My 6.5hp only starts for 5 to 10 seconds whats rong with it

Google the model and codes. You should find instructions in how to to retrieve the codes and that will point you in the right direction.

Have the fault codes read to find the faulty sensor.

Sounds like timing belt.

I WOULD CHECK FUEL PRESSURE IF YOUR NOT GETTING AROUND 40 TO 45 PSI. THIS CAN CAUSE THIS AND CLOGGED CATYLITIC CONVERTERS CAN ALSO I WOULD START THERE GOOD LUCK

better look at carb-probly medium n hi jets need ajust-and shud hav a pro do that cause to lean or rich can ruin the engine--buy a clymer manual-it explains kawa carbs well

Try unhooking the negative battery cable for a few minutes. The throttle control may self correct when you reconnect that cable.

Some simple things would be new exauset system with a header, new air Intake with a big tube breather for better throtle responce. If you wanted to spend some money you could find a "aba" 2.0L bottom end with and put your 1.8L head on it p, port and polish it first and you will have a very quick gti.

Check the gears mabey they are skipping when the bike goes to fast. like at 3/4 throttle theres to much torque an it just wont catch.

Fuel starvation, try removing fuel cap and starting firstly

Ok Slow deceleration rev responce was part of the ECU software to keep the emissions down ,however if this has only just started you can try to reset the IAC valve ,the procedure is as follows.

Turn ignition key on ,unplug the IAC valve ,turn the key off ,replug the IAC valve. do this 3-4 times .Then start the engine while holding the gas pedal to 2000 rpm ,then slowley let the go of the gas pedal till the engine idles .

The IAC valve is located on the throtle body and has 4 wires to it.

Sometimes the throtle body needs to be cleaned and then reset.