Topic: Nerdos' 750K3 restoration

[Nerdos]

Right-o, I thought I'd post my project here and thus garner some advice and nuggets of wisdom as I start my rebuild/restoration of my 750K3.  Having looked at some of the bikes that have been picked up for restoration by US-based members I reckon I probably paid top-whack for mine over here in England but I'm not disheartened by that.  It appears to be almost entirely stock but pretty unloved.  I mean, who would get a bike, ride it for 11,000 miles and then abandon it to blister under the sun and rust in the rain?  The PO or POs, obviously.  My aim is to do a restoration that returns the bike to as near stock/new condition as possible but I also want to be able to ride it without fretting about getting it dirty.  I also intend to repaint it from its original Candy Bacchus Olive to Flake Sunrise or whatever it's called.  Green just isn't good.  Let's start with some pictures of how it was when I got it.  Apologies to those who may have seen a couple of these already elsewhere on this site.

I examined the bike up on the ramp/table and found, as the seller pointed out, some bits that were better than I expected and some that were worse.
Good points:
Engine turns over and compression seems good when measured unscientifically through the kickstart.
Front end seems OK
Headlight reflector looks like new (I'm used to these blistering on pretty much every vehicle I have ever had)
No modifications done to the bike except the taller bars.
Only 11,000 miles (if this is true)
Doesn't appear to have been dropped

Bad points
Exhausts shot through
Switchgear seized
Tank contaminated with red sludge and white petrol
Carbs won't even open, either via twistgrip or even by manipulating the linkage
Clutch seized
Both wheels need new rims and spokes
Rear mudguard split though the seller did provide me with another in very good condition (so maybe this should be in the good points section)
No keys supplied so I had to hotwire it
Battery spilt and therefore useless
All control cables a horrible rusted mess
Clock faces warped and bleached and clock bases hideously rusty.

[Nerdos]

Replying to one's own thread: is that bad form?
Anyway, having got the battery out and connected up a mahoosive Land Rover battery I can confirm that a lot of the electrickery is working.  There is no spark at the plugs though although there is 12v on the black/white supply to the coil.  I suspect the points, even though they look clean, and it is my intention to replace them with electronic ignition.  I have a spare Newtronic/Piranha electronic ignition from a CB400F that I bought for spares so I will probably use that.  I believe it is the same kit.

My plan is to see if I can get the engine running to check for nasty noises before I strip the bike down for painting and/or powdercoating.  Since the engine only has 11000 miles and no oil leaks I have no intention of taking it apart unnecessarily.

The carbs however did not want to leave the bike but, thanks to some sterling advice from Eric (ekpent), the judicious application of heat from a hot air gun got the rubbers loose enough to let go of the carbs and also allowed the throttle slide of No4 carb to be freed up from the varnish that had accumulated.  The carbs looked like this inside...

[seanbarney41]

looks like a solid start for a project...rusty exhaust and wheels looks to be the worst of it...carbs look pretty typical...wishing you luck and encouragement

[SOHC4 Cafe Racer Fan]

Thanks for sharing your project build with us.  Looking forward to seeing the progress!

[Nerdos]

I've been in denial about the state of the exhausts for a week or so now but, to my mind, a proper 4 into 4 exhaust is an iconic part of this bike and, regrettably, cannot be replaced with a Motad.  Not for me anyway.  I'd always planned to get a pattern set from David Silver for about £700/$1200 + tax but, as eagle-eyed people may have spotted, these have been on back order at DSS for some time and then, maybe last Friday, they disappeared from the site altogether so I called them and asked what was going on.  The replica pipes were initially expected at the end of 2013, then that was revised to sometime in 2014 and when I pushed them on it with a line of questioning akin to "can you say you are definitely expecting some more in 2014 or is the future availability of these pipes unknown?" I was told that while they wanted to get some more made there was no sure date.  With that in mind and feeling a bit nauseous I loaded my credit card to the tune of £1,100/$1,800 plus tax from CMSNL for genuine items.  I figure that if the replicas become available before I finish my build I will buy those and flog the genuine Honda items.  I can't imagine the price of genuine 341 items can go anywhere but up.  In the meantime here's a wistful shot of my poor, rotten silencers.

Also, yesterday my 4 carb repair kits by K&L arrived from the US.  These are made by K&L which I hope are of reasonably quality. Can anyone advise?  The kit does not include the emulsification tube so I guess some careful poking through of wire will be required there.  Then, if I can get the sparks working we might hear the beast lumber into life.  maybe

[seanbarney41]

General consensus on the K&L kits is the gaskets and o-rings are fine, but don't use the brass parts...just clean up what you have very carefully.  K&L jets, needles, and float needles have been found to be incorrectly sized.

[Nerdos]

Wow.  That's a disappointment.  I mean, the brass parts have to make up 90% of the cost of the kit I would have thought.  And to clean the brass parts what would you recommend?  Please bear in mind that this miraculous SimpleGreen stuff is akin to unobtanium in the UK.

[Dream750]

Looks like you're off to a great start.

