what speed should the ST70 go?

Hello,
I have a few issues,the mixture screw and spring has droped off,so I will try and replace that.

Although the bike is almost running correct ,the 3 speed gearbox,it seems to need another gear!

40mph is about its lot is this the correct for a standerd bike?

40mph is quite a good speed but it depends on a lot of factors!

Factors include:

- Rider weight
- Type of tires
- Condition of engine
- Age of fuel
etc etc

From memory I believe the manual says it will do 47mph but this has to be wrong surely? I used to get 40mph on the flat and I weigh 12 stone. When my bike was 'poorly' I used to get 35mph on the flat even with better tyres. Down a steep hill, off the speedo (50+ mph)

make sure its set up right with chain and sprockets. good luck

I can definetly recall getting 50mph out of mine, 55 at a squeeze. i am thinking though that the choice of front/rear sprockets would make a difference.

That, and the condition / type of the speedo.
Among all the other things James mentioned + spark plug, general condition of the drive train + engine + air filter, carb setup.
40mph is pretty normal.

Even 40 mph on a monkey bike feels like 70 on a normal bike.