Someone might remember me, couple years ago I had my engine rebuilt:
After that I only drove like 20-40km and then started a problem. Car has been sitting in the carage since. Now I have time for fixing it.
So problem is, car idles well, no misfires or anything. If you start giving it more gas, it starts coughing and doesn't take revs. Where to start fixing?
First, test if you have a good fuel supply. Open the valve under the tank and the drain valve under the carb with a can under it. The fuel should have a good flow and continue to flow until you close it after at least a minute.
If the flow is good, then maybe there's dirt in the main jet? Screw out the adjustment a turn while you have it running and trying to rev and check if you can get it to loosen up. If no luck, tear down the carb for a thorough cleaning.
Another fuel related problem now after it has sat in a garage for years could be the age of the fuel - sometimes fuel in the lawnmower goes bad after just one winter, so some new gas in the tank could help?
Did you get your coils adjusted? What timer do you use? Did you get a new one? All timers needs cleaning from time to time and most of them needs frequent oiling. Some repro timers are junk that'll develop problems in short order. Check for a wavy worn timer case - that'll cause misfire at higher rpms:
(picture by Chris Bamford)
(Message edited by Roger K on June 04, 2015)
What Roger said. Very concise logical progression for diagnosing your problem.
Valtteri, I had that same problem with my first T about 35 years ago.
It turned out that my new coils were designed to work on 12 volts DC Battery voltage and never even tested with 24 volts AC Magneto voltage.
I sent the coils to a well known coil rebuilder with a request to repair them so they would work. He said they were trash and he would put them where they belonged or mail them back and let me trash them, if I wanted to pay the return postage. I let him trash them.
The extra voltage caused all kinds of misfires and internal short problems when switching to Magneto.
There was also another problem with my coil box, as I painted the wood with black paint that contained lead, which conducts electricity.
That paint allowed each spark terminal to share some sparks with the adjacent terminal. Sparks at the wrong time made the engine make all kinds of bad noises.
Now I blacken the new coil box wood with liquid shoe polish and apply about 12 coats of clear polyurethane, lightly sanding after each 3 coats.