Topic: 78 cb750k cafe build

[02z06dave]

Hi all,
this is my first bike, not counting the honda mr50 dirt bike I had as a kid.  Im being a little ambitious taking on a build when I havent ridden a bike in a while but I think it will go ok.  Im not a mechanic but I do a lot of work on cars.   For the last couple years my 2002 corvette z06 has been my project but ive been wanting a cool bike to play with lately, so i started my research and ended up with my new to me 750k. I picked it up about a week ago. It wasnt running but it turned over and wasnt leaking anything.  The po only had it for about a month and in that time he didnt do anything to it. The owner before him started putting in a new wiring harness but didnt finish connecting it all.  Im hoping it just all needs hooked up and itll start but if not, ill figure it out.

This is what im starting with


my plan for the bike is to do a complete tear down and rebuild to have a nice simple cafe bike I can cruise around on.  My budget is 3k, unless the motor needs rebuilt or replaced then ill allow another 2k.

Here is part way through my teardown


The first things im doing is replacing most of the old electrical components, wheel bearings, new brakes, suspension rebuild, carb rebuild. I used the wiring diagram to get everything labeled so I can hook it all up easily as parts come in.  So far I got a new starter solenoid, regulator/rectifier combo, coils, plugs, and wires, new points plate with points and condensers.  Im just waiting on my new fuse box and battery to come in the mail and ill be done with the electrical overhaul. 

I shortened the front forks and rebuilt them with new 550 springs, and new seals.  I am waiting for a lot of stuff to come in the mail so I am polishing all the nuts and bolts as I go. Im planning to get most of the little things powder coated so im leaving those be for now.


thats about as far as I am now.  My week of vacation from work is about done, so I probably wont get as much done each week, but I hope to finish by next spring, I want to start the motor by next week.

[calj737]

You're off to a good start, but making some mistakes by choosing things to do/replace without knowing their condition. I say this because your budget is tight and you're spending money on ignition and coils without determining if they're bad.

Also, why use 550 springs and not Progressive? You may have downgraded there, not upgraded... You say you short ended the from t forks... But do you mean you lowered the bike by pushing the trees down on huge fork? If so, you have altered the handling. Another way of accomplishing this "look" is by using clip-on bars. If the extended shocks is a look you like, best to replace uppers with new 1-2" longer tubes. Maintains the geometry while changing the look.

If you are hindered upgrading your ignition, either electronic or a new stock replacement from Hondaman on this forum seem to be the overwhelming recommendations.

By the way, I love the original baby blue mirror ;-)

Bike looks like a great salvage/donor. Peel that black rattle can engine paint job and she will look like $1M

[02z06dave]

I used 550 progressive springs. By cut the forks shorter, I meant that I cut them shorter. They were already pushed up an inch or so further into the tree.  I put it back the same way but may consider putting them back how they should be.  I ordered some clip ons the other day, so it depends if I like the feel of them higher up or down below the triple tree top.  I replaced some of the electronics because they were either damaged or missing and others because they were cheap and this way its all new.

[calj737]

If you shortened the overall length of the forks, you have altered the geometry. Two things are likely to be the result: under steer when cornering, and if the frame no longer lies parallel to the ground, then fuel levels in your carbs will be off. This can create other problems for you.

You might want to look closely at the bottom of the frame under the engine and see if the change has sloped the frame too far forward. Also might be introducing some clearance issues under the frame/exhaust (depending on the exhaust configuration you use).

[02z06dave]

What is the preferred method of getting the bike to sit lower if shortening the fork tubes is bad?

[calj737]

There are a few methods. Smaller diameter wheels front and rear. Shorter shocks and forks. Lower blocks are used by some. What is it you are truly trying to accomplish? Is it seat height, more aggressive posture, better handling?

I guess the advice I'd give you is whatever you do to the front, ripples across the bike. Perhaps similar adjustment to rear will level the bike out and equalize the changes to geometry.

[02z06dave]

I am wanting a little more aggressive stance. I did get 1 inch shorter shocks for the rear the balance the inch I cut off the forks, so hopefully itll be ok.

[02z06dave]

Well I haven't updated this in a while but I have continued to work on the bike. 

I did a little bit of a rebuild on the engine.  I didnt replace everything but I had a local shop that works on older bikes inspect what I had and replaced what they recommended.  The cylinders were bored 2nd over and I got the cycle x 2nd over pistons.  The machine shop that did the cylinders also redid the head.  I had cycle x rebuild the carbs because it was something I didn't really want to do and parts for a 78 are hard to find. This is what I ended up with.

