No matter what I do top speed stays constant.

Are you able to ride in a position to get the least amount of wind resistance? How much have you invested into your wheels? Is there any weight you can get rid of without compromising safety?

Some times you've done all that can be done with a particular engine. So unless you change to a higher performance engine, you have to start considering other factors which can add speed.
I've got a junker 80cc 2 stroke. I ported the jet in the 22cfm carb(not the little stock 16cfm),the intake tube and intake port in engine are larger than stock, exhaust is only slightly ported to provide some slight back pressure, using custom longer exhaust pipe with muffle chamber effectively almost rendering engine silent, drive sprocket is a 36T, and it runs on modified fuel i.e. gasoline 1 gal with 40 -50:1 oil mix plus 4oz super high octane racing fuel. it runs like a raped ape. top speed on flat ground using GPS speedometer 84mph.

Incidentally I had to repack the rear and front axle bearings with red high performance grease cause after that run down the old drag track both hubs were smoking and bubbling the old lighter weight grease out. the bearings weren't prepared for that kind of speed. I'm just glad I didnt seize bearings or blow out a hub cuz the ensuing crash would've been very painful.

I don't run it balls out anymore so putting along at 30mph while having the throttle only slightly turned is nice and it will burn rubber if I hard twist the throttle...oh btw no I do not have that stupid rubber gasket sprocket mount setup. I'm using the actual sprocket bracket that also clamps solidly to the hub. if I was using that other thing it would've twisted every spoke off the rear wheel the first time I took it out.

I also modified the bracket as it has 3 screws that tap in the bracket and into the hub housing securing the torque solidly where it should be.....where the rubber meets the road.(and I reduce the racing fuel to 2oz per tank. it's still a hell of a boost.
 
it runs on modified fuel i.e. gasoline 1 gal with 40 -50:1 oil mix plus 4oz super high octane racing fuel. it runs like a raped ape. top speed on flat ground using GPS speedometer 84mph.
You better reconsider that fuel/oil ratio if your running this motor like that...No less oil than a 32:1 ratio unless you want to burn up your motor in quick order.

GPS speedometer 84mph.
I would definitely be questioning that GPS speedo if it is reporting that as your speed.
 
I've got a junker 80cc 2 stroke. I ported the jet in the 22cfm carb(not the little stock 16cfm),the intake tube and intake port in engine are larger than stock, exhaust is only slightly ported to provide some slight back pressure, using custom longer exhaust pipe with muffle chamber effectively almost rendering engine silent, drive sprocket is a 36T, and it runs on modified fuel i.e. gasoline 1 gal with 40 -50:1 oil mix plus 4oz super high octane racing fuel. it runs like a raped ape. top speed on flat ground using GPS speedometer 84mph.

Incidentally I had to repack the rear and front axle bearings with red high performance grease cause after that run down the old drag track both hubs were smoking and bubbling the old lighter weight grease out. the bearings weren't prepared for that kind of speed. I'm just glad I didnt seize bearings or blow out a hub cuz the ensuing crash would've been very painful.

I don't run it balls out anymore so putting along at 30mph while having the throttle only slightly turned is nice and it will burn rubber if I hard twist the throttle...oh btw no I do not have that stupid rubber gasket sprocket mount setup. I'm using the actual sprocket bracket that also clamps solidly to the hub. if I was using that other thing it would've twisted every spoke off the rear wheel the first time I took it out.

I also modified the bracket as it has 3 screws that tap in the bracket and into the hub housing securing the torque solidly where it should be.....where the rubber meets the road.(and I reduce the racing fuel to 2oz per tank. it's still a hell of a boost.
Here I'm going to assume you're using 26" tires and a 10t engine sprocket. So on 26" tires, using a 10/36 to do 84 mph on level ground means your engine was doing 16,029 rpm. That's double what these engines are designed to do. One has to question your GPS app.
 
Here I'm going to assume you're using 26" tires and a 10t engine sprocket. So on 26" tires, using a 10/36 to do 84 mph on level ground means your engine was doing 16,029 rpm. That's double what these engines are designed to do. One has to question your GPS app.
Maybe he meant 84 kph? or 48 mph? I wonder..
 

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Its just scientifically impossible to make a 69cc china girl motor go 84mph.. with no expansion chamber and slightly ported. the transfers design limit what these motor can achieve. The top dogs can barley hit mid 50s. Is the gps app called raped ape? cause i think it got the best of ya
 
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