Topic: cross your fingers for me!

[bikebitzofvt]

I did a bunch of work to one of those for a buddy a few years back.  The inside of the fuel tank was rusted terribly, carbs were filled with crud.  He drove it running on the choke only for several seasons!  After I got it all mechanically right (tires, chain, sprockets, fork seals, battery, carbs overhaulled & ultrasonic bath, tank POR 15'd, fuel valve rebuilt, new clutch and a lot of new bearings) I had to replace all the fuses 'cause they were fracturing, etc, etc, etc I took it for a shake down ride.  The bike would only accelerate to 5K rmp then shut off like it had a rev limiter!  It took many, many hours to figure out there wasn't enough voltage to the coils!  I added a 30 amp relay directly from the battery to the coils, (think fog light relay) triggered by the stock power to the coils.  Bike woke right up after that, surprisingly fast!

I'll follow along and offer any pointers as you go along.

Good luck and good find, those are a great bike!

BTW - www.CB750C.com is a great forum full of support for your new bike.

[mono]

haha well i got it home at about 4:30PM EST, hosed her off and put her in the garage.  the rear wheel won't hold air, so it's up on the center stand.

lock on the tank would not accept the key (tumblers were totally rusted), so i pulled the tank.  had to cut the fuel hose because it was too stiff to slide off the petcock.  petcock was frozen on OFF, so i unscrewed it.  tube on the petcock was covered in slimy rust, and i dumped about half a tank of dark brown watery gas out of it.  after it drained i shook the tank and there was so much rust in it that it sounded like there was a handful of pennies inside.  too bad too cause the tank is 99% rust free on the outside and has no dents or scratches in the paint.

i could not get the camera to capture it, but there was actaully moss or lichen growing on some of the aluminum tins and on the fins of the engine.  i'm pretty concerned about whether it is frozen at this point, but we'll see.

going to pull the plugs tomorrow and look inside, spray some PB in there as suggested, and let it cure for a couple days.  also going to pull and clean the carbs.  am also going to drain the oil and pull the oil pan to see what has rested at the bottom.

amazingly there is very little pitting on any of the chrome - just rust "sweat" which is coming off easily.  the rear fender and lights are probably 95% clean, although they are getting removed.  should be able to resell them OK.

sissy bar and luggage rack are removed. ack the 80s were ugly.

[grcamna2]

You've got a fresh start on it  Wait to remove the oil pan & change the oil & filter until after you allowed the PBBlaster to sit in the cylinders for the required duration you choose;if you put in fresh oil too soon the PBBlaster will soak down into it and wash down the quality of you're new motor oil,you want the oil to be as good as it can be to lubricate that old engine.
I'm hoping you're carbs will clean up nice..sorry to hear about the inside of the fuel tank,see if you can soak the gas cap w/ PB to loosen the tumblers up & it'd be good to spray WD-40 or the PB on all the exposed electrical connectors to help fight some of the corrosion so they can make good contact..

[mono]

^ thanks - i'll hold off on the oil then.  i already sprayed WD40 on the tank tumbler because if it frees up it would be nice to use the cap at least (since i have the keys).  also, i may have to resort to trying to salvage the tank since i checked the old internets and there are very few tanks for sale (not sure about crossfit from other models, though).  i'd ideally like to stick a 750F tank on it, but i'm pretty sure they do not mount anywhere near the same.  may need to go with a hawk tank or something.  just wanted something kinda cafe'ish, but it looks like the Ks are mainly used for the cafe projects.  if so, i may just be shining this bike and selling it  

[grcamna2]

mono,
  You can pretty well coat the inside of that tank w/ some good heavy sealer;I've found from a sub contractor that use to do them for me,that a product called Redkote will work good if the tank is rusty.Google it and then try to find a good shop or member here who uses it regularly and find out the careful Preparation that is required to fully coat the inside of that tank you have.
I remember the man telling me he would wash it out w/ wash fluid(gas,denatured alcohol,etc.)a few times.He had to remove ALL the loose stuff first w/a chain or a bunch of nuts & bolts and he'd shake them around in there until he removed the loose rust that was hanging on the verge of flaking off anyway & then he'd wash it out a lot after he removed all the loose stuff until it washed out clear.I'd be careful how much shaking you do w/ a very thin tank from the heavy corrosion it has.The last step was he washed it out w/ MEK and then he'd do a SUPER job of COMPLETELY drying that tank out inside in every crevice;he'd put a low pressure air pump hose inside it and leave it for 24-48 hrs...,yeah,it's got to be REAL dry.Then he'd coat it.
If you're interested in the rest of the process,I'll tell you the final steps.You can save that tank w/ that RED KOTE..even w/ the rust problem you've got,but it's a big Job. It's a Nice looking tank..why not make it last for the duration ? !

[mono]

depending on the availablity of a different tank, i may end up trying to save this one.  what you're telling me is good news, though!  i am just trying to avoid having to seal a tank since i have heard that after a few years the sealant tends to goo up and needs to be redone.  if i can find a clean tank that will work, great - if not, i'll redo it.

if i *do* end up cleaning and sealing this tank, i was going to scrub it with the nuts+bolts method (small ones i guess so it doesn't punch a hole) and then use the electrode method to draw off any remaining mocro-rust before sealing.  i'm confident that i could do this on my own ( i have the tools, and if i don't it's a good excust to buy more tools! ) but the tips you're giving me are awesome.  i've never done it and don't know what brands are good.

any info anyone can give me about cross-fitment using tanks from another honda model that would be super helpful!  i'm surprised i haven't been able to find a list out there of what frames will accept what tanks.

thanks again,
  mono

[onepieceatatime]

You may want to check out this sealer too.
http://www.caswellplating.com/restoration-aids/epoxy-gas-tank-sealer.html

[wedoo2]

That was my last project, and although the fairing and seats do not appeal to most people here, they are a plus on a long ride.  I agree with bikebitzofvt about the Custom forum.  There is a busy, and informative, following there but they do not suffer fools gladly.  Make sure the valves are done soon, no matter when you think they were done last.  They are the shim type and a PIA if you don't know what you are doing.  And don't even think of putting pods on those CV carbs.  When you get running on the bike you are going to be forever looking for a 6th gear.

[mono]

thanks wedoo - i have already joined the DOHC Customs forum, and you're right - they are very.... "honest and straightforward" on that forum.

honestly, though, i think i've decided to just get it running and sell it.   from what i've found, there are very limited cafe parts for this bike, and i don't feel like making my own.  i think a mid-70s 750 would do me better for a cafe bike.

also, as i've been working at this one, i'm finding that time has taken more of a toll on it than outward appearances suggest.  lots of super rusty hardware inside - i still haven't been able to free the battery bolts! - and many other things that make me not want to try taking it apart any more than i have to.  i'm terrified that all of the gaskets are bone-dry and rotted too.

i may feel more inspired to wrench on this one after my 550's put back together, though.

and thanks for the advice about the pods.  i wasn't planning on using them right away, but was considering it for later on.   now i am not! 

[wedoo2]

I sold that bike for $1800.  Running good, good Honda fairing and clean from head to toe.  Not showroom, mind you, but I made a nice profit and had a great winter working on it.  I agree that the earlier 750s make a better cafe platform.

One guy on that site, fasterspider, really knows what he is talking about when it comes to those bikes.  He has a new handle now, but Ray is great and happy to help anyone who has an interest in the bikes.  He has quite a CBX.  Can ride too.  Seen a few of his California freeway videos.  I'll never be on the back with him in control.