Topic: 1978 750K cream-puff

[wheeliepop]

Well, I have to admit that there are nothing but "Champagne" problems on this bike. It was a Craigslist find in the Tacoma,WA area. 100% original and parked since 1983. Original tires, air filter, bulbs...even the tool kit had never been unrolled. The only problems are a tank that needs to be treated, a buggered stopcock and whatever else rubber/seal related stuff that just doesn't make it stored for 30 years. There is a bit of a swollen area on one of the silencers and the "broker" who flipped the bike cracked the oil tank side cover and destroyed the stopcock. So far I've soaked and rebuilt the carb but am waiting on the new float bowl gaskets and my Colortune and Carbtune kit to arrive. I decided on the Evapo-Rust option since I don't want to take any chances with the (perfect!) tank paint and a converter product seemed much safer (although a bit more expensive.) I soaked the intake boots in 4:1 Xylene:wintergreen oil and that was just right.

If anyone has any suggestions or warnings related to a bike that has been sitting this long, please feel free to chime in. Also, if there are pitfalls or common mistakes with keeping a bike original, I would like to hear about it. This bike will be ridden, but I don't want to hang anything but NOS parts or pristine used bits on it. It's just too nice.

Anyway, thanks for looking and I will post pictures from the good camera just as soon as the sun starts shining again here in Seattle.

[Ryan6838]

love it some hate the k7/k8 but i like them. that thing is pretty.

[BeSeeingYou]

Nice find.  Got my 76 750 F1 in similar circumstances.  I would take apart the master cylinder and caliper and put in new seals and maybe replace the rubber brake line hose.  It's common for them to get plugged up from sitting.  New tires of course.  Change the fork oil.

[Ryan6838]

Yeah tires, fluids and anything rubber that degrades over time.

[wheeliepop]

Nice find.  Got my 76 750 F1 in similar circumstances.  I would take apart the master cylinder and caliper and put in new seals and maybe replace the rubber brake line hose.  It's common for them to get plugged up from sitting.  New tires of course.  Change the fork oil.

I forgot to mention that the master cylinder had been rebuilt, but I don't think the PO replaced the line or anything with the caliper. Actually, I was kind of disappointed to see any "recent" work on the bike when I found it. Almost everything that they had messed with looked suspect. I wish they had just left it alone. sigh.

Anyway, the reservoir cap seems to seat a little high and the aluminum reservoir shoulder shows a lot of cleaned up pitting. My guess is the original cap was corroded on and then destroyed getting it off for the rebuild. I wouldn't know if they vary much year to year, but they may have found another year cap that's not quite right.

What is the consensus on fork oil? I was dazzled by the multitude of Automatic transmission fluid options at the auto store. My guess was that I should first replace the oil with a thinner detergent style fluid and then replace again with something a bit slower after all the seals and passages had been flushed out. I'm completely unfamiliar with shocks (so far!)

And tires...A cursory investigation revealed that nobody has NOS tires like were mounted at the factory. I'm sure there is some old codger somewhere that has a dark closet full of them but I can't find him. As a practical matter, the bike needs new tires to be safe (although the originals are in remarkable condition!) But, since I am motivated to keep this bike true to era and as original as possible, I am uncertain what to do.

Who has a tire suggestion from a restoration perspective? I would really be thrilled for a "CB head" to walk up on the bike and wonder to themselves " Are those the original tires!? They look great!"

Something ribbed up front? Nylon casing? Block pattern for the rear? Japanese?

Thanks for reading and any suggestions.

[wheeliepop]

love it some hate the k7/k8 but i like them. that thing is pretty.

Thanks Ryan. I don't think there are any SOHC bikes I hate. I owned this same year bike before as a pretty clean runner, but far from stock. It had a shorter rise bar, older style F carburetors with velocity stacks and pipes painted high temp white. I loved that bike but I also secretly wished it had been true to stock. When I saw this one in the ad, I just couldn't pass it up. Incidentally, I found it the 1st day I decided to look for a bike! It was meant to be...

