Topic: Introduction & café project -'71 CB750

[Project750]

Hello all,

I thought I would introduce myself and begin a thread about my '71 CB750 café racer project.  

A few years ago a friend gave me his father's old CB750 that he just needed to get rid of.  I had been out of motorcycling for a several years and hadn't thought much about getting another bike.  So this one sat in my garage for quite some time without much interest from me.



I was very close to selling it for a parts bike.  But I decided to look it up online.  That's when I discovered a picture of a CB750 café racer.  Man it just looked cool.  And it inspired me to build one myself.  

My plan was to get my bike running last fall.  Once I knew it ran well, I could start the conversion.   That didn't happen though.  I got sidetracked with another project around the house that lasted until the snow came.  So, I built a shop in my basement and disassembled the bike over the winter.

Here's the before and after of my shop space:




Yeah, my daughter likes to play in the sink.  Maybe I can get her to do some wrenching on the bike.

It's getting late, so I'll continue this thread tomorrow, documenting some of the tear-down I did over the winter.

 I'm pretty new at working on bikes, so I'm learning as I go.  I've been poking around here for a few months, and it's obvious to me that everyone is very helpful.  I'm looking forward to some good advice, so I will thank everyone in advance right here and now.

[zzpete]

  Welcome and nice job on the shop.

[Project750]

The gas tank was really rusty inside.



So I used some water and a bunch of tiny finishing nails, figuring they would be able to get into the tiny wedge-shaped spaces in there.  The gunk that came out was pretty gross.




Then I used some diluted muriatic acid and let it sit over night in the this tub.



I couldn't find my "after" picture.  But it came out looking a nice dull gray inside when I was done.  I didn't get around to lining the tank before winter.  I had been reading all the debates over Kreem vs. Por etc.  And I never decided what was best.  So there is some light surface rust in there now.  But that will come right off when I'm ready to coat it.

I Kreemed a tank on another motorcycle years back.  I have recently reacquired that bike, and the lining seems to have held up well.  So I may use it again. 

Here is a link to a build thread on that bike, documenting a few minor changes I made, including modifying new bars to run wires through them.http://www.hondatwins.net/forum/viewtopic.php?f=5&t=3876

[Project750]

When I cracked open the float bowls, they looked like this



I spent some time scrubbing the carbs, but was looking for an easier fix.  I had read about people boiling them in diluted lemon juice and decided to give it a shot. 




I followed the recommendations of people who had done this before, but for some reason it all went terribly wrong for me.  The carbs emerged with a thick chalky coating on every surface.  This made it difficult for any moving parts to function.  When I actuated the choke lever a couple of times, I wound up breaking the little sliding choke mechanism.



I ended up buying a replacement set of carbs from Perry Cycle Works.  One good thing...they were nice and clean when they arrived.  I installed them but didn't get a chance to get the bike running before winter hit. 

I was  amazed at how incredibly difficult it is to get the carbs back on!  This was my solution and it worked really well.



Anyone else try the lemon juice method of carb cleaning and have bad results? 

[KB02]

Get yourself some new carb insulators (the rubber bit between the engine and carbs). You'll be amazed at how much easier they go on and off.

Nice job on the shop, too!! And yes, you should get your daughter working on the bike. Get 'em hook when they're young... 

[Project750]

Thanks.  The shop was a lot of work.  I had to dig the floor down and reinforce that ancient foundation I have there.  Had to do some electrical work and plumbing too.  I'm pretty happy with the result.  Cutting in to that main drain pipe made me nervous. 

There's still a lot to do, but at some point I had to stop working on the shop and start working on the bike.

[Stev-o]

Nice work on your shop, you just boosted equity in your home.
Wow, those carbs were unbelievable.

Keep us posted...

[Project750]

Once the bike was tucked away in the basement shop I was able to start the tear-down.



That rusty gas tank is one I bought so I could practice making the knee dents before I tried it on my 750 tank.



I quickly realized that some pieces of 2x4 were not going to be sufficient for resting the bike on, so I bought myself a proper jack from Harbor Freight of course...where everything is either on sale, or will be next week.




Anyone know which bike that gas tank is from?  It has the fill cap offset to the right.  I just found it hanging on the wall at a bike dismantler.

[Zig]

""But it came out looking a nice dull gray inside when I was done.  I didn't get around to lining the tank before winter.  I had been reading all the debates over Kreem vs. Por etc.  And I never decided what was best.  So there is some light surface rust in there now.""

Do you need to coat tank? If is clean inside and doesnt leak i would leave it. My Triumph tank was Kreemed before i got it, wish it wasnt. No problems so far but the day will come.

[Roach Carver]

I would go with no coating if possible. My choice to throw another option in is RED COTE.(sp) I used it and like it really well. I think it is what BMW tanks came with from the factory.

[Project750]

I'm glad you guys brought this up, because I was thinking about this myself.  The tank can't rust if it's filled with gas right?  But what if it remains half-full for several days or a couple weeks?  Wouldn't that uncoated steel above the gas start to rust?  I know it got some flash rust on it right after I cleaned it.  I think I noticed some the next day.

[Roach Carver]

there are different way to remove the rust. acid is the most popular. there are threads about the bathroom cleaner called " the works" i think. it will remove the rust but flash rust is an issue. The acid to use is phosphoric acid. it will leave a stable black coating that is not as succeptible to flash rust. Short version is, go to a home depot and get a product that has phosphoric acid and as long as you have no leaks when finished you should be good to go.

[Project750]

Needed a way to get the bike off the jack and onto the floor so I could lay it on it's side and get the frame off the engine.  So I cobbled together this pulley system from leftovers from an old device I used in my garage.  It looks bizarre, but worked really well.  I could raise/lower the bike with one hand.





I also played around with my media blaster.  What an awesome device.






Tomorrow I will document my steering head bearing mishap.  And that will bring me up to the point that I stopped working a couple months ago so I could get my 450 on the road.   

Making this project thread has made me really eager to get back to work on it.  My next step is to blast and paint the frame and do some engine cleaning and reassembly.

[Project750]

So in my haste to remove the steering head bearings I attempted to pound one of them out from the back using a flat punch instead of waiting until I had the right tool.  What I ended up doing was making it cock-eyed in the steering head.

When I finally did get a bearing puller, I found I still couldn't remove it, no matter how hard I pounded at it.  After I seated it back down in I discovered why.  The bearing race had scraped a little lip of metal that was acting as a stop.  You can see it in the following picture.



I had to grind it away with my dremel.  Once I did that, I was able to pound the race out with no problem.  But it was certainly a lesson learned.





Anyone know where I can get the proper tool for removing the race from the stem?

[Project750]

Well I finally soda blasted the frame in my makeshift blasting-cabinet/spray-booth that I made completely from materials I had laying around.  It works quite well at recovering most of the blast media.  Keeps it off my driveway, and I can re-use it.




Then I hit it with three coats of self-etching primer



And today I shot it with the base coat.



Hopefully tomorrow I can clear coat it.

[Zig]

that looks GOOD!!!!