SQ4 only runs with choke

[paul.jameson]

This is the gasket with notch at the bottom which is needed on a bi-starter Solex for it to run properly.

Bi-start gasket and slot.jpg (147.56 KiB) Viewed 703 times

[simon.holyfield]

... it is hard to understand why your carb worked on your bike but not on his.

Something I discovered a while ago was that my Bistarter wasn't going fully 'off' as it was fouling the HT lead bundle. I'd been playing with the HT lead routing at the time.

Another one was the use of one of those large chrome and glass fuel filters in the early days of getting to know my SQ4 - fit them in the wrong place and they'll cause a nice air lock.

The only other problem relating to the fitting of the Solex, rather than problems within the carburettor itself is heat - there's a lot of heat conducted and radiated to the carburettor which causes a few problems. You need a Tufnol spacer as a minimum; I used a stainless heat shield between the head and float bowl for a while, but I've removed that now with no ill effect.

[kevin.mcdiarmid]

didnt know about that gasket, neither carb has it and mine runs good..hmmmmm

today i put a piece of tape across the top half of the carb intake and it does run with the choke in, not perfect but runs
then i tried to find a vacuum leak using a little propane bottle and a piece of vacuum hose but didnt find anything
we will try to make a gasket and see what happens

[kevin.mcdiarmid]

We also tried my carb on his bike, now we will try his carb on my bike.......

[kevin.mcdiarmid]

tried for an hour to upload a 2 photos, i put them on IMBGG and tried that and from my computer
also tried searching the forum on How to upload photos.......i give up lol

[will_curry]

Kevin,

Try: viewtopic.php?t=193

[paul.jameson]

The gasket is pretty thin - say something like 7 or 8 thou thick, from memory. (And no, I haven't got one to measure!).

[robjameson]

The easiest way to find an air leak (in my opinion) is to buy an aerosol can of brake cleaner and spray it all around any joints on the intake, if the revs increase, you have a leak, and you can pinpoint quite accurately with little sprays around the area.

My personal thought with this particular problem is that you have a head gasket issue. I think the easiest way to diagnose this would be with a cylinder leak down test.

[kevin.mcdiarmid]

solex.jpg (45.96 KiB) Viewed 492 times

[kevin.mcdiarmid]

Aha, easy peasy, thanks for the help, as you can see the gasket does not have the notch and the centre bore is raised slightly which cuts of the notch in the body anyway