Topic: 76' CB500 Four?

[Sebba992]

Hello all, new to the SOHC/4 scene, and this forum.

Hopefully someone can help me make sense of my recently aquired CB 500 Four (havent had it a week yet  ).

I have searched far and wide, googeling, and any other means of information gathering i could think of, but all of this only serves to up the confusion.

So, the thing is, my CB 500 Four is, according to the registration papers a 1976 model, and i cannot for the life of me find any good information on parts and the like on the 500 beyond 73' it all leads back to the 550 beyond 73'. I can't really make sense of the frame number either as i have checked that against various lists available online. The frame number plate says Type: CB500 and frame number is CB500-2088737.

Found one source that mentioned a K3 (?), but i lost it and dont remember how i found it.

What i am trying to figure out is what parts i can use, it's running and in daily use, but it needs some attention down the line. Parts are hard to come by in Norway, and i dont want to order the wrong parts from overseas, waiting forever and paying the import taxes for parts that dont fit.

The most pressing issue is the carbs, as some previous owner has put individual air filters on it, and i dont have the original airbox, what they forgot to think about is jetting, so knowing what carbs i have (they are stock) would be nice as i see there are some variants of jets for the Keihins, depending on year and so forth.

And yes, i have read most of the information about individual filters, and the fact that they are a bad choice (especially the ones used on mine, as they do not fit  ), but I'll have to make do for the time being, until i can source a suitable alternative. (No i do not have the stock airbox  )

Anyways, sorry for the long post, any help at all is much appreciated, and can't wait to have a lot of fun with this lovely bike! Even though it's been (badly) modified it's a fantastic bike to ride, eventually it will get all the attention it deserves, to fix all the little things and make it a properly awesome bike again 

[bryanj]

Honda produced the 500 K1 for UK  and some European countries until the 550 K3 came along in late 76 early 77. If you get my email address from profile and mail me pictures of the instruments, side panels and indicators i can ID it for you.

[Stev-o]

Welcome...yes, your bike is most likely a Euro model.   Euro members may be able to help you.

Get an airbox, it will be worth the money spent.  They pop up on ebay regularly or start a thread in the parts wanted section on this forum.

Good luck...

[Sebba992]

Thank you so far.

Bryanj: I will do that, as soon as i get home. #$%* weather so left the bike at home today 

Stev-o: I believe it's a euro model, unsure about the history as it's undocumented, and I'm the third owner in Norway, i do know it's an import (to Norway), as the registration papers document that. The guy i bought it from believed it was from Germany or thereabout.
About the airbox, I am aware it might not be a popular way to go, but judging from the state of the bike i will use it as a base for a build, Scrambler/Cafe style, and the stock airbox doesn't fit into my plan.... Been looking at the Cognito Moto intake box (no idea about the performance, but i like the look so I'll make it work).
Also I'm not exactly known for taking the easy way out, i like the challenge and learning experience of it all.


Also a little update. I did some exploring yesterday, trying to find some electrical gremlins and get a better look at the total state, and found some interesting information that helped clear up a couple of things.

So the carbs are Keihin 649A's, and i found that these are well known units on this forum so lots of good helpful info to find on those 

Also found the engine number: CB500E-2175440

Maybe that info can help assertain the build year/variant?

It might be a rebuildt bike with frame/engine from different years?

Anyways, thanks for your responses so far.

[Stev-o]

Member Deltarider from The Netherlands should be able to help more, he is an expert on the Euro bikes.

Where are you Deltaman?!

[Deltarider]

Here. I think it's about a CB500K2 (ED, F, G). It's a model, marketed in 1976 in continental Europe, that shared quite some things with the CB550K2 like the central grease nipple under the swingarm. The best advice I can give you is to consult the right Parts List for that particular model. I have one in print, but you can go to: http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb500 and then select: CB500K2 (ED, F, G) [1976.05.20]. One or two years ago I contacted CMSNL to inform them that, although they have a lot of CB500 Parts Lists on line, there was still one missing: the CB500K2 (ED, F, G). They now have it, although it is a bit hidden and I don't understand why they named it CB500K2 (General Export). That's not the title, but, anyway, it's the same parts list. https://www.cmsnl.com/honda-cb500k2-general-export_model50441/partslist/#.XNRBddhcJVc I always recommend to go the Honda4Fun site and have a look at the first few pages of forsaid Parts List. There you can compare your engine- and framenumber with those listed on p.4 and you will be able to exactly determine what model (area code!!!) you have. You will also learn there about colour codes and carb numbers. Online fiches like at CMSNL do not show this. However I consider it valuable information. Honda4Fun also has the original Owner's Manual: http://www.honda4fun.com/materiale-documentazione-tecnica/libretti-uso-a-manutenzione I don't understand why they named it 1975. I have one in print. Unfortunately Honda made some errors in it. The clutch shown on p.72 is not found on ours and neither does our model have that breather filter element shown on p.66. Arent'we lucky! http://www.honda4fun.com/materiale-documentazione-tecnica/libretti-uso-a-manutenzione
I think you have enough to read now this weekend  . If you need further info, feel free to ask.
Btw, below is mine. It's almost 100% original. I have removed all amber plastic stuff, although the front indicators will flash amber. Furthermore Koni's in the rear, crashbars, Voxbell horns, a luggage rack and that's about it.

