a chainsaw engine wont turn the rpm to make your racer fast.
How fast does it need to be?
A home made car is good enough as long as it moves at all.
Chainsaw motors have lots of torque and with the right gearing it will be fast enough.
Second, what makes you think that it doesn't need a suspension?
It's not crucial to have suspension.
I've built a couple of cars without suspension that worked just fine within the expectations of a home made car with no suspension.
People always slam homebuilds and say it will need this and that and it will be too heavy and it will be too slow and blah blah blah.
Nobody's trying to make something that will compete with a factory built and engineered RC car. (apart from Vassilis and a couple of others who are in a league of their own)
We're just having a bit of fun.
Putting some random pieces together and seeing how/if it works.
It doesn't have to do 100km/h and be able to jump 2 metres in the air.
Think outside the box and you'll see that the world is full of other shapes than square.