Running iffy from cold sometimes (845cc, Zenith IF 32)

[Niels Svane]

Hi
This winther I've had a small issue with my R4 for the first time in my five years of ownership.
When cold it sometimes can't run more than 3/4 of the revolutions it normally would. It seems like it can't get enough fuel somehow when reaching a certain speed in all gears.
Then after 5 mins of driving (app. 5 km) it gets better. I've cleaned the carb. but it didn't help, so my question is: Can the membrane in the fuel pump stick initially thus not feeding enough fuel?
The problem is especially present the day after a long trip. When left alone for a week or two, it doesn't happen as often.

 

[Niels Svane]

That is: I've had issues before, THIS issue is just a first

 

[mr-reno-139]

Have you got the air filter set to pull hot air of the exhaust manifold as the heat is needed for efficient cold running in the winter months

 

[Niels Svane]

I've run with the tube attached to the exhaust some winters and without other winters without noticing any difference. This has been in -5 to plus 5 degrees C.
I am of cause running with isopropyl butanol in the petrol too.

I'll follow up on the issue when the temperature rises from now on, and the car also will be running daily soon. On top of this I have a new petrol pump ready in the car.