[02z06dave]

I finished the front end next.  I redid the forks with new seals and oil and I powder coated the lowers.  I got a cognito moto triple top and installed a toggle switch for the kill switch and a little push button for the starter.   I got new china left and right controls. They seem pretty decent and were cheap.  The front disc was drilled by cycle x and I rebuilt and powder coated the caliper and hooked it up with a new braided stainless line.  The front wheel got new bearings and just a quick paint job for now.  I wanted to get a new 18 inch rim and stainless spokes but I can't afford it right now.

[SOHC4 Cafe Racer Fan]

Well I haven't updated this in a while but I have continued to work on the bike. 

I did a little bit of a rebuild on the engine.  I didnt replace everything but I had a local shop that works on older bikes inspect what I had and replaced what they recommended.  The cylinders were bored 2nd over and I got the cycle x 2nd over pistons.  The machine shop that did the cylinders also redid the head.  I had cycle x rebuild the carbs because it was something I didn't really want to do and parts for a 78 are hard to find. This is what I ended up with.

Hopefully, they recommended replacing the cam chain, tensioner and all seals and gaskets.  Those things are relatively inexpensive (and many "look okay" on inspection) but can give you a headache if you don't replace them.  Plus, why not, if you are tearing your motor apart, right?

[02z06dave]

For the fuel tank, I went with manx lyta from legendary motorcycles.  The quality is very good and daves customer service was fantastic.  I will definitely buy from them again in the future.  After a lot of searching for an off the shelf seat solution, I ended up having bedlam works make me one.  It was a little more than I wanted to spend but its exactly what I wanted and very high quality.   I had talked with a couple other people about a seat before them and I was given nothing less than 6 weeks wait time.  I got my seat from bedlam works in 3 days! 

I bought and welded the cafe hoop to the frame and powder coated it gloss black.

[02z06dave]

Hopefully, they recommended replacing the cam chain, tensioner and all seals and gaskets.  Those things are relatively inexpensive (and many "look okay" on inspection) but can give you a headache if you don't replace them.  Plus, why not, if you are tearing your motor apart, right?

Absolutely!   It got all new seals and gaskets, cam chain and tensioner, as well as new primary chains and tensioner.
Thanks

[02z06dave]

This is where it stands now.


I'm waiting to get my swingarm back from hondaman, then I can get the rear wheel back on.  I also need to figure out how I will mount the seat and get it upholstered and decide on a tail light and license plate mount.   Otherwise,  its pretty much done.  I tried starting it up today for the first time since I took it apart and ran into a couple issues.  Fuel is leaking from each petcock right where it screws into the tank.  Im going to try a copper gasket to stop that. The other issue is as soon as I open the petcocks fuel starts pooring out of all 4 over flow tubes on the carbs.  I tried opening only 1 petcock instead of both but that didnt solve the problem.   At this point im stumped and open to suggestions.
Thanks,
Dave

[SOHC4 Cafe Racer Fan]

For the fuel tank, I went with manx lyta from legendary motorcycles.  The quality is very good and daves customer service was fantastic.  I will definitely buy from them again in the future.  After a lot of searching for an off the shelf seat solution, I ended up having bedlam works make me one.  It was a little more than I wanted to spend but its exactly what I wanted and very high quality.   I had talked with a couple other people about a seat before them and I was given nothing less than 6 weeks wait time.  I got my seat from bedlam works in 3 days! 

I bought and welded the cafe hoop to the frame and powder coated it gloss black.

Dave,

This is coming along great!  The seat and tank look great, and it sounds like you have your motor properly buttoned up.  Now onto to fuel/air issues!

Are you using a genuine Honda petcock or a repro.  Some repros have issues.  You mentioned a copper gasket, so I'm not sure what type of petcock you are using. 

[02z06dave]

Dave,

This is coming along great!  The seat and tank look great, and it sounds like you have your motor properly buttoned up.  Now onto to fuel/air issues!

Are you using a genuine Honda petcock or a repro.  Some repros have issues.  You mentioned a copper gasket, so I'm not sure what type of petcock you are using.

Thank you!

The tank has 1/4 npt bungs on it and I couldn't find Honda petcocks for that.  The ones I got are Paughco brand from dime city cycles.  They didnt come with washers or gaskets but they are both leaking from the threads. I was thinking a copper washer gasket might help.  Might the petcocks also be the issue with the fuel pouring out of the over flow tubes on the carbs? This only happens when they are open, not closed.

[calj737]

Probably your floats are off in the carbs. Especially if your bike is jacked way off the ground, it could be part of the problem...

Else, verify your float height to eliminate the overflow from the carbs. Copper gasket sounds like a good approach on the leaky petcock.

[02z06dave]

Probably your floats are off in the carbs. Especially if your bike is jacked way off the ground, it could be part of the problem...

Else, verify your float height to eliminate the overflow from the carbs. Copper gasket sounds like a good approach on the leaky petcock.