I think there is something about the K7/K8 that just roars "motorcycle" and I like that. What a refined machine! It's appealing to me to hold the final year production of such a popular and successful model. I like the broad tank, the comfortable seat and great pipes!

Truth is I like all the SOHC's, this one just happened to be the one that found me (this year!) Who knows which one will find me next...

[BeSeeingYou]

love it some hate the k7/k8 but i like them. that thing is pretty.

I think there is something about the K7/K8 that just roars "motorcycle" and I like that. What a refined machine! It's appealing to me to hold the final year production of such a popular and successful model. I like the broad tank, the comfortable seat and great pipes!

   That's what is important.  You have to like/love what you ride.  There is a lot of "one up-man-ship" here about bikes somehow being better if they are a certain vintage and it's just a load.  Ride it with pride because it's a unrestored survivor in great condition.
    There is a lot of info on tires here if you do a search and there are modern replacements that will be a close fit and an improvement in handling over the old designs.  I am not as familiar with your bike but aren't the rims a bit wider giving you more choices over the older bikes?  You don't want NOS tires by the way.  An unused tire 25-30 years old is no good but you can get some new tires in the old style tread pattern.
    If you do a search on fork oil you will probably find an answer that suits you.  Tires and oil are things that have been discussed endlessly so no need to do it again.
    Flushing out the forks sounds like a good idea to me.

[wheeliepop]

The Evapo-Rust arrived today so I can get going on that front. New rear tank rubber is en route (the wintergreen won't heal cracks!) I need to bench sync the carbs and ready for the pristine treated tank. I discovered that there is an ethanol free gas station just 5 blocks away so I've got a 5 gal can ready for the first tank. I have read a bit about jetting but does anyone have a suggestion off-hand as to whether the #110 jets stock are going to work well with the 87 octane ethanol free pure gas? Should I jet up? I live nearly at sea level and it doesn't get too hot here in Seattle.  

[BeSeeingYou]

Run it as is.  The 87 octane will be fine.  Since you have the carbs off I would guess you have checked the air filter. 

[theofam]

Super nice find!  I can't believe how nice your scoot looks.  I bought a 78K that had been largely abused.  In hindsight, I'd have paid much more to find something complete and in great condition.

Can't wait to see it complete and on the road!

[wheeliepop]

Thanks theofam! I new it would cost a bit more to find a good starting spot. Believe me, I've had my share of heartbreakers and learned a bit or two how much more they can cost (time, money and soul!)

With two kids and running a business, I don't have the resources to tackle a top to bottom build. Someday maybe, but not now. And I know myself; If a sank my teeth into a whopper, I'd never get anything else done until it was buttoned up - it's just too much fun.

I wanted a bike to be easy, a joy to ride and just right for 1 or 2 hour projects. So far so good!

[theofam]

Sounds like cream puff fits your life perfectly!  Based on previous rides, looks like you already learned some 750K8 lessons! 

Keep us posted on the progress of those projects.

[brandEn]

Nice F you got there. The problems you mentioned I think are fairly common on these old bikes. I have learned a ton about these F models during my rebuild. You can get awesome side covers in the for sale section from member frankenstuff. Not genuine Honda but exact copies. They dont make the originals anymore. Also have a look at your rear master cylinder. Those have a tendency to corrode. They discontinued those as well so salvage what you can and rebuild it with new seals and such. New petcocks can be found on Ebay or at Dime City Cycles. I have a few parts from my rebuild that I don't need so pm me if you need something before you go shopping.

Oh yea your jetting should be fine since you are staying with the stock airbox. Just make sure to clean those carbs REAL good.

[wheeliepop]

Nice F you got there. The problems you mentioned I think are fairly common on these old bikes. I have learned a ton about these F models during my rebuild.

