Topic: Dual Disks - Flip the forks - calipers behind forks

[cben750f0]

cheers for that. i just used the rubber ones..ha ha

peace

[ev0lve]

Hey there,

Got a little progress made this weekend but wanting to confirm I'm not totaling my fork leg in the process.

Following the FAQ I concluded that the bottom mount needs to be parallel to the disk just like the one that was machined at the factory. So I did that. The FAQ talks about shimming the top mounts out but that doesn't look right to me. Here's what I've got so far with some washers to straighten out the bottom.



and a pic of the factory machined leg



I think I need to file away at the top to make the thing come parallel. Seem right?

Would you guys mind taking some pics of your modified rigs from the same angle so I can compare and contrast?

Really appreciate it!

[snowfighter2]

Very cool mod. I'll wait till next winter to try and do a dual disc mod. I might even do the fork flip, cuz it is COOL! Right now I'm just trying to get the old K5 out of hibernation.       COME ON Springtime!

[Frankencake]

I'm a bit confused.  Where do you get the right hand fork?  I have a CB400F that i have been wanting to put dualies on but damned if I could figure out how.

[MCRider]

I'm a bit confused.  Where do you get the right hand fork?  I have a CB400F that i have been wanting to put dualies on but damned if I could figure out how.

I'm about 98% sure that all 550/750 legs have the lugs already there for the dually. I'm 50% sure the 400 doesn't have the lugs.

IF I had a 400, I'd look into a larger diameter disc and a twin pot caliper, rather than a dually.

[ev0lve]

I'm a bit confused.  Where do you get the right hand fork?  I have a CB400F that i have been wanting to put dualies on but damned if I could figure out how.

I'm about 98% sure that all 550/750 legs have the lugs already there for the dually. I'm 50% sure the 400 doesn't have the lugs.

IF I had a 400, I'd look into a larger diameter disc and a twin pot caliper, rather than a dually.

Pretty sure I read somewhere that the second unmachined leg is there on the 750s because it needed to be a production racer...

Yep, Hondaman posted that here
http://forums.sohc4.net/index.php?topic=23503.msg242398#msg242398

Which, by the way, is how the front hub got narrowed 4mm by Honda: it was required that a street-bike-stock front hub be used at Daytona in those days ("stock" production bike racing rules back then), and Honda wanted to run the 750 in 1970 there (which it did, taking all honors). So, in the late K0, the front hub suddenly changed to the 4mm narrower design, with a shoulder cut on the other side to allow for set-on of the other disc. All that was then needed was another caliper, assembled backward, 3 shim washers (2-4mm thick) for the stock caliper mount, a second hose and a longer banjo bolt, and you were "twinned". I ran mine like that from 1971 until 1979...

So if Honda wanted to race it in the 70's I suppose you end up with the rough mirror lower fork

[mateo tomas]

best part, the reversed speedo will take miles off the OD 

[754]

c-ben,
 shim the big bolt first, My K3 took about 1/8 or so, cut it from plate to match profile of the pivot.

 THEN measure the top, and cut a spacer to match top pivot piece, making sure it is parallel..

I get rid of the adjusters, just a PITA IMO..

[Frankencake]

I'm a bit confused.  Where do you get the right hand fork?  I have a CB400F that i have been wanting to put dualies on but damned if I could figure out how.

I'm about 98% sure that all 550/750 legs have the lugs already there for the dually. I'm 50% sure the 400 doesn't have the lugs.

IF I had a 400, I'd look into a larger diameter disc and a twin pot caliper, rather than a dually.

I declare a brain fart.  It has been a year since I built my 400's and two years since I built my wife's 550's.  This year I'm on my 78f model which has altogether different forks that the older 750's.  I did know that the 400 didn't have the lugs, but it sure would be nice to find a pair that did.  I'm sure that somewhere it has to exist.
I have enough parts around to do this to her 550F.  Maybe.  Hmmm. 

[cben750f0]

due to the other leg not being machines properly, everyone is goin to have a different shim set up, my bottom bolt mount wasnt parralel to the disc and required filing and when i managed that, the top was waaaaaaay out of true with the disc requiring ME to shim the top, many will have different experiences, which is why everyone is gettin difference outcomes. i originaly  (?) just bolted the caliper on and didnt pay any attention.... first time i used the brake the pad cocked and jammed solid in the caliper!!!!... requireing me to remove the caliper to get the bike rolling ( lucky i was only moving it across the shed).

The second leg was never intended to be used on the street, so was never finished.... just check it out, and file/shim where required... its a well worthwhile mod...OH and BTW, the speedo drive will still be on the same side, just need to make sure the rotor bolt heads are on the same side, otherwise they hit the drive... meaning you can use the old guard stay guide for the speedo cable, hope this helps a bit...

peace out brothers

[ev0lve]

due to the other leg not being machines properly, everyone is goin to have a different shim set up, my bottom bolt mount wasnt parralel to the disc and required filing and when i managed that, the top was waaaaaaay out of true with the disc requiring ME to shim the top, many will have different experiences, which is why everyone is gettin difference outcomes. i originaly  (?) just bolted the caliper on and didnt pay any attention.... first time i used the brake the pad cocked and jammed solid in the caliper!!!!... requireing me to remove the caliper to get the bike rolling ( lucky i was only moving it across the shed).

