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Author Topic: AUXILIADORA 1981 HONDA CB750K BUILD  (Read 2262 times)

Offline Ryan Stecken

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #10 on: Jun 25, 2017, 20:09:06 »
Wow amazing man!let me watch!

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Offline PRIMEWORKS

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #11 on: Aug 20, 2017, 22:10:53 »
Ok so it's been a while. Not a ton has happened since last posting but the reason for my absense was due to school and me finishing a summer class. Since last posting I've finished the frame completely with a friend of mind and have sent it off to get sandblasted and powder coated. I went with powder coating the frame gloss black because I wanted a stockish look but something that was durable. Now Im in the process of trying to figure out what left I have to get ready so that when the frame comes back from powder coating I can just reassemble everything (although I'm sure it will be harder then I think it will be since its been so long since the bike was in one piece).

As of right now this is the list:

1. Wire the bike

I purchased a Motogadget M unit, M button, and the wiring kit for the M unit to simplifiy the wiring as much as possible. I'll start the wiring once I get the bike assembled for the most part becasuse I want to ensure the wiring is a neat as possible and well hidden.

2. Get a seat made

Kinda need the frame done for this to.

3. Fix the carbs

When I last rode the bike after getting a safety I found that one or two of the carbs seemed to just be pissing out fuel non stop. I read around and saw that some people say this is due to floats sticking but I just removed the bottoms of the carbs and the floats seem fine (atleast visually seeing as they move freely so I'm stumped). Anyone have any ideas about this? Cause the last thing I'd want is to have fuel on my freshly painted engine :(

Anyway till next time.

Offline CrabsAndCylinders

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #12 on: Aug 21, 2017, 15:51:56 »
They move freely but they may need adjustment or the needle jets may have deposits which prevent a good seal.
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline PRIMEWORKS

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #13 on: Aug 21, 2017, 19:26:52 »
They move freely but they may need adjustment or the needle jets may have deposits which prevent a good seal.

How exactly would one adjust the float?

also ordered some new headlight brackets. Nice simple look. As well as Motogadget M-blaze mini pin turn signals for the rear of my bike.


« Last Edit: Aug 21, 2017, 19:34:57 by PRIMEWORKS »

Offline jpmobius

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #14 on: Aug 21, 2017, 22:09:28 »
Likely you simply need to clean and polish the needle and seat assemblies.  Some floats are adjustable and some are not.  Probably you need to replace no parts in your carbs. 

Old carbs always need to be cleaned.  100% disassembly is required.  Seldom is a rebuild kit needed, and I ALWAYS recommend against them.  If you need parts, get the OEM parts as needed.  None of the brass parts will need replacement unless damaged by incompetence or severe difficulty in dissasembly.  Ultrasonic cleaning is ok, but not good enough.  PERIOD.  Learn how the carbs work , and you will find them pretty easy to clean properly.  Spray carb cleaner and knowledge are all you need to have perfectly operating carbs.  Most carbs have two systems that overlap - the pilot system and the main system.  The important thing to understand is that the fuel is mixed with air before it is introduced into the main bore of the carb.  failure to understand this and clean accordingly is why most carbs work poorly.  Look at the pilot system.  In most carbs, air for idle is first provided by a hole bored into the intake bellmouth of the carb.  The amount of air is determined by an adjustable needle valve which adjusts with a straight blade screwdriver.  Usually it is the only adjustment on the exterior of the carb except the idle speed adjustment which usually is a simple mechanically adjustable stop for the throttle.  Fuel for idle is provided by the pilot jet.  It is submerged in the fuel in the fuel bowl.  When the engine is running, vacuum is applied to the well above the pilot jet.  Fuel can enter into this well through the pilot jet, and air can enter the well through a passageway from the pilot air needle valve and they mix together.  The adjustment for the fuel is to change the size of the jet, and air is adjusted by turning the air screw in and out.  The mixture of air and fuel is then sucked into the main bore of the carb and mixed further with air flowing under the throttle plate or slide.  If you want your carb(s) to work properly, find these passageways and make sure they are clean.  The main system works exactly the same way, but uses different passageways and does not have any adjustable needle valves.  All the adjustments are accomplished with interchangeable jets for both fuel and air.  There are more parts, but the important thing is to understand this pre-mixing of fuel and air before that mix flows into the main bore of the carb, mixes with the main intake air ind is consumed by your engine. 

Once you have the carbs clean, you can address your fuel overflow.  Most floats adjust by bending a small tab on the brass lever arm the floats are attached to or operated by.  Usually this does not need to be adjusted.  You will need the factory manual to know how to correctly adjust the float level, but by far most floats are parallel with the float bowl gasket surface when the body is upside down and gravity is holding the floats in the up position.  This is not the reason your carbs are leaking fuel.  Likely the needle and seats simply need to be cleaned and no adjustment is necessary.  Take the floats and arm(s) out and also the needle and seat assembly.  Get some polishing compound (like for polishing paint after wet sanding), put it on a Q-tip and spin it by hand in the brass seat.  Put some on the needle as well and spin it by hand on a paper towel.  Clean and dry.  Put it back together and if there is no mechanical issue or crazy excessive wear on the needle - or some previous parts replacement with incorrect or incompatible parts,  the valves should be fine.  Be sure to polish the bore of the seat and shank of the needle as well, these parts have to slide freely and loosely with the cone shaped seal perfectly smooth and clean to work.

Mobius


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Offline PRIMEWORKS

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #15 on: Aug 28, 2017, 04:00:26 »
So I got the bike frame back from powder coating






Got all the major stuff on. now it's time to install the controls, a few remaining engine parts, and wire everything up.

One thing I didn't expect to be a problem however was the kick stand. Because the bike was lowered the kick stand is way to long to allow the bike to stand on its own properly so im a bit stumped. I may try and find a new short one online otherwise I'll be cutting and reweld the old one I think. Any suggestions? Also please note the bikes ride height has NOT been set in properly in these pictures. The bike does have suspension travel and the last picture is not what it will actually be.

Offline 1fasgsxr

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #16 on: Aug 28, 2017, 13:30:15 »
Looking good !!

Offline CrabsAndCylinders

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #17 on: Aug 28, 2017, 16:01:52 »
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline CB MIKE

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #18 on: Aug 28, 2017, 21:48:18 »
I actually had the opposite problem with the kickstand, mine was too short. I was able to swap the c model kickstand for an f which was slightly longer. I'm not sure the length difference between k and c models but I'll measure it and post pics tomorrow and if it works for you I'll mail it out.

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81 CB750C

Offline PRIMEWORKS

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #19 on: Aug 29, 2017, 11:52:07 »
Thanks a bunch guys!!

I actually had the opposite problem with the kickstand, mine was too short. I was able to swap the c model kickstand for an f which was slightly longer. I'm not sure the length difference between k and c models but I'll measure it and post pics tomorrow and if it works for you I'll mail it out.

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Wow that would be awesome ! Thanks!