Here is the forum post of my buggy.
I'm making a buggy. And I want it to go 45 MPH. But I need the engine to go 4200 RPM reliably and safely. I'm willing to overbuild it in order for it to last longer.
What would I need for a 420cc Predator to be reliable and safe under continuous load with 4200+ RPM?
What I know so far for sure that I want with some info for anyone doing research:
- Billet flywheel (#1 for sure) - stock cast flywheels can fail, billet is mandatory above ~3800 RPM.
- Billet Rod - stock rod is a weak link; billet rod with proper bearing inserts keeps the bottom end alive.
- Chromoly Push Rods - stock ones flex at higher RPM.
- Heaver springs - 26 lb or similar to handle sustained RPM without float.
What I might need or want:
- Performance piston/rings - forged if budget allows for possible extended life.
- Billet side cover - stiffens block, helps keep crank/rod in alignment.
- Chromoly head studs - prevent head gasket leaks and pulling threads.
- Balanced rotating assembly – machine shop balanced crank, piston, rod, and flywheel.
- Heavy-duty lifters – to match stronger springs.
- Camshaft – stock cam is mild; a torque or mid-range cam helps at 4200 without valve float.
- Billet retainers/keepers – stock stamped ones can fail with stronger springs.
- Gasket set – copper or performance head gasket for reliability.
What I already have:
- High-flow carb & intake – 34–36mm carb or jetted stock carb, plus good filter.
- Velocity stack - Speeds and straightens airflow into the carb, improves cylinder filling at higher RPM, and reduces turbulence vs. a filter jammed straight on the carb.
- Exhaust header – tuned length header to let it breathe.
This is a lot but I'm looking to make the engine last a long time at higher RPMs, as the rest of my buggy is over-built for the most part because that's how I like it.
Please let me know if there is anything I'm missing or that's incorrect.
I'm making a buggy. And I want it to go 45 MPH. But I need the engine to go 4200 RPM reliably and safely. I'm willing to overbuild it in order for it to last longer.
What would I need for a 420cc Predator to be reliable and safe under continuous load with 4200+ RPM?
What I know so far for sure that I want with some info for anyone doing research:
- Billet flywheel (#1 for sure) - stock cast flywheels can fail, billet is mandatory above ~3800 RPM.
- Billet Rod - stock rod is a weak link; billet rod with proper bearing inserts keeps the bottom end alive.
- Chromoly Push Rods - stock ones flex at higher RPM.
- Heaver springs - 26 lb or similar to handle sustained RPM without float.
What I might need or want:
- Performance piston/rings - forged if budget allows for possible extended life.
- Billet side cover - stiffens block, helps keep crank/rod in alignment.
- Chromoly head studs - prevent head gasket leaks and pulling threads.
- Balanced rotating assembly – machine shop balanced crank, piston, rod, and flywheel.
- Heavy-duty lifters – to match stronger springs.
- Camshaft – stock cam is mild; a torque or mid-range cam helps at 4200 without valve float.
- Billet retainers/keepers – stock stamped ones can fail with stronger springs.
- Gasket set – copper or performance head gasket for reliability.
What I already have:
- High-flow carb & intake – 34–36mm carb or jetted stock carb, plus good filter.
- Velocity stack - Speeds and straightens airflow into the carb, improves cylinder filling at higher RPM, and reduces turbulence vs. a filter jammed straight on the carb.
- Exhaust header – tuned length header to let it breathe.
This is a lot but I'm looking to make the engine last a long time at higher RPMs, as the rest of my buggy is over-built for the most part because that's how I like it.
Please let me know if there is anything I'm missing or that's incorrect.
Last edited:
