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Messages - K2-K6

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31
Some good alternative methods there.

I'm similar in trying to first pump them out with mastercylinder pressure if possible. 

In MTB brakes they have more currently moved to "bleed blocks" that are more or less as described with a tyre lever or similar to put between the piston to lever them out by holding some in.
More specifically they are used in place of pads for bleeding the caliper when off installation to then leave a bled system with space to fit a new set of pads during installation.  Usually they're just plastic blocks and maybe supplied with a new caliper to facilitate this and being of correct shape to fit.

People are 3D printing them though with say one piston space deleted so that you can focus on one stuck piston individually, while any others are held bake in their bore.

I'm up into the hundreds of these in freeing them up ftom corrosion around that piston seal (they ate similar to our Honda arrangement for that aspect) so many not maintained or excessively jet washed to their detriment. 

32
As John indicates, a system to rotate crank with charging system and thus start the car.

One type "Siba Dynastart" was manufactured near where I grew up, the man who lived at the bottom of our garden (well not in our garden you'll understand, but abutting property  :) ) was a director there.

https://schmittparts.co.uk/products/siba-armature-sachs-0686-072-002 as example of the type.

Fitted in Meshershmidt as well and obviate the need to have reverse gear fitted when used on a two stroke motor.  Invalid cars with Villiers motor used them too, I believe.

33
CB750 / Re: Best workshop manual cb750
« on: January 29, 2024, 09:21:38 AM »
The dry sump was a poor idea, giving a notchy and loud gearchange, the main reason I didn't like the 750 over the 500 which has a gear change like a knife through butter.

The dry sump has absolutely nothing to do with how the gearbox runs and works. Lubrication is even pushed through it via takeoff from return /scavenge side of pump.

The two engine, although they may superficially look similar in layout, are very, very different in overall design.

The smaller engine uses more reduction going into transmission, runs hyvo chain (consequently low oscillation space on input route from centrifugal characteristic , even when chain is knackered) with gearbox running at lower speed and needing less final drive reduction.

The 750 has no mitigation for its primary drive chain (slack is slack on this one) larger clutch inertia on the end of that chain in conflict with crankshaft to effectively have a more nuanced remote flywheel effect. Gears have reduction ratio on exit of box to drive sprocket and still need fairly large rear sprocket to complete drive train. If there's any final drive compromise on 750 chain, lubrication, adjustment, tight spots etc it'll play havoc with gear change quality.  The change is quite "industrial" in quality, but works well with all components finely fettled.

Dry sump on any engine is all about getting oil away from spinning crankshaft and ensuring completely reliable supply side to lubrication, thats all.

Honda learnt a lot between these two design, the 750 relatively crude and with excess weight etc (they didn't develop or repeat this design ) the 500 was logical in moving to hyvo chain for refinement and with lighter components. The dry sump "effect" is done on these by making the sump deeper to keep the oil out of the way of other components, essentially followed by many other four stroke engine design even today.

The 400 shows probably a little more of this design concept in having that drop down sump with all the exhaust pipes routed to one side of it, this now seen in many production engines.

34
Misc / Open / Engineering interest
« on: January 28, 2024, 11:30:35 AM »
For those interested in engineering thinking, design and application, this is a really really good watch

https://youtu.be/m7uZu_Wsdis?si=6lJopnvW44Uqvx11

A very lucid walk through of race car design engineering, Honda powered  :)  with many gearbox and clutch component design shared with bikes.

Quite long, but very worthwhile viewing.

35
Anorak's Corner / Re: Power coating rims
« on: January 25, 2024, 12:48:43 PM »
Many of the aluminium rims have been powder coated over the years, workable but you need to be careful with use of rim protectors etc if you go near them with any type of lever.

Is it just the rims without spokes etc ?  I've seen some like this complete assembly coated, that have cracked off the layer around spoke nipples etc, that's from general flexing in use.

36
CB350/400 / Re: This piston must need replaced?
« on: January 24, 2024, 09:57:45 AM »
To the original question....the stainless piston option is a good one. Experience on here is that they are well made and work well.

