Engine noise

Duffman

New Member
Dec 29, 2018
22
2
3
56
Hi everyone, I just built a 66 cc engine kit and have noticed that at little over half to full throttle my engine makes quite a bit of noise like the Piston is slapping! Any suggestions on this would be greatly appreciated!
 

Greg58

Well-Known Member
May 1, 2011
4,143
1,033
113
62
Newnan,Georgia U.S.A.
Welcome to the forum, noise is common on a new engine especially gear whine. They rarely come with enough grease on the gears, if you add a little grease to the right side it will help if that's the problem.
 

Duffman

New Member
Dec 29, 2018
22
2
3
56
Welcome to the forum, noise is common on a new engine especially gear whine. They rarely come with enough grease on the gears, if you add a little grease to the right side it will help if that's the problem.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,611
419
83
Los Angeles, CA.
Sometimes the piston can touch the head, & sometimes the compression is a little too high...
Add a 2nd head gasket & the sound will go away. ;)


I've done this many times over the years. (^)

Also.... Be sure to only torque the head bolts to 12 ft/lbs. (any more & you'll bend the head & have a head gasket leak)!
 
  • Like
Reactions: Duffman and Greg58

javy mcdees

Active Member
Jul 30, 2018
143
58
28
49
mine with stock head and hot temps 90F days the engine would make piston slap noise at rpm that was my sign to slow back down to grandma pace till the motor cooled off a bit. changed to a fred head and that noise never happens anymore. runs runs runs just got off it, still warm new steel liner cylinder and rings 1st couple miles break-in. got tired of the plated junk jugs always flaking off from carbon. Now she pumps air! runs excellent even at idle speed in gear and moves out under throttle. The stock jet in the RT carb working good at the moment. Bad news is I only have one steel liner cylinder in my possession.
20190114_221050.jpg