I have a 2007 CRF 450X. I just checked the valves and for the first time I had to shim because one exhaust valve was out by 2 thou and the other wasn't far behind.

I am wondering what some of you have seen as far as clearances. I don't ride a whole lot, and I have never seen any movement before.
When you check, is it normal to find the valves out by 2, 3, 4 thou, or even worse? How long between adjustments does it take to get that kind of movement?

Loose or tight?

Mike

It is common to see these motors needing adjustment, 99% of the time they go tight do to valve stretch and seats getting hammered.. Seems once they really start moving though the valve are starting to stretch and will need more frequent adjustments.. when this happens its time for a new top end .. A lot of time you will need a slight adjustment right after break in and then they will be good for a long time.. If you have never even checked them and depending onhow much time is on the motor this may be what you have and may not need another adjustment for a long time.. But Keep checking..

It is common to see these motors needing adjustment, 99% of the time they go tight do to valve stretch and seats getting hammered.. Seems once they really start moving though the valve are starting to stretch and will need more frequent adjustments.. when this happens its time for a new top end .. A lot of time you will need a slight adjustment right after break in and then they will be good for a long time.. If you have never even checked them and depending onhow much time is on the motor this may be what you have and may not need another adjustment for a long time.. But Keep checking..

That's completely true if they're getting tighter...

If they're getting loose, there's another issue... On these things, it's usually something stuck between the valve and seat, or a slightly bent valve...

Mike

And like I said 90% time they get tight.. That is what is the norm for these motors.. getting loose is not too normal..Of all the 450f's I have had and worked on never had one get loose unless there was big damage

If he had a loose one do to being bent or something between seat and valve he would be asking a lot more questions :D

And like I said 90% time they get tight.. That is what is the norm for these motors.. getting loose is not too normal..Of all the 450f's I have had and worked on never had one get loose unless there was big damage

If he had a loose one do to being bent or something between seat and valve he would be asking a lot more questions :D

That's why I asked which way they were out... I've seen a few guys on thumpertalk (and other bike forums) go to adjust them because it wasn't running at "peak performance" any more, and they're loose... Only after we've told them they've probably got another issue did they open it the rest of the way up to find that they had a slightly bent valve or an "air filter malfunction"...

Either way, it would be great if OP could let us know whether his are loose or tight, so we can say "yes it's normal", or "you're looking at spending some money"...

Mike

Loose or tight?

Mike

Thanks for the replys.

They were tight, well tighter.

I know all about why you need to do this and I have checked them many times before but this was the first time they were actually out of spec. Last time I noticed they were a little tight but still in spec.

What I want to know is, if I put another hand full of hours on it and check it again later in the season, should I expect similar slow movement, or do they accelerate or what?

I am also wondering from those guys that really push their bikes in races, do you commonly find them out by only 2 thou, or is it common to check after a race and find them out by a larger margin?

I guess I am just wondering what others have experienced with these things.

Pretty much answered it in my first reply.. But check them more often now since it can be a sign they are getting worn.. I ride mine hard and race so I push my bikes, plus I am a big guy so I ring their necks a lot:D.

Pretty much answered it in my first reply.. But check them more often now since it can be a sign they are getting worn.. I ride mine hard and race so I push my bikes, plus I am a big guy so I ring their necks a lot:D.

Yeah, thanks for the info. I guess I was looking for a number, I'm an engineer.

I do very little track, mostly trail and road travel, but speaking of "ringing their necks" I had a few rides with studded tires on ice and snow this past winter and I found I was using a lot more throttle. I can normally make 150km on a tank, I only made 80 km in the snow.

No body can predict exactly how much if at all they will change.. To many factors.. The best advice is to check them a little more frequent and if it starts needing adjustment a lot do the valves before you snap one and it costs you big numbers

You can tell when they get tight as it will be hard to start. If you adjust them and a week later they are tight again they ned replaced. I have done lots of them.

i have a trx 450r, i believe they have the same cams from what i have heard, i just adjusted my valves it was way over due, my intakes were loose by 9 thousandths :eek: but the exhaust valves were still where they should be, its an 05 and this was the first valve adjustment it has ever seen:homer:

i was happy with the increase in compression too after it was adjusted

i have a trx 450r, i believe they have the same cams from what i have heard, i just adjusted my valves it was way over due, my intakes were loose by 9 thousandths :eek: but the exhaust valves were still where they should be, its an 05 and this was the first valve adjustment it has ever seen:homer:

i was happy with the increase in compression too after it was adjusted

Increased compression fro adjusting loose valves???? How do you figure that one?

I also want to know what caused valves to be .009 loose, I bet there is some bad shit wrong with that engine.

I also want to know what caused valves to be .009 loose, I bet there is some bad shit wrong with that engine.

That would be my guess, as well...

I bet he ment tite not loose. For the rest of you I was told that it is all most always the intake valves that nead ajusted not the exhaus and that is what I found on my bike to I have a 04 450f has it changed on the new one's.

I bet he ment tite not loose. For the rest of you I was told that it is all most always the intake valves that nead ajusted not the exhaus and that is what I found on my bike to I have a 04 450f has it changed on the new one's.

I would be willing to bet that if they were more than .001-.002" tight it would be a bear to start and .009 tight it would probably have very little compression.

It was an 05 that has never ben messed with I bet he road it tell it would not start.