Where is this high pitched noise coming from?

Ethan Katowitz /

I know this is kind of vague and hard to diagnose but I’m hearing this high pitch noise almost like something is rattling so fast that it’s screeching. It only happens after about 33 mph and starts winding up louder and louder. Also I’m only able to go 38-40 on flat ground with it screaming so loud. Ive tried different kinds of trans fluid, Messing with clutch springs, bought another 2 shoe clutch from the buy/sell, checking for air leaks, nothing is stopping it. Could it be that bearings are shot? I had a similar post a few weeks ago, don’t mean to overload the forum, just am lost at what this could be.

70cc Puch

15mm bing clone carb and intake - 80 jet 2nd to richest needle setting

Metal mesh air filter

Boss pipe

ESO springs at around 25 pounds

New spark plug

Brakes not engaged

17 40 gearing

Re: Where is this high pitched noise coming from?

Overpriced Parts /

Post Video

Re: Where is this high pitched noise coming from?

Air leak on cylinder/head?

Re: Where is this high pitched noise coming from?

Pushrod Fifty /

Starter clutch plate rattling?

Re: Where is this high pitched noise coming from?

Ethan Katowitz /

[url=http://

]Video[/url]

Sorry this video is probably not very helpful but you can hear the sound for like a second at the end before I let off the throttle. Also, how would I prevent a possible cylinder air leak or rattling clutch plate?

Re: Where is this high pitched noise coming from?

Pushrod Fifty /

There is a spec for starter clutch fiber min height, I think .060" but its been awhile since I had my Maxi. The manifold ears warped leading to a massive air leak, and alot of noise. Easy fix, but then the studs started to pull out of the cylinder, leaving a bulge where the manifold mounts. Fixed that, leaving only the rattly clutch.

Re: Where is this high pitched noise coming from?

Maybe the wheel bearings? You are right that video did not do much for me. I would start checking things outside of my engine first and start working my way inside, leaving bearings and other things you have to split the cases for until the last.

Re: Where is this high pitched noise coming from?

Ethan Katowitz /

I checked the rear wheel but I’ll look at the front tonight. Just to get a gauge, roughly, how fast should I be able to go with my setup?

Re: Where is this high pitched noise coming from?

Depends on the 70cc kit you have. Some are easy to hit 45 right out of the box as long as it is installed correctly. Some may need a little help getting the most out of it. But with your gearing and only a boss pipe with 15 bing, you are in a good spot.

If you upgrade your pipe to something with a higher powerband you might see a little more out of your top end. The nice thing about the boss is it has a really wide power band so you get decent mid and some high but it will end up hitting a wall at the top.

The 15 bing is not a bad carb, but maybe a bit small if top speed is your goal. I have seen 50mph+ bikes with a 15 bing. You just really gotta know your tuning to make it happen.

Re: Where is this high pitched noise coming from?

Does the bike make an abnormal knocking sound at idle? Sometimes if your piston is old and the pin is loose inside, it'll make this weird screeching noise at high rpms.

To check, you gotta take your piston off, insert and center the pin, then with your thumb on the bottom and one finger on the top, shake it up and down.

If it makes a clacking sound, you need a new piston.

Re: Where is this high pitched noise coming from?

Overpriced Parts /

> baird co Wrote:

> -------------------------------------------------------

> Does the bike make an abnormal knocking sound at idle? Sometimes if your

> piston is old and the pin is loose inside, it'll make this weird

> screeching noise at high rpms.

>

> To check, you gotta take your piston off, insert and center the pin,

> then with your thumb on the bottom and one finger on the top, shake it

> up and down.

>

> If it makes a clacking sound, you need a new piston.

And sometimes the wristpin bushing Is shot, You don’t have to take piston off just the cylinder to move piston up and down to see for play, If piston at wristpin is worn it can ruin bushing if you continue to run it,

Re: Where is this high pitched noise coming from?

Richard Eberline /

The inboard bearing on your output shaft and gear is whining.

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