This pipe needs a home!

If it's broken or just needs tweaked

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leeshayler
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This pipe needs a home!

Postby leeshayler » Fri Jul 22, 2016 9:06 am

I recently obtained a 1981 cb650c which had stopped a few years ago. Solved a few problems already but now baffled where a 0.5inch pipe connects. One end is connected to the lower front left side of the air box from a stub that exits the box. the pipe is about 12inches long and kinks upwards after exiting the air box. It is an air pipe for vacuum I presume but I cannot determine where the open end fits on the carb or engine. Can someone verify where this pipe fits please?

cb650
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Re: This pipe needs a home!

Postby cb650 » Fri Jul 22, 2016 3:56 pm

pics? sounds like the engine vacum. connects to the nipple on the center valve cover
Did you clean the tank out?!?!?!?!

leeshayler
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Joined: Thu Jul 21, 2016 5:04 pm

Re: This pipe needs a home!

Postby leeshayler » Sat Jul 23, 2016 6:23 pm

As requested here are additional Photos the pipe comes from the front left side of the airbox.
on this diagram Part Number 8
http://www.hondapartshouse.com/oemparts ... ir-cleaner
Part number 8
TUBE, AIR VENT
17231-460-730

cb650
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Re: This pipe needs a home!

Postby cb650 » Sat Jul 23, 2016 9:55 pm

and to the nipple on the center valve cover
Did you clean the tank out?!?!?!?!

leeshayler
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Re: This pipe needs a home!

Postby leeshayler » Sun Jul 24, 2016 10:45 am

hmmn ok I will look for that today. I cleaned out all the old fuel from the tank but have not applied any cleaners into the fuel tank. What do you recommend to clean the tank out?
thanks
Lee

cb650
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Re: This pipe needs a home!

Postby cb650 » Sun Jul 24, 2016 12:49 pm

There are many things to use. Look at the SOHC4 site and see them all. I used liquid plummer and ruined one. apple cider vinegar is another. If its light rust just some solvent and a length of dog chain and lots of tumbling. Take the petcock out and just plug it.
Did you clean the tank out?!?!?!?!

leeshayler
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Joined: Thu Jul 21, 2016 5:04 pm

Re: This pipe needs a home!

Postby leeshayler » Sun Jul 24, 2016 4:41 pm

my friend found an air box on ebay and it is showing a T piece with 2 pipes coming from this T piece. I do not have this T piece which maybe the proble for locating this pipe correctly for me. He provided this link -
http://i.ebayimg.com/images/g/17AAAMXQV ... s-l300.jpg

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Volker_P
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Re: This pipe needs a home!

Postby Volker_P » Tue Jul 26, 2016 1:37 am

Welcome here! :D

- The shorter pipe on the picture goes to the bottom of the air chamber between airbox and carb boots. The second pipe on the "T" is supposed to go downwards behind the engine. Its special end can be squeezed to drain possible condensate.

- The longer pipe splits into two small pipes by a "T". The two ends go on the nipples between carbs 1+2 and 3+4. They carb side parts are often referred here as "vacuum tees".

- Missing on this picture is the upper hose from the airbox to the center valve cover.

Hope you can figure it out now.

Hints on cleaning the fuel tank may be found here: viewtopic.php?f=4&t=1411
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

leeshayler
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Joined: Thu Jul 21, 2016 5:04 pm

Re: This pipe needs a home!

Postby leeshayler » Tue Jul 26, 2016 8:54 pm

thanks for that detail. I must be missing the splitter and it seems the nipples you refer to are connected with one pipe between across the carbs. I cannot find anywhere to plug additional pipes.
I notice when I attempt to start the bike and place my hand over the open air of the carb to choke there is strong suction on the first right side carb. The other 3 carbs do not suck when I close them off in sequence. Does this suggest the diaphragm on the top of each carb is leaking? They look okay though.
I rechecked and tightened every clamp on the inlet manifolds so do not think they are a factor here. I have a strong spark on each cylinder when viewed outside the cylinder earthing plug to the engine.
Could the original unconnected vacuum pipe prevent the engine starting at all?
thank you for your thoughts.
Lee

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Volker_P
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Re: This pipe needs a home!

Postby Volker_P » Wed Jul 27, 2016 12:50 am

With regard to the CV carb related vacuum hoses, please have a look here: viewtopic.php?f=4&t=4036

The CV carbs do not suck that much even at full throttle because you only open the throttle flap but the piston will be moved by the carb vacuum mechanism/piston. It however seems suspicious that one of the carbs behaves different.

Some CV carbs have a vacuum shutoff valve sitting on the top of carbs 3+4. If its vacuum line is unconnected (or -not unusual- the diaphragm in there is cracked) you won't get fuel into the carbs and the bike won't start. This shutoff may simply be bypassed for a test, though.
However this is a small vacuum line on the carbs themselves, not to the airbox or to the air chamber.
It should start and run "somehow" with the other vacuum lines missing.

Always worth a check at starting issues: cables from left coil go to cylinders 1+4, from right coil to 2+3. :wink:

Good luck!
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

leeshayler
Posts: 6
Joined: Thu Jul 21, 2016 5:04 pm

Re: This pipe needs a home!

Postby leeshayler » Fri Jul 29, 2016 10:08 am

thank you for everyones assistance and the bike is now running. it transpire the pipe was left open to air and someone previously had simply connected a pipe across the carbs from the nipples between carbs 1-2 and 3-4. I reseated the carbs in the inlet manifolds, retightened all clampns and felt strong pull thru each carb with the airb box disconnected. reset all the throttle butterflies to 3 turns out, cleaned all cv diaphragms. Was reluctant to start until I placed a hand across all carbs air intake in sequence and then it fired up quickly. runs smoothly on gradual throttle movements but does not like blipping the throttle at the moment. also smoky white but it has been stood for years and I used wd40 liberally so maybe need time to burn off. Will connect the air box and retry it over the weekend and recheck it out.
thank you again to the forum.
Lee

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Volker_P
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Re: This pipe needs a home!

Postby Volker_P » Wed Aug 03, 2016 3:08 am

leeshayler wrote: Was reluctant to start until I placed a hand across all carbs air intake in sequence and then it fired up quickly. runs smoothly on gradual throttle movements but does not like blipping the throttle at the moment.

This sounds quite all right. Cold start usually is tricky and throttle response is poor as long as it is cold. Might be a bit better with the airbox installed, but basically it probably will remain like that.
Anyway everything should be fine when warm. :wink:
Check if all four header pipes get equally hot, then go for a test. White smoke typically is oil, one will see if it vanishes after the engine got to operation temperature for the first time.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


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