Author Topic: Any idea what this is?  (Read 3946 times)

Offline Bryanj

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Re: Any idea what this is?
« Reply #30 on: November 25, 2021, 03:56:43 PM »
Probably cos the US insisted on the recirc for emmisions but Europe complained about oily air filters

Offline McCabe-Thiele (Ted)

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Re: Any idea what this is?
« Reply #31 on: November 25, 2021, 04:20:21 PM »
The "Muskie Bill" circa 1970's that resulted in U.S. legislation to reduce emissions and performance in the bargain on most new vehicles.

Hence the recirculation vent pipe ?
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Re: Any idea what this is?
« Reply #32 on: November 25, 2021, 04:53:22 PM »
That blow-by gas system was forced on Honda and other bike manufacturers by US legislators. Some claim it was to reduce fumes into the open from the crankcase. I doubt that. I think it was more a consequence of legislation that already existed for trucks and cars, which in the past have fouled the turmac as these gasses always transport to some degree droplets of oil. Problem is that Honda had to improvise an extra on an already existing model and that shows. The design was poor (the CB400 and CB650 were better). In Holland there was no such legislation and some dealers would simply disconnect the breather tube from the airfilter case, if they had seen the paper filter elements got wettened/fouled. It's your choice, but know that the recirculation system does nothing good for the running of your engine. Personally I don't like the risk of other hydrocarbons than gas fed to the inlet valves.

Offline beardylondon

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Re: Any idea what this is?
« Reply #33 on: November 25, 2021, 06:19:26 PM »
Sorry, I’m a bit unclear, are you saying to leave my bike as is, and not bother with this?

That blow-by gas system was forced on Honda and other bike manufacturers by US legislators. Some claim it was to reduce fumes into the open from the crankcase. I doubt that. I think it was more a consequence of legislation that already existed for trucks and cars, which in the past have fouled the turmac as these gasses always transport to some degree droplets of oil. Problem is that Honda had to improvise an extra on an already existing model and that shows. The design was poor (the CB400 and CB650 were better). In Holland there was no such legislation and some dealers would simply disconnect the breather tube from the airfilter case, if they had seen the paper filter elements got wettened/fouled. It's your choice, but know that the recirculation system does nothing good for the running of your engine. Personally I don't like the risk of other hydrocarbons than gas fed to the inlet valves.
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Re: Any idea what this is?
« Reply #34 on: November 25, 2021, 08:25:13 PM »
It's up to you. You can have it original, but then I'd check the air filter element regularly, or have it like the CB500 that didn't have that recirc system.

Offline beardylondon

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Re: Any idea what this is?
« Reply #35 on: November 25, 2021, 09:44:27 PM »
This is very confusing. Do you mean original as per pg. 170?
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Re: Any idea what this is?
« Reply #36 on: November 26, 2021, 08:27:22 AM »
That p. 170 is a puzzle in itself, as we have no knowledge of any CB550K2's that actually had it as pictured. Maybe markets elsewhere, but sofar we have no indication that particular K2 model was marketed but in the US. The CB500K2 GENERAL EXPORT however has it like depicted, but... that was no modification, as no CB500s ever had that recirc. system. Has Honda mixed up things here? Could be. Note that all the modifications in that chapter specific for the CB550K2 model, also applies for the 'European' CB500K2... So we can't rule out, there is an error here. Notwithstanding that I personally would choose to have it as depicted, but that's is my personal choice. I could then continue to use the OEM paper airfilter elements and would not be tempted to turn to inferior foam air filters, like many Americans did. You could also stick to how the US had it, inspect the air filter element more frequently and see how it goes. Having the oil level no higher than halfway the upoer and lower mark seems to have helped also. Did the problem occur with some oils and others not? We don't know.
« Last Edit: November 26, 2021, 08:50:46 AM by deltarider »

Offline beardylondon

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Re: Any idea what this is?
« Reply #37 on: November 27, 2021, 01:40:22 PM »
Thanks very much!
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Offline Nurse Julie

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Re: Any idea what this is?
« Reply #38 on: November 27, 2021, 01:49:27 PM »
Thanks very much!
Personally, I wouldn't worry either way. I'm assuming your not going to use it as a commuting bike doing over 12,000 miles a year and I'm assuming you're not taking on a race track either. Many owners run bikes these days with bits missing or routed not quite correctly without any issues.
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Offline Nurse Julie

