Regarding the 2008 CRF250R

[adam8781]

youre not gonna want to get titanium OEM valves. The problem with those is that they are not 100% titanium. They are valves coated in titanium. As soon as a little dust gets on them, it will sandblast the titanium coating off, and your valves will be shit. Get stainless steel. Cheaper, better.

 

since he doesnt rev to the moon i agree the stainless is the way togo with the next rebuild.  Just need to correct you. The oem ti valves are in fact titanium. They also have a titanium coating. Once this coating is gone from wear or dirt dust in sand it exposes the raw ti which is soft and wears very quickly. 

 

Oem ti valves are great, its the stock valve seat material that is the main problem. That and the sheer size of the intake valves makes them heavy even by ti standards.

[martin truszkowski]

Nothing wrong with ti valves if you keep the dirt out they last. 180hours on fastheads rebuild no shiming at all runs great. stainless is good but you can feel there extra weight and valve spring poundage causing extra internal drag in the motor.

[AlmostaCowboy]

youre not gonna want to get titanium OEM valves. The pr roblem with those is that they are not 100% titanium. They are valves coated in titanium. As soon as a little dust gets on them, it will sandblast the titanium coating off, and your valves will be shit. Get stainless steel. Cheaper, better.

You know, I was wondering about that. I have some experience working with Ti and I couldn't figure out how the SR-71 Blackbird (Ti skin) and the turbine blades of all jet fighter aircraft and the landing gear of all US Navy jets could be less abusive than a 250cc motorcycle engine. Now, it makes sense. If it's just a TiNi (titanium nitride) coating it makes sense.

Well, I've got good compression (by foot, not by test) and the clearances are right on the money. So tomorrow (Monday) I'm going to put the appropriate jet in it for my altitude (3400') and start putting it back together. This bike was rode hard and put away wet so I,ve got a lot of cleaning up to do on it before I start it again.

Thank you for that info. I appreciate it.

[Eddie8v]

Tough to compare something actively forced back and forth smacking a seat about a hundred times a second vs the stationary skin of an aircraft or a turbine blade which simply spins around and takes pretty constant aero & centrifugal loads.

You know, I was wondering about that. I have some experience working with Ti and I couldn't figure out how the SR-71 Blackbird (Ti skin) and the turbine blades of all jet fighter aircraft and the landing gear of all US Navy jets could be less abusive than a 250cc motorcycle engine. Now, it makes sense. If it's just a TiNi (titanium nitride) coating it makes sense.

...

Edited May 4, 2014 by Eddie8v

[Crf250x kid]

You know, I was wondering about that. I have some experience working with Ti and I couldn't figure out how the SR-71 Blackbird (Ti skin) and the turbine blades of all jet fighter aircraft and the landing gear of all US Navy jets could be less abusive than a 250cc motorcycle engine. Now, it makes sense. If it's just a TiNi (titanium nitride) coating it makes sense.

Well, I've got good compression (by foot, not by test) and the clearances are right on the money. So tomorrow (Monday) I'm going to put the appropriate jet in it for my altitude (3400') and start putting it back together. This bike was rode hard and put away wet so I,ve got a lot of cleaning up to do on it before I start it again.

Thank you for that info. I appreciate it.

glad I could help. Let me know when you get your bike fired up and fixed. One huge thing that will make your valves last a lot longer is to oil up your air filter properly and use grease along the edge of the filter where it meets the air box. Also, the air filter design really sucks on these bikes so lining up the filter on the airbox is hard but it is so important. Taking the seat off helps.

[AlmostaCowboy]

glad I could help. Let me know when you get your bike fired up and fixed. One huge thing that will make your valves last a lot longer is to oil up your air filter properly and use grease along the edge of the filter where it meets the air box. Also, the air filter design really sucks on these bikes so lining up the filter on the airbox is hard but it is so important. Taking the seat off helps.

Ok, kid. Bike is back together (second time) and muuuch cleaner now. Carb is clean and rejetted for my altitude & temp per the Service Manual (#185 main/ Needle clip on 2nd position from top). Valve clearances checked, air cleaner clean, No Toiled, and sealed with Li grease from No Toil.  No air leaks found. 

Starts up with choke, a couple of twists of the wrist and a couple of kicks. Revs pretty high with choke, backfiring all the time. It accelerates like striped-butt baboon with no backfiring except on deceleration.

 

Is it possible the valves are gone and still have the valve clearances correct?

Edited May 10, 2014 by AlmostaCowboy

[Crf250x kid]

Ok, kid. Bike is back together (second time) and muuuch cleaner now. Carb is clean and rejetted for my altitude & temp per the Service Manual (#185 main/ Needle clip on 2nd position from top). Valve clearances checked, air cleaner clean, No Toiled, and sealed with Li grease from No Toil. No air leaks found.