Thanks.  I will check the floats and see. I will try leveling the bike out first and hope that's all it needs.

[02z06dave]

Well, I checked all the float levels and leveled the bike out and that didn't solve the issue with carbs.  Since cycle x rebuilt them, I sent them an email to see if they have a solution.  Hopefully they do. 

Aside from that, I added copper washers to the petcocks and oil plug and both leaks are now fixed.  I also got my seat mounted today and finished off my wiring.  My only electrical issue now is that my blinkers don't flash.  They are led so I used a flasher relay for led and it didn't work.  My thought is maybe its because I only have rear turn signals and not front?

[calj737]

Does the bike run at this point? If so, start and run the engine, then if the carbs are leaking, rap in each carb body with a screwdriver handle. This might help the floats seat properly. I've had this problem during a rebuild.

My carbs sat for a year after rebuilding them. Then, during the first few fires, each carb would leak, alternating which one. It took a day or so of scratching my head, opening the petcock, running the engine, etc until they settled down and stopped. Either, I had small debris sticking the floats (no proof) or the o-rings had dried up a bit. (I was told by a local vintage bike guy I trust, that it takes some time for them to rehydrate). Either way, running the engine and rapping on them, or them getting hydrates, everything is good now.

Cycle the engine, fill them, shut the petcock, run them dry. Something is amiss with your floats. I'd think CycleX would have done a top notch job and set them properly.

[02z06dave]

Does the bike run at this point? If so, start and run the engine, then if the carbs are leaking, rap in each carb body with a screwdriver handle. This might help the floats seat properly. I've had this problem during a rebuild.

My carbs sat for a year after rebuilding them. Then, during the first few fires, each carb would leak, alternating which one. It took a day or so of scratching my head, opening the petcock, running the engine, etc until they settled down and stopped. Either, I had small debris sticking the floats (no proof) or the o-rings had dried up a bit. (I was told by a local vintage bike guy I trust, that it takes some time for them to rehydrate). Either way, running the engine and rapping on them, or them getting hydrates, everything is good now.

Cycle the engine, fill them, shut the petcock, run them dry. Something is amiss with your floats. I'd think CycleX would have done a top notch job and set them properly.

The bike should run at this point.  I tried starting it but the best I got was a couple pops but it hasnt started yet.  I checked timing and spark and both were good, so I would guess fuel is the issue but I gave up trying for today. 

Thanks for the advice.  Ill give starting it another shot tomorrow.

[02z06dave]

Well I finally had some time today to try and get the engine fired up.  After checking over the carbs again, I realized the source of the fuel pouring out was due to the drains being open not the floats.  I thought that might be why the bike wouldnt start also, but no dice.  Its sputtering but wont get over the hump and fire.  I checked timing again and it seems the points are opening at the T mark insead of F.  I tried adjusting it but couldn't get it any closer.  I checked all 4 plugs again and im getting good spark so perhaps its a timing issue?  This has really been quite an experience so far trying to learn this old technology.

[02z06dave]

I was finally able to get it started by giving it just a hair of throttle with the starter.  It dies immediately though if I close the choke or let go of the throttle.  I kept it between 1000 and 1500 rpm.  When I let off the throttle it drops to around 800 then dies.  At least its progress.

[02z06dave]

After adjusting the idle settig on the throttle cable, the bike will idle on its own now without stalling.  Its got a pretty choppy idle though and doesn't sound smooth.  My first task I think will be dialing in the timing then I'll start to mess with the carbs.

I tried going through the gears to make sure I put that all together right and that was a success.  However, the clutch doesn't disengage the gears.  I readjusted the clutch cable but that didn't solve the issue.  I'm thinking since it hasn't been run in at least a year maybe more, perhaps the plates are sticking.  It may also need replaced. I'm going to dig into that in the next couple days as well.

[02z06dave]

I haven't done much with the bike in the last week or so.  Just messing with the rearset linkage to get the feet position just right.   Today I got my lossa engineering muffler in the mail.  I ended up cutting my header pipe 4 inches shorter and I needed to cut a couple slits in it so the muffler would slide over.  I like the look of it and it sounds pretty neat.  I also sent out my seat to get an upholstery pan made for it so I can get the upholstery done.

Does anyone know if there is an easy way to know if I'm getting oil to the top end?  I opened a tappet cover and looked in and it looks oily but I did put some oil in there before I put the cover on.  I tried running the engine with the 1 and 4 exhaust side tappets off and no oil sqirted out so im a little unsure. Are there signs I can look for if the top end is being oil starved?
Thank you in advance,
Dave

[SOHC4 Cafe Racer Fan]

Looking good, Dave. That Cone Engineering/Lossa muffler looks great. I'm not a huge fan of header wrap but I like yours.