The second leg was never intended to be used on the street, so was never finished.... just check it out, and file/shim where required... its a well worthwhile mod...OH and BTW, the speedo drive will still be on the same side, just need to make sure the rotor bolt heads are on the same side, otherwise they hit the drive... meaning you can use the old guard stay guide for the speedo cable, hope this helps a bit...

peace out brothers

Awesome. So I'm on the right track. My top is way out. Well, a few mm. Another quick question since the top is pretty close in already - if I need to pick up a couple mm can I take it from the hanger without having to worry about it fatiguing or causing other noob killing harshness?

I would think so but... I like being alive and it would kind of negate the pluses of the duals.

I'm running a play by play of my setup here for anyone trying this that might find it helpful
http://forums.sohc4.net/index.php?topic=38242.msg493516#msg493516

[754]

Looks like you may need more on the bottom. ..Pull top one right off to check.

If I remember right you might be able to reverse top to change clearance.

[ev0lve]

Looks like you may need more on the bottom. ..Pull top one right off to check.

If I remember right you might be able to reverse top to change clearance.

Man I hope not. The angle of the pic may be playing tricks but the bottom mount is parallel to the outside of the disk at this point. When I mock it up it's the tops that are the width of the spacers out of whack (there are some washers in between the hanger and fork in the pic).

Looking at the factory leg with the hanger on it the stripe (raised bit) is visually down the center of the rotor.

Let me know if I'm not understanding what you're saying though. Would really like to get this right.

[754]

Looking at the pic, if you loosen the bottom, and it moves out.. it needs more shim..

[ev0lve]

Hmmm, I should have taken the pic without the shims in the bottom so there would be open space there. As I understood the FAQ I wanted to make all the hanger mount points parallel to the outside of the rotor?

Currently when fitting up the caliper it's offset a couple mm to the left of the rotor (looking from the front). Is it not important that the bracket be parallel AND centered up on the rotor so the caliper hangs in the right position?

Or will the pads in the calipers suck up a mm or 2 as long as everything is parallel?

Am I making this harder than it is? 

[cben750f0]

best way i found was put the edge of a steel rule on the side of the disk, the see if the side of the caliper hanger is parallel as well, that will give you a good idea what needs to be done, also i would be disinclined to take metal off the hanger brakets, there is more than enough on the fork leg.

hope this helps.

peace

[ev0lve]

Sounds like a plan. I won't be able to get back to it until Friday but it's good to have the marching orders worked out 

Thanks!

[754]

You have to start off doing one piece at a time, like the big bolt..

ANY shim used MUST be parallel, cant stress this enough.

A washer is not necessarily flat it should be miked. A spacer cut out of plate is better, spreads the load properly without digging in, and looks better, did I mention it will be parallel.. Then when you have the bottom spaced, ACCURATELY measure the top, and machine a spacer to fit or use plate and shim stock.

If you cant get in there with a caliper, grab a set of drills in an index, they will be in 1/64 increments (16 thou) if the shanks are not too roached.. and be fairly accurate..

[goon 1492]

You have to start off doing one piecat a time, like the big bolt..

ANY shim used MUST be parallel, cant stress this enough.

A washer is not necessarily flat it should be miked. A spacer cut out of plate is better, spreads the load properly without digging in, and looks better, did I mention it will be parallel.. Then when you have the bottom spaced, ACCURATELY measure the top, and machine a spacer to fit or use plate and shim stock.

If you cant get in there with a caliper, grap a set of drills in an index, they will be in 1/64 increments if the shanks are not too roached..

Now that is a hell of a tip right there. espically with the drill bits you wouldn't believe how many times that trick alone will work in other instances.
Man I wish I had the right caliper for the right side of mine so I can get it finished....

[ev0lve]

You have to start off doing one piecat a time, like the big bolt..

ANY shim used MUST be parallel, cant stress this enough.

A washer is not necessarily flat it should be miked. A spacer cut out of plate is better, spreads the load properly without digging in, and looks better, did I mention it will be parallel.. Then when you have the bottom spaced, ACCURATELY measure the top, and machine a spacer to fit or use plate and shim stock.

If you cant get in there with a caliper, grap a set of drills in an index, they will be in 1/64 increments if the shanks are not too roached..

Here's where I get to show my ignorance. Set of drills in an index is? What?

I guess my conceptual problem is that I think I need to shave down the top mounts for the hanger to be in the right position instead of shimming.

I know it's a pretty wide question but what am I not seeing in that pic that you guys are?

[cafe750]

When I help my brother with his flip the fork/twin disk swap, we wound up just bolting the calipers to their respective arms, placing them in position on the disc, and applied the front brakes. With new pads, the arms will now point in the direction you need them to be in, and show the gaps that need to be shimmed on the other end...kind of a quick and dirty way, but it worked great!

[754]

!/2 drill index in 64th usually starts around 1/16 inch or smaller, and goes up to 1/2 inch in 64ths increments..
 Feeler guages work pretty good for measuring up to around a hundred thou.. then it gets harder to measure.

 Did you try turning the top (2 hole) around, ie mount face towards wheel?

[ev0lve]

Did you try turning the top (2 hole) around, ie mount face towards wheel?

It hadn't even occurred to me! Looking at it that might eat the offset up without having to shave any more off the fork and then I would be shimming the top.

Lots of options. I like it!

Thanks!

Edit: Turns out I was way off in visualizing the relationship of the fork, hanger, caliper and rotor. Took a quick look at turning the hanger around but its offset would have meant having to file the fork leg to clear the pivot.

Should have taken a picture but it's pretty clear when you give it a shot it's a no go.

[754]

Hey, happy to help folks out..

People (that dont own fine measuring tools), tell me all the time they cant measure to under 20 thou, so I show them...

[cben750f0]

im a fitter aswell, and yes 20thou can be measured...lol

peace