it is an 02 and i havent adjusted the valves yet, i am the second owner but i dont think the original owner rode it much, so that person probably never adjusted them. how do you know when they need adjusted? are there any clues to look for? im kind of paranoid about this bike, i dont want something to go wrong with this engine because i know its probably going to be fix if something does happen.
yz250f valve adjustment, when is it necessary?
- Thread starter Lonewolf
- Start date
- Nov 25, 1999
- 7,924
- 43
Buy a manual. They probably need adjustment now and it is done with shims. If your running the bike hard, I'm sure someone can give you the specs and you can pull the valve cover and check the tolerances.
- Thread starter
- #3
i do ride hard when i get the chance to, the weather here in pa sucks, its always raining, i hate riding in mud but this year i had no choice. i usually ride about 4 hours a week. i have a service manual with the specs in it, i was just curious if there are any signs or symtoms that let you know when its time to adjust the valves. thanks for responding.
Mike Hubert
Member
- Apr 22, 2001
- 164
- 0
When you find TDC (Top Dead Center) to start the bike you will often notice that the compression is weaker.
If you wait until you can FEEL the need to check/adjust the valves, you have waited WAY TOO LONG. If you ride regularly you should check the clearances every couple of months. Racers should make it a part of their regular maintenance.
The valve seats and the valves themselves can take a real beating when the clearance is off. Without pulling the head it's hard to say for sure if you did any harm. A leakdown test might give you some clue, but without a baseline test to compare against it's only minimally useful.
If you did beat up the seats a proper valve job and a new set of valves (and probably springs) will bring it back to life, and you'll see a nice performance increase over stock if the valves and seats are properly massaged. ;)
For now just adjust them to factory clearance and see how it goes. Keep an eye on them over the next few months. If the clearances move a lot in that time period it's a good bet the valves are damaged and need to be replaced.
The Ti valves don't seem to have the same durability as the original steel YZ400F valves or the stainless replacements like the KIbblewhite valves. When the time comes, replacing the OEM Ti valves with stainless steel is a good upgrade for nearly everyone but the guys who live on the rev limiter.
If you did beat up the seats a proper valve job and a new set of valves (and probably springs) will bring it back to life, and you'll see a nice performance increase over stock if the valves and seats are properly massaged. ;)
For now just adjust them to factory clearance and see how it goes. Keep an eye on them over the next few months. If the clearances move a lot in that time period it's a good bet the valves are damaged and need to be replaced.
The Ti valves don't seem to have the same durability as the original steel YZ400F valves or the stainless replacements like the KIbblewhite valves. When the time comes, replacing the OEM Ti valves with stainless steel is a good upgrade for nearly everyone but the guys who live on the rev limiter.
- Thread starter
- #8
i can honestly say that i didnt notice ant differece in the way the bike ran or anything, it only felt a little different when i started it thats all. i actually plan on getting rid of the bike during the winter to buy one of the other new 250cc four strokes. i wish i didnt have to adjust these valves, not because i dont like to maintain my bike, but because knowing me ill probably drop something down in that engine or something. also, i think the yamaha service manual does a lousy job on adjustint the valves too.
It's funny, but I thought they did a good enough job explaining it that even a first-timer should have no trouble at all. It's all a matter of perception I guess. ;)
- Thread starter
- #10
in the yamaha manual that i have, the one the dealer gave me with the bike, it seems to leave some little steps out with the timing chain tesioner. like i said im kind of paranoid about messing something up and doing some damage. i found some info on thumper talk last night that does a way better job of expaining things step by step with pics. also another thing, i went down to a local parts shop where i buy most of my parts and i was talking with the one guy who works there, he has a yz 426f and he said i shouldnt have to mess with the valves yet. im not quit sure what he is talking about but he had me completly lost and he said something about there is something in the back of the motor and said something about the valves are self adjusting. i have no clue what he was talking about, he does know quit a bit about bikes though, he said his friend has an 02 250f and he has never been inside the engine yet.
The cam chain has an automatic adjuster, there is NOTHING self-adjusting about the valves.
It's your bike. Do what you think is best.
- Thread starter
- #13
the chain tensioner has to be what he was talking about. i am going to start working on it tomorrow. also, to the part for the compression release out of the cyl. head do i have to remove the radiator? do most yamaha dealers stock the shims too?
You don't have to remove the radiator or the compression release to do this work.
Most good dealers will have a stock of shims. The friendlier ones will even trade shims with you.
- Thread starter
- #16
well i didnt get very far yet, i got the tank off, spark plug out, the timing mark accessing screw ,and the crankshaft end accessing screw out. is it normal for oil to come out after you remove these two screws? just want to make sure everything is good so far.
Yes, that's why they have o-rings on the sealing surfaces.
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