[Sebba992]

Amazing! Thanks guys this is a lot of info to go through, and I will do so diligently.

I think this should be enough to figure out the things I need to know, for now at least.

When the weather clears up I'll get some pics to put up on the introduction forum, and when I get that far I'll probably start a build thread for those interested in the future of my Four

Stev-o: You're a legend! Thanks for the help and pointing me in the right direction!

Deltarider: Heel veel bedankt for de informatie! Dat is en hele mooie motor u heeft! (sorry bout that, heard a rumor you were Dutch )

Again, thank you all, and keep an eye out, I will be back with progress updates and more questions!

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[Deltarider]

Heel veel bedankt for de informatie! Dat is en hele mooie motor u heeft! (sorry bout that, heard a rumor you were Dutch )

Hey, I appreciate that ^ one! Let me know if you can handle other languages like German and French. I could share some docs.
Consider yourself lucky you have found one of the old SOHC Fours with (I hope) oldstyle Keihin carbs (probably 649A). Honda later really messed up with the models: CB550F2 and K3 or should I say was forced to mess up (by new EPA legislation in the US).

[Sebba992]

Haha, no problem, I can decipher written German with some time, also trying to learn Japanese (slow going with all my other projects ). I do know Dutch because I'm actually half Dutch, born and raised in Norway, but spent many summers in Rotterdam with family

Yeah, I think I'm in luck then, think I mentioned it, but I found that it's the Keihin 649A carbs on mine, just randomly stumbled upon that stamp you pictured while going over some electrics, and figured the rest out with some googeling.
Really helps when you have something to Google, because "Keihin 649A" turns up gold in Google I found out!

No doubt about that, the USDM market both bikes and cars have a lot of ups and downs caused by regulations

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[Deltarider]

The CB500s for many countries in continental Europe were equipped with the 649A carbs. The settings were: slow jet #40, main jet #78, jetneedle in 3^rd (middle) position and the airscrews are recommended at one turn out ⁺/_- ¹/₈. These models have an air duct over the airfiltercase that other markets did not have. These bikes run best the in original state.
I did quite some research to find out the 'why' of this particular carb setting and the air duct. I've come to the conclusion that what I had already read in a test review*, probably is true: the CB500 had to comply with German legislation on air intake noise levels. In the official German 'Zulassung' you will read that that air intake noise level for the CB500 was 83dB. In the same document you will see the CB500 performed equally well as CB500s in other markets that had different carb settings. With that original air intake, there's no advantage to go #100 main jets. Some Germans and I myself have experimented with this and the airduct removed. It didn't bring anything extra but noise. 
* in: MOTOR, 30 juli 1971 p. 1096 http://cbfourclub.nl/wp-content/uploads/PDFarchief/oudedoos/motor_1970_cb500f.pdf

[Sebba992]

Interesting theory, makes a lot of sense.

I do not expect to make any more power, nor do I feel like the bike needs it. I am a sucer for induction noise though and I love the sound of the open filters currently on the bike, that combined with the stock airbox being hard to come by has helped me make up my mind about not going back to stock.
I am not keeping the individual filters I currently have though, the plan is to use the CognitoMoto filter box made for the Four. It's a 50/50 split between looks and sound.
As I'm not expecting more power all I'm after is a jet/carb setup that works well, and hopefully doesn't lose any power over stock

Knowing the stock jet sizes helps a lot because its a good starting point, I will buy a range of sizes starting at #78 main and #40 pilot, and with some input from some other threads here that I found, a lot of testing and learning, hopefully I can find a setting that works for what I want.

Tried fiddling with the air screw setting based on the 1 +- 1/8 turn out, that the shop manual specified, and got it running a bit better by going 3/4 turn back in.
But more testing and experimenting is needed to get a definitive answer, also a carb overhaul is a priority to make shure I start from a good basis.

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[Deltarider]

To give you some guidance for if you are to go experimenting. Other markets had the CB500 with the 627B carbs. Until proven otherwise, we think it is safe to assume the 627B carb bodies (venturis) are identical to the 649A. The models with the 627B carbs had #100 main jets and lacked the air duct. Slow jet is also #40. Models for the UK and France had the jet needle - like the 649A - in middle (3^rd) position and also - like the 649A - had a recommended airscrew position of one turn out ⁺/_- ¹/₈. According to a specifications booklet edited in 1977 (!) by American Honda Motor Co., Inc., the CB500s overthere had the jet needle's clip in 4^th position and a recommended airscrew position of two turns out. It seems US was particularly interested in reducing emissions at idle.