cylinder resonances

Are they normal? My polini kit is quiet at low end, but as you get up there, it starts to sound like a bell :) It's not metal on metal sound, more like when you rub your finger on a wineglass. It only affects a small rpm range also.

Re: cylinder resonances

chuck russo va /

i dunno abvout the noise but how does your kit run? my should be here soon, i ordered it last wendsday so hopefuly it will be here anyday

Re: cylinder resonances

runs awesome. best built engine I have ever seen.

Re: cylinder resonances

anybody?

Re: cylinder resonances

yeah ... motors make all kinds of weird resonating (and vibrating) sounds .. and sometimes its a part of the chassis with a 'sympathetic' resonance that chimes in with the motor at certain RPM's.

I wouldn't worry unless its a harsh metal-to-metal noise (like you said) .. or a grinding or banging.

Have you ever ridden side by side with another bike for several miles ?

The two sets of motor noises can resonate off each other ... then you can get some even stranger noises...... pretty funny actually.

Re: cylinder resonances

david f martin /

A resonance is a type of positive feedback, a vibration that is reinforced and amplified.

Feedback in audio equipment can blow an amp or a speaker.

Soldiers crossing a bridge have to break step (march out of rhythm) to keep from collapsing the bridge.

That's why motors and such are often attached with rubber mounts, to help dampen these resonances.

If you can run your bike on a stand and rev it up to where the resonance occurs, maybe you can isolate the part of the chassis that's being affected, then figure out how to get rid of the resonance.

My center stand vibrates at a certain rpm, which caused it to almost rub a hole in the engine case. Turns out it was missing a rubber stop for the stand to rest against.

david

Re: cylinder resonances

it is the cylinder fins that resonate.

Re: cylinder resonances

david f martin /

How is the motor attached to the frame?

david

Re: cylinder resonances

huh? It's a puch maxi motor. it's bolted on, securly, if that's what you mean :)

Re: cylinder resonances

david f martin /

Looking at pics of Puch Maxis...

How long have you had the Polini kit?

I'm wondering if you're getting enough oil...

david

Re: cylinder resonances

i'v had it aboaut a week, and it's broken in already. i'm running 40: 1 with racing oil

Re: cylinder resonances

david f martin /

You checked your gear oil, too, right?

I think any vibration coming from anywhere on the drivetrain could transmit and radiate sound from the cooling fins, with all that surface area...

I could be totally wrong, but I'd be concerned about it, if it were my bike. Even if it is a common, harmless characteristic of that bike, I would want to know exactly WHY it's making that noise.

david

Re: cylinder resonances

yup, me too. that's why i'm asking.

Re: cylinder resonances

david f martin /

Did it just start making that noise after you put the Polini kit on?

Has anyone else experienced this with a Polini kit?

david

Re: cylinder resonances

yeah, it started immediately with the polini kit. It seems to be getting quieter though, as the kit breaks in. I saved the original cylinder in case the kit explodes, but some people have 30,000 miles on theres and they are still going strong. I opened up the head, and everything looks good, and the cylinder is getting nicely polished.

Re: cylinder resonances

david f martin /

Maybe it's just break-in noise...

Hopefully it will go away.

david

Re: cylinder resonances

yeah. it doesn't sound like a BAD noise, like the buzzing in my other cylinder

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account