Author Topic: Repro Loopframe Header pipe fitment & brake shoe arching  (Read 438 times)

Offline Mayor_of_BBQ

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Repro Loopframe Header pipe fitment & brake shoe arching
« on: June 07, 2021, 05:27:52 AM »
Really in the final stages of getting my Ambo on the road, she starts, she runs!!!

Two issues giving us fits---  the FIT of my header pipes & poor brakes up front....

The headers are reproductions from MG Cycle, PO bought them in 2014/2015. They *look* right, but the bend is *just* off. (yes they are on the correct sides).  After modifying the center stand to clear the MAC mufflers, I am now seeing that the header pipe runs too high along the lower frame rail. Was not able to fit the stock pipe-to-frame rail clamps/mounts.  I did not think this is a big deal, so left them off. Now I am seeing that the pipe interferes with the shifter in first gear, pretty touchy to find the gear... and the shifter is banging the pipe on downshifts.  My bike is a 1970 Ambo with Pegs.  I know these are not going to work for me, I guess I am just curious if these work better for floorboard bikes, or do people just live with it, or can anything be done?  My shifter is the standard stock heel/toe shifter, but I have cut off the heel portion because it did not get along with my sz13 boots.
I have a set of stock MG header pipes from a 1973 Ambo that I could send out for chrome and use to replace these repros..  Do you think that would be the way to go? Any leads on where to send pipes for chrome in the SE USA?

My brakes work, but the front is terrible. It is set and adjusted as outlined on the usual places, did a lot of research here to find that info... I would like to have the (new) pads arched to the drum, maybe I will also have the drum machined (ever so slight pulse in the brake from an oval drum?).  Is there somewhere to send the pads for arching?  If so, I do not need to send the entire wheel? Just the pads correct?  Or am I looking for a local brake shop to do this work?  I assume I will take or send the pads somewhere and then tell them the brake drum size it needs arching to? Or do I have to have the pad + wheel together and it is somehow arched specifically to the wheel it's mated with?  I have never owned a drum brake motorcycle.. I have probably driven some cars with drum brakes, but never worked on them for sure.


I am sure I will run into further issues as the bike hits the road

Chad (Shadrach) in Asheville NC
1970 Ambo (shiny resto-mod)
1984 V65 Cafe Racer (ongoing cafe project)
2007 Breva 1100 (Sport 1200 tribute)

Offline ttietjen

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #1 on: June 07, 2021, 06:13:30 AM »
CK out the Race Tech web site, they require the wheel w/o tire, backing plate  w/new shoes and axle ($200) but you have to ship a wheel to California. Don't know of anyone on the east coast the does it, There is a shop in Hendersonville that works on vintage BMW's maybe they could help. I think its called Boxer2valve.

Online Kiwi_Roy

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #2 on: June 07, 2021, 06:53:28 AM »
My Eldorado came without the exhaust clamps so I made a spacer out of square section about 1" long roughly shaped to the curve of the pipe with a worm drive clip to hold it snugly against the frame rail.
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« Last Edit: June 07, 2021, 10:50:36 PM by Kiwi_Roy »
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Online Antietam Classic Cycle

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #3 on: June 07, 2021, 08:52:50 AM »
What "pads" (shoes) are you using? In my experience, the shoes from MG Cycle and other parts suppliers aren't all that great in several respects: 1) the aluminum casting aren't well finished and usually require a little work to fit correctly, 2) the friction material used doesn't seem to be suited to the job.

IMO, the best bet is to have the original shoes relined. With what compound and by who? Two question I need to answer myself since my "local" shop closed up a few years ago. I'll be talking to these guys as soon as I have a chance:
https://industrialbrakeclutch.com/classic-cars-and-motorcycles-brake-clutch-relining/

Bead blasting the drum helps to bed the shoes in quicker and makes them work better afterwards.

Cable: the original brake cables had a thick (nearly 3 mm) inner wire of tightly wound strands and an outer housing that was wound of square section wire. Very little stretch when the brakes were applied. Most off-the-shelf cables available now (especially those from European suppliers) have a much thinner inner wire of not particularly tightly wound strands and an outer housing wound from round section wire. The result is a cable that is very stretchy, and gives little braking power or feedback. Add a switch into that and they're useless.

The only ready-made cables that are even worth buying in my opinion are those made by Barnett. They not perfect, but far better than others. MG Cycle sells a few cables made by them, any with a "B" at the end of the part number.
Charlie

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #3 on: June 07, 2021, 08:52:50 AM »

Offline Mayor_of_BBQ

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #4 on: June 07, 2021, 12:25:29 PM »
What "pads" (shoes) are you using? In my experience, the shoes from MG Cycle and other parts suppliers aren't all that great in several respects: 1) the aluminum casting aren't well finished and usually require a little work to fit correctly, 2) the friction material used doesn't seem to be suited to the job.

