started by removing the float bowls and checking and cleaning all of the jets. I found that they were in pretty good shape, I think that the only petrol that they had seen was from when I test started the engine.
After I used some carb cleaner through the jets and all of the little vents in the carb body, I blew them through with some compressed air.
I then checked and reset the float heights. In my first rough check I thought that they were set a little too low at 28mm. But when I got out the gauge I had made to set the carbs on my K0 project I found that they were mostly OK, and that I only had to reset one of them.
When I came to strip the mechanism that opens and closes the carbs so that I could address the surface rust, I realised that I had never stripped that part of the carbs before. This made it a bit of a struggle, especially as a bit of corrosion made them a little harder to get apart.
I made sure that I took some good photos when I stripped them. The mechanisms on carbs always seem to be very complicated, with lots of fiddly parts. The hardest part of putting them back together is the spring that goes between the plate that the throttle cables connect to, and the part that opens the slides. I think it is some kind of damper, because it is so stiff I can’t see it allowing the parts to move very easily.
The longer spring that actually closes the carbs is quite strong. I know that some people replace this with a lighter spring to make the throttle action lighter. I will see how it goes before thinking about changing it though.
I also adjusted the slides so that they all open at the same time. This is quite easy once the rubber boots, that have really perished, have been removed.
Overall the job was pretty straightforward, and the carbs should be OK when I get them back on the bike. They will need the idle setting and balancing with gauges. But I think the initial setting should be OK.
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Great job and video. This is a real 50 years old Superbike
Thanks, I hope I do manage to ride it this year. It is certainly throwing up a few challenges, but hopefully it will be worth it in the end.
Can't wait to see the next video to see how they work on the bike. I have a 1975 CB750. It has the stiffest throttle spring of any bike I've ridden. I may try a lighter spring next time I have the carbs off the bike.
When I was cleaning my carbs a couple years ago I had the same worry about missing a tiny brass piece on the two end carb vent holes. I had to go look at a bunch of photos on-line to realize they're not meant to have that brass piece there.
I remember riding an early GSXR 750 through Manchester traffic and really struggling with arm pump from the weight of the throttle. I don't think the CB's are as bad as that, but we have got used to much lighter controls. I'm glad it isn't only me that worried about those little brass pieces, and putting the control mechanisms together on these carbs and the later ones is a really challenge. I think they were designed by a sadist, with lots of unnecessary complications.
Yes. "Why is there a hole here? Who stole my brass!"
Daveco: I've got a K6. In case it slipped your mind, I just changed my throttle cables and they were horribly stiff. Silicone spray lube did the trick for me. It's not "buttery smooth" but it's much, much better. Also, I'd tightened my return cable too much. Slacked that off a bit and now things are good.
Good video Les. Have not done the early 750 carbs but done many a 400/4 set. Did you notice the slot on the shaft with the woodruff keys? This is a "gotcha" there is a pin in the alloy body to stop the linkage moving side to side. you have to drill out the pin or you bust the brass bush/sleeve in the link casting. and the shaft will now move a bit. Also that bit where the cables go round do not clean it in acid before you plate it. it is rivited with metal that dissolves in the acid and you have to rerivit or bolt it together (ask me ho i know) look forward to teh running video.
Cheers Rob. I didn't notice the pin you are talking about, maybe I didn't strip them down far enough :) I decided that I wasn't going to plate the parts yet, just clean and coat them in a wax to stop them getting any worse. I can't undrstand why there is the very strong spring between the tow parts. I can not imagine what it does. I will bear in mind the comment about the acid, I am surprised I haven't been caught out by that before, but to be honest I have only used plating for single items, nothing that was built up.
Looked very fiddly but you got them back together 😊
Yes, thanks. Typically a bit of a learning curve when you do something for the first time. The exploded parts diagrams were not that helpful.
Very fiddly indeed. My 750 has an over-abundance of fiddles throughout the thing.
Great video les and well explained 👍
Thanks, glad you enjoyed it! 👍
...got this same set of carbs. Mine were left in a dishpan, all in pieces for...20 years? Hahahhaah. It's so sad, all I can do is laugh.
Everybody thinks they will get to them LATER! :)
I have an off-topic question that any of you motorcycle loving Brits could help me with.
Does anyone in the UK still say "Goes like the clappers" "Bitsa" (for a Frankenbike) or "Bodger"? Would you call your gauges "Clocks"? Outdated? Any others you care to share?
Apparently, here in the US I'm an "Atgatt". All the gear, all the time. Squids are the guys who wear Crocs and shorts on their crotchrockets...
Guilty as charged. If you look at the earlier playlist you will see wanton use of all of these kind of terms. The gold bitsa was a classic.
That Candy Gold was pretty great all right. Best Honda color in my book, and a great bike. It's not often you can sell something to somebody and make them feel like they were the one who got the bargain. I imagine he's grinning all the way down the road by now.
@@CB750K I like the Gold but really love the Candy Blue Green best. I think the new owner of the Gold bike is very happy with it so far, but the buyer of the Candy Blue Green one got the best deal, he rang me a few time aksing if I had any more bikes for sale :)