No Power at High RPM

[SharpMan]

Whats going on y'all.

My VMax has been acting a little strange. It rides fine, but suddenly when I get around 6 or 7k RPM, the engine freely revs to redline without any power going to the wheel. When I roll off the throttle within that rev range, it FEELS like the bike wants to accelerate, and sometimes does.

Almost 100% stock bike.

I don't think it has to do with fuel or air. The engine runs perfectly, although its getting around the time to adjust the valves. The carb was cleaned and rebuilt by the best guy in my city about a month ago and I've put about 3k miles on it since then. I also replaced the fuel filter around that time and the gas tank is spotless. I mostly run ethanol-free gas. Not a carb issue. Brand new OEM air filter before that. I've tried limiting the air flow to see if it was running lean, but it made no difference in the high rev issue.

I don't think its the V-Boost, but it could be... I hear it cycle every time I engage the kill switch prior to firing it up so it isn't stuck or anything.

I saw this guys post High RPMS no pull but it seemed like he just changed the oil and never tried to solve the problem.

Like many were saying in that post, it is quite likely the friction plates. That said, I've had bikes with worn friction plates before and the symptoms were totally different. It doesn't seem the same at all. My MT-09 had bare friction plates from doing ****** burnouts. It had trouble moving no matter the revs. My VMax scoots fine until it gets up there. I really hope its not an issue with the transmission or driveshaft.

I have no problem swapping out friction plates, I just don't want to invest that time and money if that isn't the problem. My clutch master cylinder has a very slow leak but there's no chance its related.

I wanted to see if anybody else has experienced that problem and can offer some guidance. It feels like I'm riding a Rebel out there in the high rev range. A ****** in a mustang wanted to race and I had to say no like a weenie because of my neutered bike. I'm an amateur home mechanic, I'm fine with doing some DIY work and diag. Need some ideas, fellas. Thanks.

 

[Fire-medic]

For the cost of a gasket, measure the friction plates and steelies. Are the steelies blued (bad!)?

Scuff the steelies to give 'em some grip again after seeing they're in-spec. I suggest replacing the innermost 1/2-width friction disc with a standard one (full-width) and eliminate the spring steel ring sitting inside and concentric to that 1/2-width friction disc. PCW offers a kit of OEM friction discs, including a replacement for the 1/2-width one, and a gasket. They also have a heavy-duty clutch diaphragm spring, much-easier on your hand than a double-spring set-up. PCW Racing Home Page (artedelstein.com) Call them to order.

 

[Radioguylogs]

Bad transmission (slipping dogs) usually happens lower gear, like 2nd gear...although some have had it happen in other gears.

Slipping clutch usually happens in higher gears.

In which gear(s) does your problem occur?

Is there an abrupt jerking motion or just a slushy acceleration feel?

 

[desert_max]

Sure sounds like clutch to me. Pretty common and easy to address.

 

[MaxMidnight]

From what you say my gut feel would also be to look at the clutch. My clutch started to slip before the friction plates were at the minimum so if they are anywhere near that I'd replace them.

One other possibility could be the ignition advance unit? I've no experience of what symptoms this would give but perhaps something to keep at the back of your mind.

 

[DreamV4]

Weak clutch spring most likely. Clutch springs are under tension all the time, ride or not. 9 times out of 10 clutch discs are fine, but people replace them for no reason.

 

[sdt354]

What kind of oil ya using? Every few years I clean my steels then put it back together and it's like new again. Like FM said, increase the clamping pressure after inspection. Me, I like DD, but after market clutch springs I've put in work fine too. For DD, I suggest the extra spring not be brand new.