Running 13.5:1 490cc Big Bore on 94 Octane – Safe or Not?

S_brar07 · Oct 2, 2025

Hey guys, I’ve got a 2006 TRX450ER that I’m rebuilding and modding. Here’s my setup so far:

Athena 100mm 490cc big bore kit with CP 13.5:1 piston
Stage 2 cams
HMF exhaust
K&N intake
Re-jetted carb
Kibblewhite intake/exhaust valves
Fresh OEM crank bearings, cam chain, guides, seals, gaskets
NGK Iridium plug

I ride mostly trails and don’t push wide open a lot, but I do want to open it up once in a while. I have access to 94 octane pump gas.

Question: Is 94 pump gas safe enough for this build if I’m not pushing it hard all the time? Or should I be mixing in race gas to be safe? Also, do octane boosters actually make a difference at this compression ratio?

Appreciate any input from people who’ve run similar setups.

CJM · Oct 2, 2025

100 octane or better all the time or get a lower compression piston. az quad sells 12:1 pistons for that size bore i recall. could use octane booster like vp madditive or boostane but i wouldnt chance it

why risk blowing it up after spending so much coin?

hoser · Oct 2, 2025

Just remember, a 13.5:1 piston with a stroker crank is actually around 13.9:1.

Running 13.5:1 490cc Big Bore on 94 Octane – Safe or Not?

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