Can't hit redline, and feels like I've tried everything

[ender2009]

Hey guys, I bought a 2015 Honda Ruckus a couple weeks ago. It’s completely stock, barring a tach I added.

Unfortunately, there are some issues I can’t seem to figure out. I can’t hit 7,000 RPM (~8000 is the redline), and my top speed is about 32 mph, full bore, down hill with the wind at my back. As soon as I hit that, which is usually around 6,900 RPM, the engine seems to cut power, and I’ll actually slow down, even if I’m like halfway down the hill. On straightaways, I can’t exceed 25mph.

I’m more of a software guy—this mechanical stuff is new to me. But I’ve tried everything I can find online to fix things, with no success. I've tried replacing the spark plug. I’ve cleaned the carburetor twice, eventually replacing the slow and main jets. I replaced the air filter, reseated it a handful of times, and even replaced the fuel pump and fuel filter. No changes.

I’m probably going to bring it to a mechanic next weekend, but thought I’d reach out to y’all for help on anything I could have potentially missed. Sorry, I know there are tons of similar threads, but I truly feel like I've done my due diligence scouring everything I can find and still haven't gotten to the bottom of this. Thanks!

[ender2009]

Thanks Drew! I haven’t really dived into the CVT much yet, because I had read somewhere along the line that it probably would affect top redline. But I don’t even know if that’s correct.

I have pulled it off once, previously, but I’ll investigate today. From what I remember, a few of the roller weights seemed to have some minor flat spots, but nothing too crazy. I don’t know how much is enough to affect performance significantly.

One thing I did notice is that the belt seems to be kind of wobbly/loose. Hard to describe, but it seems to have some give from side to side instead of just staying in its path. Any idea how to fix that—assuming it’s the proper length width still? I’ll replace it if it isn’t

[Baizy]

One thing of note is that having a worn out cvt system would allow you to redline sooner but at a lower speed. I'd suggest you pull the CVT cover off and put it up on the kickstand and just rev it right out. See if the ECM catches the rpm at a certain point or if something looks off in the cvt when everythings in motion. Doing this test up in the air with the engine unloaded means you can rule out ECM issues and discover CVT issues.

[ender2009]

Thanks Baizy. I’m not super clear on what seeing if the ECM catches would look or sound like (I’m a noob), but I did try revving it out on the center stand, just now. Everything seemed to sound okay from that area, but I could only get to 6800 RPMs. So if still seems to be falling short of that 8000 RPM factory redline. Would that rule out CVT issues?

[Baizy]

Jun 12, 2021 13:45:13 GMT -5 ender2009 said:

Thanks Baizy. I’m not super clear on what seeing if the ECM catches would look or sound like (I’m a noob), but I did try revving it out on the center stand, just now. Everything seemed to sound okay from that area, but I could only get to 6800 RPMs. So if still seems to be falling short of that 8000 RPM factory redline. Would that rule out CVT issues?

If you cant get it past redline on the centerstand then its not a CVT issue, so don't go throwing parts at it yet. You need to be diagnosing the computer and the engine now. I recommend you do an ECM reset and see if that help at all. You'll need a strip of wire to play with in order to do the reset. There are lots of helpful youtube videos for this: youtu.be/Aw3faHcBZ78 do this and then try another run up on the center stand.

[Baizy]

Also I have to note that you'll be hunting for 8800RPM as your rev limit in a 2015 model.

[ender2009]

Ah okay thanks. That means I’m falling even shorter of redline than I thought.

Okay, I did the ecm reset. The light flickered, heard the fuel pump re-engage, and everything. Unfortunately no changes. 🙁

drew, yes it’s a Trail Tech brand tachometer that I wrapped around the spark plug cover. So it might not be super accurate, but it had good reviews. I’m trying not to get fixated on the RPMs, but the fact that it runs so poorly makes me think it’s a safe bet that they’re indicative of an issue.

[Baizy]

Well I'm almost out of ideas as you really have done all your due diligence with this. There's just 1 bug dumb that I can guess at. You've got a restrictor plate between the intake flange and the engine block itself like the metro 2 did. Or for some reason you need to shim the carb needle on a stock setup. Those are my last grasps at the straws for internet diagnosis. Best of luck and I hope the mechanic can fix it since we internet nerds couldn't hahaha

[ender2009]

Haha I’ll take a look and play around with some more things. I appreciate the help. I have an appointment Thursday, so we’ll see what he can find. If he discovers the issue, I’ll be sure to report back

[ender2009]

Alrighty guys, I promised to come back if the mechanic figured out the issue…. And he did! I can now hit redline rpms and 40 mph.

The only issue is I’m not 100% on which of the two main things he did fixed it because he did them at the same time. I had cleaned the carb already (twice), but he vapor blasted and it basically looks new now. He also did a valve adjustment on it. So one of these two, or both, skyrocketed the rpms and allowed my ruckus to run like it should! Wahoo!

[Baizy]

Thanks for the follow up! Valve adjustments are sorely neglected so its great you got that done! Have fun out there!