Honda-SOHC
SOHC.co.uk Forums => Project Board => Topic started by: chrisbmxr on April 30, 2020, 11:55:23 AM
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Hi all.
So, as per my intro post, 4 years ago I inherited a 1977 CB750 F2 Super Sport from my late father in law.
He had owned the bike since 1995, but it was garaged in 1999 when he developed health issues. That is where it stood until I moved it to my garage last year. The bike has covered just under 22,000 miles and it looks like most of the parts on the bike are original. There are however signs that the bike has been dropped at some point. There is a small dent in the front of the tank and the left side cover is black, not Candy Presto Red like the rest of the bike. I guess this all part of the bike's history, but I may opt to completely return the bike to original eventually.
I've attached a couple of pictures of the 'starting point'. I'll try and post updates here as progress is made!
My plan is to first get the engine running. This will have its own challenges with bike having been stood for over 20 years! Then I will get the running gear sorted, and finally bring the bodywork and everything else up to standard.
Although I am not new to bike, I am new to SOHC's. So the help here will be greatly appreciated!
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Update 30.4.20
So, the past week has finally enabled me to make some progress on the F2.
I have removed the carbs from the bike. I really wish I had the knowledge to strip them down, clean them and put them back together myself … unfortunately I just don't! The throttle wouldn't actually open so I fear something has seized anyhow, so it's probably best that I let an expert work on them. That may hold me up though unless I can post them due to COVID-19. Any recommendations for someone to do this for me would be gratefully received!
[attach=1]
I've also been having a quick look inside the tank and the barrels using an endoscope camera. The good news is that the barrels look OK, but the inside of the tank has quite a lot of rust! I'll need to treat/remove this and flush the tank out before trying to start the bike.
I've also been doing some online retail therapy. New oil, oil filter, air filter, fuel lines, fuel filter and battery are on the way.
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After I'd left my 750F1 in the garage for 10 years while I worked overseas I too could not operate the throttle, turned out the float bowls were full of nasty looking gum which had glued everything together.
(https://imagizer.imageshack.com/img923/7801/sqVZM6.jpg)
Cheers
Dennis
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Looks lilke a nice project :)
I reckon that will polish up nicely when it's done, and most importantly...looks complete and unmessed with. Apart from seeing a bit of life ;)
Carbs are quite complex, but the floatbowls and related assemblies are fairly simple. My advice is... take LOTS of photos when taking bits apart, as it makes it so much easier to see how stuff goes back. I made that mistake with the throttle linkages, and had a devil of a time working out how the two halves of the throttle spindles linked together. It was the one bit I missed.
Also...with floatbowls...if you take one apart at a time, you have 3 others for reference.
Also grab all the manuals and other scanned reference materials here. It's absolutely vital!
My floatbowls were also horrid....and the petrol in their had basically solidified in places, and left all sorts of nasty sticky mess. A good soak in a bucket of petrol followed by a bath in an ultrasonic cleaner did the job. Carb rebuild kits for jets, seals etc. are readily available too. I need to get 4 of them myself!
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That does it then! Looks like I'll be giving it a go myself! Stay tuned for an update.
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I wouldn't be having a go yourself unless you have experience of carbs. The carbs on an F2 need to be done perfectly or you wont ever get it running correctly. For instance, there is a vent on the side of the carb bodies that needs cleaning, if you miss it the bike runs like crap. The only person I have ever seen mention this vent is me as nobody appears to be aware of it. You can also experience problems with the accelerator pump mechanism. Just one of the many pitfalls of PD carbs. I would contact this guy, sales@harpers-ultrasonic.com The guy is superb with these carbs and wont rip you off, plus he will do any standard from a simple clean to a full renovation. You will be glad you did. Cheers, and best of luck with the rebuild looks like a gud un.
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I like it.... is it a USA model, I’m looking at the vin plate on the headstock, UK bikes don’t have one if I’m correct....? Not that theres owt wrong with a USA bike, its likely to be in better nick than a UK model... mine is a USA model. Clean out the oil tank before refilling, turn over the motor on the starter before firing up to make sure the oil pressure light goes out.... test the compression before trying to start, run it on the starter for five seconds with throttle held wide open... you should see 150 psi give or take...they should all be the roughly the same... If you can, take off the tappet covers and shine a light in there to see if you can see fresh oil coming up into the head.. If all looks good you should be ok to try and fire her up.. Good luck with it! 8)
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Update 5.5.20
First of all, thanks for all the comments and advice.
Yesterday I decided to see what horrors lay waiting inside the carbs, and I was actually pleasantly surprised! There was plenty of varnish, but in general the insides were in pretty good condition. All jets seem to be as they should. I also manages to free the 2 stuck slides which had been 'varnished' shut with the help of the wife's hair dryer. Once they were heated they slowly slid out without much force at all! Very happy! I then used STP carb cleaner to remove the varnish from the metal parts and give them a good clean. I do think they would benefit from a complete service so I have reached out to Harpers for that (thanks for the recommendation Roy).
