Topic: 72 CB 750.Carb Install Questions

[Honda3]

Ive had it with these damn carbs that have been on my bike since 1972. A guy on ebay sells immaculately rebuilt carbs for $400 plus $23 for shipping.

I bought a set from him for my 1973 Honda CB500F and they are top notch. But....I didnt install them. The Mrs. limits my time in the garage and since I have 5 bikes, I cant do everything, so I farm it out.

Anyways, Ive never changed carbs on a 750 before. Whats involved? Is it straight forward? Im getting brand new front and rear rubber boots, so i'll just cut the old ones out when removing the carbs.

Is there anything else I need to know? Do I have to fiddle with the airbox of linkages or anything else?

I was on the bike today and its so fun, but the carbs still leak intermittently from the overflow tubes, onto the ground, missing the engine crankscase.

Carb rebuild in NYC is about $500 so may as well get the  "brand new" $400 rack from my cali dude.

Here is me and the bike today:

[Scott S]

 Probably the same crap that was in the carbs before:

http://forums.sohc4.net/index.php/topic,178687.msg2073645.html#msg2073645

 Yes, the bail clamp holds the bowl on. You can try removing and checking the bowls for debris. You can also operate the floats by hand to see if you can get lucky and dislodge any trash.
 The JB Weld usually doesn't set up in gas. It's probably some other trash.

[754]

 don't put anything on the nozzle , it's a tapered fit.
 if the fuel lines grab hard , just use a bent pic or screwdriver, go around between hose and nozzle to break things loose.

[Honda3]

Probably the same crap that was in the carbs before:

http://forums.sohc4.net/index.php/topic,178687.msg2073645.html#msg2073645

 Yes, the bail clamp holds the bowl on. You can try removing and checking the bowls for debris. You can also operate the floats by hand to see if you can get lucky and dislodge any trash.
 The JB Weld usually doesn't set up in gas. It's probably some other trash.

LOL Scott. I guess you were right.

[Honda3]

don't put anything on the nozzle , it's a tapered fit.
 if the fuel lines grab hard , just use a bent pic or screwdriver, go around between hose and nozzle to break things loose.

By nozzle, I meant this brass part. One of them completely pulled out:

[Scott S]

 He's saying that you shouldn't need any glue or sealant to make the barb/nozzle fit in the petcock body. It's a tapered fit and can be pushed, or gently tapped, back into place.

[Honda3]

He's saying that you shouldn't need any glue or sealant to make the barb/nozzle fit in the petcock body. It's a tapered fit and can be pushed, or gently tapped, back into place.

Well when i put it in and put new hose on it and had to pull the hose off again, the nozzle came out with the hose. I just bought another petcock. I dont feel safe riding with that one. Id hate for the nozzle to come loose from the petcock while Im riding.

[Scott S]

 It's probably fine. They just push in tight. I've had them come off with the hose before....I just push them back in.

[Honda3]

It's probably fine. They just push in tight. I've had them come off with the hose before....I just push them back in.

Whew. Thanks. Im going to cancel the other order then

[754]

 That depends on if you put JB weld on it, without a reamer, you may not get it all out for proper fit.
  work the hoses loose first if you can bend them to the side  it sometimes loosens them. I have the translucent yellow hose and it will stick if it's been on a while.. I don't use clamps.

[rotortiller]

Any brass nipples that I had come loose that would not install in a secure manner I have installed with loctite sleeve retainer, after cleaning with MEK. I don't like to do things twice. Works on overflow tubes in float bowls too.

[Honda3]

So, I took the bowl off today and cleaned them. Bike doesnt seem to leak when its on.

However, if I left the petcock on after I turn the bike off, about 3 or 4 min later, fuel comes out of the overflow tube. Is this normal or still and indication of a problem?

I know vacuum petcocks operate differently, but mine is manual on my 1972. I know if a petcock is left "on" it will cause overflow. Am I correct?

[Scott S]

 It happens sometimes, but it's not supposed to.
 It's a function of the floats/fuel valves. Either fuel level is slightly off or the fuel needle isn't fully seating; either because of wear or trash in the seat. Float height could be off slightly,  causing it to overfill when not running.

 There's also a slim chance that the overflow tube inside the bowl has a hairline crack in it.

 I always turn off the petcock when I park the bike. Always.
 If it runs ok and only leaks when sitting, I think I'd live with it and remember to turn off the petcock.  Maybe even turn it off at the end of the block or driveway. Pull down the fuel level just a bit before parking.

[Honda3]

It happens sometimes, but it's not supposed to.
 It's a function of the floats/fuel valves. Either fuel level is slightly off or the fuel needle isn't fully seating; either because of wear or trash in the seat. Float height could be off slightly,  causing it to overfill when not running.

 There's also a slim chance that the overflow tube inside the bowl has a hairline crack in it.

 I always turn off the petcock when I park the bike. Always.
 If it runs ok and only leaks when sitting, I think I'd live with it and remember to turn off the petcock.  Maybe even turn it off at the end of the block or driveway. Pull down the fuel level just a bit before parking.

Awesome and thanks a lot Scott for the speedy response. Your help has been invaluable throughout this process!

[Honda3]

Ive had it with these damn carbs that have been on my bike since 1972. A guy on ebay sells immaculately rebuilt carbs for $400 plus $23 for shipping.

I bought a set from him for my 1973 Honda CB500F and they are top notch. But....I didnt install them. The Mrs. limits my time in the garage and since I have 5 bikes, I cant do everything, so I farm it out.

Anyways, Ive never changed carbs on a 750 before. Whats involved? Is it straight forward? Im getting brand new front and rear rubber boots, so i'll just cut the old ones out when removing the carbs.

Is there anything else I need to know? Do I have to fiddle with the airbox of linkages or anything else?

I was on the bike today and its so fun, but the carbs still leak intermittently from the overflow tubes, onto the ground, missing the engine crankscase.

Carb rebuild in NYC is about $500 so may as well get the  "brand new" $400 rack from my cali dude.

Here is me and the bike today:

[Keith]

Changing the carbs isn't a big deal....especially if you are buying a complete set. The rubber intake boots only go on one way; the openings on each end are different diameters. The chokes should be all set up, make sure they all close completely and open all way. Rebuilding your existing carbs is actually not that difficult; just four of them.

[Honda3]

This dude has sold me carbs for my CB500F. They came jetted and synched. Was pretty much plug and play.

I ordered new carb boots (front and back) for the carbs so install should be easy.

Ive never put on carbs before so Im a bit tentative. My only concern are the throttle linkages.

If anyone has any advice, feel free to let er rip.

https://www.ebay.com/itm/1970-76-Honda-CB750-Four-carbs-carburetors-Complete-restoration-Clear-coat/333153221984?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

[Scott S]

 Topics merged. You already had a thread going on this subject

[Honda3]

Topics merged. You already had a thread going on this subject

Yep. I sent you an PM thanking you. Thanks again! Sometimes I forget....i post a lot...