As Bryan has already contributed, the seal, its groove, how clean that is, are one of the most crucial aspect of getting this (and any caliper) to work correctly.

They should be assembled with silicone grease (it's directed even in the very first 750 Honda manual) to work well and protect it from corrosion.

I noticed that the Haynes book suggests smearing the piston with Brake Fluid before inserting back into the caliper body. Is the  silicone grease a better choice or is there a good reason to use it?
Thanks

They have absolutely no weather sealing on these caliper, the silicone grease excludes water from piston seal to effectively do this function.

Silicone grease is highly hydrophobic (near zero water attractive) with brake fluid the opposite in it's vulnerability to water ingress. Combine this with any available salt from road use gives effective electrolyte solution, causing the corrosion you've already got in the old piston.

Silicone grease is advised in the original Honda (first product disc brake really) and very effective.

It's your choice, but I use it on all caliper builds.

37
CB350/400 / Re: This piston must need replaced?
« on: January 24, 2024, 07:53:45 AM »
To the original question....the stainless piston option is a good one. Experience on here is that they are well made and work well.

As Bryan has already contributed, the seal, its groove, how clean that is, are one of the most crucial aspect of getting this (and any caliper) to work correctly.

They should be assembled with silicone grease (it's directed even in the very first 750 Honda manual) to work well and protect it from corrosion.

The seal on a single piston caliper must retract the piston to give running clearance for BOTH pads (the static side on this is assisted in keeping the pad off the disc while running, but needs the seal to "give" initial clearance) and makes a big difference to how effective the brake is..you should be able to feel the free piston go out when lightly squeezing the lever, then definitely retract as you let the lever go. If it doesn't do this (that's about 0.4mm) a very visible retraction, then either the groove is not clean or the seal is not toleranced correctly. 
It may be of use considering the genuine Honda seal IF you dont get that retraction correctly established.

38
CB350/400 / Re: This piston must need replaced?
« on: January 22, 2024, 09:32:10 PM »
Yes, replace the piston.

FWIW, I overhauled the front brake on my 400 last year.  It had been worked on by the shop that sold it to me, which included a new SS piston/aftermarket seal.  The brake was ABYSMAL and that's generous; the rear brake generated more stopping power!

I went through the brake, removed the (new) SS piston they had installed and replaced it with a (way more expensive) Honda piston, replaced the (new) aftermarket seals with Honda (way more expensive) seals, and replaced the brake lines.  With a new set of pads and some serious attention to breaking them in properly, the front brake was transformed into a very good brake!

Not being funny here Mike but the fact you did so much work on it all at the same time sort of confuses what was causing the poor brake performance, doing one change at a time is far more informative as it highlights what was the problem, it could have been such a simple thing as air in the lines and you changing the lines fixed that problem.

While it may not give us step by step analysis of the brake in question, it does serve to show that performance in a properly operating std system is much better than general statements that pervade the great wide Internet will have us believe....that what do you expect, they are just old brakes....that's often trotted out.

The performance isn't that bad, they were easily under 30ft stopping distance from 30 mph when new and we should be able to get them perfectly up to matching their performance capabilities now.

39
CB350/400 / Re: This piston must need replaced?
« on: January 22, 2024, 02:39:49 PM »
Definitely.....it'll not seal well and damage a good seal if used.

40
CB500/550 / Re: 1978 USA import CB550 K4 PD46C CARB
« on: January 22, 2024, 12:43:00 PM »
I pulled the ones out of my PD50’s by heating carb body with a hot air gun. Wrapped a pice of rubber tube around the jet and it pulled out pretty easy.

I thought this was a good start point, and obviously avoids potential damage.

Failing that though, a good mechanical grip, if they are very resistant, will be of value to get them moving.

Those knipex twingrip are a good tool to have anyway if you've something that's already been compromised.  My son bought my pair recently for a birthday present as I'd been looking at them in a tool shop.  Positively surprised at just how good they grip in comparison to some of my old and quite well used tools. Quite a neat size to carry in an emergency tool pack as contingency as they can be set to open quite wide in accommodation of different components.

