Topic: 1980 CB50

[steved650]

I wanted to post the work I've completed over the last couple years on my 1980 CB650.  Not looking for bragging rights but wanted to show my appreciation for the great information and great guys on SOHC that helped me out as a novice.  A little history....I picked up the bike for $500 from a second owner who inherited it and could never get it running.  Brought it home, pulled the air boots off, held the choke closed as the cable was seized and sure enough it kicked sputtered and ran...like crap but ran.  Awesome!

[steved650]

Like everyone else I have talked to I then pulled the carbs on and off about 100 times lol until I figures out how to really soak them....ran perfect.  I bought a complete parts bike for $200 to get a replacement rotor and minor electrical stuff then rode it like that for the first year.  My intention was to build a bobber but the more I looked around the more I appreciated the look of some great Cafe racer work.  I decided to pull the rear tail light assembly, build a slimmed down bracket and carve my spare seat into something move sleek.  Not exactly Cafe but my freedom of fabrication.  I didn't change anything on the frame in case some day I decide it needs to be 100% original again.

[steved650]

I drew up the bracket on cardboard, traced it out on some flat plate, put the bends in and tacked it together....fit great first try.  More luck than skill I'm sure but I was happy with that.  The seat took alot longer haha.  I used a hacksaw to cut-off the last 4" or so of the back of the seat, after about 4 beers to get the courage to go ahead and amputate lol.  The I used a marker to trace lines and a 90 deg air angle grinder to slowly remove foam and shape the back.  I dropped the seat height by about 3/4", made the area between the legs narrower (I'm short) and tapered off the rear.  Surprisingly it is a great comfortable seat even after a few hours in the saddle.  I was going to re-upholster it myself but decided wisely against it....I have seen some bad jobs from guys with good skills.  Had a local canvas shop do and only charged me $75....looked fantastic.

[steved650]

Next I decided to tackle the oil leaks.  I have an engineering background but I've never pulled a motor apart.  After I pulled it out I had a local guy blast it for me with crushed glass to get all the old crap off and give me a good painting surface.  I decided to blast and paint then pull it apart.  I figured if I pulled it apart first and got oil onto the fins I would never get it clean enough again for good adhesion.  Worked well.  Even with the engine sealed up solid I still got tiny amounts of crushed glass into the cylinder bores...word of caution to anyone consider blasting and paint.....gotta pull it apart after.  I hung it from the roof in my shop and spent about 3 hours doing about 5 passes.  That was two years ago and not a single spot with any paint issues.  I didn't cover the side covers well as these were from the parts bike, there just to seal things up.  I made a set of blocks to support it upright while I pulled the jugs.  With new seals and rebuilt carbs I put back into the frame, which I wish now I had stripped and powder coated.....next project.  At this same time I became versed in polishing....purchased some different wheels, material and spent hours doing and redoing parts.  I still can not get the surface finish I have seen from guys on SOHC.....well done guys.  Unbelievably it started within the second turn of the engine....great because of course I had an audience of beer drinking buddies to watch how long it would take me.

[steved650]

Pics for last post.

[snowfighter2]

I have an 81 and I want to do something along these lines.  I don't want cut on the frame either.  Tell me about the handle bars you are using. I'm going to start shopping for a spare seat tonight!

[steved650]

After I had he engine back in and running strong it was time to tackle that damn air box...I had done the carbs enough times to get it down to about two hours to pull, clean and put back in but 2/3rds of that time was wrestling those pricks back in there haha.  I pulled the air box and added cone filters.  I had already removed about 10" of baffle inside all 4 exhausts.  I really liked the 4 into 4 look so I didn't want to go 4 into 1.  I read here to use 120 mains and 42 slow jets.  With my mixture screws turned out 2-3/4 turns it runs perfect, pulls like a champ and sounds fantastic.  Of course after doing that I could notice a significant increase in engine temp.  I had expected some but was a little worried.  I kept an eye on my spark plugs and running slightly rich so figured my setup is good.  I wanted to have a temp gauge but because I'm thrifty I figured I could make one.  Using the parts bike dipstick I picked up a thermometer from C'Tire.  It actually turned out nice.  The gauge was the perfect length.  I cut off the dipstick portion, carved it out a little and used jb weld to bond the two together.  Found out I'm running at about 185 deg F in the city traffic and about 165 def F on the highway.

[steved650]

To snowfighter   I had a hard time finding something I liked and actually ended up with motocross bars.  They aren't very comfortable to be honest, likely due to the angle but I do like the look.

[steved650]

Final shots as it sits in the garage today.  Thanks for all the help guys.  If anyone has any questions please don't hesitate to ask.

[SOHC4 Cafe Racer Fan]

So glad you pulled the motor apart after blasting.  When I was reading your post, I started cringing -- thinking that you just painted and put the motor back into the bike without taking apart the motor.  Glass bead gets in everything!  Not the best lubricant either.

[mrfish2]

Great looking bike Steve, I've got an 80 CB650C I'm trying to get running myself. Really digging that oil temp gauge!

[SOHC4 Cafe Racer Fan]

Steve,

Yes, good job cleaning up the bike and tidying up the seat/fender/taillight.  I'm a fan of the 650 motor but not as much of the 80-92 frame, but that's just me; I'm less into the cruiser aesthetic with how the frame and tank are designed.  Ride the piss out of it and enjoy it! 

[steved650]

Thanks Mrfish  I'm pretty happy with the way it turned out for $10 and a couple hours messin around. 

And ya CB750 Racer Fan.....with only 26000 km on it I've got lots of life left in it.  And I'm not much of a cruiser so crankin the throttle alot!  So far I'm impressed with the power for a small bike.

[SOHC4 Cafe Racer Fan]

Excellent. A couple of us are working on projects with 550 frames and 650 engines (with 674cc kits and porting).

[steved650]

Hey CB750...very cool.  I bet those 550 frames are light.  Is there a big performance increase with the 674 kits?

[SOHC4 Cafe Racer Fan]

Supposedly a Google uptick in hp and torque accross the rev range. The 674 kit is not a huge displacement increase but increases compression significantly - similar to installing a Wiseco high compression 836 in a 750 or a 592 in a 550. That combined with porting will yield the best improvement.

Since I'm putting that package into the much lighter 550 frame and shaving extra weight, it might be faster than my 836. We'll have to see.

[70CB750]

Looking good!