82 CB650SC air filter housing hose?

[Beetlegeuce]

Just picked up this 650 today, and in pulling the carbs (yeah the typical "been sitting too long) I noticed a rubber hose just hanging loose above the carbs.  It is item 8 in this image...one end is attached to the bottom of the air filter housing, the other end is just hanging loose right above the carbs.  This doesn't seem normal.   

(I don't have manuals yet...)

[Beetlegeuce]

<bump>

Any ideas on where this hose goes?

[freebird]

There should be a vent tube towards the back of the motor on to top of trany it should slide on and clamped.

[Munkey]

I sold my 82 650 and I can't remember exactly what hoses it had. There is one on the top of the valve cover that goes to the air box I think. Could it be that one?

[Beetlegeuce]

The crankcase breather tube is there...it runs from the cylinder head cover to the top of the airbox.  This one comes from the bottom of the airbox (left side) and just hangs there right on top of the carbs.

I was out at a salvage yard that had the same bike in the yard...the same hose was there with a bolt stuck in the open end of it.  Weird.

[Laminar]

If I'm not mistaken, #8 is the crankcase vent tube that goes from the top of the valve cover to the bottom of the airbox. Tube #7 is the airbox drain.

Pictures of the bike would help greatly.

You mention that the current crankcase vent goes to the top of the airbox. Which number is this tube in the parts fiche?

[Munkey]

This one comes from the bottom of the airbox (left side) and just hangs there right on top of the carbs.

I don't remember mine having that. Maybe a California emissions thing?

[Laminar]

You had an SOHC Nighthawk?

[Beetlegeuce]

If I'm not mistaken, #8 is the crankcase vent tube that goes from the top of the valve cover to the bottom of the airbox. Tube #7 is the airbox drain.

Pictures of the bike would help greatly.

You mention that the current crankcase vent goes to the top of the airbox. Which number is this tube in the parts fiche?

Yeah I should have taken some pictures before tearing stuff apart. 

The crankcase vent tube is in another parts diagram (for the "cylinder head cover", item 12) and is listed as "Tube, Breather":



Mine looks just like that...from the top of the engine to the top of the air box.  The connection at the air box is not just a simple open port, the air box has ducting molded into it to route the crankcase vapors (it seems) to the rear of the air box.  I'm pretty sure this is correct.

Interestingly enough...the original "mystery" hose in question is described as a "TUBE, AIR VENT".  Having an open vent makes sense...but the location doesn't make much sense at the bottom of the air box.  I would think it would be at the top.

[Laminar]

Your best bet is to get the manual. It will have a diagram of the PCV system.

[Beetlegeuce]

This one comes from the bottom of the airbox (left side) and just hangs there right on top of the carbs.

I don't remember mine having that. Maybe a California emissions thing?

Well the service manual only distinguishes between US and non-US models as far as these hoses go.  But who the heck knows!

[Laminar]

(Click the image for full size)

[Beetlegeuce]

Hmm...CB650 must be different than CB650SC.  Mine doesn't look quite like that, it looks like the picture in the first post.  However there may be a clue here...in that picture there is a hose running from the bottom of the "chamber" to the air box itself.   

The diagram in the Clymer manual is pretty useless.

[Munkey]

I think that first diagram may be a California model. Mine did not have part #17 and all it's related hardware and hoses.

[Beetlegeuce]

Ok mine does have a hose connection on the bottom of the "chamber" (as in Laminar's picture), and it connects to item 34 hose in the first picture I posted (the hose coming off the top of that "tee" fitting).

Item 8 hose is still a mystery!  (super thanks for all the replies though!)

[Beetlegeuce]

I think that first diagram may be a California model. Mine did not have part #17 and all it's related hardware and hoses.

Interesting...

Was there an actual "California" model?  According to this manual all of the US models had the PCV system, non-US models did not.

[Munkey]

Is it supposed to go to the fuel shutoff valve? My valve had an extra nipple on it that did not have a hose connected to it. Never seemed to bother it.

[Beetlegeuce]

I doubt it...the hose is MUCH larger, and I think that extra "port" on the fuel valve is just a vent.