Another resource is our UK sister site: http://www.sohc.co.uk/

The K3 came in three colors: flake sunrise orange, candy bacchus olive and maxim brown metallic.

Re-installing the carbs is easier if you first line up the boots with a straight edge.

[Nerdos]

Thanks for that tip.  It's obvious when you see it like that in a picture but probably would not have occurred to me while I cursed and sweated and broke something as I tried to coerce the things on.  I already caused a little fin damage getting the blighters off.  I thought a wooden batten would spread the load.  You live, you learn.  Thankfully that damage is out of sight with the carbs on.

[edwardmorris]

Nerdos, those pipes aren't nearly as bad as the set I was conned into buying. But, after calling about 14 different welders, one of them agreed to fix them up and he did a pretty great job. If the ends are all that have rotted through, I suggest you find a welder who might be able to patch it up for you. It IS possible to salvage these for the interim. More on my disaster set here http://forums.sohc4.net/index.php?topic=126914.0

[mono]

looks like you've got your hands full, although as they say with homes "looks like it's got good bones"...

restorations are fun, but expensive.  personally, I'd suggest starting with the engine work since you know that's an issue.  full teardown, and get the frame painted/powdercoated while the engine is being sorted out.   then you can tackle everything piece-by-piece as you put it back together.

[seanbarney41]

  personally, I'd suggest starting with the engine work since you know that's an issue.  full teardown, and get the frame painted/powdercoated while the engine is being sorted out. 

what engine work?...he already said the thing has 11k original miles.  I will be surprised if it needs any beyond a timing chain tension and valve clearance check...of course it will probably leak some.  Simple Green is only a miracle cleaner for those who cannot get the good stuff...commonly known as "carburetor cleaner".  However, I have no idea what is available in the UK.  I once cleaned a rack of carbs with urethane paint reducer...so any strong solvent that evaporates quickly with compressed air might work.  I often read Uk bike mags, and judging by the ads, their are many specialist services that will clean your carbs with an ultrasonic cleaner, but I have no idea on what they charge...those K&L kits still cost less than buying just the gaskets and o-rings from Honda.

[mono]

Lol Ignore me!  -- sorry, I was reading threads while waiting for code to compile and must have mixed up responses.  Thanks for the slap upside the head!   

Sent from my SPH-L710 using Tapatalk

[Johnie]

Nice pics...we have seen a lot worse carbs than those so count your blessings. Be careful when you pull those float pins and do not force them. You could break off the post that holds those pins and then you are in a tough spot. 11,000 miles...that K3 is barely broke in. I bet you will be able to free up that clutch once you get it running. Sounds like you are in need of new throttle and maybe clutch cables. I would suggest getting Honda parts as they are still available and a number of guys have had issues with the length of aftermarket cables. Clean that tank out good or you will be cleaning those carbs again soon. And do not forget to check out the petcock for crap too. There is a screen in the bowl you can access by removing the bowl. Last, drain that crankcase, oil tank and change the oil filter before you try to run it. Save some of the oil to put into the top valve adjustment holes to get that lubricated faster when you turn it over.
That K3 looks to be a good project and you will be happy with the result. It is amazing how Mr. Honda made such a great product with good longevity. With just a little work these bikes start and run good. Best of luck with your project and we will be with you all the way. Let us know how it goes and make sure to take plenty of pics when you dismantle...as you will be surprised at how fast you can forget where stuff goes  And welcome to the forum...

[Nerdos]

Thank you all for your input.  if I can start with replying to
edwardmorris; the pipes are really bad.  Maybe the original photo did not do them justice so I have included a few others.  I believe the technical term is fuct.  However, as I type the new 341s are on the back of a UPS truck somewhere in the environs of Nottingham and I will have them today. Just need to sell a kidney on eBay to pay them off.  I think maybe the headers could be saved but who wants a set of headers on their own?  No-one, I'd imagine.
mono; notwithstanding you may have replied to the wrong thread but it's good advice nonetheless.  The lazy part of me says 'check the engine runs OK, clean it and paint it intact and get it back in the frame'.  My conscientious side is urging me to split the cases and use plastigauge to measure main bearing wear and all that malarkey.
seanbarney41; I am fortunate enough to have an ultrasonic cleaner already.  I used it on my CB400F carbs as well as sundry other items (wife's engagement ring too) and it's a good bit of kit.  In the UK I think it's about £150/$240 for a set of 4 to be cleaned by a professional.  Since the ultrasonic cleaner cost this already I am now quids-in.  We do have carb cleaner chemicals over here - Wynn's springs to mind - so I'll get some of that.  Maybe that's the stuff I need to lift the varnish off the original brass parts if I really shouldn't use the K&L components.  I'm still a bit sad about that.
Johnie; The carbs are already fully apart and I am glad to be able to confirm that the pins and all other components gave up without a fight and are presently resting in their own tray in my garage.  Yesterday the brass parts were on death row as K&L were going to replace them, now they may live to run again.  As regards cleaning out the tank - what method, materials and tools would you suggest I use?  I've already cleaned out the petcock and have a new petcock bowl gasket and the petcock rubber disc with four holes in it thingy coming from CMS with the pipes.   <Homer mode>...mmmmm....pipes.

