WARNING: This is one of the pages where you can actually gain some real top speed, but proceed carefully as you can also do some serious damage to your engine.
Default RPM limits:
- Gen1: 10,100rpm
- Gen2: [unknown – if you know please let me know]
- Gen3: 11,200rpm
The good:
The advantage of raising the RPM limit is that you’re adding top speed (mph/kph) exactly where you want it…at the top, and even small changes here (e.g. adding 500rpm) can raise your top speed quite noticeably.
The best bit is that unlike going up a tooth on the front sprocket, just adding RPM doesn’t lose any acceleration. If you go up to a 15t sprocket- yes your theoretical top speed increases, but the bike (stock gen1) won’t have enough power to actually ever reach that speed most of the time, unless you happen to be going downhill. Just adding RPM you don’t mess with your gearing, you just give yourself a little more headroom.
If you go on gearingcommander.com you can see how much difference it makes. Please bear in mind on that site for gen1 they have the rpm limit incorrectly specified as 10.5K when it’s actually 10.1K (read directly from the OEM ECU) – which then also happens to correct the top speed to 82.9 which is about what I observed on a gen1 with stock gearing (82-83mph).
The bad:
The tradeoff for that is if you’re not careful, or if you run constantly at the redline you’re *going* to damage your engine. Increasing the RPM limit here should be seen as something you can push into now and then rather than a limit you can bang all day long safely.
I would also suggest to ensure you’re not lean at extended RPM as that could compound the potential problems. Rather a little too rich than the other way is potentially a good approach.
Baby steps ftw:
If you’re doing this, start small and see how the engine sounds/feels. e.g. add 500rpm, test a while, repeat.
I’ve been running my gen1 180cc up to 11,500rpm for 6-months or so, with no special valve springs or any changes to the head, and *so far* it’s been fine (that may change any day). I don’t spend long there but I do hit the limiter at 11.5K quite regularly, and this has included for some sprint/drag racing. That engine has a re-balanced bottom end to make up for the extra weight of the 180cc piston and tends to actually be smooth at a slightly higher RPM than stock. YMMV, proceed with caution as if it goes wrong it’ll probably go Very Wrong Very Quickly.
I don’t think I would push any higher than 11,500 on a gen1 without some stiffer valve springs and if your engine isn’t in good shape, maybe err on the side of caution or you might be heading for a rebuild.
Look up “valve float” if you’re interested in what happens when you push too far.
The Gen3 seems a little happier at higher RPM so maybe a little higher might be ok, I haven’t really tested yet. I’m hoping the gen3 will run up to 11.7-12K or thereabouts.
Unfortunately I don’t have a gen2 so can’t really comment much there yet. I would likely proceed as if gen1.