IMO, the best bet is to have the original shoes relined. With what compound and by who? Two question I need to answer myself since my "local" shop closed up a few years ago. I'll be talking to these guys as soon as I have a chance:
https://industrialbrakeclutch.com/classic-cars-and-motorcycles-brake-clutch-relining/

Bead blasting the drum helps to bed the shoes in quicker and makes them work better afterwards.

Cable: the original brake cables had a thick (nearly 3 mm) inner wire of tightly wound strands and an outer housing that was wound of square section wire. Very little stretch when the brakes were applied. Most off-the-shelf cables available now (especially those from European suppliers) have a much thinner inner wire of not particularly tightly wound strands and an outer housing wound from round section wire. The result is a cable that is very stretchy, and gives little braking power or feedback. Add a switch into that and they're useless.

The only ready-made cables that are even worth buying in my opinion are those made by Barnett. They not perfect, but far better than others. MG Cycle sells a few cables made by them, any with a "B" at the end of the part number.

I am 90% sure these are new shoes bought from MG Cycle in the last 5-6 years...  I have a ton of receipts & docs from PO and it looks like he thought he could buy everything repro from them and it would all fit together like a lego set. I have deff struggled with the cables. I even had to take the oem barrel adjusters off my stock levers on the parts bike and swap them onto the shiny new repro levers he had mounted because the cable ends were so loose in the barrel adjusters.  Dont even get me started on the sugar cube petcocks (ended up fitting the tonti-era ones when I couldnt stop the leaking).

as for now I have some used brake shoes installed and those are better. I will take my front wheel from the parts bike to a local machine shop I know with a brake lathe, I am going to have them look at it and see if they could skim the rotors--I will check on the bead blasting while I am there, thank you for that.

Do you know of anyone around that would rechrome my stock headers?

Also, I am so sure that my choke lever is mounted correctly, but the lever fouls at about halfway thru its travel? This is with it mounted on the front brake lever mount & using the CEV pillbox switches on both sides. Does that ring a bell?
Chad (Shadrach) in Asheville NC
1970 Ambo (shiny resto-mod)
1984 V65 Cafe Racer (ongoing cafe project)
2007 Breva 1100 (Sport 1200 tribute)

Online Antietam Classic Cycle

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #5 on: June 07, 2021, 01:04:58 PM »
I am 90% sure these are new shoes bought from MG Cycle in the last 5-6 years...  I have a ton of receipts & docs from PO and it looks like he thought he could buy everything repro from them and it would all fit together like a lego set. I have deff struggled with the cables. I even had to take the oem barrel adjusters off my stock levers on the parts bike and swap them onto the shiny new repro levers he had mounted because the cable ends were so loose in the barrel adjusters.  Dont even get me started on the sugar cube petcocks (ended up fitting the tonti-era ones when I couldnt stop the leaking).

as for now I have some used brake shoes installed and those are better. I will take my front wheel from the parts bike to a local machine shop I know with a brake lathe, I am going to have them look at it and see if they could skim the rotors--I will check on the bead blasting while I am there, thank you for that.

Do you know of anyone around that would rechrome my stock headers?

Also, I am so sure that my choke lever is mounted correctly, but the lever fouls at about halfway thru its travel? This is with it mounted on the front brake lever mount & using the CEV pillbox switches on both sides. Does that ring a bell?

I had some V7 Sport headers rechromed by Paul's Chrome: https://www.paulschrome.com/index.php/for-the-restoration-shop and they did a good job at good price. Now that I think about it, they could have also been done by St. Louis Plating too - I can't remember what I sent where now. http://stlplating.com/Gallery

Sounds like you're missing the round spacer that goes between the choke lever assy. and the brake lever perch. It's about the same diameter as the base of the choke lever, with an M7 hole in the center and an M3(?) hole along the outer edge for the pin that keeps the lever assembly from rotating, approx. 10 mm thick.
Charlie

Offline pehayes

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #6 on: June 07, 2021, 01:09:11 PM »
We discussed this at length over on the LoopFrame forum.  You can't just arc the shoes to match the drum.

If you had a car, one end of the shoe would be pushed by a hydraulic cylinder.  The other end of the shoe would have some form of adjuster.  Thus, when properly adjusted, the shoe moves mostly perpendicular to the drum surface and a matching arc will make mostly good contact.

