I have recently fitted a new 172 kit to my T5 classic.
After putting the engine back in, I found that it was running really rough and struggling to reach anything above mid revs. The throttle was very slow to respond. On closer inspection of the carb (24/24 G), I found that the mixture screw had pushed the threads through so that some metal was poking out into the inlet of the carb… so I bought a new carb and decided to go for a 26/26 G instead.
After fitting the new carb last night, the engine has a flat spot as soon as you pull the throttle. I have tried every possible setting of the mixture screw, but the flat spot won’t go away. It even backfires and stops as I am adjusting the mixture screw. It will tickover OK, indicating that there isn’t an air leak problem anywhere.
The timing was on 14 degrees, so I put it back to standard in an attempt to stop the backfiring, but it didn’t work.
Over the last two months I have replaced practically every part of the engine with new parts… new crank, bearings, oil seals, CDI box, HT lead, spark plug cap… I could go on forever.
Can anyone help?.. / suggest things to try. :\