Walbro / Tillotson carb overhaul

Due ongoing starting problems on my 3W 70, decided to fully strip the Tillotson carb and for the first time remove the fuel jet Welch Plugs. (no idea why an Irish company uses welsh plugs). There are plenty of You -Tube bodgers out there so this is my method.
- Drilled a prize hole using a centre drill as this limits the breakthrough depth.
- Found a main jet filter screen which is not mentioned in the Tillotson manual which had collected significant "crud" most of which i had cleaned out before taking this pic
- Used the drill press to refit new Irish welch plugs

History of the Welch Plug -
According to Nevin Hubbard of the M.D. Hubbard Spring Company, the Welch plug was originally designed in the 1900s by the Welch brothers at the Welch Motor Car Company of Pontiac, Michigan. Hubbard claims that "at that time core holes in the engine blocks were fitted with pipe plugs. During one of these run-ins a pipe plug backed out. In order to get back on the road one of the brothers drove a quarter or half dollar into the hole. From this they developed the Welch plug, some with the help of my great grandfather Martin Hubbard. They then patented the plug and the M.D. Hubbard Spring Company became the sole manufacturer of the Welch plug for the life of the patent."[6]

Colin.A

Hey Folks

Re Walbro carb rebuild, the carb kits come with what appears to be an extra couple of gaskets.

Not much info readily available on tinternet, found this on a cart racing web site.

Any one got DA or aero specific info that is more relevant?

Thanks in advance.

Phil M

hi phil
Think you've downsized the the jpg's a bit too much so see any detail

Its not uncommon for carb kits to contain extra gaskets - As long as you've fit like for like.

Ok I’ll try some bigger files....

Walbro kits usually come with all the gaskets for the different types of 'pumping' options. E.g some are pumped by a pulse from a small orafice connecting the crankcase directly to the carb (built into the inlet flange), and some have an external pipe connecting to a nipple. There are diffent chambers in the pump side of the Walbro to allow a common casting to be for all the different options - and sometimes similar gaskets for different fuels. Just select the gaskets which look most like the ones you removed (in colour and shape) and you will be Ok!
Ps if you are replacing the pop-off needle valve, the little b*st*rd and its spring and fulcrum have a tendency to make a break for it :blink:

Philmac wrote: Ok I’ll try some bigger files....

The instructions you've downloaded advise which gaskets to select . May be correct but based on karting experience.

For the main pump gasket it advises to select the tan (ptfe) which i agree with as they seem less likely to stick when the carb gets dry (Tillotson uses these by default )

I have no experience with the secondary device. so irrespective of karting experience, i still recommend like for like

suspect your carb might be Walbro WB series

FYI - this carb is obvious designed for the larger motors with higher fuel flows so has dual inlet check valves ( to allow better low pressure fuel flow) .
Have now studied the secondary device in the fuel chamber which is a high speed fuel jet check valve. Without this when the carb is in idle position, the idle jets would be able to draw air the wrong way from the high speed jet, vent fuel chamber and loose "suction" to open the fuel regulator.

So if the engine were to cut when returning to idle, or fails to draw fuel from the tank to start. this check valve would be a likely candidate.