Timing

I am working on an 07 CRF150RB and can't get it to run without retarding the cam sprocket one tooth.  There is some back story to this bike.  Bought it new, had the cam recall and swing arm both replaced.  Bike ran fine for years with routine maintenance.  Sold it to a friend whose kid ran it for about 2-3 weeks prior to a race.  During race, bike lost power and no resistence on kickstart. Volunteered to look at it for them.  When I pulled the valve cover off, cam chain was broken.  Everything on top end was scorched black. Pulled head and cylinder.  Cylinder was still within specs.  Replaced piston and rings, intake valves and exhaust valves.  Also noticed the plastic gear that drives the oil pump, was missing three teeth and the oil pump would not turn, so I replaced those. put everthing back on motor with timing set to TDC.  Kicked it a couple of times, didn't sound right.  Pulled the head, noticed slight marking on piston from ex valves.  This is where I decided to retard the timing. Fired right up.  Took it to a race yesterday, the kid said it was bogging at full throttle.  Pulled it in and could not keep it runnung  at low throttle.  Any chance the cam shaft  could be causing the problem.  It is the only thing I didn't replace.  The lobes were also scorched.  Don't know what else to try.  Any suggestions would be greatly appreciated.  I know the bike was solid when I sold it. 

 

Thanks

 

ps  Sorry the post was so long , just trying to give all the facts.

Thanks for the link Old Plonker.  Is there any way to check the cam shaft to see if the flange has spun or moved out of its proper position.

 

Thanks

If you can find a friendly parts guy that will let you compare a new cam with yours you should be able to eyeball any difference. And if your cam is twisted, you can buy the new one!

Edited by Old Plonker

If you can find a friendly parts guy that will let you compare a new cam with yours you should be able to eyeball any difference. And if your cam is twisted, you can buy the new one!

Ours was twisted slightly and no way you could have seen it. After some measurements with another stock cam, a difference was there. Swapped out to a Wiseco (nearby and cheaper) all is well. Stock cams are weak so if you go back to stock have it welded/pinned!

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