I'm trying to figure out the source of an annoying rattle on my son's 150. It seems to be the loudest right ofter you let off the throttle. I can't even figure out where it's coming from. Any ideas or has anyone experianced this on your 150?

I would start by checking all the engine mount bolts.

-------------------------
07 Jetmoto 250 Sport
07 90cc Mini Ute
06 Jetmoto 200 Enduro
06 Jetmoto 200
06 Jetmoto 150
06 Jetmoto 125
04 Yamoto 150
01 KTM 400 EXC
92 WR 250
91 CR 250
88 YZ 80
85 CR 500
83 XL 600
82 XR 200
79 XR 75
79 Odyssey
73 Bultaco 360
71 Rickman Montessa 250
70 Rupp Enduro
69 Honda 50

There is two things I have found that rattled on my 150's. First is the Muffler, the inside baffle pipe fit's loose inside the muffler and it rattles around when you ride. You can feel it and even rotate it by sticking your finger up the tail pipe and moving the part. To solve this I removed the end cap (had to drill out the rivets) then I High Temp siliconed the inside pipe to the end caps.
The second and this is most likely what you are hearing is the chain rubbling in the rear skid plate just under the rear sprocket. The way that is designed and stamped out when you release the throttle the chain drops down and rubs on the skid plate til the power is put back on. I took a jig saw with a metal blade and cut off kind of following the same original lines about an inch from the front of the plate just under the chain. You will see where the chain had been hitting!

-------------------------
Our riding Videos: http://myjetmotos.8k.com/whats_new.html
Jetmoto ATV 250 Sport Blue
Jetmoto ATV 250 Sport Red
Jetmoto ATV 150 Sport Blue
Jetmoto ATV 150 Sport Red
Honda CM450c
78 Honda CB750
79 Honda XL500

Thank you!