Hey brandEn, Thanks for checking out my rig. I have been following your project with interest the last few weeks since I signed up on SOHC4. Very cool undertaking you have going on there; I shudder to think want you've spent...but like most investments in quality, the rewards eventually eclipse the memory of cost. I can't wait to see that tank in the sun! Who knows, maybe we can hook up for a gawking session once we're both rolling?

I think you missed a detail (which seems very out of character from your project chronicles) but my CB is a '78K. I have worked on an F before with the disc rears and they were certainly a handful. I guess that hydrophilic Dot 3 just doesn't sit well for decades here in the PNW?!

I found a petcock at Bent Bike Lynwood. It polished up very nicely and seems to turn smoothly. I also found a NOS Right pipe on Ebay to replace the one that seems to be rotting a bit and I also ordered up Hondaman's book. I'm getting antsy to tinker, but I have to roll it out to work on it.

Pray for Sun!

[Ryan6838]

did you already buy the pipe? i have to look idk what ones i have.

[brandEn]

ooops! K model, rear drum. I new that. My bad. Anyway, yea always down for a ride. Seems like we have a gang of 750 owners popping up around here, the more the merrier!

[wheeliepop]

did you already buy the pipe? i have to look idk what ones i have.

Hi Ryan, thanks for checking/offering on that pipe. The one I found is a NOS so I couldn't pass it up! Actually the one mounted on the bike currently is in great shape, just not perfect. I'll probably just save the box the replacement comes in and put the old one up for sale.

Here's a pic of that replacement:

[wheeliepop]

The pipes arrived and they are beautiful! Never installed and just right. I'm waiting on the gaskets to arrive before I button them up.

I pulled the carb bank again.  After the first rebuild, #1 was running cold with good spark so something was up. I blew out all the jets again and double checked my float valves and height. After re-installing and flushing with fuel it fired right up on all four. The Carbtune equipment was a pleasure to use and now she purrs and roars!

I decided on a set of Bridgestone Battleaxes. This bike looks like a cream-puff but that is not how I ride...I figured great modern rubber is the best choice and tires can always be changed later. I'll just set about wearing these out first!

I still haven't photographed this bike yet. When I get the new pipes and tires on, I'll post a few.

Cheers!

[motocyconomad]

i'm jealous, I want some stock pipes for my stocker.

[wheeliepop]

Well it's been nearly 18 months since my last update. Is that a record?

Life happens and I've since moved houses and added a few other bikes in the interim. I'm finally taking some time to finish a few of the small projects remaining on the '78 CB750K.

Battleaxes mounted on wheels that I touch-trued, spot de-rusted and otherwise detailed.

Repaired and re-installed the horn (the PO handed it to me on delivery saying he couldn't get it to work while proudly pointing to the scooter horn he slapped on in it's place. This is the same guy who used a sheet metal screw to "fix" the petcock)

Removed, stripped, painted and prepped front brake components. New SS caliper piston on the way as well as OEM seal, bleeder w/cap and Master cylinder rebuild kit. Also fresh pads.

Finally installed the #3 & #4 NOS mufflers. While I had the old ones off I detailed the head around the exhaust ports and scrubbed and buffed the hard to get areas around the pipes, case and frame.

Removed, cleaned and waxed the chain guard and generaly deep-cleaned the rear wheel-well. Not the easiest task.

Installed DE7 NGK's for the cooler northwest clime and dercarbonized the cumbustion chambers and ports with Seafoam and H20.

I also ran the engine 20 minutes or so at 3500-4000 RPMS with a 50/50 mix of plain 30w oil and ATF to scrub the case internals and scour the rings a bit.

Drained that mess and replaced with Rotella T6 Synthetic and a fresh filter.

I'm excited to see fresh rubber on this bike, it almost looks like it want to be ridden! I've only got about 10 miles on the bike since I bought it.

Waiting on a few items from Mother Honda and this bike will be buttoned-up.

What a beautiful machine...

[wheeliepop]

another

[wheeliepop]

another..

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another..

[wheeliepop]

And another, I'm going to bed.

[Stev-o]

Looking great, nice update. Time to ride!