M-88 Carb floods on 42-WLAMy friend

[dukekleman]

With the carburetor fully assembled and held upside down,
test the needle and seat function with a vacuum tool. If things are all correctly assembled it should hold 25 inhg.
As mentioned earlier by Rubone, is there a fixed jet being used along with the high speed needle?

[T. Cotten]

One more scenario, Hack...

The common WLA fuel lines compell the bowl to be indexed with the floatvalve of the bowl to be inboard of the HS needle, almost square to the body, when sidebowl Linkerts were designed for it to be directly beneath the HS needle assembly.

The float can be properly offset for this, but the entire carb, with indexed bowl, must be inverted so that you can suck upon the valve to be certain it closes completely, as the float easily hangs up upon the bowlstem.

(A rubbing float allows the level in the bowl to rise above spec, enrichening both idle and power circuits beyond their design. The bowl assembly is considered to be its own metering circuit.)

....Cotten
PS:"Indexed" just means its clocked for a trial. Hope that makes it more clear.... .. . . .

[Rubone]

My friend swapped out a Mikuni for a pro rebuilt Linkert M-54 that did not work then a 20230623_104429.jpg20230627_133527.jpg M-88, from the same supplier that is currently on his stock motor WLA bob job.
Problem is the machine runs consistently rich, real rich to where it won't run in traffic or idle down.
As soon as he shuts off the gas at the petcock in a few seconds it runs great as it always did until it starves and stops.
He/we have swapped out floats (both Duckies) needles and seats, levers and lowered the float a bit to increase pressure on the needle. He also installed and checked the intake seals, peek, although it never had a previous problem with the brass seals.
Still runs like crap. Is consistently running rich even with the low speed needle turned all the way in.

I have an assortment of old OEM used seats and valves, some have smaller internal diameter and have round valves and some are bigger with square shaft. Since they all have the same part number I wonder what is the difference?

I'm basically a Panhead guy and have very little knowledge of the 3 bolt and other flathead carb business so any help sorting this out will be most appreciated.

Panhead or flathead makes no difference on how the carb works. The pictured carb has an adjustable high speed needle in it, M88s did not come that way and it may be a clue. Does it still have the fixed jet in it? Has it been converted to external vent? Was the venturi changed? Is the float offset correctly?

[T. Cotten]

My friend swapped out a Mikuni for a pro rebuilt Linkert M-54 that did not work then a M-88, from the same supplier that is currently on his stock motor WLA bob job.
Problem is the machine runs consistently rich, real rich to where it won't run in traffic or idle down.
As soon as he shuts off the gas at the petcock in a few seconds it runs great as it always did until it starves and stops.
He/we have swapped out floats (both Duckies) needles and seats, levers and lowered the float a bit to increase pressure on the needle. He also installed and checked the intake seals, peek, although it never had a previous problem with the brass seals.
Still runs like crap. Is consistently running rich even with the low speed needle turned all the way in.

I have an assortment of old OEM used seats and valves, some have smaller internal diameter and have round valves and some are bigger with square shaft. Since they all have the same part number I wonder what is the difference?

I'm basically a Panhead guy and have very little knowledge ofthe 3 bolt and other flathead carb business so any help sorting this out will be most appreciated.

They run rich, Hack,..

When they cannot run any other way. This is usually because of a vacuum leak.

Please review Diagnostic #1:
http://virtualindian.org/11techleaktest.html

Unless the manifold is absolute, any fiddling with the carb is futile. Beware you must use a constant, regulated air supply. Many get false negatives with tire pumps, etc. (And please beware that mass-produced PEEK seals have ruined the "brand"!)

...Cotten
PS: The round needle design was '50 or so and later OHV.
PPS: The "pro rebuilt" Linkert is unfinished.
PPPS: Unless the Duckies have swollen from fuel, they really should remain at a quarter inch.

[Hack]

My friend swapped out a Mikuni for a pro rebuilt Linkert M-54 that did not work then a 20230623_104429.jpg20230627_133527.jpg M-88, from the same supplier that is currently on his stock motor WLA bob job.
Problem is the machine runs consistently rich, real rich to where it won't run in traffic or idle down.
As soon as he shuts off the gas at the petcock in a few seconds it runs great as it always did until it starves and stops.
He/we have swapped out floats (both Duckies) needles and seats, levers and lowered the float a bit to increase pressure on the needle. He also installed and checked the intake seals, peek, although it never had a previous problem with the brass seals.
Still runs like crap. Is consistently running rich even with the low speed needle turned all the way in.

I have an assortment of old OEM used seats and valves, some have smaller internal diameter and have round valves and some are bigger with square shaft. Since they all have the same part number I wonder what is the difference?

I'm basically a Panhead guy and have very little knowledge of the 3 bolt and other flathead carb business so any help sorting this out will be most appreciated.