[attach=1][attach=2][attach=3]
Next on the list of things to tackle is the petrol tank. I have to say, when I cleaned the 20 years of dust off the tank, the original candy presto red colour in the sunlight is stunning! Though there are a couple of minor blemishes to the paint work I may need to remedy at a later date.
The main issue is … rust. Pics are attached. I am undecided how to tackle tis. I know some people recommended the POR15 sealer kit, and others steer clear from sealing and use an acid. Any advice in this area is welcomed! My main concern with the sealer is the horror stories I've heard of it going wrong, or even peeling apart at a later date. Again, maybe I should just take the plunge and give it a go! Also there is a small dent in the front of the tank which I may try and get removed using PDR, but I wouldn't be able to do this once the inside is sealed.
[attach=4][attach=5]
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Do not use any type of sealer, it will fail over time. The problem with any sealer is: the tank has to be spotless inside for it to bond and if it is spotless then, there is not point whatsoever in trying seal it ;)
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The tank doesn't look too bad. Just give it a good clean it will be fine. As Graham says a liner is really for when you have no other options. If your worried about debris getting into the carbs fit an inline filter for a few months and see what it collects.
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Update 15.5.20
Hello! First of all, thanks for all the help so far! There really is a wealth of information here.
On Boris Johnson's orders, a few more weeks at home have meant good progress on getting the CB running! I even let her enjoy some sunshine!
[attach=1]
Apologies for the late update … I've been either in the garage or trying to keep a 3 year old entertained!!!
So, I'll summarise the progress since the last update …
I managed to clean up the carbs. All jets are clear and I've cleaned the bowls. I also rebuilt the accelerator pump as the diaphragm was hard and brittle. After reading every bit of info I could find (and then some) I decided it was a good idea to check the function of the accel pump before refitting the carbs. The new diaphragm gave a good squirt of water when tested assembled in the bowl … but I had a blockage in the nozzle of carb no. 2. Plenty of perseverance on cleaning the nozzles (and STP carb cleaner) later and all 4 were squirting as they should! New seals and gaskets and the carbs were rebuilt.
Fuel tank cleaned! It turned out that the tank was in pretty good condition, with just a few mild spots of rust. SO I decided to use a less aggressive method of cleaning and went for Bilt Hamber DeoxC. This worked really well! I would highly recommend it. The inside is now looking nice and clean. I also cleaned the filler cap and chain whilst doing it.
[attach=2]
Oil has been replaced. I drained the old oil from the crankcase, oil tank and filter assembly over a couple of days. New oil filter has been fitted and new oil put in. I put a very small amount of oil in to the inspection holes at the top.
Engine turned over by hand. Spark plugs out, I very nervously leant against the kick start with my hand … half expecting it not to move, half expecting it to feel horrible. I'm very happy to say it turned over nice and smooth. Very pleased!
Electrics checked. I fitted the new battery and tried the electrics … everything seems just fine! Every single bulb is working as it should! Horn works. Indicators flash (accompanied by a rather annoying buzzer. Do they all have these? If it's 'Honda' it stays. If not it's going!). Starter motor also works well (tried with the plugs out after refilling with fresh oil).
[attach=3]
Next steps:
Set and fit the spark plugs … fit the tank and put fresh fuel in and see if she wants to start!
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The buzzer is an American model thing.... I'm not sure if it can be disconnected, other than with a club hammer 😁😁😁😁
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Julie, buzzer was everywhere not just US but Honda UK sent out an unoficial request via reps to disconect them as they sounded like the old pelican crossings
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Buzzer mine sounds more like a strangled cat but at least the indicators don't get left on. Other makes had them as well back then.
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One of the first things I did when I bought my F1 was to remove the buzzer.
Cheers
Dennis
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I have no issues with the buzzer. I don't have one. Or the correct headlamp...or the ears.... so for me it's handy to know....but I won;t be fitting one.
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Nice work, it looks like you're making leaps in the right direction to getting it back on the road again.
I'm keeping my fingers crossed that cleaning my carbs will be as straight forward when I get to them shortly!
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Hello! Sorry I've been away for so long ... my Kit Car was getting jealous of the attention the CB750 was getting, so started jumping out of gear (worn dogs on a Fireblade engine). So I spent the next couple of months replacing the engine and then enjoying the car 8) . Now winter is here (along with lockdown mk2) I am putting my efforts back in to getting the bike ready for summer 2021.
The good news is, before having to concentrate on the car the bike started pretty much straight away after I cleaned the carbs and put fresh oil in etc. I had an issue with cylinder 4 not firing due to the lead coming loose from the coil, but that was a quick fix.
Now although it's running which is great, it is very lumpy, so I am thinking my next step is to send the carbs off for a proper clean and rebuild.
What other adjustments/checks should I be looking to make on a bike that's been sat for 20 years? Valve clearances? Cam chain tensioner?
Thanks as always for your help!
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I would be looking at anything that hardens & falls to bits with age like valve stem seals, O rings, some engine seals, pipework etc.