You don't have a car,  you have a Guzzi.  One end of the shoe is moved laterally by the cam action of the brake actuator system.  The other end of the shoe rests on a fixed pivot pin.  While that other end can pivot, it can't move laterally to contact the drum.  You can't adjust that other end like you did on the car.  So, all of your brake movement action is only at one end of the shoe.  If you perfectly matched the shoe and drum arcs,  you would ever only get the slightest of material contact against the drum.

Thus, you have to arc Guzzi shoes when they are installed onto the backing plate and  have all of the adjusters in place.  You can then gently spin the whole lot and cut the friction material on the shoes for a maximum amount of drum contact.  Not easy.

Patrick Hayes
Fremont CA

Offline Mayor_of_BBQ

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #7 on: June 07, 2021, 01:17:38 PM »
We discussed this at length over on the LoopFrame forum.  You can't just arc the shoes to match the drum.


Thus, you have to arc Guzzi shoes when they are installed onto the backing plate and  have all of the adjusters in place.  You can then gently spin the whole lot and cut the friction material on the shoes for a maximum amount of drum contact.  Not easy.

Patrick Hayes
Fremont CA

does that mean you have to remove the shoe, cut material, re-install and adjust again each cut to check at each step incrementally?  Sorry, I have only ever seen a pic of a brake shoe cutter that Cliffrod sent me this AM... total neophite on this subject.
Chad (Shadrach) in Asheville NC
1970 Ambo (shiny resto-mod)
1984 V65 Cafe Racer (ongoing cafe project)
2007 Breva 1100 (Sport 1200 tribute)

Offline Tom H

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #8 on: June 07, 2021, 02:42:50 PM »
If we could adjust the fixed pivot like a car drum brake with the adjuster, then arcing to the drum would be great. If Guzzi would have made the fixed pivot like a cam lobe for adjustment, I think that would have made the brake even better.

Tom
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Offline pehayes

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #9 on: June 07, 2021, 02:47:22 PM »
does that mean you have to remove the shoe, cut material, re-install and adjust again each cut to check at each step incrementally?

No, it means you have to spin the entire assembly and cut the shoes while they are mounted in the backing plate.  You could make a custom jig if you were doing this task repeatedly. Same issue on the brakes of my Falcone single.  I did make a jig for those.

Patrick Hayes
Fremont CA

Online Antietam Classic Cycle

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Charlie

Offline LesP

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #11 on: June 08, 2021, 01:54:46 AM »
does that mean you have to remove the shoe, cut material, re-install and adjust again each cut to check at each step incrementally?  Sorry, I have only ever seen a pic of a brake shoe cutter that Cliffrod sent me this AM... total neophite on this subject.






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Offline n3303j

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #12 on: June 08, 2021, 08:42:23 AM »
There's always the Ural way.
Make up a sanding block with 80 grit paper and lightly sand the surface of each shoe. Assemble the brake to the bike and apply the brakes while spinning the wheel by hand. Hard application is not necessary. Just get drum shoe contact while still being able to rotate wheel. Disassemble the brake and shoes will be marked where they contacted the drum. Sand the marking off the shoe with the sanding block. Keep repeating this assemble, brake,check, sand until you have a shoe that is completely marked after the test. That shoe matches the drum and the fit will become intimate after a bit of break in.

PS The Vintage BMW guys refine with 232AF (  http://www.stillchampion.com/232af.html. )
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Offline Mayor_of_BBQ

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Re: Repro Loopframe Header pipe fitment & brake shoe arching
« Reply #13 on: June 09, 2021, 07:37:55 AM »
There's always the Ural way.
Make up a sanding block with 80 grit paper and lightly sand the surface of each shoe. Assemble the brake to the bike and apply the brakes while spinning the wheel by hand. Hard application is not necessary. Just get drum shoe contact while still being able to rotate wheel. Disassemble the brake and shoes will be marked where they contacted the drum. Sand the marking off the shoe with the sanding block. Keep repeating this assemble, brake,check, sand until you have a shoe that is completely marked after the test. That shoe matches the drum and the fit will become intimate after a bit of break in.

PS The Vintage BMW guys refine with 232AF (  http://www.stillchampion.com/232af.html. )

this sounds like quite a PITA but effective! and attainable to someone without specialty equipment!  Perhaps this is the way to go for me
Chad (Shadrach) in Asheville NC
1970 Ambo (shiny resto-mod)
1984 V65 Cafe Racer (ongoing cafe project)
2007 Breva 1100 (Sport 1200 tribute)

 

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