Author Topic: CB650SC CUSTOM, my first motorcycle/build (Read 4927 times)

methebmxer · « **on:** July 23, 2014, 01:18:33 PM »

Some time around a year ago it dawned on me that I'd always admired motorcycles and yet never owned one. My riding experience consists of crashing my friends pit bike when I was five, trashing mopeds around in the woods as a teen and getting a couple of rides on the back of friends bikes as an adult. I realised things had to change and getting a motorcycle would also be a great opportunity to learn more about them and have another project, win win!. So shortly after letting a friend know of my interest he told me of a bike going for free and I snapped it up.
Here it is as in all its purple and yellow glory

It's a 1982 CB650SC CUSTOM

It must have been rebuilt to some extent in the last ten years roughly as its been fully resprayed. it's a bit tatty but not much rust and mostly intact other than a missing tank. The loom is chopped but I can work with it and the engine looks brush painted really badly so needs a lot of cleaning although I'm hoping doesn't require a full rebuild.

As I'm new here I'll include this one of me rolling her home

SOHC4 Cafe Racer Fan · « **Reply #1 on:** July 23, 2014, 01:37:29 PM »

The good news is that it's close to being "all there" but has some of the ugly stripped from custom model. There are some huge "pros" to the 650. The primary one being the motor (more power and better porting) and another being the upgraded brakes from the 550 (mounted behind the fork). Another good thing is that 650s are less collectible than 550s so used parts are fairly plentiful and not overpriced (except for the engine cam). A huge plus with the motor is installing a big bore kit, which will ending up yielding you power comparable to a 750 in a much lighter (80 lbs plus) package. This translates to a more nimble and faster bike.

If you goal is to get the bike rideable ASAP, you may wish to delay any big bore kit for now and just get the bike running and stopping. Ah yes, you will need brake calipers for that! I would consult a salvage yard or ebay. While your at it, buy yourself a petrol tank and get rid of that hideous yellow!!

methebmxer · « **Reply #2 on:** July 23, 2014, 01:41:44 PM »

big bore kit has got me listening I must admit! although I didn't plan on an engine rebuild if it's not necessary to keep cost down. I have the brake and callipers are just about visible draped over the light in the second shot (due to being a bit seized).

The yellow is going for sure! haha

methebmxer · « **Reply #3 on:** July 23, 2014, 01:48:43 PM »

The colour isn't to my taste so a full rebuild is in order. I also know the best way to learn is to do it myself and I'm confident with mechanics due to being a full time bicycle mechanic and having worked on cars.

Once I got it home I stripped it down to a rolling chassis and started to get to know the bike

cb650 · « **Reply #4 on:** July 23, 2014, 02:45:08 PM »

Hello. cant beat free. What you have is a luxury custom. Here in the states its known as a nitehawk. One year only and is very hard to find body parts for. The engine is supposed to be a factory black wrinkle finish. I would get it running and see if its worth doing anything with.

SOHC4 Cafe Racer Fan · « **Reply #5 on:** July 23, 2014, 03:06:42 PM »

The great outdoors workspace! I wouldn't waste your time trying to restore this bike to its stock glory. I'd focus on making a reliable runner cafe, brat, scrambler or tracker. Keep the weight and the ugly off of it.

Is the motor seized or free? That may dictate whether you are just trying to get it running or doing a full engine rebuild.

650: Did the 82 come with dual front discs? What is the diameter of the 650 fork tubes (35mm or 37mm)?

methebmxer · « **Reply #6 on:** July 23, 2014, 03:28:35 PM »

I only have a shed to work in so stripped it outside before moving in to the shed as I had no lighting in the shed then. Now I have a fairly good space to work with good light but a little cramped, it'll do.

I don't think I'd go restore as it would be too expensive and I like the idea of having some creative freedom with it. I have a rough idea of what look I like and what fits with the bike but I think it's going to evolve as I work on it rather than set out with a final plan. Weight and ugly are definitely not welcome here though.

As far as I know the engine is not seized but I could do with confirming that as I've not seen it run and it was sat for up to a year before I got it. I have pulled the engine out though so not sure how I can check it's not seized.