[Munkey]

OK, it's coming back to me now. I sold the bike a month or so ago and it's been awhile since I had to do much work on it. I'm getting old and my memory is fading.

How about it connecting to part #20 in the carb diagram? The 2 (#19) hoses connect to the T (#20), then your hose connects to the T (#20).

I had my 650 for 11 years and the hose you are questioning was missing. Never seemed to affect the way it ran.

http://www.bikebandit.com/houseofmotorcycles/1982-honda-motorcycle-cb650sc-nighthawk-650-carburetor-assy-link/o/m1980sch3366

[freebird]

Yes that's right its a crankcase ventilation hose. It has to come off the crankcase.

[Beetlegeuce]

OK, it's coming back to me now. I sold the bike a month or so ago and it's been awhile since I had to do much work on it. I'm getting old and my memory is fading.

How about it connecting to part #20 in the carb diagram? The 2 (#19) hoses connect to the T (#20), then your hose connects to the T (#20).

I had my 650 for 11 years and the hose you are questioning was missing. Never seemed to affect the way it ran.

http://www.bikebandit.com/houseofmotorcycles/1982-honda-motorcycle-cb650sc-nighthawk-650-carburetor-assy-link/o/m1980sch3366

Hey I think you may be onto something there.  Only problem is...that "tee" doesn't exist on mine.  Looking at that diagram, seems there are two different options for tubing between carbs.  Item 7, a single piece of tubing between each carb...or items 4, 10, 11 and 20 (going to that "tee" fitting).  That would certainly place that "tee" fitting right where the mystery hose ends up...right between the tops of carbs 2 and 3.

However, mine does not have items 4, 10, 11 and 20...only the single piece of tubing between the carbs.  So I'll just plug that line and be done with it.

Thanks for the help everyone!

Bill

[Munkey]

Hey I think you may be onto something there.  Only problem is...that "tee" doesn't exist on mine.  Looking at that diagram, seems there are two different options for tubing between carbs.  Item 7, a single piece of tubing between each carb...or items 4, 10, 11 and 20 (going to that "tee" fitting).  That would certainly place that "tee" fitting right where the mystery hose ends up...right between the tops of carbs 2 and 3.

However, mine does not have items 4, 10, 11 and 20...only the single piece of tubing between the carbs.  So I'll just plug that line and be done with it.

Thanks for the help everyone!

Bill

I'm betting that you have #4. It's a piece of copper tubing with o-rings seals on the ends. It carries fuel from the inside carb to the outside one. Without it, your carbs will piss fuel all over the place and the ouside carbs will get no fuel. This is an essential piece.

#10 is a rubber T that connects the inside and outside carbs, then goes up to the other T that then leads to your mystery hose and eventually the airbox. These are very prone to drying out and cracking. I think mine were pretty cracked and barely hangin on. There are some posts here somewhere about whether these are needed or not. I think the consensis is that the bike runs fine without them.

[Beetlegeuce]

Ahhh you're right...after looking further both items 7 and 4 are listed as "Joint set A, fuel" and "Joint set C, fuel".  No idea what "A" vs. "C" means...but its not really important.  Obviously those are in place.  hahah

There are however no hoses connecting the two outer carbs...heck I can't even tell where something like that would connect to (on the carb).

[Munkey]

Not sure what is meant by A vs C either.

There should be 2 small pipes connecting the inner to the outer carbs. If I remember right, one of them is copper and one is aluminum with the copper one being slightly larger than the other. They will have o-ring seals on them to prevent fuel from leaking. Maybe the A means "aluminum" and the C means "copper". You'll definately need these for the bike to run. I wouldn't worry much about the rubber T's though.

[Beetlegeuce]

Yeah I see those two...one is the main fuel supply (copper) and the other appears to be plumbing for the pump valve (aluminum).  I see the "tee" hose assembly in several of the pictures in the manual...but I can not find any point on the outer carbs where this would connect, and of course the pictures are not detailed enough.

I do notice that there is a single rubber hose between the two center carbs (Item 21 maybe?).  I guess I'm just concerned that there may be open ports on those two outer carbs.