Intake leak

[tattoomark]

Hello I know there's been a lot of discussion on intake leaks I have a question I have done a pressure test on my intake manifold I am using viton o rings original intake clamps when I do the pressure test 15 lb of air using soapy water I have no bubbles at all none whatsoever around the intake manifold clamps around the intake ports nothing around the cylinders I put the carburetor back on I do not move the intake manifold at all I've become a professional doing it now I believe because I've done it so many times the bike starts on one Kik cold it also starts on one kick hot I have not ridden the bike yet because if I take the bike while it's running in spray pJ1 (using the spray tube)cleaner around the intake ports the bike starts to stumble and fall because of an air intake leak problem I'm spraying around the outside edges of front and rear cylinder and they're both doing it I have no clue I have never seen anything like it I would imagine if the bike was hot it wouldn't start and it starts on one kick if anybody has any suggestions please feel free to tell me because this is driving me crazy I know it's not right but the bike is running

[1950Panhead]

The nipples can leak where they screw into the head or the O rings can leak.
If you spray soapy water at these locations with the manifold 15 psi you will see bubbles if there are leaks.
If the manifold is not leaking and the bike runs poorly then there are other issues.

[tattoomark]

Sorry i guess i should have said this is a 55 fl

[panheadrider1961]

are you doing your spray test with air cleaner off? another place would be through throttle shaft . and not a good flat seal at carb to manifold , you are using a linkert ? what do your plugs tell you rich or lean? this type of test with wd or other types of sprays are good for car motors to isolate vaccum leaks this is true I have not had success doing it to a harley motor because they are a big vaccum pump so to speak and carb to maniold distance to short spray volume creates large fume cloud and it picks this up making for a bad day.

[tattoomark]

Air cleaner is on its a m74b i spray directly on clamps front of carb and rear it doesnt matter where you spray it boggs down i have sprayed around the throttle body its fine the plugs are rich but there identical in color like i said i would have thought with that bad of a leak the bike wouldnt start hot or cold? Also once you predsure test and carb is all back together is there a better way of checking for intake leaks all i have done is wd40 and pj1
thanks
Also bikes running rich not lean plugs are pretty black carb is 3 1/2 turns out on main 3/4 turns out on fast

[Scrap]

Do you have a support bracket on the carb? Maybe you are tweaking the position of the manifold when you tighten it.

[Buddhahoodvatoloco]

Scrap, excellent suggestion, good job..........

Do you have a support bracket on the carb? Maybe you are tweaking the position of the manifold when you tighten it.

[tattoomark]

Yes to the support bracket before i do a pressure test i bolt the carb to manifold clamps are barley snug tighten up the clamps remove carb carefully put tester block on etc

[panheadrider1961]

have you checked for high float level? smutting your plugs, also on kickstand if it is high will let more gas in and cause rich ,have you rode motorcycle to see if any other symptoms arise ,spitting back, bucking, coughing, stalling with throttle roll on , if you have no bubbles i would say you have a tight seal and go from their

[tattoomark]

Yes to float level its good as far as riding her yet no i been a little leary if it had a big air intake leak burning a whole thru a piston
Im going to repressure test it then see if it changes or fixes it this will be the 4th time

[Bigincher]

Okay, I've read and re-read this issue--
Are you certain that over-spray isn't entering the intake causing the stumble? I've done that myself, so I know it can happen.

[panheadrider1961]

is your intake manifold the original one , if so it may have fissure cracks in it , Mr. Cotton spoke about it on here many years ago get manifold good and soapy a strong flashlight and look for tiny bubbles its not going to blow any big ones

[blewcrab]

Okay, I've read and re-read this issue--
Are you certain that over-spray isn't entering the intake causing the stumble? I've done that myself, so I know it can happen.

I have also ran into this problem ....You need a helper to hold one end of a shop vac hose to carb throat , and the other end up and away from the manifold area ....This will assure the carb is not sucking any of the spray !

[tattoomark]

Ok also these are new vtwin heads(i know) i have checked for porosity none i have a large barrel fan blowing the opposite direction im spraying I have had several conversations with Cotten about this he has walked me thru all of it, maybe get a priest? Do a exercisim?

[Northman]

Okay, I've read and re-read this issue--
Are you certain that over-spray isn't entering the intake causing the stumble? I've done that myself, so I know it can happen.

I have also ran into this problem ....You need a helper to hold one end of a shop vac hose to carb throat , and the other end up and away from the manifold area ....This will assure the carb is not sucking any of the spray !

I was thinking the same thing. Could it be pulling in from another location on the body as well....?