It does have dual discs and the fork tubes are 37mm. I've looked in to changing the top yoke as it uses a two piece handlebar system but I'd prefer to fit a scrambler style I think. It seems I may be able to use some gold wing yokes? but Im unsure of compatibility of the steerer/stem length etc. Any pointers welcome.

SOHC4 Cafe Racer Fan · « **Reply #7 on:** July 23, 2014, 03:54:08 PM »

Quote from: methebmxer on July 23, 2014, 03:28:35 PM

I only have a shed to work in so stripped it outside before moving in to the shed as I had no lighting in the shed then. Now I have a fairly good space to work with good light but a little cramped, it'll do.

I don't think I'd go restore as it would be too expensive and I like the idea of having some creative freedom with it. I have a rough idea of what look I like and what fits with the bike but I think it's going to evolve as I work on it rather than set out with a final plan. Weight and ugly are definitely not welcome here though.

As far as I know the engine is not seized but I could do with confirming that as I've not seen it run and it was sat for up to a year before I got it. I have pulled the engine out though so not sure how I can check it's not seized.

It does have dual discs and the fork tubes are 37mm. I've looked in to changing the top yoke as it uses a two piece handlebar system but I'd prefer to fit a scrambler style I think. It seems I may be able to use some gold wing yokes? but Im unsure of compatibility of the steerer/stem length etc. Any pointers welcome.

I suspected that the fork tubes were 37mm. That is the correct diameter for a GL front end, but I'm not certain whether the distance between the fork tubes is the same between the two models. The GL fork tubes are longer than a CB750, and therefore much longer than a CB550, but I am not sure about the stock length for a CB650. Perhaps member 650 can chime in.

cb650 · « **Reply #8 on:** July 23, 2014, 05:35:46 PM »

81 custom and 82 nitehawk/lux cust did have dual disks. Although not the same. in 82 they went with dual piston calipers and the bigger tubes.. Not sure how long the tubes are. Both mine are together.

methebmxer · « **Reply #9 on:** July 24, 2014, 12:12:41 AM »

Once I pull the fork apart I'll do some measuring and go from there.

I have the dual piston callipers but the master cylinder has been replaced for one that comes on a Yamaha XS1100.

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cb650 · « **Reply #10 on:** July 24, 2014, 03:01:20 AM »

Did they seem to work? The 1100 had dual disks so it should. Did it have a break switch on it? can u post a pic? Ok no more ?s I'm looking to replace mine and dont like the stock plastic one.

methebmxer · « **Reply #11 on:** July 24, 2014, 03:18:07 AM »

Yeah they worked well from what I could tell but the pistons had stuck a bit due to not being used. Otherwise the Yamaha master cylinder is good and looks ok

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methebmxer · « **Reply #12 on:** July 24, 2014, 03:18:49 AM »

Not sure about the brake switch?

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CBJoe · « **Reply #13 on:** July 24, 2014, 04:49:10 AM »

Quote from: CB750 Cafe Racer Fan on July 23, 2014, 01:37:29 PM

A huge plus with the motor is installing a big bore kit, which will ending up yielding you power comparable to a 750 in a much lighter (80 lbs plus) package. This translates to a more nimble and faster bike.

Can you clarify what you mean by Big Bore Kit? Are you referring to the Dynoman DP674 Piston Kit? Or are you referring to Paulages Thread, where he uses CB750 sleeves and pistons and has the 650 case bored and the sleeves machined?

Cheers, Joe

SOHC4 Cafe Racer Fan · « **Reply #14 on:** July 24, 2014, 02:31:46 PM »

Quote from: CBJoe on July 24, 2014, 04:49:10 AM

Quote from: CB750 Cafe Racer Fan on July 23, 2014, 01:37:29 PM

A huge plus with the motor is installing a big bore kit, which will ending up yielding you power comparable to a 750 in a much lighter (80 lbs plus) package. This translates to a more nimble and faster bike.

Can you clarify what you mean by Big Bore Kit? Are you referring to the Dynoman DP674 Piston Kit? Or are you referring to Paulages Thread, where he uses CB750 sleeves and pistons and has the 650 case bored and the sleeves machined?

