Project Complete

Ratchet

Ratchet

Club Member
Afternoon all,
Just a quick post to celebrate the completion of my current project. Since it's finally stopped raining I've managed to get a few miles done around the local roads and the bike is running very nicely indeed.

It's a bog standard 1200 motor from 1975. Has later front forks so that I could use a two more modern Harley calipers up front. Have used a banana caliper at the rear. To get the most out of the brakes I've used an aftermarket 12mm front master cylinder (in place of 9/16") and a 5/8" on the back (in place of the 3/4" original) In my opinion two very worthwhile upgrades, the brakes are now very effective, very progressive and very predictable.

I've replaced the original Keihin butterfly carb with a second hand CV carb from eBay. Internally I've installed a 180 main jet and a 45 pilot jet. I replaced the needle and the diaphragm / slide assembly both with items from CV Performance. It also has a little brass choke assembly again from eBay. The bike starts easily on the kicker, it idles evenly and pulls very smoothly in all gears.

A couple of niggles - I am getting a flicker of the oil light at idle, I think I need to do a bit of fettling with the steering head bearings and I'm having a bugger of a job trying to stop a slight weep of brake fluid from join between the 3 way brake switch splitter and the inverted flare on the rear most brake hose.

Fingers crossed for a long summer of warm sunshine and dry roads:)

All the best,
CV Carb.jpg
Front Brake.jpg
Rear Brake.jpg
Shovel Left.jpg
Shovel Right.jpg


Stu
 
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nice. you can't go wrong with a k-cv.
i don't know why more people don't fit later HD lowers and calipers to get better brakes? it's easy and relatively cheap with 'take-offs'?
i had 84-99 showa forks on my shovel with twin 1-pot floating 'pie' calipers, changed the lowers to '07-up that took the dyna et al twin 4-pot 'butterbean' jobs.
i'm not a fan of the brembo/tokico caliper upgrades, they look like what they are a jigsaw of plates and adapters and a caliper that looks awkward?

interesting you reduced the front MC size for twin disc? i believe 11/16 (17.5mm) would have been oem for twin calipers?
so you've reduced the size, increasing line pressure giving more braking force, but a softer lever/more travel, so more 'feel' maybe?
i have the 11/16 mc for my front twins, i'm happy, but always interested in 'real world' experiences from others.
i might try something smaller.

out of interest do you know the diameter of the piston(s) in the calipers?
my calipers have x4 33.3mm diamter pistons each.

nice to see someone retaining a banana too. in spec and operating correctly, they are more than enough?
never get why people 'over-brake' the rear wheel with six-pot calipers or so, even a pair of 'em?
to me thats asking to lock-up the rear wheel easily under hard-braking, dunno?

is the 'nana a later one with a more conventional piston/seal config or the typical pressed in piston with 'sprung' limited travel?
those later ones aren't easy to find. always on the lookout for one, but don't think identifiable from the casing alone?
i have a number of 'nanas and project on the go. an 11" disc, 2-pot 'nana being the main.

i think you can still get 'quality' ones new from girling, as they're used on some light aircraft?
but i might have dreamt that?

hope you get the weather to enjoy your machine.

if you know, you know (y)?

banana.jpg
 
Hi JayZedKay,

I'd been doing a bit of research around master cylinder / caliper ratios and found some info on various forums that suggested that a good ratio for twin disc set ups was somewhere between 15:1 & 18:1.
The front calipers I've got have 2 x 24mm pistons so with a 12mm master cylinder (and according to my maths) I get a ratio of 16:1.

The banana caliper on my bike has a conventional piston but I think it might be aftermarket rather than HD OEM kit. Seems to work well enough though. That's interesting info about Girling and light aircraft applications, might do a bit of digging.

I've got an Evo glide as my daily with two single pot calipers on the front and an 11/16 master cylinder; it does stop but it doesn't inspire much confidence. I have however just secured two used Billet 4s on eBay for not very much money, so I might do a bit of experimenting. It seems that they bolt straight onto Evo fork legs so I shouldn't need to get into making up adapter plates and such like.

Link to Vintage Brake

Link to CustomFighters.com
 
vintage brake is where i based my dealings too.
but i find it somewhat confusing and fully understand the calculating procedure?
that page talks about 2-pot *opposed calipers (implying twin) a ratio of 27:1.

*does the opposed mean twin-calipers or the pistons are 'opposed' as in opposite each other in the one caliper?
don't think that would matter? i's total area we interested in. the fluid doesn't care 'where' they are?

single-pot calipers about 13.5:1, which is half of the previous 27:1 favoured.
so bit confused for a 'definitive' ratio/guide?

for example, just going by that artical:
you have 2-pot opposed calipers, so lets aim for the authors favoured 27:1.
your 1809.55mm^2 total area divided by 27, and transposed for diamter gives 9.23mm or about 3/8"?
3/8" maybe good, maybe bad, thats just what it calculates too.

your chosen 16:1? is that guided from streetfighters? that link comes back blank unfortunately?
maybe they explain it better?

my calipers have 6967mm^2 of total area.
11/16" MC gives about a 29:1 ratio?
i'd need 23.5mm mc to get 16:1 for comparison?
a 3/4" would be around the 27:1
i'm leaving the 11/16 for now, i'm happy with it. but would like to optimise it, possibly?

it seems the ratio thing isn't normalized want for a better word? i.e. single use this, double use that?
i'd undertsand it better if it was just based on total piston area and required piston area to move apoproipriate amount of fluid?

in the real world, you'd just fit next size up and down mc and see whats best suits?
but it would be nice to fully understand the caluclated principles, if just as an excercise?

all good fun and brain food.
 
