PLEASE Help - CB72 Carburetors

[ojwilliams1]

I’m looking for help with a partially restored 1962 CB72 Hawk that I just purchased. The bike starts and runs great but only with the choke 1/3 to 1/2 closed. If the choke is raised to full open the bike stops. This is true at idle and while running at any speed. I’ve checked and thoroughly cleaned the carburetors; compression is great at 135 psi.

I just received my copy of Bill Silver’s 250/305 Engine Repair Guide and it’s saying that this bike should have the old “round bowl” carburetors with the power jet system. My carbs are “square bowl’ with no power jets. Closer examination finds that they are carbs for a later model CL72. Before I look for replacement carbs (so far not easy to find!), I want see what help I can get on this forum.

Does anyone out there have any CB72 22mm carbs they want to sell?
Can anyone suggest where I might find them?
Is there any way I can make the CL72 carbs work?
Any other suggestions?

[LOUD MOUSE]

Private Message sent. ..................lm

I’m looking for help with a partially restored 1962 CB72 Hawk that I just purchased. The bike starts and runs great but only with the choke 1/3 to 1/2 closed. If the choke is raised to full open the bike stops. This is true at idle and while running at any speed. I’ve checked and thoroughly cleaned the carburetors; compression is great at 135 psi.

I just received my copy of Bill Silver’s 250/305 Engine Repair Guide and it’s saying that this bike should have the old “round bowl” carburetors with the power jet system. My carbs are “square bowl’ with no power jets. Closer examination finds that they are carbs for a later model CL72. Before I look for replacement carbs (so far not easy to find!), I want see what help I can get on this forum.

Does anyone out there have any CB72 22mm carbs they want to sell?
Can anyone suggest where I might find them?
Is there any way I can make the CL72 carbs work?
Any other suggestions?

[G-Man]

It sounds like you need to try some different jets or needle position. Do you have air filters? What jets do you have currently? What is the float height?

The CL72 and CB72 are similar engines so those carbs should work with teh right settings.

Round bowl power jet carbs are quite hard to find.




G

[LOUD MOUSE]

I have at least 10 sets. .............lm

It sounds like you need to try some different jets or needle position. Do you have air filters? What jets do you have currently? What is the float height?

The CL72 and CB72 are similar engines so those carbs should work with teh right settings.

Round bowl power jet carbs are quite hard to find.




G

[G-Man]

Over to you, LM........ :-)

G

I have at least 10 sets. .............lm

It sounds like you need to try some different jets or needle position. Do you have air filters? What jets do you have currently? What is the float height?

The CL72 and CB72 are similar engines so those carbs should work with teh right settings.

Round bowl power jet carbs are quite hard to find.




G

[LOUD MOUSE]

It's the square bowl type that are scarce here. ...........lm

Over to you, LM........ :-)

G

I have at least 10 sets. .............lm

It sounds like you need to try some different jets or needle position. Do you have air filters? What jets do you have currently? What is the float height?

The CL72 and CB72 are similar engines so those carbs should work with teh right settings.

Round bowl power jet carbs are quite hard to find.




G

[ojwilliams1]

Started working the problem over the phone with LOUD MOUSE this afternoon. G-man, LM confirms what you said. Should be able to fix with jets and settings. First we went over the things that I had already checked (float level, cable adjustments, etc.). Then he had me properly adjust the idle air screw and raise the needle setting. I'm to ride it tomorrow and let him know how it runs then he'll decide what to do next. Attached a couple of photos for grins.