What needles are supposed to be in 1969 diecast 4 cable carbs ?
Marked B750A, i have 27201 .. are these correct ?
I set the floats a long time ago, so cant remember, but should have set 26mm.
40 pilot, 120 main, clip in the middle.
Air screws, 1 turn out.
Carbs are synced, intake manifolds are new.
Compression is 130psi across
Stock air box filer and hm300 pipes
I do get decel pop, intermittently
Plugs are nice and tan, idles good, strong low and midrange.
Will pull red line 1-3, 4th becomes an effort, but will.
5 th tops out at 6k.
Plugs show lean in fifth WOT.
Carbs are as clean as can be. Brass floats.
I did not replace the floats.
Plugs are suspiciously too tan, i havnt had a cb run this clean plugs ever in low mid range.
Possibly float height low ?
Do you have all 4 of the carb's vent hoses routed up and over, behind the airbox? If these are too short or in turbulent air it can affect the torque, especially at high speed, because it reduces the bowl's ability to push fuel up the jets.
Another thing that can cause poor top-end performance (if carb-related) is fuel delivery, either from a [partially or fully] blocked fuel tank vent (in the fuel cap). This slows fuel delivery, especially in fast-moving air around the tank (which is then at lower pressure than still air).
I've also seen the [brass] floats set incorrectly for the K0/1 bikes. They should be staggered 1mm between them, with one float (kickstand side of the bike) at 25mm and the other at 26mm. This was true until the 657b series carbs with the plastic floats came out, around 3/1972.
Yes, vent hoses are routed behind airbox.
Petcocks is clean, tank is a yamiya replacement.
The only thing that comes to my mind, well two things;
One of my k0’s has its original camshaft, the other one .. cant remember, may be a k4-k6 ..
Secondly, i saw you mention fuel level in the bowl should 3-4mm, below gasket seam, but at 26mm, its more like 10mm. More a pull up, the richer it gets.
Ot may be i should try raising the fuel level to 4mm, go down a notch on the needle, and perhaps go to a 115 main ?
Both bikes have 4 cable carbs, one has early correct cam, and some intake port work, runs a little rich but more power everywhere, compared to the other, but the other does have perfect tan plugs lol well a tad rich lol
Is there an aftermarket cam which is kinda similar to the early cams ?
