no gas getting to the cylinders on 1980

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

no gas getting to the cylinders on 1980

Postby john44526 » Fri May 12, 2017 11:30 pm

Hi all, I just purchase a 1980 CB650 Custom with the mechanical slides and i am getting gas in the carbs but none to the cylinders. The 2 vacuum/accelerator pump lines that come from between the 1&2 and 3&4 accelerator pump rail were not connected to anything. I joined them together with a T like in the schematic says but i am wondering where that goes, The schematic does not say and i dont have a manual. The bike does not start and barely stutters but if i blow into the line mentioned it runs great... Any clues as to where this line goes or if there is a problem somewhere else?

cb650
Posts: 2908
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: no gas getting to the cylinders on 1980

Postby cb650 » Sat May 13, 2017 2:24 am

Those are just vent tubes that originally go to the airbox. Sounds like you floats might be stuck. Did you clean the carbs?
Did you clean the tank out?!?!?!?!

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Sat May 13, 2017 7:00 am

carbs are clean, jets are clear, bowls are full of gas but for some reason the motor is not sucking any of it in. i put silicone lube on the boots on both sides as well so there are no leaks. I went through the carbs but i did not separate them and look at every accelerator pump diaphragm, i looked at the ones on the end and at the bottom of #2 carb and all looked fine in those but im dumbfounded as to why there is gas in the carbs but none getting to the motor unless i blow in that vent.

User avatar
Folsoml
Posts: 1375
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: no gas getting to the cylinders on 1980

Postby Folsoml » Sat May 13, 2017 10:26 am

There is a free manual here in the General Discussion forum.

What is your compression like?
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Sat May 13, 2017 11:57 am

I have not tested the compression but i dont think that could be the issue as the bike runs fine with gas sprayed through the airbox and when i blow in the vent, the bike only has 7k miles.

cb650
Posts: 2908
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: no gas getting to the cylinders on 1980

Postby cb650 » Sat May 13, 2017 3:25 pm

did you clean the idle jets?
Did you clean the tank out?!?!?!?!

User avatar
Folsoml
Posts: 1375
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: no gas getting to the cylinders on 1980

Postby Folsoml » Sun May 14, 2017 10:08 pm

What process did you use to clean your carbs? I've known people who've said they've cleaned their carbs when they were soaking the entire assembled bank in pinesol and water.
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Mon May 15, 2017 7:32 am

I just used some carb spray and poked through the Jets with a wire carb cleaning tool I have, they were not dirty and probably did not even have to come off. All the passeges are clear as I can shoot carb spray right through

User avatar
Folsoml
Posts: 1375
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: no gas getting to the cylinders on 1980

Postby Folsoml » Mon May 15, 2017 11:08 am

I think we have found our culprit. Obviously there is something still in these carbs that is gunking up the process. I take my carbs completely apart and ultrasonically clean them, but sometimes I still have to redo them because something is not right. Sadly, I am not as familiar with the PD carbs that are on your year of bike. I wish someone as knowledgeable as the man who wrote this manual would create one for those style carbs:

viewtopic.php?f=4&t=14053

Take a look at this manual anyway. It will give you an idea of the kind of treatment a carb bank needs before you can say it is "clean."
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

cb650
Posts: 2908
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: no gas getting to the cylinders on 1980

Postby cb650 » Mon May 15, 2017 1:47 pm

the isle jets and emulsion tubes for the mains have small holes off to the sides so just poking through them wont get it all.
Did you clean the tank out?!?!?!?!

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Mon May 15, 2017 6:32 pm

Yea il pull then again tomorrow and update... Thanks all!

cb650
Posts: 2908
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: no gas getting to the cylinders on 1980

Postby cb650 » Tue May 16, 2017 5:21 am

also its not uncommon to get the floats upside down
Did you clean the tank out?!?!?!?!

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Sat May 20, 2017 2:09 pm

Unfortunately I haven't had time to play with it but it does get gas in the bowls but i am not the first to go through these carbs so i will definitely look into that. Will update if i get to it today or tomorrow - again very helpful and i appreciate the advice

john44526
Posts: 7
Joined: Fri May 12, 2017 9:15 am

Re: no gas getting to the cylinders on 1980

Postby john44526 » Mon May 22, 2017 12:23 pm

I just wanted to update as im still working on the carbs but i found a great guide here for the PD Carbs - http://forums.sohc4.net/index.php?topic=146893.0

All my jets and idle screws were clean when taken out, my issue lies in the accelerator pump or air cut off valve so i will be splitting the rack today or tomorrow, I got the accelerator pump to work on carbs 2-4 but there is something stuck in the #1 carb spout but i dont have a wire thin enough to poke through so i am looking for a solution to that now.


Return to “Technical Discussion”

Who is online

Users browsing this forum: No registered users and 11 guests