Re: DA85 on pipe! Results please.
Even with 24x12 prop, your rpm might be quite high.
Below are my test results on an 80cc engine, with header probably a little too long for that prop.
(Sagging of an engine when the muffler gets hot is indicative of a too short header.)
Prop 24x10x3 Mejzlik.
Exhaust Header 14”, outer dia 28mm.
TD 75KK, shortened, 6390, 7.7hp (muffler first chamber volume reduced to 400cc) - no sagging
TD75K, 6460, 8.0 hp - no sagging
TD75, 6420, 7.8 hp (has longer internal header) - no sagging
MVVS 3204, 6350, 7.6 hp - no sagging
Scrapbox 4-chamber canster, 6950 rpm (sagging to 6750), 9.9 hp (14” header too short?)
MTW T3 tuned pipe 7000 slowly rising to 7100, 11.0 hp - no sagging
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