41
CB500/550 / Re: 1978 USA import CB550 K4 PD46C CARB
« on: January 22, 2024, 09:06:52 AM »
Probably not worthwhile just for a single job, but these Kniipex twingrip pliers have a "bore" in the nose that's particularly effective in gripping a cylinder https://www.amazon.co.uk/KNIPEX-82-01-200-atramentized/dp/B09FPZPY96/ref=asc_df_B09FPZPY96/?tag=googshopuk-21&linkCode=df0&hvadid=641638718575&hvpos=&hvnetw=g&hvrand=6235607503535841976&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9045915&hvtargid=pla-1640846664898&psc=1&mcid=e02a7d1495603634ba0636b3393dbad5&th=1&psc=1

Obviously a limited use here but very effective. Usually when you turn to get the pliers out something has failed, stuck or broken, these really do grip like hell to avoid slipping and seem a good addition to a toolkit.

42
CB750 / Re: Head Bolts
« on: January 20, 2024, 09:04:31 PM »
For no real purpose I find it interesting, along with other's views as that is how we acquire knowledge or exhamine our own.

All discussions are good I feel.

I was idly wondering recently about tbe famous Pink Floyd album cover that is clearly of Refraction, when if you were to be generally hanging around the Dark side of the moon, then would probably be seeing Diffraction, which wouldn't look like that.

 ;D ;D ;D

43
CB750 / Re: Head Bolts
« on: January 20, 2024, 06:01:27 PM »
It's making me intrigued as to what is correct, not because it's in any way practical.....for reference, I use a plastic syringe about 100ml stuck into the fuel feed pipe and secured to frame by elastic band when carb balancing. Same one has been in my tools since the seventies  :)

Can we apply the "atmosphere" calculation to a static head of fluid though ? The example of going down intomthe sea doesn't seem to apply to me as you are effectively within the fluid that is supported on the seabed. Each movement downward gives you a layer now above you that's compressive. The total gain taking into account that increases in mass to give the typical calculation figure.

In water tower or the high level fuel feed, the mass is supported through a route down to the ground and so doesn't enact a force on the outlet.

The column weight is what we could measure at base level, this then depending on bore size (capacity in vertical now unsupported by the structure) with a column of 60 ltrs that would be 60 kilos in water into whatever sized outlet we have.

Oil derived fuels are ordinarily less dense than water, but not by much to affect our consideration here.

It looks more like volume of pipe above float valve (possibly 100 ml ) when on ceiling, approx 100 grams resisted by the float force through leverage on the entry valve. 

44
CB750 / Re: Head Bolts
« on: January 20, 2024, 02:55:49 PM »
     

     Typically mc fuel pumps delivers 3psi.  Float valves are generally overcome at approx 4.5 / 5psi.  1ft head of water gives 0.433psi do the maths.
     One thing many don't think of is that in use float valves open very tiny amounts so the smallest of debris is likely to stay in the valve and never
     be flushed through unless the carb is drained or stripped and cleaned properly.
     Anyone wanting to check simply put a airline with a pressure reg on a upside down carb on the carb inlet and see at what point the valve leaks
     air when using leak detector spray.
   

Isn't that accumulated figure 0.433 psi going downward under sea level ? Usually at one atmosphere for each 10.06 mtrs (33ft) effectively the accumulation of the ocean above you.

In air, and by lifting 1 ltr, then its nothing like that surely.

I'd doubt much difference between a tank say at 20 ltr sitting just above the carbs, in comparison to 1 ltr at 6 ft higher. 

45
CB750 / Re: Head Bolts
« on: January 19, 2024, 07:02:05 PM »
It doesn't change much at all.

 1 ltr of fuel hung on the handlebars is exactly the same weight as it is hanging on the ceiling, just the volume of the pipe (minimal at that bore) is added to the total weight. If you had it on the bars with tube running horizontal to the carbs, then lifted it up high, you just add that tube volume in weight.

Water towers are about distribution over distance to supply surrounding areas I believe. The volume has to be above all of the outlet else the pressure will not be enacted at the outlet when you open that tap if its not reliably below the head tank.

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