Pro open dirt flat kart engine

My local track is starting a RWYB single cylinder open class I have a 15 Kinetik roller I want to stick a power house on. I’m split between a built animal on alcohol, a blockzilla 3” bore, a built flat head on alcohol, a 2stroke 250cc dirtbike engine or a KT100. What would y’all recommend. I’m running slick tires and just want something that will scream. Only issue I have with the dirtbike engine is having to shift and use clutch. Any expertise opinion is greatly appreciated. Mostly racing small bull ring tracks.


Site Supporter
The 250 will likely overpower the tires for your small track, maybe, maybe not.
Westerfeld would be a good source to get rid of that transmission, clutch, etc.
Of the engine combinations, this would likely be the most power and most reliable.

Open flatheads can be fun, but real pricey for the output and not very reliable at the rpm you'll need to spin it.
The Blocky will be better, but you are still limited to flathead technology and durability.
100cc is giving up too many cubic inches, and is too peaky for small tracks unless you gear it with a jackshaft.
The alcohol animal will need built up considerably (ie stroker crank, billet head, etc) to get the most out of it.
You can build a fairly inexpensive "mild" open animal on the cheap and grow with it as needed - that would probably be my suggestion without going the all-out 250.

?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN

Ted Hamilton

Helmet Painter / Racer
I'd get a 100 reedjet or 125 Sudam... Depending on how grippy your tracks are. Both pretty bulletproof and a step above a KT and cheaper to build and maintain than a 4 castor fumes. :)


2A supporter
250 dirt bike engine
I'd get a 100 reedjet or 125 Sudam... Depending on how grippy your tracks are. Both pretty bulletproof and a step above a KT and cheaper to build and maintain than a 4 castor fumes. :)
+1 for the sudam


Dawg 89
Great advice above . 250 or parilla/sudam .
You say your local track , then state run mostly small bullrings .
If your going too differnt tracks switching engines the kart specific engine combo might be better then the 250.


Site Supporter
Forget buying numbers.
Anyone can throw numbers around, especially when they are trying to sell something.
Dynos can be manipulated to produce whatever numbers the operator is willing to sell.
A little something called "correction factor" comes into their sales pitch.
Dynos are only as accurate/honest as their operators.

Buy something from a reputable builder that has used good internals and you will be much happier than buying "numbers."
I found a good deal on this
New JRPW machine work hasn’t been ran since work has been done. What would y’all say something like this was worth?

Jrpw block. Jrpw carb. Raised compression height flat top piston, billet rod and billet side cover
Billet flywheel
Racing ignition
Fully worked hemi head with 36Lb springs
308 billet cam


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Most if not all don't shift anymore, if you want to run with the Big Dogs get out the check book or credit card LOL Chuck.


If you can't flat foot the track now with what you have then you probably don't need any more power just my 2cents. Chuck.