Engine running rough

[MikeBoyles]

Hi all.
I have a 1970s Early Bay 1600 single port, when I start it cold and after a run it sounds like its not firing on a cylinder, after about 5/10mins driving it does improve but not quite as good as it should do, also idles okay after engine is warm. Recent tune up (100 miles ago), I have checked all spark plugs and they look okay, taken apart carb and cleaned all jets, changed the coil. Any suggestions what next to check/change please?

 

[mike202]

Try taking a plug lead off to see if the engine note changes. If one cylinder isn’t getting a spark there won’t be any change in the sound.

 

[MikeBoyles]

Thanks mike, will give this a go.

 

[ozziedog]

Thanks mike, will give this a go.

As said above, but just pop the leads out at the dissy cap, as it’s a lot more prominent and easier to access.

Ozziedog,,,,,,,,you maybe already knew that

 

[kjb01]

If you have points check the gap. They could have slipped

 

[MikeBoyles]

After further investigation, I have a stuck inlet valve on cylinder 4… thanks for all the suggestions.

 

[ozziedog]

Everything is clearer once you have the answer. Just goes to show that a compression test isn’t maybe first call but certainly worth a shot if initial checks fail. At least you know where you are now.

Ozziedog,,,,,,,,,,,not as bad as it could have been.