2013 Top end rebuild only or bottom end as well

I have a 2013 CRF 250R that needs new intake valves.  The intake valves went out of spec last week, I shimmed them and after a couple hours of riding they are back out of spec.  So do I just replace intake valves or do full top end, replacing both intake and exhaust valves, piston, rings, cam chain or should I replacing crank, camshaft, and bottom end bearings etc.  I have read that some people are replacing bottom end parts after only 100 hours.  My bike has around 230 hours.  First 100 hours were trail riding minimal full throttle.  Started racing hare scrambles last year so have 30 hours or race time and 100 hours or so of practice time.  I change oil and filter after every 4-5 hours of riding and clean air filter after every ride.  I have replaced piston and rings twice.    Also when I do the valves should I just have the valve seats cut or do I need to have them replace.  I have 5 more hare scrambles and was hoping to get through the season before having to do any of this but with the intake valves going I am trying to decide if I should tear into the whole engine or just do top end.  I have been tempted to just do the intake valves and deal with the rest after the season is over.  Thanks for your input.

Edited by upontheridge

I would for sure rebuild the complete bottom and top end if the bike truly has 230 hrs.  My 450 has 114 and I just ordered everything to do a top and bottom end rebuild.

New intake valves/springs/seats/retainers/seals and get the seats cut.

At 230 definitely do the crank and bearings. Id also throw a camchain and tensioner at it too.


Okay will bite the bullet and the wallet and do top end and bottom.  Question on crank bearings, it doesn't look like they call them crank bearings but rather, Bearing, radial ball Honda Part # 91001-KRN-671 and bearing, special roller, Honda Part # 91002-KRN-A11.  Is that the bearings I will need.   Thanks.

To the OP you were given solid advice on this. Yes those are the bottom end bearings. Do the top end as mentioned and either replace the crank or have it rebuilt with a new bearing and rod and trued. Your bike has gone way past the service limit on these parts so be grateful it didn't have catastrophic failure. If you do the head, piston, and crank/cam chain make sure the cylinder is good too. I realize this is a big expense but do it right and you'll get a lot more hours out of your bike.

Edited by Dklassen

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