Carb mounting

[Peterwh]

I've never had the cars off of a CB 750 until now.  I'm struggling to get them back on.  Do I put the boots on the intakes and then get the carbs onto the boots (seems impossible), or do I put the boots on the carbs then get the boots onto the block?  Or, is there another way of doing it?  Help!!!!

[TOOLS1]

You have to put the boots onto the head first. Spraying the boots with silicone spray will make them go on a lot easier.
TOOLS

[Peterwh]

OK, I will keep persevering and try the silicone spray.

[Re-run]

Watch carefully to make sure the boots are turned the right ways when you put the carbs back on.
A method I use is to get the bottom lip of the carb mouths on the boots and then swivel them up as I push them on. My carbs have always gone on well doing this.

[nilsthenomad]

Completely loosening the airbox obviously helps. I've gone as far as removing the air filter and reaching up into the airbox to adjust the boots on the back side. It has certainly helped me get the space I need to get the carbs in the head boots.

[motogrady]

mannnn........a few weeks ago I figured out a system that's killer.

it's cold in my garage, and just could not get a set on my 750c.

the rubber boots were hard as a rock.

pulled a set of rachet type tie down straps out of the trunk of the car.

got the carbs lined up and started in the rubber boots as best I could,
maybe 1/8 of an inch on one side of the carbs was in.

fed the strap around the back of the carbs, around the engine and in front of the
downtubes of the frame.  Was careful not to lay on any fins that looked like they would break.

slowly, I cranked on the tiedown, and tapped with a rubber mallet all around the
float bowls and body of the carbs, working left side, then right side, crank a bit here,
tap a bit more, crank a bit more, and poof, those suckers set all the way to the square
parts on the carbs like was nothing.  with no lube.

was like taking candy from a baby

just remember to have all the cables hooked up, once they're in....................

[vingtsous]

Using an hair dryer to warm and smooth them up a little bit

Could it be a good idea??

[sgtslag]

The carbs may have some gasoline inside.  A hair dryer uses electric heating elements, which get red-hot, literally; electric igniters are used inside of natural gas home furnaces, glowing red-hot (actually, almost white-hot in my furnace), to ignite the gas -- food for thought.  I would recommend against it, due to liquid gasoline evaporating, and once it is vaporized, it becomes quite volatile, and dangerous.  Tools use of a silicone lubricant is the best idea, combined with some slow, firm force, like the tie-down strap idea -- be careful of those cooling fins, though!  Best option would be to wait for warmer weather, if possible, as the rubber will be more pliable.  Cheers!

[vingtsous]

Damn right!

I should have think about it!!!

[Peterwh]

I'm embarassed to say this but I'm still struggling to get the carbs on.  This is a complete build from the bottom up, literally, from parts I've bought on ebay, from Vintage CB750.com and from Tools so there's no chance of there being traces of gasoline anywhere in there.

I'm using a set of pd carbs - the ones with the keyhole tops, and a set of rubber connectors for a 78 model that I bought from VintageCB750.com.  The connectors are the stubby kind rather than the "longer" ones that were used on the earlier SOHCs.  The are two pairs of connectors.  One pair is bent a bit more than the other pair.  One problem is knowing which cylinders each connector goes on.  Do the "more bent ones go on 1 and 4 or on 2 and 3?

The second problem is that no matter which cylinder/connector combination I use, I don't seem to be able to get all the connector centerlines on the same centerlines as the carbs and there's not enough flexibility in the connectors to force them into the correct position.

I'm wondering if maybe these connectors are just no good.  They are an after-market item with no numbers (ie 1,2,3,4) and maybe they are just not a good copy.

Any and all advice gratefully received at this stage.

[rich]

Don't know if the pics will help or not. I made them pretty big. They're of a 77K (same carbs as your 78)