[iron_worker]

"Fuct" is right!      

lol

IW

[Nerdos]

Happiness is...a box of chromed pleasure from CMSNL.  Utrecht to Nottingham in 3 days.  Good service, my clog-wearing chums.

[Johnie]

Nerdos...there is a lot of stuff on this board about cleaning out the fuel tank. I would suggest doing a search which will discuss cleaning and possibly a tank liner depending on condition. I hate to fill up your post with info already available to you. Those 341's will make that bike stick out nicely...very nice.

[edwardmorris]

Yea, didn't know the whole story on the pipes, makes me feel SLIGHTLY better about my lousy set. I'm guessing the new ones from ebay were hard hitting on the wallet? If you don't mind sharing, what did they cost you with shipping?

[Nerdos]

The new 341s (which were not from eBay but from CMSNL) were 1395 Euros.  Then there's 20% tax on top of that,  Shipping was free for orders over 500 Euro.  So, in my language that's £1,415 or $2,290.  Effing expensive.  At least I didn't have to pay import duty.  That's one of the few benefits of being in the EU.  CMS did also include a nice poster of a bird in a leather jacket and leather hotpants.  I think there may have been a motorbike in the background too but I can't be sure. 

In response to Johnie; yes, sorry to ask the banal question about tank cleaning.  That was just idle of me. I read up on the battery charger/brine/rebar method.  Sounds interesting.  I took the petcock apart yesterday to fit a new packing disc and it had crud in the bowl already so some sort of proper cleaning is in order.

[Nerdos]

I've managed to clean up my carbs using my own soda blasting kit.  This is a spotblast gun coupled to my tiny compressor.  The spotblast gun is supposed to blow sand against a flat surface.  The sand is held in a bag that hangs down from it and the sand ends up recycled into it.  Anyway, I just bought some boxes of soda (500g each), stuck the feed pipe into a box and used it that way.  I do this outside and catch the spent soda in a large curver box.  Then, being a bit tight about things, I spoon it back into the box and use it again.  Anyway, the carbs are clean, and I decided to use the K&L pilot jets and gaskets but leave the rest as is for not.  I have also fitted the optical electronic ignition just so I can try to fire it up and see how it all sounds.  The problem is...no fuel.  This is a proper mystery to me.  I had the petcock off and it was full of muck (or clart as we say round these parts).  I cleaned this out and replaced the packing - that rubber disc with four holes in it.  The bowl gasket doesn't appear to leak so I retained the original.  If I take the fuel bowl off then petrol flows out of the tank and into the little bucket I have to catch it.  If I put the bowl back on then nothing comes through the brass fuel pipes that you attach the rubber fuel hose to.  So, take the petcock off again, disassemble and check that when I blow through the brass pipe that protrudes into the tank there is no obstruction.  Shine a light through the reserve tank hole and I can see the light brightly  inside the petcock body.  No obstruction there.  Reassemble petcock and switch to reserve: nothing.

Any ideas?  Incidentally the brass fuel pipe that takes the main tank feed is cracked.  I don't see how this could affect the operation of reserve function but I thought I'd throw it into the mix.

As an aside I just picked up a copy of this month's classic bike which features 9 page article about why a SOHC CB750 will make you happy.  This apparently can be distilled into these points:
1) ]It's the bike that defined the path of Japan's eventual omnipotence
2) They make an ideal first restoration
3) It's still a superbike

[taggat]

nice bike, jeez to the weez 2k on some exhaust! man..., pictures of the soda blasting plz! All-aboard!

[Nerdos]

It runs!  It liveth!  The petcock problem referred to in an earlier post turned out to be just not enough fuel in the tank.  I had probably 1 pint or so in there and that seemed to be just too little to make it through the  petcock.  Add the best part of a gallon and away we go.  As we saw earlier the exhausts are pretty bad.  When it started up I was more than surprised.  The ignition timing was set by eye and the bike started on the button after about 2 seconds.  There's a fair amount of smoke from all manner of places including even the cam cover.  I assume this is just 20 years of dust and filth burning off.  The clutch remains seized but I'm confident that can be freed.  I'm just a little concerned about the smoke from No4 pipe.  I will be doing a compression test after lunch and we'll see how the land lies.  Meanwhile here is what the bike deposited on the ramp as soon as the engine fired up.  It does sound good with all those huge holes in the exhaust but they will be off and scrapped in a few days.

[Johnie]

Another saved!!!! Congrats

[Nerdos]

Tiny update: I was hoping with a 12,000 mile engine that I would not have to strip it down but simply to clean it up and maybe even repaint it intact as one guy has already done with in his homemade cardboard curing oven.  However, a compression test yesterday showed 100psi on cylinders 1,2 and 3 and 170psi on cylinder 4.  I will retest again this evening with the carbs removed but that level of disparity in readings can't be good can it even if the figures themselves can't be trusted.