Walbro zama petrol carburetters.

[Paul De Tourtoulon]

I need some advice, I received another carburettor to replace the ch-system one that wasn't that successful on my Saito 150 petrol conversion that I got second hand as a non runner ( yes I can't help myself buying these lame ducks ) no choke, but I can always make one up,
there is a bulb to pump the fuel up, so do I leave it as is and put a tube to the tank with a second clunk, or a tee on the inlet side and stick to one clunk, block it off with a rubber bung, the other solution is to take it off and blank the system with a metal plate like other carburettors what do you suggest ?.
Thanks, Paul

[Frank Skilbeck]

Sort of like the old british bike carb "ticklers" which allowed some raw fuel into the air intake to richen the mixture for cold starting. Normal starting procedure for a.Walboro carb'd petrol engine is to.apply full choke and flick or.apply starter until engine fires, then choke off and restart, without any means to richen the mixture you'll struggle to start it, so you'll either need a choke, the priming device or prime using an external source.

[RottenRow]

You only need one clunk. The second pipe is a return pipe back to the tank which doesn't need a clunk. The return is the one closest to the bulb.

 

The bulb is pushed a few times until it is full of fuel and fuel is seen to be going back to the tank via the return pipe. Then close the choke if one is fitted and start the engine. As it fires open the choke, as Frank says above. Sometimes the choke is part of the air filter housing (which you won't have).

 

This is a typical 2 stroke strimmer / hedge cutter carb. The small hole above the fuel / air passage is for crankcase pulses to operate the fuel pump once the engine is running.

 

Brian.

[Paul De Tourtoulon]

Thanks, Brian, I found a French video explaining it, just putting tubes everywhere and pumping to see what is what, so I will have a go later on,

first I have to finish my Laser .90 powered PC-9, only a couple of things left to do.

[Engine Doctor]

I had a 26 cc petrol engine fitted with a walbro carb without a inbuilt choke. It was a nightmare to start once fitted in a cowled model . I binned iit an found a walbro type carb on ebay with built in choke for £9 ! 

Also fit a velocity stack if you have room . This will prevent fuel mist blowing back and making a mess in the cowl. It also make for more economical running as that mist is drawn in an used intead of being wasted.

[Paul De Tourtoulon]

I couldn't find anything else with a 10mm aperture.

[Paul De Tourtoulon]

My Saito 150 petrol conversion is now running well with it's new carb, it took a bit of fiddling on the L and H screws as when throttled up it just cut out, it was much too lean, it needed an extra 1/2 a turn to the L which brought it to 1 turn from closed, and 3 1/8 turns on H, I have to throttle up slowly, or it cuts out.
A Master airscrew 15 x 8 gives 8.200rpm, 400 up on the original carb, as for the bulb, I connected it to the tank, it's only an overflow when the carb is full, I didn't have to choke it, it started straight away, now all I need is a plane or flog it