Topic: CB650SC CUSTOM, my first motorcycle/build

[CBJoe]

If you are lucky those carb models on your '82 should have removable slow jets (hopefully).  I think you can tell by the carb model number.  The previous CV carbs on the '81 models had pressed in slow jets and were a real PITA to clean.

EDIT:  I believe that the VB44A's had pressed in slow jets and VB44B's had the removable ones.

Cheers, Joe

[methebmxer]

Been a couple of weeks but I've made an engine stand so I can get serious about pulling the engine apart and have bought a TIG/MIG welder which I've begun to get used to before I touch the frame.

I'm currently more distracted than ever by the top triple tree nightmare that came on my bike. I'm sure most of you will be aware of the unusual double handlebar design and I've read plenty on the subject of changing it for a regular handlebar but can't seem to find a conclusion and its bugging the hell out of me.

I would like to if possible only replace the upper triple tree/yoke section and tick this off my to do list but I fear that I'm way to hopeful.
The stanchion/fork uppers are 37mm diameter. http://organ-donor.org/motorcycle-data/fork-tube-diameter-list/#tube37

It seems I have three options but each with their own set of problems.

1. I found a CB900C (80-82) upper but the spacing of the fork uppers is around 10mm wider than the CB650SC so I would need to buy the matching lower. I think I may just need to fit a wider axle, hub spacers and space the callipers to make this work but the steering bearings also vary and I don't know if this is possible to adapt? also the stem length may be way out?

2. I fit a different triple tree set with the same fork leg spacing, bearings and stem size. Please enlighten me if this exists.

3. Somebody tells me what I'm looking for doesn't exist and I swap out the entire fork, deal with the related issues and go back to sleeping at night.

[Bankerdanny]

I would look for a 78-79 GL1000 upper. It uses 37mm tubes and also the twin disk reverse Comstar that is on your bike. It would not surprise me if the spread were the same.

[SOHC4 Cafe Racer Fan]

I would look for a 78-79 GL1000 upper. It uses 37mm tubes and also the twin disk reverse Comstar that is on your bike. It would not surprise me if the spread were the same.

The 75-77 GL1000 also uses 37mm fork tubes and reverse mounted brake calipers.  I'm not sure if the spread is on any of the 75-78 GL bikes is the same as your CB650.  My 650 is in storage so I cannot readily take measurements on the fork tube spread.

[Bankerdanny]

I know you can't just install Comstars onto a wire wheel GL and vise versa, but the reason may have nothing to do with spread and might be related to axle size or speedo drive. That's why I recommended the 78-79.

[SOHC4 Cafe Racer Fan]

I know you can't just install Comstars onto a wire wheel GL and vise versa, but the reason may have nothing to do with spread and might be related to axle size or speedo drive. That's why I recommended the 78-79.

Good point. 

[methebmxer]

Food for thought, I've been looking at the GL1000 as a possibility so will do some more research, thanks


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[MiGhost]

Food for thought.
To use the GL1000 tree you will need a complete front end (forks, tree, axle, spacers, speedo drive hub, Wheel?, Brakes?).

Your forks will fit into the 81-82 CB900C tree.
To use the 900C tree you will need both upper, and lower tree. (Fork offset unconfirmed)
The 650SC uses the same front axle, and fork spacing (192mm) as the 900C (same wheel). The 76-79 GL1000 fork spacing is 204mm.
The stem of the 650SC, and 900C use the same bearing ID. Use the 650SC bearings.
The ignition switch uses the same base (same wiring) as the 900C. You can use the switch for the 900C (80-81 650 also).
The gauge cluster on your bike has already been changed from stock. The 900C uses a wider gauge mount than the 650. You will need the gauge mount from the 900C.

Note: The 81-82 CB900C triple tree can be used to upgrade the 79-81 CB650/CB650C to 37mm forks with dual disc, dual piston brakes.

Tarozzi Fork Brace (will fit CB650SC)
Fast from the Past:  http://www.fastfromthepast.com/servlet/the-Fork-Braces/Categories
37X60X192A  CB900FB-F2 CB750F 1981-1982 22-0025
37X60X192, CX650 Turbo 1983 22-0015, CX650E 1983 22-0016, CX500E 1982 22-0019

edited to correct errant info.

[methebmxer]

Thanks Ghost, I'll forget about using a GL1000 tree then as I want to change as little as possible.

I have the upper tree from a 1980 CB900C and know where to get the matching lower but just want to be sure before I order.

