250F Top Ends

John250

John250

PR Founding Father
OK, for some of you guys that have run your 250Fs a lot of hours. At how many hours are you putting a top end in them?
 
I think 20 hours is the magic number for 250f tops. People claim 40-60-100 hours but I'd be worried taking a bike that far past what the book says. I don't like pushing bikes, I race/ride a lot so that's why I'm going away from only having a 250f since I don't rebuild 4 strokes myself.
 
When I was riding 250f's I was checking out everything in the top end around 40-50hrs
 
From what I was reading in a long thread on Vital, I think 50 hours seems to be a safe place. I honestly think some of these guys are replacing way too soon. Some OEMs recommend 15 hours. That is crazy. I have also heard of guys with like 250 hours on 450s putting top ends in for the first time.
 
40 is a comfortable number to me. You can probably go 80 hours without issues. I know of people that have 200+ hours and their bikes are still kicking.
 
The YZ450F has 38 hours on it, Just did the complete top end on it since the fire. Matt's 250F has 41 on it, I'm doing his this winter.
 
I think my brothers husky 250f went 80. Then again at 130ish. That seems long but I rode the bike with the high hours and it wasn’t much different than my low hour same year bike.
 
I kind of went by the rule of how it’s been ridden or used. A faster rider heavy on the throttle I would go every 30 hours. With my kid I start planning it around 60. Better safe than sorry, jugs, heads, and rods are expensive.
 
I have 40 hours on my 17 crf450... most hours are from GP and woods races where you’re not too hard on throttle. Owners manual says 25 hours to adjust valves, I’ve always went off of if the bike isn’t hard to start cold valves are fine. So far I’ve just done basic maintenance, oil and oil filter every 7 hours and air filter every ride.
 
30 hours on a 250f is at the very top ! Like to do them with a bit less hours like 23 to 25. There is NO way I would run the ridiculous hours that I have seen people talk about online ! Fixed too many and have seen the damage done from running them too long !
Just My opinion !
 
I put 50hrs on mine. Cylinder had some abnormal wear patterns but valves were all in spec. Replaced cam chain as well.
 
saplakc said:
I put 50hrs on mine. Cylinder had some abnormal wear patterns but valves were all in spec. Replaced cam chain as well.
Click to expand...

What was Your abnormal cylinder wear ? I have had to junk cylinders before from people running the piston too long !
 
The shop that cleaned up the cylinder and checked valve clearance said it was excessive wear on one side of the piston. Figured some dirt got into the airbox. I tried to be as careful as possible but with the location of the filter on the newer 250f everything falls straight into the intake.
 
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