Starts up with choke, a couple of twists of the wrist and a couple of kicks. Revs pretty high with choke, backfiring all the time. It accelerates like striped-butt baboon with no backfiring except on deceleration.

Is it possible the valves are gone and still have the valve clearances correct?

defiantly a carburetor problem. Try adjusting the fuel/air mixture screw.

As for your valves, I bet they're alright judging that your clearances are in spec and you had no issue starting the bike.

Check your spark plug, if it's black and wet, too much fuel.

If it's white and dry too much air.

It should be a nice tan color.

Also, did you replace the crush washer that connects your head pipe to your head? If not, replace.

Any other questions?

Edited May 11, 2014 by Crf250x kid

[AlmostaCowboy]

defiantly a carburetor problem. Try adjusting the fuel/air mixture screw.

As for your valves, I bet they're alright judging that your clearances are in spec and you had no issue starting the bike.

Check your spark plug, if it's black and wet, too much fuel.

If it's white and dry too much air.

It should be a nice tan color.

Also, did you replace the crush washer that connects your head pipe to your head? If not, replace.

Any other questions?

I didn't remove the header pipe from the head. Only the exhaust joint pipe ('Y') & mufflers. But now that you mention it, the manual has the little "new" symbol that I couldn't see out on my laptop out in the garage.

I'll check the plug (which was new). I was thinking about going back to the stock (low altitude, #188 main), too. But, crap! Disassembling the hole bike to get the carb off is already getting old. Not like my first BSA 250 or my Yamaha flat tracker!  ;-)

As an aside, I live 25 miles out in the Mojave Desert from the nearest Honda dealer (closed Sun-Mon) so, going for parts isn't like going for milk.....

And thanks alot. I really appreciate the help.

[Crf250x kid]

I didn't remove the header pipe from the head. Only the exhaust joint pipe ('Y') & mufflers. But now that you mention it, the manual has the little "new" symbol that I couldn't see out on my laptop out in the garage.

I'll check the plug (which was new). I was thinking about going back to the stock (low altitude, #188 main), too. But, crap! Disassembling the hole bike to get the carb off is already getting old. Not like my first BSA 250 or my Yamaha flat tracker! ;-)

As an aside, I live 25 miles out in the Mojave Desert from the nearest Honda dealer (closed Sun-Mon) so, going for parts isn't like going for milk.....

And thanks alot. I really appreciate the help.

you won't have to disassemble the carburetor. The air/fuel screw can be accessed from outside the carb. You will have to loosen the boots that hold the carb in place so that you can rotate the bottom of the carb to face you. The screw is a bitch to get at. But if you look on YouTube or whatever, search "af mixture screw crf250r" you should get some tips on how to adjust it for you altitude and whatnot.

You should check your service manual, it will tell you how many turns out to put your af mixture screw.

[AlmostaCowboy]

you won't have to disassemble the carburetor. The air/fuel screw can be accessed from outside the carb. You will have to loosen the boots that hold the carb in place so that you can rotate the bottom of the carb to face you. The screw is a bitch to get at. But if you look on YouTube or whatever, search "af mixture screw crf250r" you should get some tips on how to adjust it for you altitude and whatnot.

You should check your service manual, it will tell you how many turns out to put your af mixture screw.

Ok. Thanks again! I very carefully turned it 1 5/8 turns out. I see I can access the main and needle by rotating the carb, too. :-)

I haven't checked the air vent tubes to see if any of them are clogged.

[AlmostaCowboy]

you won't have to disassemble the carburetor. The air/fuel screw can be accessed from outside the carb. You will have to loosen the boots that hold the carb in place so that you can rotate the bottom of the carb to face you. The screw is a bitch to get at. But if you look on YouTube or whatever, search "af mixture screw crf250r" you should get some tips on how to adjust it for you altitude and whatnot.

You should check your service manual, it will tell you how many turns out to put your af mixture screw.

OK! Carb recleaned and rejetted with #195 main (Stock is #188). Starts, idles, runs good. Also, completely washed No Toil out of UNI dual element air filter and re-oiled with UNI oil. 

Can't figure out why it was running so lean and at this point I don't really care. 

 

Thanks to everyone for all their help and "opinions". This has been an education.

[Mike in OK]

My son and I both bought 07's in 2009, they were both new in the crate. Both of them had to be started completely differently but once you learn the drill they will start easy. These are high bred bikes though and require a lot if maintenance compared to, say an XR. I still have mine and am already having to replace the water pump seals and it has under 50 hours on it. It's on it's second piston too. And I don't race, I can't imagine the maintenance costs if you were to race one.