What rpm

mike97760

Site Supporter
Mine are like RP's. Out of the box they turn 3650 and I have seen 2 newbies unknowingly take them out of the box and bolt them untouched to a chassis and try to go race. It aint pretty. 4900 is the limit and that is on the track, not on a couple of sawhorses in the garage.
 

Komet99

Member
I got mine up to 5400 peak last weekend with every lap being 5100-5200. It seems to keep pulling and going faster with more rpm. At what point do I need to not do this any more?? will it go 5500? 5800? 6000? I was kinda shooting for valve float but I dont know where that is with 10.8 springs.
 

95 shaw

Site Supporter
I dont understand...new to this. If I raise rear teeth and go faster why go back down to where I started?
Did kart go faster from gear change, or from the track changing?

To keep up with track changing, need to check lap times of classes around you to validate the gear change.
 

racing promotor

Moderator
You gotta analyze every change not just the rpm increase, including lap times of the front runners from other classes that tells you the track is getting better and in that case you better be pulling rear teeth
 

"J'-remy

Member
just because your engine is screaming doesn't mean your going fast. the engine develops torque at certain rpm ranges. Horse Power is nothing more than torque x RPM. A real box stock predator is making 7-8hp at 3700 rpm. at 5000-5500 its making around 3-4 hp. you do not want to pull out of the corner and down the strait with only 3 hp you want the motor pulling with all 8. At the track I run at im on a 20t driver and 59 rear. Im just breaking 50mph and last weekend only 6 tenths off a clone. I do not want to hit 5000 rpm ever the motor is a weakling there and slow.
what gears are you on?
 

Komet99

Member
Started off with 13-68. I didnt have a recall tach or recordable info, but could see just short of 5k when I dared to look. then tried 69 with no noticeable difference. Then next race, I had a mychron and put a 13-72 on. it seemed much faster. I could pull mid pack karts on the straightaway. Sometimes if I got a good enough corner exit, I had enough to pull 1/2 kart next to them to get the bottom line in the next corner.
Its a pretty tiny track. Maybe 1/12. corner exit rpm is 3600-3800. Average top rpm 5100-5200

Ive only raced this thing twice, so I'm learning how to tune. Motor builder pits next to us and helps me with input.
 

Komet99

Member
Did kart go faster from gear change, or from the track changing?

To keep up with track changing, need to check lap times of classes around you to validate the gear change.
I would say the kart went faster with the gear change. The track started to break up and forced the very bottom of the apex to be used for the best line.

I am on board with pit discussion about lap times.
 

racing promotor

Moderator
Started off with 13-68. I didnt have a recall tach or recordable info, but could see just short of 5k when I dared to look. then tried 69 with no noticeable difference. Then next race, I had a mychron and put a 13-72 on. it seemed much faster. I could pull mid pack karts on the straightaway. Sometimes if I got a good enough corner exit, I had enough to pull 1/2 kart next to them to get the bottom line in the next corner.
Its a pretty tiny track. Maybe 1/12. corner exit rpm is 3600-3800. Average top rpm 5100-5200

Ive only raced this thing twice, so I'm learning how to tune. Motor builder pits next to us and helps me with input.
In your post number 8 you make no mention of it not being stock, If that's the case and your on a 13/72 pulling the others in the class, I'd be questioning your builder you have a legal motor.
 

"J'-remy

Member
if you're only using 3 hp then yes a bigger rear driver will be easier for a motor making so little power. how ever if it is a true box stock gearing it down to run at 4700-4800 you will be way ahead of people turning 5000+ my guess that your ability to run a predator at that RPM means its not legal as compared to mine that is out of the box lash set broken in chainguard, tuck and run throttle linkage, and a clutch 5000 max rpm on stand. Sounds like you have a cam and a built motor to me
 
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