DIYbanter - Makenco Generators

I purchased a Makenco Diesel powered generator model 2500CLE in 2005
and have had nothing but problems with the company that sold it to me.
The company is RAMCO power systems and I have not been able to get
a service manual that they promised me when I bought the generator.
I have tried to find a company that would be able to help me but
nobody I have talked to would be able to help me.
The engine runs at slow speed but leaks Diesel fuel like a sieve and
I have no way to determine what is causing it.
And if I put on full speed it does not allow the generator to run at
a standard speed, it backfires like crazy and the voltmeter fluctuates
from 120v to 80 volts.
Does any one have any information about this generator system ?