You're right there's lots of seemingly conflicting information out there. I guess a lot of it is also "horses for courses" with regard to feel etc.
I did use the "sweet spots" as advertised on the Custom Fighters forum and they seem to suit my personal riding style quite well.

It's all a bit fraught with risk too - wouldn't want to say "what you want is one of these master cylinders" only to find my mate parked in a hedge two days later :oops:

www.customfighters.com

Matching a Front Master Cylinder to your Caliper(s)

www.customfighters.com www.customfighters.com

This is where the other thread is located if it helps.
 
i got the link working now, seemed vpn was messing things up?
anyway, matey at CF states 17:1 target for twins and 13.5 for singles.
VB states same for singles, but 27:1 for twins? maybe that is a typo and never corrected?

highlighted below also adds to the confusion, i've read and read it and stared at it. it doesn't make sense?

Then you need to work out your ratio. Here is the formula, in plain english:
(total surface area of pistons on one side of each caliper [so you will get the same result on a 2-piston sliding caliper as on a 4-piston fixed caliper]) x (number of calipers) / (surface area of master clinder piston)
In maths terminology that's:
(((Pi x R^2) + (Pi x R^2))x n) / (Pi x R^2)

i.e. for the same size caliper piston, consider
a pair fo 2-pot sliders will give 1(half caliper pot) x 2(calipers) = 2 pots of total of area.
a pair of 4-pot fixed will give 2(half caliper pots) x 2(calipers) = 4 pots of total area, twice as much?

i can't see how 'same results' can be obtained? i must be misinterpreting it, dunno?
what if a 1-pot slider, like the old 84-99 pie-calipers 🥴

i could not download the spreadsheet, even with a pass-link sent?
sometimes seeing numbers can help you reverse-engineer it and the penny drops.
anyway, i won't sweat it for now.
stupid calipers.
 
What they mean is, for example:

2 piston sliding caliper - total area of pistons on 1 side of caliper is total area of 2 pistons (no pistons on the other side)
4 piston fixed (opposed pistons) caliper - total area of pistons on 1 side of caliper is also total area of 2 pistons (ignore the 2 pistons on the other side)
 
Yo G-man.
Thanks for taking the time to attempt to make it clear for me. Unfortunately i still don't really geddit?

a) 2 piston sliding/floating caliper. Yeah totally get that. UPDATE: At least I htought I understood it - see later.
b) total area of pistons on 1 side of caliper is total area of 2 pistons (no pistons on the other side)
above is twisting my melon man? 1 piston area equals piston area of 2 pistons, but there isn't a piston on the other side? but it's a 2 piston floater?
c) 4 piston fixed (opposed pistons) caliper - total area of pistons on 1 side of caliper is also total area of 2 pistons (ignore the 2 pistons on the other side)
i get this, simply taking the total area of one-half of the caliper, no worries.

to me it appears this procedure is trying to normalize or homogonoze the ratio, 'fudging' total areas, so it's applicable to varying 'n-pot' calipers?

WOAH!
whilest thinking/typing my reply, I htink the penny has just dropped :cool:.
2-pot 'floater' i took as opposed pistons, 1 in each half. not 2 on one side. Goddit.
i guess i couldn't see the wood for the trees?

mmm, i still think it's fudging it? the more pistons/area you have the more fluid you have to move to get the same piston movement. how the size of the mc correlates to braking performance and feel must be a case by case basis. wheel & disc diameters, pad material, disc material etc etc all play a part?

the only way to nail this is empirically, which is kinda obvious really?
start with an already 'generically' established mc size for given caliper(s) and try sizes either way. see whats best?

i apologise to ratchetmeister for rail-roading his thread and obsessing on this subject.
 
Ron said:
Are you running a very slow idle, it will sound great but wont do the bottom end any favours. Any idea at what revs the oil light goes out.
Click to expand...
So --- time for a confession. I was going to keep this to myself but in the spirit of full disclosure. The reason that the oil light was flickering was because during the build it stood for long periods of time between me giving the kickstart a prod and running the engine for a bit before switching it all off again. Each time I started it the engine had sumped and it pumped a bit of oil out of the breather.

On project completion day I kicked the bike over, started nicely and I was pleased to see that the sumping issue appeared to have mysteriously resolved itself. The reason it was no longer sumping was connected to the flickering oil light, that being the lack of oil in the oil tank.

I've topped up the oil and now it's all as it should be. I do have a check valve ball and spring on order so I hope to sort the sumping in due course.

A bit embarrassed but there you go - I never said I was perfect :)
 
Got a few miles under the tyres today - all appears to be going well - nothing fell off. Noticed oil on the front exhaust when I got home which appears to be coming from somewhere behind the points and dripping out of the hole in the bottom of the nose cone. So I expect I'll be investigating that next week some time.
 
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Ratchet said:
Got a few miles under the tyres today - all appears to be going well - nothing fell off. Noticed oil on the front exhaust when I got home which appears to be coming from somewhere behind the points and dripping out of the hole in the bottom of the nose cone. So I expect I'll be investigating that next week some time.
Click to expand...
oil seal behind the points
 
Cam oil seal behind the points now replaced and seems to be holding up.
I've also attempted the "A 3/8" ball bearing, a punch and a hammer" solution to the sumping issue. I'll start it this afternoon and see what squirts out of the breather. 🤞
 
Yeah it was a "three ball bearing" operation - The one that was in there to begin with, the new one that I used with the punch, and the other new one that I kept pristine in a zip-lock bag so that I knew which one it was. So I've now got two in the bin and one in the oil pump. The only unknown variable at the moment is the spring. It's an S&S pump which I think takes the later "1981 up" spring. Not sure what the difference is between that and the earlier spring though...
 
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