Squeal, loud obnoxious sqealing



New Member
Aug 1, 2008
After 3 tanks [maybe 4] it seems the China girl on the prototype/test bike is already begging for some wrench loving.

This bike gets me to my day job and back up some pretty long and fairly steep hills. The last few days it's been developing a squealing sound at higher rpms. Sounds like a dry bearing, something is going to blow type of squeal. Almost as loud as the engine.

Since I noticed that the rear mounting stud was sheared at the block, I hauled the mess out of the frame for a shakedown. Some pieces of clutch material inside the clutch cover were the first clue. I pulled the drive sprocket and removed the clutch shaft to inspect the case bearings [fine] and other parts [also lubed well and fine].

While it was on the bench I pulled the head and cylinder to make sure the piston wasn't pulling on the cylinder... all that also looked fine. Locktighted the head studs while there. Slapped it all back together.

Note that these latest "80cc" motors have small round clutch pads instead of the angle shaped ones. Most likely because it saves .0001C per motor in production cost or some crap. Had to run the star nut in quite a bit to get it adjusted for maximum compression and still free when disengaged.

Heated the case, pulled the sheared stud then tapped and replaced both with 1/4 threaded rod.

Slapped her back together and it ran like a top today. I can only assume that the dry scraping squealing sound was the clutch slipping under high rpm load since all parts looked ok. Could maybe have been loose mount parts vibrating dry too... but im bettin on clutch.

Just thought i'd share... If it's squealing, open the clutch cover and see about running that star nut in a few turns. But remember the big gear has to spin somewhat free when the clutch lever is pulled in. ^5