[bs2usa]

i bought a '04 crf250f. it had good compression when I bought it, and it started ok. shut it off once and became hard to start, usually is easiest to pop start it cold but will kick start when warm. I've pulled the motor apart, piston, valves, everything looks good and its timed right on. I've pulled just the valve/head cover off and when you kick it over you hear a bubbling noise. the compression is less than it was. it doesn't like to idle to well either....any ideas???

[Monkeywrench]

WHen was the last time your valve clearances were checked?

Taking the model year into note, I'd bark up that tree for a bit. They could have closed up to nill, leaving you with a compression leak keeping you from getting it started.

The bubbling and hissing noises you hear with the valve cover off are normal. Your auto-decompressor system is causing the hiss, as it cracks open the exhaust valves a small amount to relieve some compression and make it possible for you to even be able to move the kick starter (a nice feature).

The bubbling noise I think is the sound of the crank and pump moving the engine oil around, down below.

Get those valve clearances checked.
Hard-to-start issues many times end up having something to do with insufficient valve clearances, which can also yield the lower compression reading you're seeing. (if the intakes are not seating well, rough idle can also happen).

Good luck.
-matt

[bs2usa]

I checked clearances. The intake valves had to be re-shimmed. It took care of my problem, started up 2nd kick! Thanks guys!

[Monkeywrench]

Good news.
Now, keep an eye on them... maybe something like every 3 tanks of gas. You have an '04. They will move again, unfortunately. Try to stay ahead of the game by checking them before you notice a problem. Once you can't start your bike, there is a very good chance that while your bike was running, the wrong side of the valve(s) was being exposed to the combustion process. Carbon deposits and pitting take place on the wrong side of the valves, which wears the seating surfaces in the head more quickly, which causes you to need to shim again, and again... until you have reached your smallest shim (which you shouldn't use anyway!)

[JAWS]

Do yourself a favor and order your parts now. Once they start moving they go pretty quickly. If you decide to go stainless, don't forget the mandatory springs.
Joe

[cromoly]

Jaws,

I shimmed my bike again last night (i am becoming a pro) and the right intake is down to a 130, this is the 2nd time i have shimmed in the last 3 or 4 tanks of gas.

Can you explain to me why the clearences change so fast and what can I do for a more permanent solution.

I have an 05 CRF250R.

Can you tell me about the titanium valves in the bike VS. going to stainless?

[JAWS]

The change occurs faster because the coating has worn off and the valves then deteriorate at a much faster rate and the seats deteriorate as well. Once they start to go they move faster and faster until you are as far as you dare go.

Order your replacements asap.

Going back stock or going stainless is a personal choice. Stock is cheaper, but you will be doing this again much sooner. Stainless is more expensive, mainly due to the springs you have to buy, but will last several times longer. Kibblewhites sell you a complete spring kit that costs about $200.00. The valves are about $38.00 apiece, so you can see where the expense is.

PM 124 to ask specific questions regarding the Kibblewhites. I believe he has had hands on experience with quite a few.

[Asmith]

Faction MX sells a kit for complete intake replacement using Ferrea coated stainless valves, springs, keepers, etc. for $ 165.00.

[redrooster65]

Faction MX sells a kit for complete intake replacement using Ferrea coated stainless valves, springs, keepers, etc. for $ 165.00.

Aside form $27.00 how do these differ from RHC's Ferrea coated valves?

[Asmith]

Faction MX sells a kit for complete intake replacement using Ferrea coated stainless valves, springs, keepers, etc. for $ 165.00.

Aside form $27.00 how do these differ from RHC's Ferrea coated valves?

Sourced from the same company. Ferrea is the company name, the coating is called "Nitroneg" which is a heat treatment in a nitrogen rich atmosphere where the Nitrogen infuses into the metal and forms nitrides. It's not just a surface coating that can be worn off like the OEM titanium.

[JAWS]

Kibblewhite Back Diamond valves are also coated with Nitroneg. Interesting.
Joe

[Asmith]

Kibblewhite Back Diamond valves are also coated with Nitroneg. Intersting.
Joe

Probably a copyright on the process.

Like when you get your stuff drycleaned at the " 1 hour Martinizing" drycleaners.