The fork legs are 37mm which is correct but their spacing is 204 c-c as opposed to 194mm c-c on the CB650SC CUSTOM, so if I use the 650 bearings on the 900 tree it should fit easily enough. This just leaves me having to space out the resulting gap between the hub and fork lowers by 5mm either side and then I assume I will need to find a 10mm wider axle?, as well as spacing the callipers 5mm inwards to reach the discs.

Also the offset on the 900 tree looks to be 10mm more than the 650 so which result in a longer trail but I have no idea if this extra 10mm is a huge difference or not?

[SOHC4 Cafe Racer Fan]

Way to go, Ghost, in providing the vital measurements.

I would buy not only the triple but the axle too. You should be able to find a good machinist to turn you some spacers.

[MiGhost]

Thanks Ghost, I'll forget about using a GL1000 tree then as I want to change as little as possible.

I have the upper tree from a 1980 CB900C and know where to get the matching lower but just want to be sure before I order.

The fork legs are 37mm which is correct but their spacing is 204 c-c as opposed to 194mm c-c on the CB650SC CUSTOM, so if I use the 650 bearings on the 900 tree it should fit easily enough. This just leaves me having to space out the resulting gap between the hub and fork lowers by 5mm either side and then I assume I will need to find a 10mm wider axle?, as well as spacing the callipers 5mm inwards to reach the discs.

Also the offset on the 900 tree looks to be 10mm more than the 650 so which result in a longer trail but I have no idea if this extra 10mm is a huge difference or not?

If the fork spacing is 204 c-c. It is not a 900C tree, and will not work with your axle, or brakes. To use that 204 width tree you would be right back to replacing the complete front end.

[methebmxer]

Damn, the part was listed on eBay as being from a CB900C ten speed custom 1980. Is this different?.


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[MiGhost]

Damn, the part was listed on eBay as being from a CB900C ten speed custom 1980. Is this different?.

OK, Had to go back through to figure this one out.
The '80 CB900C is based off the fork spacing for the GL1100. Which is 204mm.
The '80 CB900C wheel is the same as the '81 CB650C, but the '81 CB650C has the same fork spacing of the '82 CB650SC. Which is 192mm. Remember how they always say not to assume anything. This is why.

Based off the front axle for the '82 CB650SC the parts needed are as follows.
(192mm c-c)
44301-461-770 AXLE, FR. WHEEL
81 CB650C
82-85 CB650SC
81-82 CB900C
82-83 CB750SC

(37mm Fork)
53230-461-770 BRIDGE, FORK (UPPER)
53200-461-770 STEM, STEERING
81-82 CB900C
82-83 CB750SC

Edited above post to correct errant info.

[methebmxer]

That is beyond helpful, thanks so much! Things are making much more sense now.


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[methebmxer]

I found this which I think will work? Just waiting for a shipping quote.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230993701455

[MiGhost]

I found this which I think will work? Just waiting for a shipping quote.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230993701455

That is what you are looking for, but there are other options that would save you some $$.
Shop around and get the best price.

http://www.ebay.com/itm/1982-Honda-CB900-CB-900-Triple-Tree-Fork-Mount-/400550781430?pt=Motorcycles_Parts_Accessories&hash=item5d42afe1f6&vxp=mtr

http://www.ebay.com/itm/1981-Honda-CB-900-CB900-Custom-Triple-Tree-Fork-Mount-/360707740438?pt=Motorcycles_Parts_Accessories&hash=item53fbdb5316&vxp=mtr

http://www.ebay.com/itm/1982-Honda-CB900-CB-900-Triple-Tree-Fork-Mount-/360799951029?pt=Motorcycles_Parts_Accessories&hash=item54015a58b5&vxp=mtr

http://www.ebay.com/itm/HONDA-1982-CB900-CB-900-TRIPLE-TREE-w-HANDLE-BAR-CLAMPS-8-17-/131178067191?pt=Motorcycles_Parts_Accessories&hash=item1e8ad274f7&vxp=mtr

Also remember that you will need to have some way to clamp the handle bar, and mount the fuse block.

[methebmxer]

Thanks again! Now I know what I'm after. I might relocate the fuses I tidy up the handlebar area.

[SOHC4 Cafe Racer Fan]

I would recommend upgrading to a modern blade fuse block. You can pick one up cheaply and relocate it closer to you other electronics.

http://www.amazon.com/HELLA-H84960091-6-Way-Lateral-Single/dp/B000VU9D1G/ref=sr_1_1?ie=UTF8&qid=1409521157&sr=8-1&keywords=blade+fuse+block