CRF's Only Forums

Hi,

I have a 2008 CRF250R, i picked up the bike recently, i haven't had one with over a year and had to get another (once you have the bug you can't get rid of it!!!!)
After only a little riding it got hard to start, Valves!!. I am going to rebuild the head and install stainless intake valves for longer life, since i don't know what the bike has done i think i will install a new piston also.

My questions is if i am doing this much should i also do the bottom end??? i am undecided due to the extra cost!

I would apreciate any advice!!

I just went through a similar thing, i ended up changing the piston, it's not that much more work and $$ and then you know the top end is fresh and exactly what you are working with.

As for the bottom end, when you have the top end off, feel for any play in the crank etc, also inspect your oil for unusual debris. My top end was shot, but my bottom end solid.

wazdog has it exactly right. replace the piston when doing the valves. then keep track of engine hours with an hour meter so you'll know when the next service is needed. look for bronze/brass shavings in the oil filter, check for over play in the rod/crank. it's likely in good shape. we offer head/valve services so if you have questions about the head rebuild and valve selection just ask. the main thing is to give the valve seats professionally cut. don't get talked into reusing used valve spring parts.

good luck!

ken

Thanks for the info guys, I will strip it down and check the bottom end before ordering the parts. The oil filter had no particles in it. Regarding the valves, i am going with stainless intake but am not sure should i go with OEM exhaust kit or another brand, any recommendations?
Also can the stainless valve be lapped in or not?

Appreciate the help, thanks!

yes, they can be lapped. the question why would you do that to a brand new valve? lapping is an abrasive process used to "fix" valve seat cutting imperfections. it not only removes material from your valve seat but also your brand new valve! these imperfections occur because inferior cutting equipment is used (read: form tools used by hand or machine). we use a NEWEN single point cutter CNC valve seat machine that delivers perfect valve seats which are superior to any form and/or lapping process. don't settle for less as it will reduce your valve durability.

the stock exhaust valves are stainless steel. however, they are a two piece construction. the head and stem are friction welded. the stem is a lesser grade (read: less expensive) steel. i've never seen one come apart. i recommend Kibblewhite stainless on all fours with the KW high performance spring package. for the small increase in cost it just makes sense to do it with the same high quality valves and springs. just don't get talked into some off brand of stainless steel valves or mix matched springs to the valves. also, do not reuse retainers and cotters. these are wear items and we have seen them split causing a valve to drop. if you drop a valve it will cause very expensive damage.

that's good news on the filter. should be fine.

ken

Thanks Ken,
I think i will go with the kibblewhite intake and exhaust valves and spring kit and a wiesco piston kit.

that's a good plan! remember seat preparation is key to valve durability.

Hi,
Haven't had the time to do the rebuild until now, have the parts ordered from you guys and am hoping to get it done soon, I have another question before i go putting it back together. The 2008 models are known for being hard to start particularly when hot, i have been reading about this and have seen people modifying the decompressor. They are grinding a bit off so it the valves aren't open for as long. Would you reccomend this or not as if i am going doing it i may aswell while it is stripped.

Thanks.