S3 bogging on full throttle

Tim_AM · May 16, 2024

Hello,

Ive been having an issue with my Series 3, 2.25 petrol:

Upon start up I don't often need the choke, and have to shut it off pretty quickly to prevent poor running if i do use it,

Once warm I have to limit throttle input, if I floor it the engine just bogs,

I should also note, that it often 'diesels' when I shut it off,

Its got a new weber 34 ich, electronic ignition, new ish coil plugs leads and cap and rotor arm,

ive just checked the plugs and threw a timing light on it photos attached:

Ive put a video of it on youtube too:

:

Any suggestions?

kermit_rr · May 16, 2024

It's running very rich and the timing is well off wants to be just after the 6deg mark. Then set the carb, but if it's very old or a cheap copy then you might have no luck

tottot · May 16, 2024

Those plugs are black a sign of very rich running [ a light brown is good] As @kermit_rr says timing first.

Dorset_dumpling · May 16, 2024

That does seem to be very advanced timing. Mine is running about 10 btdc at idle speed with the vacuum advance disconnected and running on E5 99 octane petrol. You could also be running rich but if your timing is too far out you will also be getting incomplete combustion which will also cause sooty plugs.

Tim_AM · May 16, 2024

kermit_rr said:
It's running very rich and the timing is well off wants to be just after the 6deg mark. Then set the carb, but if it's very old or a cheap copy then you might have no luck

Thanks Kermit,

its a brand new weber so should be able to!

thanks, Ill try adjusting the timing and tinker with the mixture screw,

kermit_rr · May 16, 2024

Tim_AM said:
Thanks Kermit,

its a brand new weber so should be able to!

thanks, Ill try adjusting the timing and tinker with the mixture screw,

Get the timing right first then check the mixture after, but you might need to adjust the revs a bit as you go

Tim_AM · May 17, 2024

kermit_rr said:
Get the timing right first then check the mixture after, but you might need to adjust the revs a bit as you go

Thanks K, when you say adjust the revs you mean the throttle linkage?

kermit_rr · May 17, 2024

Tim_AM said:
Thanks K, when you say adjust the revs you mean the throttle linkage?

I mean the sprung adjuster screw on the throttle butterfly

tottot · May 17, 2024

I found the Gunson Colortune very useful for setting the fuel mix on my 2a.
A device that allows one to view what is happening inside the combustion chamber.

S3 bogging on full throttle

Tim_AM

Well-Known Member

kermit_rr

Very

tottot

Well-Known Member

Dorset_dumpling

Well-Known Member

Tim_AM

Well-Known Member

kermit_rr

Very

Tim_AM

Well-Known Member

kermit_rr

Very

tottot

Well-Known Member

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