Wondering this for a while

[Justin 250]

Hi! I have a kx 125 so I know what the maitance is like on the 2 strokes but im gettin a new bike soon and have been lookin at the 4 strokes. I rode them before and there sweet id like to buy one but I heard the maitance is crazey and to redo the motor is a lot more expencive(like $1000)then a 2 stroke and a lot harder to work on. Also I heard the valves always need adjusting. Is there any truth to this, ive had my 125 for 3 3 years now and the motor is so easy to maintain. hopefully the 4 strokes are the same. Whats the yz 250F like?

 

[oldguy]

You are looking at more work with a 4 stroke and far more expense if the worse case should happen. Adjusting valves periodically is a fact of life with 4 strokes and is easy enough to do if you follow the manuals directions. Cost for regular maintanence is a bit higher such as a topend in a 4 as opposed to a 2 stroke.
We have had 3 YZ250Fs and 1 YZ450F in the past 3 years and luckily have not had a major breakdown. This aside I have a feeling this summer my son will be picking up a YZ125 (pumped up to a 144) for MXlites and racing his 450 in MX class. I really think the 144 will bring back some skills he has lost because of the lazy 4 stroke riding. I also am looking forward to a bike that I feel more comfortable tearing into for rebuilds.

 

[NM_KDX200]

I moved from a KX125 to a YZ450F (with a brief fling with a KTM200sx in between). So far, the 450F is neither more nor less than the 125. I've changed the oil every 5 hrs, so that's 1 qt of oil every 4 gallons of gas, which is pretty much what the 125 took, too. The KX also took 1 qt in the crankcase every 3 rides, which the 450F does not. I put a new top end in the KX every 25-30 hr (play racing and recreational riding). So far the 450F has 15 hr and feels like it's just getting broken in. The 450F chews rear tires faster but no much faster than my 250 2S did. I know, if it blows up, it's going to cost $$$ but I don't think it's going to blow under my recreational use.