speedo drive hub 77 vs 78 (answer: they both run clockwise)

[puddleduck]

Hey Everyone!

I'm doing the Comstar to spoke swap on my 78.

I have been using the search button and found lots of great info, just not to this particular question.

I have followed Greg Foresi's beautiful swap with his '78, but know that he did a heck a lot of customizing to his spoked rim so he could swap his rims back and forth without touching his 78 brake calipers and fork lowers.

I'm not that talented and know you can do a total front end swap. I have mostly everything but I have a question for anyone else who's done it.

The 78 has the speedo sensor on the left. The 77 has it on the right. Can I just keep it in that right side position or will the cable be running backwards? Will the speedo clock work like that? (edit: Answer, both run clockwise in their original position)

I want to keep my 78 Speedo clock. I have an old broken 77 speedo clock but I don't want to mess with internals if I don't have to.

Can I just flip the wheel and have the sensor on the left but be upside down? (edit: You can't because the brake calipers are in the way)

I read a topic of a member who did it, but when asked if his speedo worked found bigger problems (rotors killed his calipers) and never got to answer the question.

Thanks for reading this far.

Michael

[gregforesi]

There are a lot of subtle differences so swapping the entire front end is the way to do it.
My bike is in pieces in the garage (freshening up the paint) so I can't even push it to see which way the cable turns. It will be a few days before I can do that.
My guess would be clockwise but I don't know that for sure. If you have the speedo drive hub from both a 77 and 78 then you could spin them by hand and see which direction they will drive the cable.

When I re-laced the spoke wheels I went with chrome spokes. They looked like crap after only a couple of years. A few years ago I had them re-laced with polished stainless spokes (from someplace in the UK) and they are holding up much better.

The 77 front calipers have smaller diameter pistons (79's are the largest on the 1000's). The stock 78 front master with it's 17mm piston might need a lot of pull to stop the bike. I have a repo front master with a 14mm piston and it works quite well with the 78 calipers. (I did have to replace the cheesy plastic "sight glass" by JB Welding a dime into the hole.)

[puddleduck]

Thank you Greg,

I have both drive hubs, I'll check both to see which way the cable is spinning and let everyone know.

Didn't think about the front master cylinder. I knew the 78 was a two cylinder, and the 77 being one, it would push one better than two. I'll look into adding a front master cylinder to the project.

Thanks for the suggestion for the polished stainless too.

[Old Fogey]

You may find this helpful: https://www.wingovations.com/spokescomstarsorlesters

Also:
You can't just turn the 78 speedo drive 'upside' down a) it will be turning the wrong way and b) it doesn't fit the early hub.
(if I remember rightly, Greg used a speedo drive that I had modified. Not sure about that)

Not 100% sure that the 77 calipers will fit into the 78 caliper brackets.

The thicker discs will go into the 78 calipers but it's tight and may depend on the pad thickness. Or you could try a slightly shorter piston (45107-323-020) and see if that works. Maybe, maybe not.

The 77 and 78 calipers are single piston. The dual piston calipers didn't come in until 82

The alternative would be machining the early rotors from their 7mm thickness to the 5mm of the later ones.

[puddleduck]

Thanks Old Fogey,

I read about the different sized speedo hubs from Greg's work and your contribution and thankfully I won't have to mess with it. I checked it out today and both the 77 (positioned on the right) and the 78 (positioned on the left) both rotate clockwise. I won't have to change my speedometer clock.

You are right about he single piston 78. I got confused on that one. (wasn't be the first time, won't be the last)

As for the caliper brackets and calipers. I'm going to stick with pure 77. I have the complete 78 set up, but to modify it will require milling down the fork brackets to compensate for the wider position of the 77 rotors. I don't mind having an unmolested front end from a 78 when I'm done. I read a lot of people going the other direction putting comstars on 75-77 and all they needed was a couple of washers on each side to bring the brackets in and since 78 has thinner rotors they fit great. To go the other way is a whole other kettle of fish.

Honda really did start from scratch when they changed model years.

Now I'm on the hunt for full brake calipers/brackets/master cylinder from a 77...

[Old Fogey]

Unless you already have 77 forks, the 77 caliper brackets won't fit the 78 fork sliders, which is why I said I'm not sure that the 77 calipers with fit the 78 brackets. Someone else may know.
Don't use the 77 master cylinder. Use one with a smaller bore like Greg suggested.

[puddleduck]

I did manage to get everything from the front end of a 77 except for full set of brakes and calipers.
I just purchased a full brake set including splitter from eBay.

So you are saying the 77 (15mm) nor the 78 (17mm) will not do the job getting a good squeeze on brakes and look for something like 14 mm.

I saw someone got one from an 84 Goldwing and said it was really good and looks the part. I'll look into the specs of that before diving in. (edit: Apparently it's 16mm)