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Re: Any idea what this is?
« Reply #39 on: November 27, 2021, 02:03:07 PM »
Also, I'm not sure Deltarider is talking about the correct tube. I think he is talking about the big breather tube that comes off the top of the engine and goes to the air box , that can't be correct as the OD of that tube is massive and won't fit through the hole in the clip. I think it's the skinny tube that goes from the bottom of the air box chanber to atmosphere, now that tube would fit in the hole in the clip.
« Last Edit: November 27, 2021, 02:04:53 PM by Nurse Julie »
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
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LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
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Offline beardylondon

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Re: Any idea what this is?
« Reply #40 on: November 27, 2021, 02:33:42 PM »
Yeah, it’s just for fun, so I won’t worry!  Thanks.
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Re: Any idea what this is?
« Reply #41 on: November 27, 2021, 03:53:28 PM »
A quick look at Fig. K2-1. p.170 of the Shop Manual Honda CB500-550 shows it is the crankcase breather tube.
When testing the CB550F2, which has a similar recirc. system, the German magazine Das Motorrad found out that the airfilter element did indeed got fouled by the recirc. system and that this robbed performance.
When it is about things that can be missed, that recirc. system is certainly what one can do without.
BTW, does any of you know why the site www.honda4fun.com is down? I've tried to contact them, but the two persons I know there, have an email adress ending in @honda4fun.com, so messages do not arrive.
I miss the site dearly; they have the most complete collection of documents. Moreover they are the only site - at least that I know - that offers the Parts List CB550, CB550K1, CB550K2. It is a brilliant part list as all three models' columns are right next to each other, so one can see in one glance, what has changed from one model to the other. Too bad I never downloaded it. But maybe any of you knows another source.
Beardylondon, if you have an Owner's Manual of your K2 (AKA K76), the international SOHC Four community would be very grateful, if you'd do the effort to scan and upload it to a site of your desire. It is one of the few manuals that is still missing. It looks like... [see below].
« Last Edit: November 27, 2021, 03:56:35 PM by deltarider »

Offline beardylondon

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Re: Any idea what this is?
« Reply #42 on: November 27, 2021, 04:05:49 PM »
Thanks, no alas I don't have the owners manual.
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Offline Nurse Julie

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Re: Any idea what this is?
« Reply #43 on: November 27, 2021, 04:16:28 PM »
I do agree with you Delta, the drawing on page 170 does appear to suggest it is the main engine breather tube they are talking about. But.... Firstly the main breather tube is not long enough to reach down  below the footpeg and knowing how innacurate some of Hondas drawings (and other Manufacturers) are, I'm wondering if the top tube shown in that drawing is the engine breather tube, then the person drawing the picture saw a tube coming out from under the side panel and down to the clip and did the drawing assuming this. I think the top breather tube in the drawing is correct and the tube showing coming out from under the side panel, is the drain tube that goes to atmosphere. I wonder if it had been reported to Honda that oil vapour coming out of the drain tube had blown onto someone's back tyre and caused an issue. The drain tube usually goes down behind the swing arm pivot and is in direct line with the tyre. By re routing the drain tube to come out of the side and through the clip would avoid this? Also, it appears it was only done for 1 year, why didn't Honda carry on with this re routing on the 550 F1/F2 models 🤔🤔🤔
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Online deltarider

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Re: Any idea what this is?
« Reply #44 on: November 27, 2021, 09:18:42 PM »
That's very plausible, Julie. The bracket was then meant to accomodate DRAIN TUBE ASSY, 17358-341-000, a drain tube the CB550K2 shared with the later models K3 and K4 and that differed from the one on predecessors CB550(K0) and K1, which had 17358-374-000.
Then not only the drawing in Fig. K2-1, p.170 is incorrect, but the tube also has been misnamed BREATHER TUBE where in fact it is about a drain tube.
That would make sense.
cf: https://www.cmsnl.com/honda-cb550-k2-four-1976-usa_model464/partslist/F++05.html
Question for me remains, what is that bracket 90514-323-610 doing on the CB500K2 GENERAL EXPORT model, that has no drain tube at all, that is: not from the bottom of the airfilter case? https://www.cmsnl.com/products/guidebreather_90514323610/
« Last Edit: November 28, 2021, 12:23:44 PM by deltarider »

 

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