Cheers, Joe

Joe,

I was referring to the Paulages thread with the 750 sleaves.

CBJoe · « **Reply #15 on:** July 24, 2014, 03:32:04 PM »

Thanks...just making sure I hadn't missed another thread on the topic.

For the OP...here's the thread to that if you want to read into it.

http://forums.sohc4.net/index.php?topic=40414.0

Cheers, Joe

methebmxer · « **Reply #16 on:** July 25, 2014, 06:42:51 AM »

Thanks CBJoe will take a look.

with the bike completely stripped I could check out the frame which I had concerns about early on, here's why...

Someone previously decided to go at the seam on the top of the spine with an angle grinder. Apparently in an attempt to fit a different fuel tank.

They have removed the weld the entire length of the spine!

Also they hammered some other bits randomly

This is how it looks cleaned up. There are some 1mm gaps. I don't own a welder just yet but have some experience welding and brazing although mainly torch use I am looking to buy a TIG unit. I need to work out the best way to repair this. I thought one way might be to weld a narrow strip the entire length of the seam to reinforce the area?

calj737 · « **Reply #17 on:** July 25, 2014, 06:51:02 AM »

Yup, definitely re-weld that. TIG, MIG or Stick. It won't matter as long as you get penetration and have clean surfaces. While you're at it, re-weld the neck and collars to the engine hoops. And the end of the backbone to the seat hoop. Better safe and new than sorry.

I always fear re-painted frames as you never know what's beneath there... I strip them with a blast and then inspect carefully for rot or hack jobs. Welding rod is cheap insurance for a solid frame.

methebmxer · « **Reply #18 on:** July 25, 2014, 06:56:05 AM »

That confirms my thoughts, thanks.

Looks like I need to get that welder ordered!

calj737 · « **Reply #19 on:** July 25, 2014, 07:24:25 AM »

It's easier to MIG than to TIG if you're not an experienced welder. Plus, you can get a spool gun for your MIG and lay squishy peas for beads and look like a pro! TIG is all stick and takes skilled hands else you'll be very uneven. With a background in brazing, you may be fine. But I'd get a box to do either, and 2 guns, if it were me. MIG spool, and TIG stick with a foot pedal.

I like spending others people money (as mine is running low)

methebmxer · « **Reply #20 on:** July 25, 2014, 07:38:01 AM »

I tried MIG and it was a lot easier to get the hang of but I need to Get to grips with TIG as I plan on using it to make bicycle frames in the future (I'm a bicycle mechanic by trade). I guess I will get the whole lot sooner or later as I'd like to have the choice in the future. I'm not very concerned with making it easy as I think I have a steady hand and just enough skill to match. My only concern is with spending cash as it has a habit of escaping me rapidly also.

SOHC4 Cafe Racer Fan · « **Reply #21 on:** July 25, 2014, 07:48:23 AM »

With the stamped frames, I've seen builders grind the original welds and re-weld the top seams to make the seams cleaner and stronger. I've also seen builders grind off some material on the backbone to fit a tank, but still re-weld it. This is different, since the PO left the structural integrity of the frame compromised by not re-welding the seams. What a moron! I agree with the others - MIG or TIG it.

methebmxer · « **Reply #22 on:** July 25, 2014, 08:08:12 AM »

I think the PO must have either had no idea what they were doing or just gave in half way through trying to get a non standard tank to fit. Either way I have to deal with this first or the bikes useless to me. As it was free and I'm looking to improve my welding it actually may be a blessing in disguise or at least I prefer to see things positively.

methebmxer · « **Reply #23 on:** July 25, 2014, 08:12:38 AM »

The carbs seem in good condition other than one has some horrible deposits. The other three are clean as a whistle in comparison. What would the deposits be a result of?

calj737 · « **Reply #24 on:** July 25, 2014, 08:21:47 AM »

Water mixing with gas then dehydrating. Time to get out your cleaning cap and pull it on tight!

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Author Topic: CB650SC CUSTOM, my first motorcycle/build (Read 4927 times)