Z80, Flat spot at top rev's

I have soldered shut and drilled my jet smaller to lean my bikes out and I have had pretty
good luck. I would like to know where to buy jets of the proper sizes. (.62-.65)

I put the original back in (0.70mm) and it was guttless/worse. So I put the 0.76mm back in and I might drill out the original to 0.80mm and see how it goes. Its not bad though.
What I would like to try and do is just get it to run smoother, like when the power band kicks in. Spark plug gap appears to play a big role in this too.

Steve

To get it to run smoother first thing would be to jet it correctly. If your running a complete stock set up with no mods you will need to drop a jet size or 2, but instead what Id do is chop off the internal pipe thats welded to the exhaust muffler cap. This will lean out the pipe and give more power. Now Id play around with the needle to see if you can fine tune it more.

Also try a touch of acetone to the fuel. Add 2ml to 1 litre of 2 stroke fuel - ive tried this on 3 bikes and have never had a problem. This will smooth out the bike over the rpm range and will allow you to cruze at higher rpms with less rattling and a smoother exhaust note (and combustion).

Does the engine vibrate much? On one of my bikes I discovered vibration was foaming the fuel in the carb making it run bad. I have a hard time believing going richer will help! Leaning the main jet helped my daily driver through-out the rpm range and I gained 5 mph at the top end. Also, remember a motor is just an air pump. Grind or file your intake to match the port on the engine and do the same with the exhaust. These ports do not match at all from the factory! Get some bulk gasket material from an auto parts store to use it as a template. Smooth air-flow = smooth power! I agree with Pablo too. You are to rich at WOT.

to rich, bigger jet will only make it worse......

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Its not how fast you can go, its how fast you can stop that matters....

36t sprocket fixes a lot of problems the 66cc needs to be under load thats why they go so well up hill

YES! Something I do understand. It does go much better/smoother/faster/morepower under load, so I am waiting for the 36t sprocket to arrive. I think this will sort out a lot of problems. The motor does love it under load.

Steve