CB550 Tuning Advice

[deltarider]

My bike is 50 years old now and the O-rings on the T-joints are still the originals. If you keep your carbs in a natural state - which is wet - they live forever. Honda did it really well. For a reason: the last thing Honda wanted was for mechanics to grumble about having to replace those O-rings—a task that required taking the carburetors apart— to then having to present their customers a hefty bill.

[Oddjob]

Actually Honda went out of their way to make it as complicated as possible for owners to keep on top of their bikes. Massive amounts of special tools required according to them, vac gauges, dwell meters, are prime examples. They also tried to deceive owners by saying certain production marks were to be ignored when it fact they were the exact marks you needed to work out shell bearings. They wanted you to go to the dealers and spend more, they got more profit from servicing and parts  than they did from selling the bike in the first place. You learn all this when you go on training courses.

Original Honda seals and rings should be ok until they increase the ethanol content, when it goes above 10 then expect them to start failing quite quickly.

[deltarider]

Actually Honda went out of their way to make it as complicated as possible for owners to keep on top of their bikes. Massive amounts of special tools required according to them, vac gauges, dwell meters, are prime examples. They also tried to deceive owners by saying certain production marks were to be ignored when it fact they were the exact marks you needed to work out shell bearings. They wanted you to go to the dealers and spend more, they got more profit from servicing and parts  than they did from selling the bike in the first place. You learn all this when you go on training courses.

Gee, that's quite a statement. I don't think Honda ever had owners doing shell bearing jobs in mind, do you? Personally I can't blame Honda for that.

Original Honda seals and rings should be ok until they increase the ethanol content, when it goes above 10 then expect them to start failing quite quickly.

Where did you learn that?
I stick to science. https://forums.sohc4.net/index.php/topic,206216.msg2333063.html#msg2333063
Recently I've changed from V-Power to Shell's E10 Fuelsave and I like it. I just add a small dose of Startron's Enzyme Fuel treatment: 14ml for every 10 liters. It's the favourite of yacht mechanics who service outboards which have long periods of inactivity.
I don't know what happened but gas mileage has improved a lot. My recent carb adjusting job may also have attributed.

[Oddjob]

The amount of people enquiring at parts departments in the UK for advise on how to choose what colour shell bearings to fit became a problem at our dealership. The parts people didn't know and couldn't advise anyone on what to fit. Not much was known about them at the time. People were relying on workshop manuals for guidance and Honda were not being truthful on how to select them. They wanted owners to go to a dealership and have them do the job. I knew the trick of how to work out the colours required, one of the Honda trainers passed it onto me. So in the end I was always the mechanic they were told to ask for by the parts department. I was happy to help them out. In the 70s owners did far more maintenance than today, so yes Honda would have that in mind, hence why they made it so difficult to understand the process.

If you look at the markings on Honda fuel lines for instance you can see they are only rated to withstand 10 parts Ethanol and that's the stuff Honda are still providing to this day. Orings are made of nitrile not viton, so even if they matched the same spec as the fuel line they'll fail after the content goes beyond E10. Seals MAY last a little longer but I doubt it, technology in the 70s wasn't that advanced, certainly not to the point they'd be planning for large amounts of Ethanol in fuel. They were still using leaded petrol back then, remember when they were unsure of how valve seats would withstand unleaded fuel, no forward planning at all.

Honda weren't alone in doing this, all of the Japanese manufacturers did it. They never imagined a bike lasting for this amount of time so why future proof them, it costs more and thus they earn less profit.

[SteveD CB500K0]

I did my 500 in 1976. - including the crank and big end shells.

Redhill Motors was our dealer.

I did the work in my room (student digs)


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[Neilw]

I disassembled all the carbs, removed everything, and used carb cleaner and compressed air to clear all the passages and jets, making sure no rubber fragments were left.

I've reassembled everything, including the new hoses and the new O-rings, etc., being particularly careful not to pinch anything and to lube with silicon/red grease.
Before bench sync, I've spent the afternoon getting the float levels right and testing with the clear tube method - and guess what, I'm getting small rubber fragments again on carb 3.

I've taken it apart, checked every new o ring and there is no damage anywhere, i just don't know where the contamination is coming from!

I'm going to give all carbs a final flush with fresh petrol and hope that somehow resolves matters, but honestly I can't see how when I can't find the source!

The only thing i can think is that the new hoses have some residue from manufacture in them.

Any other ideas?
 

[K2-K6]

Are you supplying from auxiliary fuel feed ? Not the bike's tank.

[Neilw]

Are you supplying from auxiliary fuel feed ? Not the bike's tank.

I'm using a clear auxiliary tank with clear tubes.

[K2-K6]

Logic would be there's something caught somewhere inside the carbs and their fuel distribution, but puzzling as you say.

A suggestion to consider, if you've a steam supply (wallpaper stripper or the like of) you can make a small nozzle out of something like brake line pipe, then blow steam through all the orifice and pipes to see what comes out.

It's something I've used before in chemical lab work to clean various apparatus of debris as it'll usually free up  anything stuck inside crevices etc to flush out comprehensively unwanted contents effectively. That can be "tarring" or residue stuck to surfaces you can't see.

[McCabe-Thiele (Ted)]

You have probably thought of this, if you cut the hose to length did you use a very sharp knife or a Junior Hacksaw, could it be coming from the raw cut.
Sometimes also if the hose is a tight fit it can cut when being pushed onto the metal connection points.

On my 400 & 500 I have fitted Aeroline fuel filters to try to minimise the risk of any debris reaching the carbs.

[Neilw]

You have probably thought of this, if you cut the hose to length did you use a very sharp knife or a Junior Hacksaw, could it be coming from the raw cut.
Sometimes also if the hose is a tight fit it can cut when being pushed onto the metal connection points.

On my 400 & 500 I have fitted Aeroline fuel filters to try to minimise the risk of any debris reaching the carbs.

Its possible. i'll check.

[Neilw]

Logic would be there's something caught somewhere inside the carbs and their fuel distribution, but puzzling as you say.

A suggestion to consider, if you've a steam supply (wallpaper stripper or the like of) you can make a small nozzle out of something like brake line pipe, then blow steam through all the orifice and pipes to see what comes out.

It's something I've used before in chemical lab work to clean various apparatus of debris as it'll usually free up  anything stuck inside crevices etc to flush out comprehensively unwanted contents effectively. That can be "tarring" or residue stuck to surfaces you can't see.

I have a steam cleaner, with a nozzle that will fit the fuel pipe. I'll flush with carb cleaner first in case its due to the cut as i did cut the pipe, but with a very sharpe pipe cutter.