Rotax pre-evo carb question

2 Stroke Kart Engine Forums
1

Hey guys, gonna be asking almost all of you to dig deep in the memory banks here as I know pre-evo rotax is much a thing of the past.

So basically the pre-evo senior carb had two specifications

Venturi: 12.5
Idle jets: 30/30
Floats: 5.2g

OR

Venturi: 8.5
Idle jets: 60/60
Floats: 3.6g

I have one of the 8.5 carbs but I’ve been told by guys out of the UK that the seniors prefer the 5.2g floats, so I switched to those but still running the 8.5 venturi and 60/60 idles. I have no intention of changing the venturi, but would there be any benefit in changing the idles out to the 30/30s ?

2

I am no expert but i would think that you are now extremely rich and jetting charts will be way off . I prefer the lighter floats and larger idle are they block less and run a bit smoother. I would think your not legal if you were racing . Its one setup or the other i sure some people mix and match but thats a bit tricky. We also run rok and when you change one thing it affects others. Hope this is helpful

3

Jessie well this is exactly what I’m noticing, my jetting is really weirdly off vs the other guys, i am like 3 jets richer for my engine to run and not pop

4

Just put it back how it was or get an xs evo carb , the new carb stops alot of that jumping when you floor it .

5

Ok gottcha. Did yours ever idle btw? Mine doesn’t for the life of it no matter what

6

Never had a problem with rotax idle , a have had problems top end or missing.

7

Ok thanks for the info bro