My little brother just bought an 87 LT250r last week, and we rebuilt the top end, jetted it correctly and got it running good. But one problem, the engine makes a fairly loud clunking sound when you let off the gas and start slowing up, sounds like its coming from inside the expansion chamber, nothing is loose and rattling around inside. But could the noise be from the powervalve? My 86 makes the same sound when it is low on gas, but we are sure of that is not the prob. So, if anyone that has one, could tell me if the powervalve makes some funky noise when decelerating, let me know ASAP. Thanks

 

Did you check the crank and rod bearings? sounds like one or the other of them might be going south. Power valve should'nt make that much noise-my '87 don't do anything like that..most of the time when you hear "clunking" it's bearing-related.
Greg Coats
'87 Lt250R
'00 Rancher ES 2X4

 

could be the crank bearings or just the powervalve. My LT500 makes that noise when it idles. But no problems with the bearings. It is probably normal its just the powervalve exhaust going to the expansion pipe chamber.

 

hey on my blaster there was a rattling noise in my pipe. i took it off and the baffle had broken off in side it and a piece was bouncing around in it. u dont want that in there because it could get sucked back up into the cylinder and sieze your motor