sq4 solex-bi-starter

[Henning G]

Hello,
My iron sq4 simply refuses to idle without choke with the solex bi-starter carburetor. As you can see, the gasket does not have the notch and the center bore is raised slightly which cuts of the notch in the body anyway. There is a hole, between the sleeve and the carburetor body, where the notch is, going all the way through. Hope you can see it on the photo. Really doesn’t make any sense to me at all, and quite a tricky carburetor with lots of jets… Anyone any idea?

[simon.holyfield]

Here's mine for comparison

Is the idle port open and the needle in good shape?

You can just see the port here, under the butterfly:

Lastly, here's a collection of blog posts filtered for Solex. There's one which records all the jet sizes.

https://ariel-square-four.blogspot.com/ ... %20AHD?m=0

[Henning G]

Hi Simon, thanks for your fast reply. Does you hole at the notch goes all the way through between the sleeve and carb Body, and does you carb idle …

[simon.holyfield]

Hi Simon, thanks for your fast reply. Does you hole at the notch goes all the way through between the sleeve and carb Body, and does you carb idle …

Hi Henning,

I believe it does, but that's because it appears to be a machined groove and not because I have ever put a wire down it.

My bike idles just fine - I've only once had a problem with some gunge in the pilot jet. The only modification I have made is to lower the float valve using two fibre washers, which makes it more lean.

[Colinbrindley]

I`m sat looking at my carb now as I took it off for cleaning. Should it have a gasket on the top of the float bowl ?

[Henning G]

Hi, I have measured the thickness of the washer underneath my float valve, and its 1,5mm thik.Hi Simon, Thanks a lot for the link to the solex carb. I’m still a bit confused regarding the purpose of the notch, should it allow air from the venture, or air from the hole where the emulation tube is placed, where my wire was placed.. Simon, is there any chance that you could pinpoint the sizes and locations of the different jets, pretty sure someone has mangling around with it in privies times. Regarding gasket at the fuel bowl, mine didn’t have one…

[simon.holyfield]

Do these help?

sq4solex.pdf

(546.93 KiB) Downloaded 27 times

[Pete.Silson]

Henning,

I don't believe the notch under the choke tube has any effect on tick-over. The four usual sites for blockage of the pilot mixture path are shown in the diagram below.

Air leaks anywhere in the mixture path (blue in diagram) cause erratic tickover. Blockage of the pilot jet (3) weakens the tickover mix, blockage of the pilot air bleed (4) richens the tickover mix. There are two small holes either side of the butterfly (1 & 2) which can also get gummed up - the size of these are important so best to blow them through with air rather than poking with wire.

Pete

[simon.holyfield]

Nice job Pete. Mind if I pinch that picture for my archives?

[Pete.Silson]

Feel free.