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Rough running on choke


s.leah
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This may not be a problem.... I've not much experience with manual chokes!

 

When I start my 13/60 (original engine/carb) on full choke it runs pretty rough. It chuggs and pops and sounds like it is miss-firing and threatens to stall if I so much as dare to push the choke in slightly. It's fine if I press the throttle the revs build up and it doesn't try to stall.

 

After a couple of minutes when the engine is warm enough to run without choke, it runs beautifully so nothing basically wrong.

 

Does this sound fairly normal or does my carb need a tweak?

 

Cheers

Simon

 

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I was a bit more scientific when I started this morning  :)

 

On full choke it was as described and it would rev OK. However, when I pulled away the power wasn't fantastic and although it wasn't warm enough to push the choke fully in, I did so as I drove down the road and there was a little boost of power as I pushed it in..

 

This leads me to think that it is probably as simple as fast idle not set correctly and I'm over compensating by pulling the choke fully out when I probably don't need to. Consequently it is running waaay too rich hence the lack of power under load.

I suspect if I tweak the fast idle so it'll run with less choke (and eventually tweak so pulling it fully out doesn't over choke) all will be well  :D

 

Sorry for my waffling, I'm more thinking out loud... does my theory sound about right though?

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pretty much all constant depression carbs be they stromberg or su need more fast idle than expected

 

less than 2000 but more than 1000 or they choke to death   on full choke.

 

might make cold starts a bit brisky but soon caan be 'pushed in'  as soon as initial warm up creeps in.

 

the fast idle cams do wear and often the tappet screww gets a groove as this is hardly ever lubricated 

 

over the years you loose revs .    

 

make sure you nip the locking nut when  re adjusted.

 

this applies to the SU jet drop , stromberg Thames barrier , and the later side mounted starting valve chokes .

 

Pete

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