Topic: CB750 Carb Mods?

[KC_Northstar]

I took the air box off my CB750 K2 and looked inside the carbs. I was surprised to see that it
was shiny close to the throttle while the rest was tarnished.  Upon closer inspection I noticed
what looks like grinding marks.  It looks like someone took a grinder and opened up the carb throat.
In the pictures the carb is still attached to the engine and you are looking in the air box side.
The throttle is wide open.  Are those grinding marks or is that normal carb casting? Why is it
shiny metal near the throttle?  Has anyone heard of a modification like this.  I'm thinking my
carb body's are trashed.

[KC_Northstar]

Here is another shot

[KRONUS0100]

looks like somebody tried to bore them to 30mm and fooked em up.  either trash em or take completely apart and get some fine sandpaper and smooth em out best ya can.  if the bike is currently running condition, how well does it pull thru the gears?

[KC_Northstar]

"looks like somebody tried to bore them to 30mm and fooked em up.  either trash em or take completely apart and get some fine sandpaper and smooth em out best ya can.  if the bike is currently running condition, how well does it pull thru the gears?"

It does not run well at all and I am trying to track down all the reasons why.  Is this a mod that someone would do to a stock
750?  Sounds like something that would be done after installing a big bore kit.

[KRONUS0100]

ok.  plan on taking htem completely apart and cleaning them.  boil the bodies either in lemon juice ( not kidding) or simple green. I didnt believe the lemon juice thing either until i watched a youtube video on it....lemons are citric acid just like oranges.

once they are clean, reassemble and bench synch.I used a 1/16th drill bit inserted from the backside of throttle slide.put on bike, warm up, and bench synch.

I reckon before that tho, make sure your ignition is up to the task and valves are set properly.

[CycleRanger]

I have several stock carb bodies that show similar grinding marks.
I imagine it was done at the factory to clean up the flashing from the casting.

[ksteve]

I have several stock carb bodies that show similar grinding marks.
I imagine it was done at the factory to clean up the flashing from the casting.

I was just about to post a question about the grinding marks in my cb750 carbs, which look just like this. Given how many of us see these, I've got to assume this answer is right: factory clean-up

Does anyone have a definitive answer?:?

[754]

If stock they should look like 2 overlapping circles.