Low RPMs

Mrdan 120

New member
I'm running the ducar 212 completely stock except a fuel pump. On raceday I could only get 4300 rpms out of it even with a low gearing(18-65). I ran the feature with a 18-58, and i ran better, but still 4300 rpms. Back at home I hooked the throttle straight to the butterfly, still 4300 on a road test. On the stand I can get 5200 max. It runs smooth always, sounds good. What am I missing?
 

Duhun71

Member
It’s prob floating the valves. If you don’t have a rpm limit in your class, order red 10.8 springs. Green or yellow 10.8’s would also help. If you have shims, try that first.
Out of the box, some turn 5k some turn 6k out the box. Good springs will get you consistent results.
 

Mrdan 120

New member
I found a larger main jet in an extra engine I had laying around. I put it in and now I can get 6k on the stand. I guess valves are floating at that point. Thanks for the help.
 

wrecit

Member
Maybe this is old info that's been proven wrong but was told by no less than 5 respected engine builders to NEVER high RPM an engine on the stand. It's a sure way to overstress the internals.
 
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