Manifold gasket

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WEM

WEM

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I’m getting ready to reinstall the Amal Premiers on my ’74 Commando. Whenever I’ve done this in the past, I’ve bolted the manifolds to the head with just the carb intake insulators with no sealant. However, I note that Norman White recommends a thin layer of liquid sealer be applied to both sides of the insulators. Is this something that others have done regularly, and, if so, what sealer should be used?
 
I didn't expect tumbleweeds.

Do you need anything, who knows.
I use WellSeal sparingly to all four surfaces (gasket and head) left to tack off before assembly, dab applied with a brush (or foam could be used)

Last time due to going to RH4 manifolds I had trouble finding quality Bakelite insulators so machined some RH1 items to suit the 32 mm ports on the FA head.
If you have one of the throttle gantries that has to be taken into consideration to make sure the carburetor tops are flat depending on the order you mount it.
The Wellseal would still have a window of fine tuning manifold movement but probably not a problem with the stock twin cable system.

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Edit.
Before that I remove the studs from the manifolds to lap all four surfaces then put a light countersink on all of the holes including those that are threaded to avoid any riser (or pulled thread risers on the studs)
Then another light lap and put the outer studs in only, the inner two being replaced with handlebar clamp cap screws for ease of access with a custom tool to suit.
 
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Time Warp said:
I didn't expect tumbleweeds.

Do you need anything, who knows.
I use WellSeal sparingly to all four surfaces (gasket and head) left to tack off before assembly, dab applied with a brush (or foam could be used)

Last time due to going to RH4 manifolds I had trouble finding quality Bakelite insulators so machined some RH1 items to suit the 32 mm ports on the FA head.
If you have one of the throttle gantries that has to be taken into consideration to make sure the carburetor tops are flat depending on the order you mount it.
The Wellseal would still have a window of fine tuning manifold movement but probably not a problem with the stock twin cable system.

View attachment 83075
Click to expand...
Well , can't beat that.
I bolt them up tight straight out of the package. Obviously a re-tightening after say 500 kms.
 
The insulators are not good at sealing by themselves and if you apply just Yamabond and bolt them up you will find that the motor has soon sucked every last morsel off the phenolic insulators. What works for me is to scratch up the insulators with sandpaper then wipe down all mating surfaces with carb cleaner or acetone. Use 2 paper gaskets per insulator, making a sandwich. Yamabond everything and allow to set up. Then assemble to the motor and tighten the bolts around 8 PSI. When everything dries it forms an air tight bond to the phenolic.
 
The manifold and the carb flanges are often warped due to overtigtening - or maybe even due to original casting tolerances. If you true manifold/carb flanges on a sheet of glass/400 wet/dry sandpaper, it will greatly improve sealing and reduce/eliminate the need for any sealant/gaskets.

When I bought my '73 850 in '06 you could see through the center of the manifold/carb/insulator mating surfaces if you took the carbs/manifolds off the bike in situ and removed all the silicone sealant the PO had installed between the carbs/manifold to "cure" the problem... :eek:
 
when you offer up the manifold and insulators to head, as the Allen set screws are a loose fit in the manifold they "drop" slightly causing small lips within the inlet tracks,
So like Time Warp using rotary drum sanders i opened up the holes slightly in the insulators & took time to centralise the manifolds against head making sure i had no internal lips
 
Wellseal here too. I don't know why, but every time I've bought 30mm insulators for my MKII they came as 28.5mm and had to be opened up a bit. I use a sanding drum on the drill press.
 
Paper gaskets both sides, no goop. Have to trim the gasket ID. I used a dremel and sandpaper to open up the insulators to match the intake ports. That was when I used Amals. I'm not using insulators currently. I still use a paper gasket between the head and spigot intake manifolds. No goop. No leaks.
 
Yamabond (actually Permatex grey equivalent sealant) seems to hang on fine for my bike. Also used Hylomar there and for the car b to mani flange. Still present upon removing mani thousands of miles later.
 
I use the Cometic nitrile gaskets both sides of the insulator. It adds a bit more insulation, seals completely everytime and they can be re-used indefinitely.

Glen
 
worntorn said:
I use the Cometic nitrile gaskets both sides of the insulator. It adds a bit more insulation, seals completely everytime and they can be re-used indefinitely.

Glen
Click to expand...
Where does one source those?
 
I purchased directly from Cometic USA.
The part number is CB335SP2032AFM.
Cometic calls it a " Vincent Carb Adapter Gasket" but it will fit a Norton Commando as well.

Glen
 
adding to my earlier post, after making the sandwich of one insulator and two paper gaskets, I will yamabond it to the manifold only which will allow me to later remove the manifold and gasket as one piece. Then I trim out any excess gasket or phenolic with an Xacto knife and reinstall using yamabond to glue it to the head. It is air tight after this.
The 3-piece gasket I make is factory made for BMW R60/2. So I copied their idea.
I like to have the intake track as uninterrupted as possible but I occasionally run into the other situation where I have to use a 32 phenolic spacer on a 30 manifold. Seems to work alright but I always wonder about it.
 
Hylomar spray works well and coats evenly plus you can easily remove also Permatex 80064 High Tack Spray works
 
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