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91 CR250 Adventure

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Hey guys so i bought my bike pretty well at the beginning of August since then it ha been a ride trying to get rid of all of the bugs.  First off it didn't run right had no power we ended up diagnosing that to a plugged pipe and restricted silencer (due to a previous backyard attempt at adding a silencer)  So out came the wallet and picked up a new pipe and silencer currently running pro-circuit platinum pipe with factory sound silencer!  Got it all put back together and it didn't have wild power so we were like okay maybe that is because its older not half an hour later did i seize it up.  Tore into the bike that night found a mangled piston (thought it might be an easy fix got excited for a minute but after removing the cylinder realized there was also trouble in the bottom end (thankfully cylinder is mint).  After that the case was split and we started to look for our problem though all the bearings were in excellent shape what we did find was a small piece of the tin wrapped portion of the crankshaft had broken off and lodged itself in the bottom end and that this had caused the seizure.  Since cranks are hard to find we welded a spot onto the little crack in the tin sanded her down and put it back together might i add the time elapsed from seizure to running again which included ordering and shipping time was 48hrs (probably the fastest ive ever rebuilt a bike haha)  After we got it running it had a 100times more power already though it still didn't seem to have that 2 stroke rip.  that basically leaves with 3 options jetting reeds and the exhaust valve.  I think the jetting is okay running a 171 main which is fairly lean already (feels like its running rich).  So that leaves reeds and exhaust valve.  Last night we ended up just detaching the linkage for the exhaust valves to see what we could get for top end and sure enough we were wheeling doing 100 kmh down the side of the road but obviously very troubled low end so now i am trying to figure out how these guys work as this seems to be the problem.  Also i have ordered new reeds because the old ones are worn and missing governor as well (which may also be contributing to the problem)  Any thoughts on valves would be appreciated tho!

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Manual should give you all the info you need for the powervalve. It will tell you how to check it's operation. It will help you troubleshoot and fix issues as well. It will also give you jetting tips. PC also has suggested jetting for their pipes on their website. This should get you close, but will still take some trial and error to get it fine tuned.

Edited by KcDavis

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