Dirt in engine HELP

[mlatour]

Reason a 250F MX race bike, even brand new are not the ideal trail bikes isn't reliability.

 

Too tall first gear / close-ratio gearbox, limited fuel capacity, stiff suspension,

tends to overheat if riding too slow, no lights, less bottom end / more rev happy engine etc.

In most cases, an 'enduro' type bike is much better suited for the average recreational off-roader.

Edited June 19, 2017 by mlatour

[aj2no]

Early CRF250R aren't known for the great longetivity, (valvetrain / cylinder head)
over the years there were some improvements in components and
luckily you can likely interchange some parts with up to the 2009 model year 250R.
 
Thing is, no matter the amount you spend making the engine 'like new'
the rest of the bike (suspension components, chassis bearings, etc. etc.) 
will all be 14+ years old and also require investments.
Having great power on a poor handling / crap suspension bike is useless.
 
Sometimes it's better to ride older bikes 'as-is' with minimal investment and,
put money aside not for a rebuild but rather for another bike altogether when the current one fails.

Thanks for the reply. What parts would be best to interchange with an 09? Also, were you saying my bike will still be getting internal damage due to the dirt being inside at one point? Or were you just clarifying that if dirt continues to get in then it will be causing damage. Sorry for all the questions I just want to get this straight and decide to keep the bike or not. Again no more dirt is getting in I tightened all the seals they were lose last time. How much longer should my bike last messing around in the trails

[CRFRida1605]

Dirt in the intake will wear the coating off the valves and most likely some nastiness on the cylinder too. Check the valve clearance now and then again in a few riding hours, that would be my primary concern as they start to mushroom quick once the coatings gone. Once they stretch a couple times, valve clearance will get smaller, the chance of them breaking increases greatly. If the valves go, usually one breaks, it will hit the piston, cylinder wall, and the head, all three will be toast and you will be probably be looking at just under $1000 without labor to fix it.

The head is the part you would want to change out to avoid any issues with the early years. 08 is best for power IIRC, 07 and up have the valve issue sorted.

I have an 04 as well and had the head totally reconditioned when I bought it, no issues since. I only trailride mine and while its not great for tight twisty trails any thing flowing is a blast.

[aj2no]

Dirt in the intake will wear the coating off the valves and most likely some nastiness on the cylinder too. Check the valve clearance now and then again in a few riding hours, that would be my primary concern as they start to mushroom quick once the coatings gone. Once they stretch a couple times, valve clearance will get smaller, the chance of them breaking increases greatly. If the valves go, usually one breaks, it will hit the piston, cylinder wall, and the head, all three will be toast and you will be probably be looking at just under $1000 without labor to fix it.

The head is the part you would want to change out to avoid any issues with the early years. 08 is best for power IIRC, 07 and up have the valve issue sorted.

I have an 04 as well and had the head totally reconditioned when I bought it, no issues since. I only trailride mine and while its not great for tight twisty trails any thing flowing is a blast.

You used the stock head with new internals basically? I would probably do what you said and get a newer head how is doing this compared to a built 04 head? And if something fails I would hope it to be a valve or something because when I have the money I would want to give it a whole new top end anyway. my biggest worry is cracking part of the case and having the whole bike become junk. What are my chances of this happening?

[CRFRida1605]

The newer heads flow a little better, besides that after having new valves installed and seats cut there isnt a while lot of difference. You wont damage the cases at all if a valve fails, but everything else in the motor will probably be junk unless you get very very lucky. Realistically, with an 04, even having to replace the head and cylinder, and all the other stuff involved, is basically the bike being junk. At that point you are better off parting it out and getting a different one, you could put that much into fixing the motor but the rest of the bike is still 14 years old and was probably neglected just as much as the motor appears to have been.

If it were me I would just have the head you have rebuilt now, change out the piston and cam chain, check for play in the crank and anything else you are able to check.

As far as chances its a matter of when, not if, something bad is going to happen.