ORIGINAL: rollmyown
The Zama carb I used on a 25cc Weedeater was a C1U also, with M29D & 86A on the side.
It is 9mm venturi. see [link=http://www.zamacarb.com]http://www.zamacarb.com[/link] - they have great info about all ZAMA carbs.
ORIGINAL: rollmyown
I don't think 8K would be possible without this porting.
I just stripped another Poulan trimmer. This will be my experimenting one. I see - ports are quite small. I'm going to do major cuts:
1. Increase compression (I need to shave about 0.5mm from the bottom of the cylinder. I should be able to fit it on my lathe.
2. Open intake port from the bottom. Allmost all the way to the pump hole.
3. Open exhaust port from the top.
I need to check if transfer ports are not blocked by the backplate. I may try to make a little smaller the space under the piston by moving backplate forward.
The carb on this engine is a little different. It has a brass choke shaft (the other were plastic), but there is no choke plate. Closing the choke (this one has a spring) will open the throttle a little. That's it.
I need to look for 11mm venturi carb. Any ideas what may be usefull?
RysiuM